Evaluation report. NeuroLogica CereTom portable CT scanner CEP09039

Transcription

1 Evaluation report NeuroLogica CereTom portable CT scanner CEP09039 December 2009

2 Contents 2 Summary... 3 Introduction... 5 Product description... 9 Methods Technical performance Operational considerations Economic considerations Purchasing Acknowledgements References Appendix 1: Supplier contact details Appendix 2: Product specifications Appendix 3: User questionnaire Author and report information... 49

3 Summary 3 The product The CereTom is a compact, portable, battery and mains powered multi-slice computed tomography (CT) scanner designed for scanning anatomy that can be imaged in the 25 cm field of view, primarily the head and neck. Field of use The CereTom can be used in support of neurological critical care, minimising movement of critically ill patients, and in operating theatres, where it may be used to provide a rapid check on surgical outcomes. Currently, the CereTom is the only such system on the UK market. National guidance Currently, in some countries of the European Union, CT accounts for nearly 50% of the collective dose from diagnostic radiology. Consequently special measures are required to ensure optimisation of performance in CT and effective patient protection. European guidelines on quality criteria for computed tomography provide technical parameters for image quality. In the UK, in addition to the general requirements of the Ionising Radiations Regulations and the Ionising Radiations (Medical Exposure) Regulations, CT is specifically addressed in certain paragraphs of the Medical and Dental Guidance Notes. Methods The technical evaluation methodology is based on the methods and protocols developed by ImPACT for CT type-testing. The user evaluation was carried out by interviews of staff at sites using the CereTom, plus questionnaires. The economic evaluation examines the relative costs of moving a portable CT scanner to the patient rather than transporting the patient to a fixed CT scanner. Technical performance The measured levels of image quality were representative of the performance expected for a portable system of this design and specification, although not as good as for a typical fixed multi-slice CT scanner. The performance reaches the standard of image quality typically used for standard brain scans and as, in general, relatively large morphology is being considered, should be sufficient for most clinical requirements. The delivered dose is higher than for a typical fixed scanner but again represents the levels that might be expected for a CT system of this type.

4 Summary 4 Operational considerations The major benefit of the CereTom portable CT scanner is the ability to scan at the patient s bedside (for example in a critical care unit) rather than having to move the patient to the imaging department. This is particularly important in cases where the patient is considered too unstable or ill to be moved and may allow scanning of patients who otherwise could not be scanned. The need for senior staff from the critical care unit to accompany the patient to the imaging department is also reduced. In general, users considered the CereTom to be a practical solution to imaging critically ill patients and post-operative patients prior to their waking up. Thus use of the CereTom may result in an improvement in service with benefits both for patients and staff. No major problems were identified in the use and operation of the CereTom although some users found the scanner unit heavy to move. Image quality was considered acceptable for the examinations performed and clinical information required. Use of the CereTom may be limited by radiation exposure considerations. Economic considerations An estimate was made of the number of cases required on an annual basis for the CereTom to break even when compared with moving patients from the critical care unit to the imaging department. Purchase, running, staffing costs, etc were considered for a range of scenarios. Typically near to 1000 scans per year (approximately three scans per day) are required for a break even point although this figure could be as low as 200 scans. These calculations do not consider the welfare of the patient and any potential reduction in adverse incidents related to transporting patients to fixed CT. CEP verdict The CereTom portable CT scanner may provide important clinical information on critically ill patients, which would otherwise be impossible to obtain. This may have an effect on clinical decisions such as whether to operate or not. It may also be safer for such patients not to be moved to the imaging department. The image quality was considered satisfactory for this type and specification of system and, although poorer than for a typical fixed CT scanner, clinical image quality was acceptable for the range of examinations performed.

5 Introduction 5 This report presents the findings of an evaluation of the CereTom portable computed tomography (CT) scanner. The system The NeuroLogica CereTom CT scanner was introduced to the worldwide market in 2004 and first offered for sale in the UK in It is a portable CT scanner, for use primarily in support of neurological intensive care where its use can minimise movement of critically ill patients. It may also be used in operating theatres to provide a rapid check on surgical outcomes. The system can be used to replace the need to move a patient to a fixed CT scanner in an imaging department or to perform a CT scan where it would not otherwise be possible. More recently the range of clinical applications for the system has been increased with the provision of a series of protocols for paediatric scanning. Currently, the CereTom is the only system of this type on the UK market. Portable CT In this report, the term portable CT is used to denote a scanner that can be moved from place to place within the hospital environment. Although this system has wheels and cannot be carried, this term is used to avoid confusion. Portable CT is analogous to mobile X-ray or mobile C-arm fluoroscopy. The term mobile CT is commonly used to designate a system that is delivered and operated as a stand-alone unit, typically in a large trailer. Scope This report gives a description of the CereTom portable CT scanner and its operation and includes a technical evaluation on a current unit. The operational aspects are addressed and include a user evaluation followed by a brief economic overview. The user evaluation includes opinions from current users of the system plus additional information from centres at which the CereTom has been trialled. This report is intended to assist NHS staff in deciding on the suitability of the CereTom system and in maximising value from its use. Literature review The published literature on portable CT scanners is comparatively limited and primarily covers two topics; image quality and dose (compared with a fixed installation) and patient welfare versus economic advantages and disadvantages (taking the CT scanner to the patient rather than the patient to the scanner).

6 Introduction 6 Although there are advantages to imaging the patient at the bedside, including decreased risk of adverse effects during transport for a critically ill patient, relative cost, image quality, diagnostic benefit, and radiation dose must also be considered. An early study by McCunn et al [1] attempted to determine the utilisation of portable CT for critically ill adult patients in a critical care unit. The study showed that severity of patient illness was the most common reason for using portable CT scanning as opposed to scanning on a fixed installation. Those with extracorporeal support and those with cardiovascular, respiratory or neurological instability were deemed too ill to transport. It was noted that if portable CT was unavailable, most physicians ordered a fixed CT scan and the patient was transported to the imaging department regardless of medical condition. The authors concluded that, if available, physicians preferred to order portable CT for critically ill or unstable patients. Portable CT offered an alternative and potentially safer means of obtaining the required diagnostic information. In 2000, Gunnarsson et al [2] suggested that transportation of unstable neurosurgical patients can involve risks that can lead to further deterioration and the possibility of secondary brain injury. The authors used portable CT over a period of approximately three years and developed their own scanning procedures and radiation protection measures. The complications that occurred in patients during transportation to the imaging department followed by conventional head CT were compared with those that occurred during portable CT scanning. It was concluded that portable CT scanning in the critical care unit is safe and reduces the risk of physiological deterioration and other potential problems linked to transport of the patient. Additionally, the time that patients have to remain outside the controlled environment of the critical care unit is minimised and the staff workload is decreased. Teichgraber et al [3] investigated the use of portable CT in a critical care unit setting and assessed the additional diagnostic gain and therapeutic consequences. A small number of patients who were considered not transportable were examined directly in the patient room while all other examinations were performed in a special interventional suite directly on the critical care unit. The results showed that for over half of the patients portable CT resulted in a change in patient management and it was considered that all patients profited from portable CT. It was concluded that the performance of portable CT directly on the critical care unit allows immediate and minimally invasive therapeutic interventions and provides improved monitoring of the patient. Mayo-Smith et al [4] investigated the comparative costs of portable versus fixed CT scanning in The costs of performing a CT examination included fixed costs (machine costs, service contract, etc) and variable costs (which vary in proportion to the number of examinations performed) such as supplies and radiographer salaries. Indirect costs such as departmental administration were also addressed. The results

7 Introduction 7 were divided into a low throughput and high throughput model. For both models the cost of portable CT was approximately 50% higher than for fixed CT. For both techniques the overall costs for low throughput model were greater than for the high throughput model (by approximately 50%). Thus the authors concluded that the cost of using portable CT is always higher than that of using a fixed scanner. However, they suggested that the overall utility of portable CT depends on a number of factors including image quality, examination costs and value to the patient. Also the utility of portable CT depends on the severity of the illness of the patient. Thus if a medically stable patient that does not require nurse monitoring is imaged with portable CT it is probably not cost effective. Conversely, for patients who are so ill that leaving the critical care unit would place them at medical risk, portable CT may be medically and economically more valuable. Hence the true value of portable imaging is dependent on the severity of illness of the patient which is difficult to quantify reliably. In 2004 Maher et al [5] conducted a study to investigate the image quality and clinical content of portable abdominal CT involving over 100 patients. The results from portable CT were compared with those for fixed CT. It was found that the quality scores for portable CT scans were consistency lower than those for fixed CT scans (both with and without contrast material). It was concluded that although image quality was inferior to that of conventional fixed CT, portable abdominal CT can provide important diagnostic information without requiring patient transport outside the critical care unit. Masaryk et al [6] suggested that there is 13% morbidity when transporting critically ill patients outside of the intensive care unit and the incidence of adverse events during transport specifically for CT imaging could be as high as 71%. The study demonstrated that the introduction of portable CT in the critical care unit is feasible and cost effective and that the use of a portable scanner can provide a full return on investment within one year. In a recent publication, Weinreb [7] reported on the benefits for stroke patients who received portable CT in the emergency department. Waiting times for CT scans on portable and fixed units were compared and shown to be approximately 16 minutes and 39 minutes respectively. This reduction in waiting time would allow faster implementation of appropriate treatment. The authors concluded that the use of portable CT facilitated more rapid assessment of acute stroke patients and would increase the numbers patients to whom thrombolytic therapy could be administered. In an article published in 2009 [8] Rumboldt et al reviewed the use of a portable CT and reported on the assessment of the CereTom CT scanner. The authors concluded that the CereTom generated satisfactory clinical images at acceptable patient doses. The contrast performance allowed the detection of 4mm low contrast lesions and the limiting spatial resolution was 7 line pairs per centimetre. The CT dose index (CTDI) for a head scan at was measured as 41 mgy for 120 kv, 14 mas.

8 Introduction 8 National guidance Currently, in some countries of the European Union, computed tomography accounts for nearly 50% of the collective dose from diagnostic radiology [9-11]. Consequently special measures are required to ensure optimisation of performance in CT and effective patient protection. The requirement for special attention to radiation protection in computed tomography was formalised in European legislation, which demands that member states pay special attention to radiation protection in computed tomography and in paediatric radiology [12]. Following this, European guidelines on quality criteria for computed tomography were published in 1999 [13] and provide technical parameters for image quality. In the UK, in addition to the general requirements of the Ionising Radiations Regulations [14] and the Ionising Radiations (Medical Exposure) Regulations [15], CT is specifically addressed in certain paragraphs of the Medical and Dental Guidance Notes [16].

9 Product description 9 Product description The CereTom is a portable multi-slice CT (MSCT) scanner designed primarily for head and neck scanning. It has a 32 cm aperture in which the patient s head is positioned. The system comprises two units, the scanner and the workstation. The system can be moved manually or an electric tractor unit is available as an option. Once in position, the system is powered from an on-board battery pack which can be charged from a standard 13 amp mains outlet (both when the scanner is in and not in use). The battery capacity (fully charged) is quoted as 2 hours (under typical use). The scanner is shown in figure 1 and is 1.5 m in height, 1.3 m in width and 0.7 m in depth. Figure 1. CereTom scanner shown during technical testing. Scanning capabilities The CereTom is an 8-slice CT scanner. The detector array can sample eight data channels of 1.25 mm thickness along the patient (z) axis. These channels can be combined to produce thicker slices, for example, four images of 2.5 mm thickness. The unit has a 25 cm scan field of view (SFOV) in the image (x,y) plane. Thus not the entire 32 cm aperture is covered by the scan beam. However, 25 cm is sufficient coverage for head and neck scans and certain paediatric procedures.

10 Product description 10 The scanner can be run in axial (sequential) mode, or helical (spiral) mode. Axial mode can be used to produce slices within one 10 mm region, repeated images within the same 10 mm region (for perfusion imaging), or many slices from neighbouring regions (contiguous imaging). The system is capable of undertaking standard non-enhanced CT scans, CT angiography scans, CT perfusion scans and CT xenon perfusions scans. Operator interface The system has a small control panel mounted on the side of the gantry, which is primarily used to move the scanner when in position ready for scanning. In an emergency situation a scan protocol can be selected and the scan initiated from this panel. However, the main control interface and image review is from a Clarus computer workstation that is separate to the gantry. This is shown in figure 2 with the optional cart. Figure 2. The Clarus workstation shown with the optional cart The workstation is used to record details of the patient, the study and the examination series. Communication between the workstation and the scanner is primarily by a wireless connection; a cable connection is also available. The scan parameters can be selected from a range of protocols or set up on the workstation and uploaded to the scanner. When the scan is complete the images are downloaded to the workstation where they can be reviewed. The workstation can export images as DICOM compatible files. Worklists and patient details can be downloaded to the workstation.

11 Product description 11 Mobility The scanner is designed to be easily transported between scan locations within the hospital. For ease of manoeuvrability, the scanner is moved on four castors (figure 3a). For scanning, the unit is lowered onto caterpillar tracks (figure 3b). These provide a suitably stable base for scanning and allow the motion of the scanner to be controlled in one-dimension along the scan axis. In axial (sequential) mode the scanner moves incrementaly between each exposure, in helical (spiral) mode the scanner moves continuously during the scan. Figure 3. Movement of the scanner Figure 3a. The scanner can be raised on to castors for transport and positioning Figure 3b. The scanner is lowered on to its tracks for scanning Accessories and options The scanner is supplied with a universal scan board as standard, which can be placed under the patient in any situation without requiring bed mounts; the patient s weight or a set of straps secures the board. A smaller scan board with a bed clamp is also available; the design is dependent on the bed type in use. Adapters for most common bed mounts are available. As many sites in the UK have a variety of bed types, the universal scan board is supplied as standard as this should be the most easily implemented. Should a site have only one bed type, then the custom scan board may a better option.

12 Product description 12 Figure 4. Scan boards available for the CereTom scanner Figure 4a. Universal scan board Figure 4b. Small scan board for use with a bed mount Other accessories available include a (radiolucent) cranial clamp for use in neurosurgery applications, a powered tractor to assist in moving the scanner and a contrast injector. A range of data processing packages for the workstation is also available.

13 Methods 13 Technical evaluation The technical evaluation of the CereTom was performed in 2009 on a current unit. The methodology was based on the methods and protocols developed by ImPACT for CT type-testing [17]. The range of tests was approved by the manufacturer s representative. User evaluation The user evaluation was carried out by questionnaire, and by interviewing users of the system. Those involved included radiographers and clinicians based at sites currently using the CereTom. Additional information was obtained from centres at which the CereTom has been trialled. Economic evaluation A brief economic assessment of the CereTom was undertaken. Equipment costs were provided by the UK supplier. Staff costs were estimated from the mid-point of current pay bands. Staffing requirements, pay bands and times were estimated from discussions with users and clinicians. This information was then used to calculate whole-life costs and to estimate potential staffing cost savings for the CereTom, compared with fixed CT. A brief sensitivity analysis was undertaken to assess the impact of different working practices.

14 Technical performance 14 Technical evaluation results The performance metrics that have most impact on the clinical image quality and use are image noise, spatial resolution ( sharpness ) and low contrast detectability (LCD). The delivered dose is also of importance in terms of justification of the procedure and related risk assessment. The technical performance of the imaging system is summarised in table 1. Table 1. Summary of technical performance of the CereTom scanner Parameter Performance Comment Image noise 5.5 HU at standard sharpness* The level of image noise is acceptable for clinical use, although higher than for a typical fixed 16- slice whole body multi-slice CT scanner [18]. Lower noise levels can be achieved by using different sharpness settings. Spatial resolution Low contrast detectablity Dose (CTDI vol, head for 28 mas scan) MTF 50/10 = 5.3 c/cm MTF 2 = 7.6 c/cm at standard sharpness 4 mm object resolved for 0.5% contrast at 30 mgy 85 mgy at 120 kv 126 mgy at 140 kv The performance matches that typically used for standard brain scans. However, the limiting resolution does not approach that of a typical fixed CT scanner [18]. The level of detectabilty is acceptable for clinical use although slightly lower than for a typical fixed 16-slice whole body multi-slice CT scanner at this contrast.. This scanner delivers a dose that is higher than for a fixed 16-slice whole body multi-slice CT scanner [18]. The related increase in risk should be considered when justifying an examination. * A 120 kv, 7mA, 4 second (28 mas) scan using the posterior fossa/vessel clinical sharpness setting is taken to represent a typical clinical scenario. A scatter diagram provided by the manufacturer is included in appendix 2. Strengths The overall technical performance of the CereTom is slightly lower than that of a standard fixed 16-slice whole body multi-slice CT scanner (MSCT) [18], which is taken to represent the alternative CT scanning option. However, performance is generally adequate for the limited range of scans that will be required of the CereTom. However, this scanner will not necessarily be suitable for all head and neck scans, and due consideration must be paid to the performance levels achievable.

15 Technical performance 15 Other considerations Image noise The measurement of noise is based on the parameters used for a typical clinical scan at user sites in the UK (120 kv, 7mA, 4 second (28 mas), posterior fossa/vessel clinical sharpness setting). As well as the exposure parameters, the degree of noise in the image will depend on the the selected clinical sharpness setting (reconstruction kernel). Measurements showed that noise performance was improved (lower noise level) for the soft tissue clinical sharpness setting (see figure 5) which is recommended by the manufacturer for a typical brain scan. However, the spatial resolution performance in terms of modulation transfer function (MTF) will be correspondingly reduced (see figure 6). The selection of clinical exposure parameters and clinical sharpness setting will depend on local requirements and practices. Spatial resolution With the current version of the CereTom software, a targeted reconstruction can be undertaken. The reconstruction is based on data within a region of interest (ROI) smaller than the imaging field that is selected by the user. This square ROI must be at least 50 mm x 50 mm (this increases the image matrix resolution from 2 pixels per mm to 9). For detail reconstruction kernels (sharp, bone, sharp lung), this can increase the spatial resolution of the system by between 7% and 10%. Should scans be required where fine detail is needed for diagnostic discrimination, it should be assessed locally whether the performance of the CereTom is adequate. Low contrast resolution A subjective comparison of images taken from the CereTom and those from typical 16-slice MSCT scanners, shows that the CereTom performance is close to that from a MSCT for objects with a nominal 5 HU contrast difference. However, for objects with a nominal 3 HU difference, the CereTom performance is markedly decreased., Users indicate that the features of clinical significance are typically of the order of 5 mm in size, which the CereTom can detect at 5 HU contrast difference. Therefore the CereTom is likely to be useful for the majority of clinical applications. Where very low levels of contrast are expected (< 5 HU), or features of < 3 mm, a fixed MSCT scanner is likely to be the better option. Patient dose The scanner as evaluated delivered a slightly higher dose than a fixed scanner. A CTDI vol of 85 mgy was recorded for a typical clinical scan (120 kv, 7mA, 4 second (28 mas), posterior fossa/vessel clinical sharpness setting). A 16-slice MSCT will typically deliver 57 mgy for a clinical axial head protocol (120 kv, 320 mas) [18]. The higher dose increases the relative risk of the scans. However, this increase in

16 Technical performance 16 radiation risk should be considered in a complete assessment of the risks, including those related to moving the patient or the possible outcome of not imaging the patient. The manufacturer suggests that a shorter scan time (2 seconds, 14 mas) can be used for a typical brain scan. This will deliver a CTDI vol of 43 mgy which is in good agreement with the value of 41 mgy measured by Rumboldt et al [8]. However, a lower dose will have an effect on image quality. The CTDI vol indicated on the CereTom was found to be within 10% of the measured value. Scan optimisation The scan factors that can be independently set are tube potential (kv), tube current (ma) and scan time. In the current version of the control software, the tube current can be set between 1 ma and 7 ma in increments of 1 ma. For axial scanning the time per rotation is fixed at 2 seconds. Three levels of resolution (number of rotations or scan time) are available; low dose (1 rotation/2 seconds), standard resolution (2 rotations/4 seconds) and high resolution (3 rotations/6 seconds). For helical scanning the time per rotation is 1 second. The system is delivered with a set of standard protocols. These can be optimised in consultation with local radiologists, radiographers and medical physics staff in order to minimise patient dose, whilst maintaining sufficient image quality. This can be achieved by decreasing the tube current or possibly the scan time. It is essential that the most appropriate reconstruction kernel is used for each clinical scenario. These are also preset in system protocols. The relative image noise for various clinical sharpness settings (reconstruction kernels) is shown in figure 5. Figure 6 shows the characteristic spatial resolution performance for various clinical sharpness settings and demonstrates the increased performance with targeted reconstruction over a selected small reconstructed field of view (RFOV) (55 mm x 55 mm).

17 Technical performance 17 Figure 5. Relative image noise for various clinical sharpness settings Relative Noise 500% 450% 400% 350% 300% 250% 200% 150% 100% 50% 0% SOFT TISSUE POSTERIOR FOSSA/VESSEL SHARP BONE SHARP LUNG Sharpness setting Figure 6. Characteristic spatial resolution for various clinical sharpness settings showing increased performance with targeted reconstruction (small RFOV) Ave MTF 50/ Standard RFOV Small RFOV SOFT TISSUE POSTERIOR FOSSA/VESSEL SHARP Sharpness setting BONE SHARP LUNG

18 Technical performance 18 Ergonomics The scanner is designed to be mobile. When moving between locations and approaching the scan position, the unit moves on castors. Measurements indicate that a force of around 160 N is required to initiate movement of the gantry. Once in motion, a force of less that 100 N is required to move the unit. It was found that it was easier to move the scanner on smooth, hard surfaces. On surfaces such as cushioned flooring it becomes more difficult to initiate motion or changes in direction. The scanner control panel is located on one side of the gantry which could restrict access for the operator. Free access to the panel must be ensured during a scan. This is important for initiating the scan and also for access to the emergency stop controls. The panel is at a fixed height, but can be tilted to allow operators to view the screen easily. The Clarus workstation is a standard laptop computer. Users may choose to connect additional devices (keyboard, mouse, monitor) but this will reduce the portability of the system. For the short duration of typical scans, the notebook keyboard and touchpad should suffice. The workstation weighs just more than 2 kg. A carrying case for the workstation is supplied and can be attached to the scanner gantry whilst moving between sites. Alternatively, an optional cart can be purchased for the workstation, which includes a full-size keyboard. However, this must then be transported separately from the scanner unit. Emergency stop controls An emergency stop button is located below the control panel on one side of the scanner unit, as shown in figure 7. It is easy to operate provided it is accessible, given other equipment around the patient. The provision of a second emergency stop button located on the opposite side of the scanner unit may prove beneficial. The emergency stop function was tested both when positioning and scanning, and stopped motion of the scanner and irradiation immediately.

19 Technical performance 19 Figure 7. Emergency stop control

20 Operational considerations 20 Clinical applications The CereTom is designed for specific clinical circumstances where the use of an existing imaging modality is difficult or unfeasible. It is in this context that the scanner offers greatest potential benefit. The clinical environments where the scanner is most likely to be used are in critical care units and neurosurgery theatres. Neurological care cases may be handled in a specialist unit (neuro critical care unit) or on a general critical care unit. In either case, the scanner may be used to identify conditions such as subarachnoid haemorrhage (SAH). Patients requiring critical care tend to be unstable, requiring intubation and mechanical respiration. They may also have depressed consciousness and require monitoring. In such cases, moving the patient to the standard scanner may not be possible. Hence, where conditions such as SAH are suspected but no diagnosis can be made, appropriate intervention may be delayed or not initiated, with potentially serious consequences for the patient. Even when patients can be moved, the process is very labour intensive, requiring clinical, nursing and portering staff (see Economic considerations). The ability to scan patients without moving them from the care environment could therefore be of major clinical benefit. CT perfusion (CTP) scans [19] may also be undertaken to assess the extent of infarct penumbra and as an indicator to the potential for thrombolysis in cases of focal ischaemic cerebral incidents, such as stroke. In theatre, the system may be used to aid with the preparation and undertaking of surgery and to assess the results of surgical intervention. After surgery has taken place, the scanner can be used to check for the complete removal of tumour, the placement of stents or unobserved bleeds before the patient is moved to recovery. As a consequence this may reduce the need for follow up surgery. Clinical impact The greatest strength of the CereTom portable CT scanner is its mobility. The ability to image patients in the ward or theatre potentially allows scans that could not otherwise be undertaken without some risk to the patient. Alternative technologies CT scans The main alternative to this scanner is to rely on a fixed multi-slice CT scanner and to transport the patient from the ward or the theatre to the imaging department.

21 Operational considerations 21 Other options are to use cone-beam CT scanning which is offered by some manufacturers on C-arm mobile flat panel fluoroscopy systems. These do have the advantage of being able to image any part of the patient. However, the scans are generally slower than those provided by the CereTom and cone beam images tend to be noisier in appearance. There is no evidence of independent direct comparison of portable CT and C-arm images for neuroradiology cases. If a mobile C-arm unit is being purchased for other requirements, it may be useful to investigate whether a suitable level of image quality for those clinical contexts addressed by the CereTom can be achieved. Other modalities Other modalities that can be considered for head and neck scanning are magnetic resonance imaging (MRI) and ultrasound (US) imaging. For optimum contrast of brain material and delineation of tumour margins, an MR scan is ideal. There are MR systems that can be incorporated into the operating theatre. Results of using such scanners in this context appear promising [20]. However, these systems are very expensive and require non-magnetic instruments to be used. For some investigations, transcranial ultrasound may be considered. As this is a nonionising radiation technique, this should always be considered as part of the justification of an examination. User evaluation The user evaluation is divided into two sections. The first part (initial user experiences) summarises observations from sites at which the CereTom has been trialled. The second section is a summary of responses given during interviews and to questionnaires circulated to current users of the system. Those involved included radiographers and clinicians. Initial user experiences The system which was used for the technical evaluation was also used at a number of demonstration sites to image a range of patients. As well as enhanced and nonenhanced general brain scans at the patient bed, the unit was used in theatre to confirm the positioning of a ventricle shunt and for CT angiography (CTA). Operation of the scanner: Details of the process of setting up a scan are covered in the CereTom user manual [21]. The following are observations on the process.

22 Operational considerations 22 Scan preparation - Prior to scanning the patient must be positioned on one of the scan boards which supports the head. The scanner unit is then aligned to the scan board. The patient and study details are set up on the workstation and uploaded to the scanner. The upload takes up to 10 seconds using wireless communication. Once the patient is positioned a scout and/or reference image can be acquired. The scout image provides a low dose, low resolution scanogram of the area of interest. The reference image is a single 1 cm low dose slice, generally acquired at the base of the brain to check the starting position, symmetry, etc. Once prepared, the scan is initiated on the scanner control panel. A user selectable built in delay allows the operator to withdraw to a safe distance before scanning starts or to allow a contrast agent injection. Protocols - The CereTom is provided with a series of pre-installed protocols. These can be modified to suit local requirements or custom protocols can be set up by the operator. Protocols are set up for one of the scan types: CT non-enhanced, CT angiography, CT perfusion, CT xenon. By default, the system sets to the first protocol in the alphabetic list for that scan type, rather than the last one used. Some care should be taken when setting up custom protocols to make the names clear and possibly to promote the more common scans to the top of the list. Operators should always check the protocol when setting up. Setting up good clinical protocols will reduce the amount of interaction required at this stage of the scanning procedure. Increased resolution is achieved via an increase in the number of rotations (per slice) and therefore an increase in the scan time. Control interfaces - The design of the control interfaces on both the scanner and the workstation is clear and informative. Some of the terminology is different from that used on typical fixed CT scanners; operators will need to familiarise themselves with the terms. (The manufacturer has subsequently re-named certain of the terms.) Protocols should be well documented in terms of the CereTom nomenclature with reference to the local or accepted equivalents. Some examples are given in table 2.

23 Operational considerations 23 Table 2. Terminology used in CereTom interfaces CereTom terminology Sharpness Resolution Alternative terms reconstruction filter kernel algorithm (number of) rotations exposure time Positioning: There is no facility to tilt the gantry of the scanner. Therefore there is the possibility of irradiating the orbits during most brain scanning procedures. However, the relative clinical benefit of undertaking the scan will often outweigh any potential risk. For each such scan the practitioner [15] must justify the scan both in terms of the overall exposure and that of the eyes. The positioning light (laser) indicates the centre of the irradiated beam. Therefore with a radiation beam width of approximately 10 mm, the operator needs to be aware that the scanned (and irradiated area) extends approximately 5 mm either side of the light. User observations: Some of the observations made by those who have seen the scanner in use include remarkably simple to perform scans once optimal positioning is achieved and nursing staff were impressed at the minimal disruption to their patients and no preparation for transfer out of the (critical care) unit. User feedback: User feedback has led to subsequent developments by the manufacturer. These include the design of the scatter shields, the inclusion of a scan projection radiograph (SPR) or scout image facility and the production of a radiolucent theatre head-clamp. Clinical image quality: The images were accepted by clinicians as being of sufficient quality for the investigations that were carried out. One user commented scan quality achieved is probably comparable to 5 mm fast scan brain sequence or 5 mm spiral brain sequence on our fixed unit. Summary of answers to interviews and questionnaires Eight questionnaires were returned from two sites in the UK currently using the CereTom portable CT scanner. These were completed by radiographic staff (with up to 22 years of experience in CT scanning) and by clinicians involved in viewing the images.

24 Operational considerations 24 Use of the system: All users considered the CereTom suitable for range of head/brain scanning applications including the exclusion of hydrocephalus and bleeds. A major benefit is the ability to scan at the patient s bedside (for example in the critical care unit) rather than having to move the patient to the imaging department. This is particularly useful in cases where the patient is considered too unstable or ill to be moved to the imaging department and was particularly appreciated by the critical care staff. A number of users commented that use of the CereTom allowed certain patients who could not be moved to the imaging department to have a have a scan in the critical care unit. This can be very useful in patient management (for example whether to operate or not) and potentially lifesaving. If a patient needs to be taken to imaging at least two nurses and one clinician are required to accompany the patient. This would take at least three senior staff members away from the critical care unit which can be a particular problem at night. In some instances the critical care staff fitted the scan board and bed mounts to the bed and moved the patient into position. This can be time consuming but does not take staff away from the critical care unit. In addition to not taking staff away from the critical care unit another benefit of being able to scan at the patient s bedside is that images are immediately available for review. Overall, use of the system was considered to be a very practical solution to imaging critically ill patients and scanning patients post-operatively prior to their waking up. Thus use of the CereTom in critical care and theatre situations may result in an improvement in service with benefits both for patients and staff. Users commented that image quality (both on the Clarus workstation and via a PACS) was coarser than on a conventional fixed CT unit but acceptable for the examinations performed and clinical information required. Use of the CereTom may be limited by radiation exposure considerations (see Radiation protection below). It was also suggested that care should be taken in selecting the correct category of patient to be scanned on the CereTom and that the system should not be used for patients that can safely be moved to the imaging department. Movement, operation and controls: The height and weight of the scanner unit can make moving the unit difficult for certain users, particularly over longer distances. This will be made easier by use of a powered tractor unit (available as an option). Movement of the scanner unit is also more difficult over uneven floor surfaces or on carpeted or cushioned flooring. All users stressed the need to have two people to move the system.

25 Operational considerations 25 Operation of the CereTom typically requires two radiographers. General ease of use and operation of the system was considered good and improved with familiarity. The location and design of the controls for the scanner was considered good and no difficulties were encountered in use of the controls on either the scanner or the Clarus workstation. The range for wireless operation of the workstation was considered good. The warm-up time of the system (after moving but before scanning) was not considered excessive. Final alignment of the scanner at the patient s bedside or in theatre caused no difficulties. No problems were encountered in positioning of the scatter shields although it was pointed out that care should be taken to prevent any tubes or cables from inadvertently catching on the shields. The ease with which a patient can be positioned depends very much on the patient s size and number of attachments and was considered easy as long as a scan board and bed mount (to suit the type of bed in use) was used. The universal scan board was not liked and made positioning of the patient more difficult. At one site the users often found it easier to move the patient s bed to the scanner (located in a convenient place) rather than moving the scanner to the patient s bed. No problems were found with selecting the correct scan protocol and the range of protocols was considered adequate. Selected protocols could easily be modified and existing protocols could easily be transferred to or programmed into the CereTom (although experience in this area was limited). The visual warning device for exposure (on the top of the scanner unit) was considered adequate although many users would have liked some form of additional audible warning. Location and operation of the emergency stop control (on the side of the scanner unit) caused no problems in use. Instructions for use Those users that had referred to the user manual considered it adequate. In the case of a fault condition the system displays an error message. In general, users found the error messages useful but in some cases not sufficiently explicit. Service requirements The CereTom is powered from an on-board battery pack which requires a standard 13 amp mains outlet for charging. Ideally, the system is used in a controlled environment to minimise the number of air calibrations required (see Calibration and quality control).

26 Operational considerations 26 Connectivity The scanner was integrated with an existing HIS/RIS at one site and a local PACS at both sites. In each case integration was carried out by the local PACS department and caused no problems. Image quality via the PACS was considered good. The system stores images in a DICOM compatible format. Wireless communication During the technical evaluation the wireless communication between the scanner and the workstation worked without issue. It is understood that if connectivity is lost, there is no loss of data as the transfer can be completed subsequently. Also this does not affect the scan, which will continue until complete. One concern would be that if there is loss of signal, a stop-scan command can not be issued from the workstation. However, the operator and/or clinical carers should always be positioned such that the emergency stop on the scanner can be accessed swiftly. The use of wi-fi technology may be of concern in some clinical environments. Where there is potential for interference with other equipment there may be local data security guidelines that prohibit the use of such systems. If this is the case, the use of a standard CAT-5 ethernet cable provides equivalent connectivity between the scanner and the workstation. This does introduce a potential trip hazard and may limit the separation between the device and the workstation. However, once the scan is prepared, there is no need for the operator to be next to the workstation during the scan. Consumables In addition to electrical power required for re-charging of the on-board battery pack, contrast media and syringes may be used for certain clinical procedures. Maintenance and servicing Current users of the CereTom considered the reliability of the system to be acceptable although a few instances of the system crashing during a scan were reported. Service engineers and technical support staff were found to be helpful and, in case of breakdown, service from the supplier was good both in terms of service visits and telephone support. Training provided by the supplier of the unit was adequate.

27 Operational considerations 27 No problems were encountered with general day-to-day cleaning and maintenance of the CereTom and its accessories. Calibration and quality control Routine air calibration of the scanner is carried out by the operator. There is a very clear indication on the scanner of the status of the most recent calibration. When this reaches amber, recalibration is recommended but scans can still be carried out with the existing data set. When at red, recalibration should be carried out. This indication system worked well during the technical evaluation. Recalibration was a simple operation that was achieved in a few minutes. In the clinical context, recalibrations may be required more often depending on the movements of the scanner and any changes in ambient temperature between locations. Ideally, to minimise any ionising radiation hazard, the scanner should be removed from the ward for recalibration. However, this is not recommended by the manufacturer who suggests that recalibration should be performed where or close to where to the scanner is to be used. The scatter shields on both ends of the unit should be closed over the aperture during recalibration. The system is supplied with a phantom for test purposes. A built in protocol runs suitable scans and an automated report is provided for the users. Users may choose to use their own local procedures for quality assurance (QA) testing. Performance of routine calibration and QA procedures was not found to be difficult and in general occupied about five minutes. Staff requirements Users suggested that two staff members are required to move the system from one location to another and two staff members are needed to operate the system. Positioning of the patient (in bed) onto a scan board ready for scanning may be carried out by the radiographic staff, the critical care unit staff or a combination depending on local procedures. Radiation protection This section includes observations and information taken from reports prepared by radiation protection groups at UK sites currently using the CereTom. Justification The convenience of the portable unit may encourage clinicians to opt for using this scanner even for lower risk patients when the reduced dose of the fixed unit may be

28 Operational considerations 28 more appropriate. Local procedures must be established to ensure this does not happen. Scattered radiation levels Concerns have been raised regarding the scattered dose that will arise when operating the scanner in public areas such as a ward [22]. Whereas fixed scanners are operated within rooms designed to shield both staff and public from ionising radiation, portable systems cannot be so shielded. Use of the scatter shields on the front and back of the scanner will reduce the scatter dose to the operator, staff on the ward and other patients. Clear local rules will be required to ensure that no constraints are exceeded. As with all X-ray equipment, a controlled area must be established when a scan is being undertaken. One concern with the use of the CereTom in an open ward is the protection of members of staff and patients adjacent to the scanning area. Staff members may be exposed to radiation for a substantial number of ward scans per year. The majority of staff are not radiation workers, and therefore, as with members of the public, have a recommended dose constraint of 0.3 msv per year [16]. Thus, depending on workloads and layout of the ward, access, dose constraints, etc may need to be reviewed. Due to the layout of a typical ward, it is likely that the limiting factor in terms of radiation dose will be the dose to adjacent beds. Rooms adjacent to the beds where scanning occurs may also need to be considered. Depending on the workload, shielding may be required in the walls closest to some beds. Scatter shields The CereTom is provided with scatter shields which attach to the outer covers. During patient exposures, the front shields should be placed as close as possible to the patient while the back shield should be kept closed. Precautions during calibration An air calibration is required more often (2 to 4 times per day) than on most fixed scanners to prevent the appearance of ring artefacts (which are not acceptable in clinical images). This is primarily due to the CereTom being used in different thermal environments during the day (as it is moved from place to place in the hospital). Frequent calibration is undesirable in terms of additional radiation hazard. Therefore consideration should be given to finding a safe place for calibration, close (similar environment) to the scanning area. However, the manufacturer recommends that the regular air calibrations need to be performed under the same environmental conditions as the clinical scan and the unit should not therefore be moved to a separate area. The manufacturer further

29 Operational considerations 29 suggests that the radiation exposure during air calibration with the scatter shields on both sides of the unit closed and no phantom implies no significant dose to persons around the unit.

30 Economic considerations 30 Literature review A small number of studies have considered the economic impact of portable head CT. Mayo-Smith et al [4] found portable CT incurred a higher cost per scan, primarily due to additional CT technologist time. Masaryk et al [6] found that, due to a reduction in the overall time required of clinical staff, portable head CT has a lower cost than transferring a patient to fixed CT. Whole life costs A number of costs have been identified and are given below. This should not be taken to be a complete list, as these costs will vary from site to site depending on local practices. Potential areas of costs and saving should be addressed in any business case preparation, even if they cannot be quantified at present. Direct costs The capital cost of the scanner and workstation is estimated to be 250,000 with annual service costs of approximately 25,000. Additional optional accessories include a contrast injector (~ 8,000), a powered tractor system (~ 20,000) and neurosurgery options (~ 40,000). The standard software upgrade for perfusion is approximately 8,000, although more advanced packages would incur an additional cost. Therefore the cost to purchase a full system with accessories might be between 250,000 and 280,000, with a typical figure of 270,000. A full neurosurgery system might cost 300,000 to 320,000. These figures are given for indication only and all current costs should be confirmed with the supplier at the time of purchase. Purchase costs There may be additional costs involved with the purchase process. There may also be costs associated with setting up the scanner, for example clearing and defining a storage area, user training, radiation protection assessment or updating documents to reflect changes to workflow. Operational costs Operational costs might include: on-going service costs replacement parts - including X-ray tube replacements operational staff costs

31 Economic considerations 31 reporting costs (radiologist, typing) consumables - contrast, single use items, clamp tips on-going training (new applications, new features, new staff and those on rotation) data storage and archive electrical power. Cost savings The areas that have been identified with the potential to deliver cost savings are: increase in availability of fixed scanner time. It is usual practice that a CT scanner is kept free once the decision has been made to scan a critical care unit patient. This can tie up the scanner for two or three normal patient slots decrease in staffing requirements to move patients from the ward to the fixed scanner. It is currently typical practice for a team of care professionals from the critical care unit to be involved for a period in excess of 45 minutes during patient transfer and imaging reduced operation costs - these may arise from: o being able to avoid unnecessary intervention due to a definitive noninvasive examination o being able to image in theatre so as to confirm if further intervention is required; thus avoiding the need to complete the operation, remove the patient to the fixed scanner, and possibly return to theatre. Estimate of whole-life cost The whole-life costs of the system depend on the workload, but might be expected to range from 450,000 to 2,000,000 over a seven year life-cycle, with a typical cost of approximately 750,000. However, the cost per scan decreases as the workload increases as illustrated by figure 8.

32 Economic considerations 32 Figure 8. Projected cost per scan for a variety of workloads Cost per scan Cost per scan Best and worst cases Annual workload (scans) Cost-effectiveness One of the potential cost savings identified for the CereTom system is through reducing clinical staff time. Substantial time is currently required to prepare and transport seriously ill patients to fixed CT. A brief assessment of the potential cost savings has been carried out, and the results are presented below. Assumptions Several assumptions were made during these calculations: no allowance for anti-social hours pay staff assigned to other duties when not involved in CereTom scans mid-points on pay scales for all staff identical consumables for portable and fixed CT same patient outcome with portable and fixed CT scanning.

33 Economic considerations 33 Staffing requirements The staffing requirements for a critical care patient to travel to the critical care unit are different to those for the CereTom system to be brought to a patient. Table 3. Staffing levels required Required staff during prep CereTom Fixed CT Anaesthetist 0 1 Neurology clinician 1 1 Nurse 2 2 Required staff during transport CereTom Fixed CT Anaesthetist 0 1 Neurology clinician 0 1 Nurse 0 2 Porter 0 2 Radiographer 2 0 Required staff during scan CereTom Fixed CT Anaesthetist 0 1 Neurology clinician 1 1 Nurse 2 2 Radiographer 2 2

34 Economic considerations 34 Table 4. Staff times (minutes) Time required Typical case Best case Worst case CereTom Fixed CT CereTom Fixed CT CereTom Fixed CT Patient prep Travel to scanner /patient Scan Travel from scanner/patient Patient return Results and sensitivity analysis Using the staffing levels and times above, and typical salaries based on the mid-point of the relevant pay-scales, and adding 20% overheads, an hourly rate was calculated for the various staff groups included. These were then used to calculate staffing costs for a range of cases, running from cheapest to most expensive case. The cheapest case considered lower grade staff (registrars, band 6 nurses, band 1 porters) and the fastest times, while the most expensive considered higher grade staff (consultants, band 7 nurses, band 3 porters) and the longest times. Table 5. Staff pay bands Staff group Pay band Midpoint of band Porters Band 1 13,588 Band 2 14,567 Band 3 16,698 Nurses Band 6 28,816 Band 7 34,410 Doctors Registrar 33,226 Consultant 81,444 Radiographers Band 6 28,816

35 Economic considerations 35 Table 6. Staff costs per scan CereTom Fixed CT Cheapest case Typical case Most expensive case Using these staffing costs, estimates of the number of cases required on an annual basis for the CereTom to break even were made for each case. As can be seen from table 7, the CereTom might be expected to break even at reasonably low workloads if the most expensive staff are involved in taking a patient to fixed CT. For the worst case, where existing practices are fast and use lower grade staff, the CereTom may not be expected to break even on cost alone. However, these calculations do not consider the welfare of the patient and any potential reduction in adverse incidents related to transporting patients to fixed CT. While justification of purchasing a moveable CT system may not be possible on simple economic terms alone, patient welfare factors combined with estimates of the cost may allow a local decision to be made. Table 7. Break-even workloads Cases required per year to break-even Best case for CereTom 200 Typical case 1,000 Worst case for CereTom Does not break even It is important to note that these figures are dependent on the assumptions made in this model. For local estimations of the cost, these assumptions should be confirmed as appropriate and adjustments made if necessary. For example, if the radiographers operating the CereTom are taken from general X-ray this may impact on the general X-ray performance and waiting times.

36 Purchasing 36 Purchasing procedures The Trust Operational Purchasing Procedures Manual provides details of the procurement process [23]. European Union procurement rules apply to public bodies, including the NHS, for all contracts worth more than 90,319 (from January 1 st 2008) [24]. The purpose of these rules is to open up the public procurement market and ensure the free movement of goods and services within the EU. In the majority of cases, a competition is required and decisions should be based on best value. NHS Supply Chain (NHS SC) offers national contracts or framework agreements for some products, goods and services. Use of these agreements is not compulsory and NHS organisations may opt to follow local procedures. Purchasing options The basic CereTom package (as offered in the UK) comprises the scanner, the Clarus workstation (laptop), a universal scan board or a scan board with a custom mount and a QA phantom. Options include: wheeled cart for the workstation universal back board or headboard (depending on which provided with unit) other bed adapters (up to 40 types available, custom adapters can be made to suit local requirements) head clamp (for intraoperative work) powered tractor (to aid moving the scanner) perfusion software package hardware and software for xenon scanning. The choice of package is dependant on the local situation and needs. The need and cost for any additional accessories; relevant scan boards, bed mounts and operating theatre equipment should be detailed and justified subsequent to the tender, when it has been shown which requirements as stated raise such needs. The need for and cost of optional software packages may be included, or may be part of a separate case and they may be used and justified on a wider basis; for example, a CT perfusion package may be used with any suitable CT data set.

37 Purchasing 37 Radiation protection As with any ionising radiation equipment, the local radiation protection committee must be involved at all stages of the purchase activity. The radiation protection advisor (RPA) will be able to address specific issues relating to the purchase and safe introduction of this equipment. This will vary on a local basis depending on local rules, room design, and working practices. Any works and costs identified should be included in the purchasing business case and sufficient time allowed in the project. Installation and preparation It is possible that wards and theatres will need to undergo modification to allow the introduction of this scanner. This must be evaluated on a local level and any costs should be addressed and included in the business case. Additional shielding may be required in some cases, this will depend on the design of the wards and theatres in each case. However, should local rules identify the need for additional screens and personal protection, these should be included in the costs. Training for staff should be identified and included in the project plan, in particular allowing sufficient time to train key staff in the safe and optimal use of the scanner. Commissioning the scanner and providing baseline performance data for routine QC testing will also need to be included in the time allowed for installation. Service contracts and warranty As with most diagnostic imaging equipment, these costs are normally established at time of purchase (contact supplier). Tenders should include details of warranty and maintenance. Further details may be obtained from the UK supplier. Sustainable procurement The UK Government launched its current strategy for sustainable development, Securing the Future [25] in March The strategy describes four priorities in progressing sustainable development: sustainable production and consumption - working towards achieving more with less natural resource protection and environmental enhancement - protecting the natural resources and habitats upon which we depend sustainable communities - creating places where people want to live and work, now and in the future climate change and energy - confronting a significant global threat. The strategy highlights the key role of public procurement in delivering sustainability.

38 Purchasing 38 End-of-life disposal Consideration should be given to the likely financial and environmental costs of disposal at the end of the product s life. Where appropriate, suppliers of equipment placed on the market after the 13 th August 2005 should be able to demonstrate compliance with the UK Waste Electrical and Electronic Equipment (WEEE) regulations (2006) [26,26]. The WEEE regulations place responsibility for financing the cost of collection and disposal on the producer. Electrical and electronic equipment is exempt from the WEEE regulations where it is deemed to be contaminated at the point at which the equipment is scheduled for disposal by the final user. However, if it is subsequently decontaminated such that it no longer poses an infection risk, it is again covered by the WEEE regulations, and there may be potential to dispose of the unit through the normal WEEE recovery channels. Vertec Scientific Limited, the UK supplier, are WEEE compliant and should be able to advise and support any concerns relating to the future disposal of the scanner.

39 Acknowledgements 39 We should like to thank the following for their contribution to this evaluation report. Anthony Bell, Professor of Neurosurgery, Atkinson Morley Wing, St George s Healthcare NHS Trust, London Suresh Pushpananthan, Department of Neurosurgery, Atkinson Morley Wing, St George s Healthcare NHS Trust, London Joe Brierley, Consultant Paediatric and Neonatal Intensivist, Great Ormond Street Hospital for Children NHS Trust, London Rowan Burnstein, Director of Neurocritical Care, Addenbrooke s Hospital NHS Trust, Cambridge Trevelyan Foy, Radiation Physicist, Royal Cornwall Hospitals NHS Trust, Truro Allison Osborne, Superintendent Radiographer, Department of Neuroradiology, Atkinson Morley Wing, St George s Healthcare NHS Trust, London Nicholas Rowles, Radiation Protection Advisor, Medical Physics and Bioengineering Department, Plymouth Hospitals NHS Trust, Plymouth Gregory Stevens, Medical Physicist, Medical Physics and Bioengineering Department, Plymouth Hospitals NHS Trust, Plymouth Yvonne Sullivan, Superintendent Radiographer, Great Ormond Street Hospital, London Halina Szutowicz, Superintendent Neuroradiographer, Addenbrooke s Hospital NHS Trust, Cambridge Stuart Yates, Radiation Protection Advisor, East Anglia Regional Radiation Protection Service, Addenbrooke s Hospital NHS Trust, Cambridge Keith Lakin, Vertec Scientific Limited The Neurologica Corporation, Danvers, Massachusetts, USA The Radiological Protection Centre (RPC); St George s Healthcare NHS Trust, London

40 References 40 1 McCunn M, Mirvis S, Reynolds N et al. Physician utilization of a portable computed tomography scanner in the intensive care unit. Crit Care Med 28: (2000) 2 Gunnarsson T, Theodorsson A, Karlsson P et al. Mobile computerized tomography scanning in the neurosurgery intensive care unit: increase in patient safety and reduction of staff workload. J Neurosurg. 93: (2000) 3 Teichgraber UK, Pinkernelle J, Jurgensen JS et al. Portable computed tomography performed on the intensive care unit. Intensive Care Med 29: (2003) 4 Mayo-Smith WW, Rhea JT, Smith WJ et al. Transportable versus fixed platform CT scanners: comparison of costs. Radiology 226: (2003) 5 Maher MM, Hahn PF, Gervais DA et al. Portable abdominal CT: analysis of quality and clinical impact in more than 100 consecutive cases. AJR Am. J Roentgenol. 183: (2004) 6 Masaryk T, Kolonick R, Painter T et al. The economic and clinical benefits of portable head/neck CT imaging in the intensive care unit. Radiol Manage 30: (2008) 7 Weinreb D, Stahl J. The Introduction of a portable head/neck CT scanner may be associated with an 86% Increase in the predicted percent of acute stroke patients treatable with thrombolytic therapy. RSNA (2008) 8 Rumboldt Z, Huda W, All JW. Review of portable CT with assessment of a dedicated head CT scanner. Am J Neuroradiol 30: (2009) 9 Brix G, Nagel HD, Stamm G et al. Radiation exposure in multi-slice versus single-slice spiral CT: results of a nationwide survey. Eur. Radiol 13: (2003) 10 Brugmans MJ, Buijs WC, Geleijns J et al. Population exposure to diagnostic use of ionizing radiation in The Netherlands. Health Phys 82: (2002) 11 Hart D, Wall BF. UK population dose from medical X-ray examinations. Eur. J Radiol 50: (2004) 12 CEC. Council directive 97/43/EURATOM on health protection of individuals against the dangers of ionizing radiation in relation to medical exposure. No L 180/22. (1997) 13 Report EUR European Guidelines on Quality Criteria for Computed Tomography. European Commission. (1999)

41 References The Ionising Radiations Regulations Health and Safety (The Stationery Office Limited, London) SI 1999/3232: (2000) 15 The Ionising Radiations (Medical Exposure) Regulations Health and Safety (The Stationery Office Limited, London) SI 2000/1059: (2000) 16 Medical and dental guidance notes: A good practice guide on all aspects of ionising radiation protection in the clinical environment. IPEM. (2002) 17 MDA. Type Testing of CT scanners: methods and methodology for assessing image performance and Dosimetry. MDA/98/25. Medical Devices Agency. (1998) 18 CEP. CEP Evaluation report 06012: Sixteen slice CT scanner comparison report version 14. NHSPurchasing and Supply Agency. (2006) 19 CEP. CEP Evaluation report 08039: CT perfusion imaging in the management of stroke and transient ischaemic attack. NHS Purchasing and Supply Agency. (2009) 20 CEP. CEP Evaluation report 07015: Medtronic PoleStar imri Navigation System - portable magnetic resonance imaging system for neurosurgery. NHS Purchasing and Supply Agency. (2007) 21 NeuroLogica Corporation. NL3000 CereTom user manual. NeuroLogica Corporation, Foye T. Radiation protection of a mobile CT head scanner for use within wards and theatres, Proceedings of the 13th annual scientific meeting, Cardiff University, IPEM. (2007) 23 NHS trust operational purchasing procedures manual (TOPPM). (2007) [Last accessed 27/4/09] 24 Office of Government Commerce, EU Procurement Thresholds (Oct 2008) ocurement_thresholds_.asp [Last accessed 27/4/09] 25 UK Government Strategy for Sustainable Development, Securing the Future. (2009) [Last accessed 27/4/09] 26 EC Directive on Waste Electrical and Electronic Equipment. (2006) [Last accessed 27/4/09]

42 Appendix 1: Supplier contact details 42 Vertec Scientific Limited Comet House Calleva Park Aldermaston Berkshire RG78JA Tel: Fax: Web:

43 Appendix 2: Product specifications 43 Table 1. Specifications (taken from manufacturer s product data) Item specification Scanner Overall dimensions (mm) 1531 x 1338 x 729 Gantry dimensions (mm) 1121 x 435 Aperture (diameter) (mm) 320 Aperture height (centre above floor) (mm) 971 Weight (kg) < 340 Power Requirements Mains input - voltage (V AC) frequency (Hz) power (kw) Battery capacity (fully charged) (hours) 2 90 to to (max) X-ray tube and generator Tube voltage (kv) 100, 120 or 140 Tube current (ma) 1 to 7 in increments of 1 Tube cooling (minutes) 2 (max) X-ray tube type Fixed anode Focal spot size (mm) 1 x 1 Beam collimation (mm) kV (mm Al) 6.8 X-ray detection Detection system Solid state, 8 rows Image processing Field of view (mm) 253 Slice thickness options (mm) 1.25, 2, 5 and 10 Reconstruction matrix 512 x 512 Pixel size (mm) 0.49 Data Transfer

44 Appendix 2: Product specifications 44 Wireless (secure transfer) Connectivity Cable (via RJ-45 socket) USB port for external data transfer Image format DICOM 3.0 Workstation: Display - type size (cm/inches) On-board memory (GB) 2 LCD 43/17 Site requirements Operating temperature (ºC) 15 to 35 Operating humidity (%) 20 to 85 (non-condensing). Floor flatness (operation) (mm) <+/-1 in 100 Storage temperature (ºC) -25 to 60

45 Appendix 2: Product specifications 45 Figure 9 (taken from manufacturer s product data) shows the radiation scatter for the scanner, based on 140 kv and 7.5 mas. Plot lines are the isodose measurements in milliroentgens (mr). For SI units, 100 mr can be taken to be approximately 1 mgy. Figure 9. Scatter plot for CereTom scanner P a t i e n t S i d e Further information relating to the CereTom scanner can be accessed at the NeuroLogica Corporation web site

46 Appendix 3: User questionnaire 46