RIVISTA DI NEURORADIOLOGIA

RIVISTA DI NEURORADIOLOGIA ORGANO UFFICIALE DELL ASSOCIAZIONE ITALIANA DI NEURORADIOLOGIA OFFICIAL JOURNAL OF THE TURKISH SOCIETY OF NEURORADIOLOGY Index Introduction 743 T. Scarabino Legislation Governing the Authorization, 745 Installation and Use of 3.0 TMR Imaging Systems A. Maiorana, V. d Alesio, T. Scarabino High Field Strength Magnetic Resonance 748 and Safety. Part I. Installation A. Maiorana, V. d Alesio, M. Tosetti, T. Scarabino High Field Strength Magnetic Resonance 752 and Safety. Part II. Use T. Scarabino, F. Nemore, G.M. Giannatempo, A. Maiorana Semeiological Features of 3.0 T 755 MR Imaging: What Changes at High Magnetic Field T. Scarabino, F. Nemore, G.M. Giannatempo, T. Popolizio, M. Tosetti, F. Esposito, F. Di Salle, U. Salvolini 3.0 T MR Imaging 765 T. Scarabino, F. Nemore, G.M. Giannatempo, T. Popolizio, A. Stranieri, U. Salvolini 3.0 T MR Angiography 777 T. Scarabino, F. Nemore, G.M. Giannatempo, T. Popolizio, A. Stranieri, A. Carriero, U. Salvolini 3.0 T Proton MR Spectroscopy 784 T. Scarabino, F. Nemore, G.M. Giannatempo, A. Bertolino, M. Tosetti, A. Di Costanzo, G. Polonara, U. Salvolini 3.0 T Diffusion MR Imaging 795 T. Scarabino, F. Nemore, F. Esposito, F. Di Salle, S. Pollice, A. Carriero, R. Agati, U. Salvolini 3.0 T Perfusion MR Imaging 807 T. Scarabino, G.M. Giannatempo, S. Pollice, A. Carriero, A. Di Costanzo, G. Tedeschi, G. Polonara, U. Salvolini Functional MRI at High Field Strength 813 F. Di Salle, T. Scarabino, F. Esposito, A. Aragri, O. Santopaolo, A. Elefante, M. Cirillo, S. Cirillo, R. Elefante 3 T MR Multiparametric Assessment 822 of Cerebral Gliomas A. Di Costanzo, T. Scarabino, F. Nemore, G.M. Giannatempo, F. Trojsi, S. Pollice, A. Carriero, G. Tedeschi, U. Salvolini Schizophrenia and 3.0 T fmri 827 V. Latorre, V. Rubino, T. Scarabino A. Bertolino 3 T MR Angiography in Spinal 834 Dural Fistula. A Pictorial Presentation R. Agati, A.F. Marliani, D. Cevolani, C. Carollo, M. Leonardi Pre-Surgical Use of Functional Paradigms 836 in Brain fmri Mapping: Our Initial 3 T Experience D. Cevolani, R. Agati, L. Albini Riccioli, S. Battaglia, H. Hacker, M. Leonardi Potential Impact of Advanced 3 Tesla 849 Diagnostics in the Management of Patients with Brain Tumours M. Leonardi, R. Agati, D. Cevolani, A. Bacci, R. Ricci, L. Albini Riccioli, S. Battaglia, M. Maffei, L. Simonetti, M. Spagnoli, H. Hacker 1 HMRS 3 T In Vivo and In Vitro and 882 Anatomopathological Correlations in Extracerebral Tumours. A Report of Two Cases R. Ricci, A. Bacci, V. Tugnoli, M.R. Tosi, R. Agati, A.F. Marliani, M. Messia, R. Ferracini, M. Leonardi

3 T MR Assessment of Pituitary 890 Microadenomas. A Report of Six Cases R. Agati, M. Maffei, A. Bacci, D. Cevolani, S. Battaglia, M. Leonardi Information & Congresses 896, 897, 898 Instructions to Authors 904 Cover: P. Ghedin, Selfportrait; Bologna 2004

Fotografia realizzata in collaborazione con Edward Hospital & Health Services, Naperville, Illinois. Vittorie di ogni giorno Oggi ci siamo ricordati perché abbiamo scelto questa professione. Da quando la sanità ha iniziato funzionare secondo le regole di ogni altra attività economica, qualche volta ci capita di dimenticare i veri motivi per cui abbiamo scelto la nostra professione. I presupposti che in passato ci guidavano nella gestione di un sistema ospedaliero non sono più attuali. Il nostro desiderio di offrire ai pazienti un assistenza di prim ordine si scontrava sempre più con la realtà finanziaria. E buona parte del cosiddetto stato dell arte della tecnologia sembrava complicare un contesto di lavoro già frenetico. Così abbiamo dato una svolta alla nostra vita. Abbiamo scoperto una tecnologia più avanzata che la semplifica. Abbiamo trovato il modo di raggiungere l eccellenza clinica facendo quadrare i bilanci. Di fare di più e diminuire lo stress. Ora possiamo affidarci a un servizio di assistenza come i nostri pazienti si affidano a noi. È per questo che oggi abbiamo avuto più tempo da dedicare ai nostri pazienti. Perché usiamo un sistema progettato per noi. Semplice questione di logica. Per dare una svolta alle vostre scelte, contattate Philips. www.medical.philips.com

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Rivista di Neuroradiologia 17: 743-744, 2004 www. centauro. it Introduction T. SCARABINO Neuroradiologia, Dipartimento di Scienze Radiologiche, Istituto Scientifico Casa Sollievo della Sofferenza ; San Giovanni Rotondo, Foggia Since the advent of magnetic resonance (MR) imaging, systems with a magnetic field intensity of 1.5 tesla (T) have been deemed the gold standard to cover different clinical applications in all body districts. Ongoing advances in hardware and software have made these MR systems increasingly compact, powerful and versatile, leading to the development of higher magnetic field strength MR systems (3.0 T) for use in clinical practice and for research purposes. As usually occurs with a new technology, MR 3.0 T imaging units will probably follow the same development trends in the years to come. These new systems are currently in routine use mainly in the United States, but despite their high cost they are increasingly being adopted for research in much broader fields than those of conventional MR systems, and also in daily clinical practice for new, more sophisticated applications bringing major practical benefits. Results to date have been encouraging with respect to previous experience with lower field strength MR systems and show that the many advantages of 3.0 T imaging (high signal, high resolution, high sensitivity, shorter imaging times, additional more advanced study procedures and enhanced diagnostic capacity) will become the future standard for morphofunctional study of the brain. When future technological advances have resolved some of the shortcomings of new 3.0 T systems (inhomogenity of the field, artifacts caused by susceptibility and chemical shift, elevated SAR, high costs), the current MR units will gradually be replaced by higher field strength MR imaging. The 3.0 T MR systems of the future will offer morphological investigation with high spatial, temporal and contrast resolution (essential for diagnosis) and also yield physiological, metabolic and functional information enhancing the diagnostic power of routine MR imaging in terms of sensitivity and specificity both in clinical practice and for applied research purposes. A 3.0 T system can quickly build up a database of information useful in different diseases and including structural and functional data. Just one MR investigation will therefore comprise basic structural imaging and also diffusion and perfusion studies, MR spectroscopy, visual fmri or even imaging of other nuclei. However, such systems should not be considered the optimum for myriad clinical applications and all body districts. It is important to be aware of the technical characteristics, image features and applications of each MR system of different field strength so as to use the various systems in the best possible way depending on the investigation required. For this reason, the new MR systems are best confined at present to tertiary care centres or institutions already using other MR systems in routine clinical practice and research. A multidisciplinary task force is essential to exploit the potential of these new systems to 743

Introduction T. Scarabino the full and I take this opportunity to thank the team of doctors and technicians of the Neuroradiology and Health Physics Department at our institution (in particular my neuroradiologist colleagues F. Nemore, G.M. Giannatempo and T. Popolizio, and physicists A. Maiorana and V. d Alesio) but also other neuroimaging experts working elsewhere including neuroradiologists U. Salvolini (University of Ancona), F. Di Salle (University of Naples); psychiatrists M. Nardini, A. Bertolino, G. Blasi, V. La Torre, V. Rubino and F. Sambataro (University of Bari); child neuropsychiatrists V. Leuzzi ( La Sapienza University, Rome), F. Carnevale (University of Bari) and M. Burroni (Fano Hospital); neurologists G. Tedeschi and A. Di Costanzo (University of Naples); physicist M. Tosetti ( Stella Maris Hospital, Pisa) and bioengineer F. Esposito (University of Naples). Special thanks are due to the entire staff of General Electric, in particular P. Ghedin (Advanced Clinical Applications), for their untiring professional support. This special issue of the Rivista di Neuroradiologia devoted to 3.0 T MR systems includes papers on: 1. Legislation in force governing authorization, installation and use. 2. Safety problems related to installation (with reference to static magnetic field, variable magnetic fields, cryogenic gases, acoustic noise and quality control). 3. Safety problems relating to use (with reference to precautions adopted by medical and technical personnel in relation to MR-compatibility and the standard of patient comfort). 4. The semeiological features of 3.0 T images including reference to advantages and drawbacks with respect to lower field strength MR systems. 5. The main clinical applications in neuroradiology. 6. Future trends. Dr T. Scarabino Neuroradiologia Dipartimento di Scienze Radiologiche Istituto Scientifico Casa Sollievo della Sofferenza Viale Cappuccini, 71 71013 San Giovanni Rotondo - FG Tel. +39 0882 410016-410817-8 E-mail: t.scarabino@operapadrepio.it 744

Rivista di Neuroradiologia 17: 745-747, 2004 www. centauro. it Legislation Governing the Authorization, Installation and Use of 3.0 T MR Imaging Systems A. MAIORANA, V. d ALESIO, T. SCARABINO* Fisica Sanitaria, *Neuroradiologia, Dipartimento di Scienze Radiologiche, Istituto Scientifico Casa Sollievo della Sofferenza ; San Giovanni Rotondo, Foggia Key words: 3.0 T MRI, legislation, high field MRI INTRODUCTION With the advent and development of high-field strength magnetic resonance (MR) imaging systems, legislation governing the authorization and use of these systems has undergone major amendments in recent years, especially in the USA where the new imaging units are more widespread. Ongoing advances and the future development of newer more sophisticated MR systems will entail further amendments to legislation in the wake of advances in strong magnetic field strength now known as a moving target. This is borne out by the increasing use in the USA of 3.0 T MR systems instead of the 1.5 T units long deemed the standard for neuroradiological imaging. In contrast, European, in particular Italian, legislation dates back to 1998. As use of the new MR systems increases nationwide, Italian regulations are likely to be brought into line with American legislation in the near future. Legislation in the USA In 1997 the United States Department of Health and Human Services Food and Drug Administration, Center for Devices and Radiological Health (U.S. F.D.A.), the classification of imaging carrying a significant risk and hence subjected to special authorization procedures was confined to MR systems in which the main static magnetic field exceeds 4.0 Tesla with a SAR of more than 4 watts per kilogram (W/kg) to the whole body for 15 minutes, 3 W/kg to the brain for ten minutes, 8 W/kg to each gram of head and torso tissue for 15 minutes, or 15 W/kg to each gram of tissue in the extremities for 15 minutes 1. A further condition is that the field gradient is sufficient to produce discomfort or pain and that the acoustic noise reaches a sound pressure level of 99 db or a peak value exceeding 140 db. According to this classification, a 3.0 T MR imaging system respecting the SAR, gradient and noise limits is broadly similar to a 1.5 T unit and does not entail significant risks and hence further restrictions with respect to conventional MR devices. In July 2003, the F.D.A. laid down new upper limits of static magnetic field for the sale of MR systems without special limits on MR diagnostic systems, replacing the 1997 guidelines. The new limits are 8.0 T for adults and 4.0 T for newborns under one month of age 2. Legislation in Italy In Italy the technical reference law is the CEI EN 60601-2-33/A11 of 1998 3, superseded in 2002 by IEC 60601 1-2-33 Ed. 2.0 4. Current national legislation, law 542 dated 8th August 1994, bans systems with a field strength equal to or in excess of 2.0 T from clinical practice and limits their use to documented research projects. Attachments to ministerial decrees dated 2nd August 1991 and 3rd August 1993, currently in force, list the limitations on SAR and gradients (tables I, II, III, IV) and basically refer to the indications of the Italian Electrotechnical Committee (CEI EN 60601-2-33). Article 6 of law 542 classified systems with a 745

Legislation Governing the Authorization, Installation and Use of 3.0 T MR Imaging Systems A. Maiorana Table I Limits of SAR to the whole body 1st level (normal working) Table II Limits of SAR to the whole body 2nd level (controlled working) Duration of exposure SAR Duration of exposure SAR t < 15 min < 2 W/kg t < 15 min < 4 W/kg 15 < t < 30 min < [30/t(min)] W/kg 15 < t < 30 min < [60/t(min)] W/kg t > 30 min < 1 W/kg t > 30 min < 2 W/kg Table III Limits of SAR per body district Duration of exposure SAR HEAD TORSO LIMBS t< 15 min < 4 W/kg < 8 W/kg < 12 W/kg 15 < t < 30 min < [60/t(min)] W/kg < [120/t(min)] W/kg < [180/t(min)] W/kg t > 30 min < 2 W/kg < 4 W/kg < 6 W/kg Table IV Value and duration of gradients Duration of variations Peak value t > 120 µs < 20 T/s 12 µs < t < 120 µs < [2400/t(µs)] T/s t < 12 µs < 200 T/s Table V Limits for static magnetic field Type of exposure Weighted average over time to whole body Limit to whole body Extremities Peak value 200 mt 2 T 5 T static magnetic field exceeding 2 T as group B, i.e. systems subject to ministerial authorization. The installation and use of these systems is confined to large tertiary level research centres (art. 4 par. 2). These MR systems must be part of a scientific or clinical research project requiring the use of ultrahigh strength magnetic fields. The same article also states that systems with a field strength exceeding 4.0 T can only be authorized for specific, documented needs of scientific or clinical research confined to the limbs. Authorization for the use of group B systems issued by the Italian Ministry of health is currently dependent on the prior technical evaluation of the Institute for Accident Prevention and Safety at Work (ISPESL), the Higher Institute of Health (ISS) and the Higher Council of Health (CSS). In relation to the protection of technical personnel from adverse effects, the International Commission for Non Ionizing Radiation Protection (ICNIRP) fixed the limits for static magnetic fields in 1994 5 (table V). It is interesting to compare these limits with those currently in force in Italy as specified in the attachments to the ministerial decree dated 2 nd August 1991 (table VI). Whereas the limits largely overlap (apart from those for limbs and extremities), the average values and time intervals on which such limits must be applied vary widely. Table VI Limits for static magnetic field (law 2 nd August 1991) Type of exposure To whole body (1 hour a day) To whole body (15 minutes a day) To limbs (1 hour a day) To limbs (1 minute a day) Peak value 200 mt 2 T 2 T 4 T 746

www. centauro. it Rivista di Neuroradiologia 17: 745-747, 2004 References 1 Food and Drug Administration Center for Devices and Radiological Health. Guidance for Magnetic Resonance Diagnostic Devices. Criteria for Significant Risk Investigation 1997. 2 Food and Drug Administration Center for Devices and Radiological Health, Criteria for Significant Risk Investigations of Magnetic Resonance Diagnostic Devices 2003. 3 Comitato Elettrotecnico Italiano, Apparecchi Elettromedicali Parte 2: Prescrizioni particolari d sicurezza relative agli apparecchi a risonanza magnetica per diagnostica medica. CEI EN 60601-2-33/A11 1998. 4 International Electrotechnical Commission. Medical electrical equipment. Part 2-33: Particular requirements for the safety of magnetic resonance equipment for medical diagnosis. IEC 60601 1-2-33 Ed. 2.0 2002. 5 International Commission for non Ionizing Radiation Protection, Guidelines on limits of exposure to static magnetic fields Health Physics Society 66: 100-106 1994. Dr T. Scarabino Neuroradiologia Dipartimento di Scienze Radiologiche Istituto Scientifico Casa Sollievo della Sofferenza Viale Cappuccini, 71 71013 San Giovanni Rotondo - FG Tel. +39 0882 410016 747

Rivista di Neuroradiologia 17: 748-751, 2004 www. centauro. it High Field Strength Magnetic Resonance and Safety Part I. Installation A. MAIORANA, V. d ALESIO, M. TOSETTI*, T. SCARABINO** Fisica Sanitaria, Dipartimento di Scienze Radiologiche, Istituto Scientifico Casa Sollievo della Sofferenza ; San Giovanni Rotondo, Foggia * Fisica, IRCCS Stella Maris ; Pisa ** Neuroradiologia, Dipartimento di Scienze Radiologiche, Istituto Scientifico Casa Sollievo della Sofferenza ; San Giovanni Rotondo, Foggia Key words: 3.0 T MRI, installation, safety, high field MRI INTRODUCTION Despite its high field strength, weight (13.000 kg) and helium load (3.000 l), a 3.0 T magnetic resonance system does not pose special installation problems. Installation of these MR devices is straightforward and no special site preparation is required with respect to lower field strength systems. In addition, the systems are only slightly larger than the 1.5 T imaging units currently in use. It is essential to position the system on a solid base able to absorb gradient vibrations: the device is usually placed on a floor made of concrete, sand and soundproofing material with a total thickness of 40 cm. The possible risks directly correlated to MR diagnostics are mainly linked to three types of electromagnetic field used simultaneously during imaging: the static field, the magnetic field gradients and the RF field. Two other possible sources of indirect risk derive from the intrinsic features of fast superconducting magnets in operation: cryogenic gases and acoustic noise generated by coil vibrations during the MR sequences 1,2,3. Static Field MR investigation is not a high risk diagnostic procedure. Unofficial data on the market as a whole show that around 150,000,000 MR examinations were performed from 1980 to 1999 with an annual estimated rate of 20,000,000 procedures a year equal to around 50,000 a day, and the accidents recorded to date have been rare. Of these, the few severe injuries documented were caused directly by the static magnetic field and consisted of magnetomechanical damage to the patient implants or devices introduced into the scan room by mistake 4,5. Thorough history-taking of patients and installation of a metal detector should rule out the presence of this type of objects as they are extremely dangerous 6,7,8,9,10. Another effect responsible for potential risk, attributed in the past to an abnormal repolarization of the myocardium, is in fact caused by blood flow in the large vessels within a strong magnetic field. This effect has been studied in individuals in fields with a magnetic strength exceeding 8 T showing that the induced potentials are below the threshold of nerve or muscle stimulation. The migration of loads of the opposite sign on vessel walls caused by the magnetic field also produces a current moving perpendicular to the speed of flow in the vessel and hence an additional force in an opposite direction to blood flow due to the magnetic field. In practice, it has been shown that this effect is negligible even in the presence of magnetic fields exceeding 10 T 11. On activating the static magnetic field of the MR system in our institution, the magnetic field was measured using a Hall isotrope detector. The measurements taken at different points in the scan room showed that because of active acoustic screening the dispersed field is limited and in any case much better than that of a 1.5 T MR device of the same type also in use at out institution but lacking active screening. With reference to the magnet s core, the 748

A. Maiorana High Field Strength Magnetic Resonance and Safety. Part I. Installation 0.5 mt isomagnet is described by an ellipsoid of semiaxes 4.5 3.0 m and is constrained within the scan room whereas the 200 mt isomagnet is described by an ellipsoid of semiaxes 2.0 1.0. In practice, this is constrained within the magnet s overall dimensions, so that staff can be exposed only partially above the legal limit for the whole body during imaging operations in the MR suite. Hence, limits have not been fixed on the time spent in the scan room by technical personnel, also in view of their limited workload. Thanks to a screen of ferromagnetic slabs, the control panel is only crossed by the 1 mt isomagnet. Variable Fields During MR investigation, patients are also subjected to gradient activation and RF energy impulses sent to generate the signal and decode it. For example, turning the magnetic field gradients on and off can trigger electric currents able to alter the cell membrane potential and, if strong enough, stimulate the peripheral nervous system and cardiac muscle. The threshold of stimulation of peripheral nerves can be painful but is reversible and considered a safety factor with respect to cardiac stimulation which may be hazardous: when the ramp lasts less than 1 ms the first threshold is always below the second 12. In any case, gradient amplitude and duration were carefully set during installation to ensure compliance with the limits fixed by technical guidelines. RF energy impulses are always accompanied by an RF electric field which in turn generates RF electric currents. Due to the Joule effect, these currents can lead to temperature changes potentially harmful to tissues, or burns caused by conductor loops casually triggered by the patient s extremities or belonging to other devices inadvertently left on the patient s skin 13,14,15,16. Technical personnel have been trained to recognize this type of risk which must be carefully addressed during patient preparation. An increase in field strength affects the operative frequency of the MR system and its RF components. At 3.0 T the resonance frequency is 128 Mhz for protons, i.e. double the frequency at 1.5 T, and the spatial distribution of the RF field produced by the coils increases in complexity as the frequency rises. At very high frequencies the wavelength of the field is comparable to the anatomical dimensions under examination and this may lead to the formation of stationary waves which degrade the homogeneity of the RF field and give rise to artefacts which increase as the coil size becomes larger and hence must be adjusted to 3.0 T. In addition, tissue conductivity increases with the rise in frequency thereby raising the density of the induced current: this signifies greater power density deposited in the tissue. High conductivity also means a reduced capacity to penetrate the RF signal and hence the demand for more power to obtain the same result in terms of signal 17. To prevent accidental thermal injury to tissues, the energy deposited per mass unit per time unit, i.e. the SAR (Specific Absorption Rate), should be carefully monitored. To ensure compliance with legislation in force 1, the MR system installed has software for preventive assessment of SAR based on the patient s weight. The scan room is electromagnetically shielded by a Faraday cage supplying an attenuation level of 80 db on a frequency interval from 40 MHz to 130 MHz. The swing doors into the suite are screened and fitted with finger-joint contact and floor battens. The observation window is protected by a thin metal mesh screen. The level of attenuation guaranteed by the a- coustic screening was measured experimentally just after installation close to the observation window, entrance and filter panel using biconic antennae and a spectrum analyzer. Measurements will be repeated every two years. Cryogenic Gases In case of quench, i.e. a sudden increase in the temperature of the magnet coils with violent uncontrolled evaporation of the helium they are immersed in, the oxygen concentration in the imaging suite can drop to values likely to cause asphyxia. The size of the ventilation and helium evacuation system is proportional to the type of magnet and size of the premises. As 700 l of gas are produced for each litre of liquid helium, for a 3.0 T superconducting magnet the 3 m 3 of helium contained in the cryostat in case of quench must leave the imaging suite as quickly as possible. The system guarantees at least 20 changes of air/hour under emergency conditions and the cross section area of the exhaust pipe is 749

High Field Strength Magnetic Resonance and Safety. Part I. Installation A. Maiorana proportional to the length of the pipe and the number of elbows. An oxygen level sensor is positioned high up in the room close to the most likely point of leakage. The oxygen level indicator is located outside the suite near the control panel. The delivery and pull-out points have been designed to avoid a short-circuit. The inlet of clean air from outside is proportional to the suction rate. To avoid transporting cryogenic gas containers inside the hospital, an insulated pipe allows the helium to be refilled directly from outside the building. Refilling is carried out only twice a year on average (1.200 l) due to the low consumption of helium. Acoustic Noise The magnetic field gradients are the main source of acoustic noise in an MR device. Noise is caused by the rapid changes in current inside the coils which are subject to Lorentz force in the presence of a strong magnetic field. Gradient changes in amplitude and ramping caused by different types of sequences can affect the noise level. Noise increases when the s- lice thickness, field of view, TR and TE are reduced 18. Ear plugs are available in the scan room to protect patients hearing during particularly noisy sequences. Quality Control Quality control is essential for effective diagnosis. This applies to MR systems in general, e- specially the new MR devices whose performance is largely the result of a balance of optimal conditions established during installation. In addition to checking the electrical safety of the new system, the manufacturer also carried out a series of tests designed to ascertain the minimum specifications of diagnostic quality for the device including congruent slice thickness, uniformity and signal/noise ratio. Some of parameters are repeated during periodic maintenance testing. In addition to the manufacturer s checks, a quality control protocol has been devised based on the quality control system proposed by the COMAC BME group to monitor key parameters for the purposes of ongoing diagnostic quality. Measurements were carried out on the Eurospin set of test objects produced by Diagnostic Sonar Ltd, comprising the signal/noise ratio, uniformity, slice profile and width and the presence of artefacts 19,20. References 1 Comitato Elettrotecnico Italiano, Apparecchi Elettromedicali. Parte 2: Prescrizioni particolari di sicurezza relative agli apparecchi a risonanza magnetica per diagnostica medica. CEI EN 60601-2-33, 2004-02. 2 The International Commission on Non-Ionizing Radiation Protection [ICNIRP], Medical Magnetic Resonance (MR) Procedures: Protection of Patients, Health Physics 87: 2004. 3 Food and Drug Administration Center for Devices and Radiological Health, Criteria for Significant Risk Investigations of Magnetic Resonance Diagnostic Devices 2003. 4 Kangarlu A, Robitaille P-ML: Biological Effects and Health Implications in Magnetic Resonance Imaging. Concepts in Magnetic Resonance 12: 5, 2000. 5 Schenck JF: Safety of Strong, Static Magnetic Fields. Journal of Magnetic Resonance Imaging 12: 2000. 6 Shellock FG: Magnetic Resonance Safety Update 2002: Implants and Devices. Journal of Magnetic Resonance Imaging 16: 2002. 7 Shellock FG: Biomedical Implants and Devices: Assessment of Magnetic Field Interactions with a 3.0 Tesla MR System. Journal of Magnetic Resonance Imaging 16: 2002. 8 Duru F et Al: Pacing in magnetic resonance imaging environment: clinical and technical considerations on compatibility. European Heart Journal 22: 2001. 9 Shellock F et Al: Cardiac Pacemakers, ICDs, and Loop Recorder: Evaluation of Translational Attraction Using Conventional (Long Bore) and Short Bore 1.5 and 3.0 Tesla MR Systems. Journal of Cardiovascular Magnetic Resonance 5: 2, 2003. 10 Kangarlu a, Shellock FG: Aneurysm Clips: Evaluation of Magnetic Field Interactions with an 8.0 T MR System. Journal of Magnetic Resonance Imaging12: 2000. 11 Kangarlu A et Al. Cognitive, Cardiac, and Physiological Safety Studies in Ultra High Field Magnetic Resonance Imaging. Magnetic Resonance Imaging 17: 10, 1999. 12 Schaefer D.J. et al. Review of Patient Safety in Time Varying Gradient Field. Journal of Magnetic Resonance Imaging, 12, 2000. 13 Shellock FG, Crues JV: Corneal temperature changes induced by high-field-strength MR imaging with a head coil. Radiology 167: 1988. 750

www. centauro. it Rivista di Neuroradiologia 17: 748-751, 2004 14 Knopp MV, Essig M, Debus J et Al: Unusual burns of the lower extremities caused by a closed conducting loop in a patient at MR imaging. Radiolog: 200, 1996. 15 Shellock FG, Slimp GL: Severe burn of the finger caused by using a pulse oxymeter during MR imaging (letter). Am J Radiol 5: 1989. 16 Mary F. Dempsey, Barrie Condon Thermal Injuries Associated with MRI. Clinical Radiology, 56, 2000. 17 Frayne R et Al: Magnetic Resonance Imaging at 3.0 Tesla: Challenges and Advantages in Clinical Neurological Imaging. Investigative Radiology 38: 7, 2003. 18 McJury M, Shellock FG: Auditory Noise Associated with MR Procedures: A Review. Journal of Magnetic Resonance Imaging 12, 2000. 19 Podo F: Controlli di qualità nella risonanza magnetica ad uso clinico. Ann. Ist. Super. Sanità 30: 1994. 20 Lerski RA: Trial of modifications to Eurospin MRI test objects, Magnetic Resonance Imaging 11: 1993. Dr T. Scarabino Neuroradiologia Dipartimento di Scienze Radiologiche Istituto Scientifico Casa Sollievo della Sofferenza Viale Cappuccini, 71 71013 San Giovanni Rotondo - FG Tel. +39 0882 410016 751

Rivista di Neuroradiologia 17: 752-754, 2004 www. centauro. it High Field Strength Magnetic Resonance and Safety. Part II. Use T. SCARABINO, F. NEMORE, G.M. GIANNATEMPO, A. MAIORANA * Neuroradiologia, *Fisica Sanitaria, Dipartimento di Scienze Radiologiche, Istituto Scientifico Casa Sollievo della Sofferenza ; San Giovanni Rotondo, Foggia Key words: 3.0 T MRI, high field MRI, safety, installation INTRODUCTION Despite the high field strength and high gradient power of the new 3.0 T MR systems, no special safety problems are encountered in using these devices in clinical practice. The new systems are not significantly different from lower field strength MR imaging units in terms of patient comfort 1-3. However, the safety and MR compatibility of different biomedical devices has been reviewed 1-2-3. MR Safety and Compatibility An MR system is considered safe if no significant deflexion or torsion movement is encountered and no current-induced heating generated when the device is placed in a static magnetic field. Instead, the term MR-compatibility is used when a given device fails to create artefacts distorting the images. This explains how an imaging system can be deemed safe but not MR-compatible 4-5. Information on the safety and MR-compatibility of different 3.0 T and other ultra high field strength biomedical systems is limited and not fully reliable 6-7. In theory, the increase in field strength from 1.5 T to 3.0 T should double the deflexion or torsion movements induced by a given device. In addition, doubling the frequency of RF energy should have a negative effect on its thermal properties 8,9,10. MR imaging with 3.0 T systems is currently prohibited in patients with biomedical implants deemed safe and compatible at magnetic fields of 1.5 T as the devices may not be safe and compatible at higher field strength. Compliance with this restriction is necessary to avoid risks in the different clinical applications of MR imaging, but should be reviewed as new safety information becomes available. In a recent study, Shellock assessed the interactions of the most commonly used biomedical implants and devices (more than 100) with a 3.0 T MR system. Only four devices (Surgiclip, EndoFit endoluminal stent graft C and E, PORTH-A-Cath needle) proved potentially unsafe according to deflexion angle (more than 45 ) and torsion measurements varying in relation to the strength of the static magnetic field, gradient power, size (especially length), weight, shape and susceptibility of the object examined 11. Plainly, the general contraindications to MR scanning remain, e.g. ferromagnetic objects accidentally introduced into the scan room and turning into bullets, and devices activated electrically, magnetically or mechanically (such as pacemakers, cardiac catheters, implanted insulin pumps, etc.) as the system s magnetic field can impair their function. A number of prosthetic implants also remain at risk (intracranial vascular or surgical clips, cochlear implants or metal devices inserted close to vital anatomical structures) as they can move or be distorted by the magnetic field and be the site of induced electric currents or thermal injury 12-13. Patients injured by ferromagnetic splinters or with tattoos or permanent eye make-up (performed as a cosmetic-surgical procedure) are also unsuitable for MR imaging. Basically, the physician in charge must as- 752