Mammography. For 35+ years, screenfilm has been the gold standard for breast cancer detection

Transcription

1 Digital Mammography

2 Upright Stereo

3 Mammography For 35+ years, screenfilm has been the gold standard for breast cancer detection

4 IN THE BEGINNING Mammography technology has come a long way since the first machine specifically designed for producing mammograms was introduced in The first dedicated mammography system was essentially a tripod supporting a special X-ray camera

5 EARLY POSITIONING AND COMPRESSION Cone MLO view done in reclining position Compression Pad CC in standing position

6 WHAT ABOUT THIS? Usually done when a patient had a very large palpable mass Limited productivity; 4-5 patients imaged per day Limited to CC and MLO views; no ability to do extra diagnostic views

7 DEDICATED MAMMOGRAPHY SYSTEMS The first systems developed specifically for mammograms were released in Rotating C-arm allowed both CC and MLO views to be taken with patient in standing or sitting position, for better efficiency Additional diagnostic views enabled Image quality was limited due to limitations in film capabilities

8 THE NEXT ADVANCE XEROMAMMOGRAPHY First introduced in 1971 Provided better image quality than systems using industrial film packs Allowed excellent visualization of chest wall Xeroradiographs (blue and white prints), as shown above, gave adequate image quality; however, the radiation dose to the breast was much higher than current imaging methods.

9 AND IT APPEALED TO THE PUBLIC Advertisement in Life and Glamour magazine promoting the new technology, xeromammography Model demonstrates the latest in mammography technology and fashion. Check out the hosiery

10 DMIST Digital Mammography Imaging Screening Trial whose objective was to determine the validity of digital mammography Results showed digital mammography is more beneficial for women: under age 50 (no matter what level of breast tissue density they had) of any age with heterogeneously (very dense) or extremely dense breasts pre- or perimenopausal women of any age (defined as women who had a last menstrual period within 12 months of their mammograms). American College of Radiology imagining Network

11 Improved Image Quality?

12 Indications Women under the age of 50 Women with heterogeneously dense or extremely dense breast Women who are premenopausal or perimenopausal American College of Radiology imagining Network

13 Advantages of Digital Imaging Improved image quality Wider dynamic range Reduced exam times Image manipulation tools Removes film variability Eliminates processing Minimizes retakes

14 Not All Digital Is Created Equal! Direct Capture vs. Indirect Capture Screen-film is an example of indirect

15 The Direct Capture Difference Direct capture converts x-rays to electronic signals In indirect conversion detectors, x-rays are first converted to visible light, which is then converted to electronic signals. Light diffuses across a large distance, resulting in reduced image sharpness and loss of tissue contrast.

16 Image Quality Measurements Digital mammography has two measurements for image quality Modulation transfer function (MTF) Measure of image sharpness Detector quantum efficiency (DQE) Measure of dose efficiency (how well the imaging system uses the x-ray photons that are absorbed)

17 Image Sharpness Modulation Transfer Function (MTF) is a measure of signal transfer over a range of spatial frequencies Higher MTF = Sharper images Higher MTF = Superior contrast resolution

18 Dose Efficiency Detective Quantum Efficiency (DQE) is a measurement of how well the x-rays are utilized Higher DQE = Superior image quality Higher DQE = Reduced patient dose

19 What s a PIXEL??? Picture a cup that collects electronic signals.

20 Pixel Size Pixel size of a detection system needs to be ~ 50% of the smallest detectable signal of an object being imaged Microcalcifications begin to emit signals visible to the human eye at 150μm Acquiring at 70-75μm enables detection and characterization of smallest microcalcifications Image acquired with indirect detector Image acquired with 70μm direct detector

21 Dose Creep Proper exposure for FFDM is adequate SNR What is adequate SNR? Technologist has no visual indication of over exposure. Using a higher technique can be a safer decision Dose Creep is allowing exposure to increase with no clinical benefits

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27 Tissue seen out to the skin line Wider Dynamic Range

28 Dose Comparison- 4 views Screen-film with MO tube - 8 mgy Direct Digital with MO tube- 6.4 mgy Direct Digital with Tungsten tube- 4.8 mgy

29 Next step in the evolution of mammography Limitation of screen-film mammography is image cannot be altered Digital image is acquired as an electronic signal which is stored in a computer and displayed as film or on a monitor

30 Digital Exposures AEC the pixels become your photocells A preliminary mini exposure assesses tissue density and thickness, then applies the needed exposure The algorithm controls your contrast vs. kvp Adequate and appropriate kvp should still be applied, however in digital we can now use higher kv than film, so the dose has come down Dose is still a factor of mas

31 MO vs Tungsten Molybdenum is ideal for screen-film kv ranges and gray scales Tungsten is better for digital imaging as the kv is more for penetration as the algorithm drives contrast now Tungsten offers lower dose with longer scale contrast

32 Benefits - Digital Mammography? Overcomes the limitations of screen-film Provides diagnostic value for many patients Platform of future technologies i.e. breast tomosynthesis Uses traditional generators and tubes The x-ray beam is converted into digital information which can be stored electronically, transmitted, displayed, analyzed and manipulated

33 Review of Prior Images before procedures

34 Dense tissue can be seen more clearly Better cancer detection in dense tissue

35 Side by Side

36 Technical Side The mammography image appears in the exam room on a monitor, not by darkroom processing, for quick review by the technologist This facilitates a quicker overall exam time for the patient

37 Technologist Workstation Review all images Ability to magnify Ability to adjust contrast and density Manipulate image Give annotations

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39 Adjustability Physician can manipulate images on a computer workstation to change the look of the mammogram to better see areas of interest Zoom into an area of interest Move or pan around to different areas on the mammogram The visibility of subtle mass or clusters of calcifications present in the image can be increased by adjusted the contrast.

40 Radiologist Station

41 More data captured

42 Dynamic Range Control enhances skin edge

43 PEM Pattern Enhancement Enhances Microcalcification detection with PEM

44 MFP Multi-frequency Processing Improves Dense Breast Visualization

45 Image Processing

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48 Greater Access The mammogram can be read where ever the radiologist is located The radiologist does not need to be at the site where the exam was performed Also allows for physicians to consult with their peers by remote viewing

49 Consistency in Storage Misplaced or lost images will not occur Images are stored electronically with unlimited access to the originals The original version can be recalled from electronic storage for review on a workstation or printed for a film copy

50 Technologist Benefits Acquire new, compare and display priors in room Instant bi-directional communication with imaging staff Short-term storage for call backs Built-in QC & service tools Flex Monitors for increased flexibility

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52 User-friendly Interface Workflow Preview image is available for QC in 8 14 seconds

53 Full Array of Technologist Tools Quick Zoom/Pan Full Zoom/Pan Region of Interest Crosshairs Magnification Measurement Window/Level

54 Radiologist Benefits Image Manipulation Zoom, annotate, measure and magnification tools Adjust contrast and brightness for better visualization of fine details Interpret digital images and compare to scanned in prior studies Customized how to view

55 R2 CAD for Mammography Computer-Aided Detection

56 Calcification Marking The system WILL mark: Clusters with three or more elements within 3mm Each element is at or within 3mm = < 3mm square

57 Calcifications What it does not mark Small cluster with less than 2 elements Clusters where each element is separated by more than 3mm Lead skin markers or clips Will occasionally mark Calcified arteries Cluster or rim benign calcifications Crossing linear tissue

58 What Calcifications are Marked? R2 occasionally marks: Calcified arteries Cluster or rim benign calcifications Crossing linear tissues

59 What Masses are Marked? R2 should mark: Regions suggestive of masses/architectural distortions Dense regions Regions with radiating lines

60 Mass Marking For Masses the system will mark: Dense regions and regions with radiating lines The algorithm will weigh the degree of spiculation and degree of density Look for right/left asymmetry, as well as similarity between views

61 Mass/ Architectural Distortion What it does not usually mark: Masses greater than 2.5 cm in diameter Will occasionally mark: Ducts and tissue radiating from the nipple Inadvertent crossing of parenchymal tissue Well circumscribed masses Vague opacities, skin thickening or nipple retraction

62 Multiple Finding Correlation R2 uses a new shape to indicate a Malc mark: Indicates a region containing mass and calcifications Highly suggestive of malignancy Tends to be very specific Should be evaluated VERY carefully!

63 Anatomical Correlation R2 uses three types of anatomical correlation to improve the algorithm performance Orthogonal view similarity Contra-lateral breast asymmetry Multiple finding correlation (malc mark)

64 R2 CAD Marks Mass marker Calcification marker Malc marker

65 Calc with low-prominence features Mass with high-prominence features Calc with neither high nor low prominence features

66 PeerView Digital Calcification Mass Malc

67 LesionMetrics R2 makes additional information available for each CAD mark May help the doctor understand what caused R2 to mark the region

68 Quantra V1.0 Future Software Option Not FDA Approved

69 Patient Comfort Slim tubehead and recessed face shield facilitates positioning MammoPad FAST Paddle enhances patient comfort and prevents over-compression at the chest wall Softness reduces discomfort from compression Warms the compression surfaces for skin comfort Reduces discomfort by 50% in 3 out of 4 women Markle study. Comfort and compression. SBI 2001, The Breast Journal 2004.

70 Lower Patient Dose Tungsten x-ray tube with (rhodium (Rh) and silver (Ag) filtration) Silver is ideal filtration for penetrating large, dense breasts Same image quality as molybdenum x- ray tube, demonstrated in multiple clinical studies Smoother grayscale in images percent less dose Tungsten dose: 1.2 mgy Moly dose: 1.6 mgy

71 Proprietary HTC Grid High Transmission Cellular Grid Integrated into the digital detector Cross-hatch design reduces scatter in X & Y direction Allows 70-80% transmission of primary beam

72 QC of Digital Mammography

73 Image Quality In Digital Mammography and Quality Control Tests The quality of an image is determined by several factors. The most important are: Contrast: the ability to distinguish 2 objects that have different attenuation properties. Resolution: the ability of an imaging system to accurately reproduce all the fine details of the anatomy. Noise: An undesirable and unavoidable interference signal that is not part of the object being imaged.

74 Image Quality and the Tests Operators follow manufacturer s quality control tests. ACR is working on a QA/QC manual for digital mammography. FDA/MQSA approves each Quality Control manual. Manufacture s QC manuals need to be approved if there have been changes made to their QC tests.

75 Quality Control: Image QC and Equipment QC Measured through: Modulation Transfer Function (MTF) Detective Quantum Efficiency (DQE) MTF and DQE are more widely recognized as true measurements. Line Pair Phantom = not so much.

76 With a new twist! Laser Printer Quality Control Softcopy Workstation Quality Control Artifact Evaluation: for the Laser Printer and Detector. Signal to Noise/Contrast to Noise Detector Flat Field Calibration

77 As with film/screen: In a facility where more than one technologist does mammography, one technologist should be assigned the responsibilities of quality control. Other qualified individuals may perform specific QC tests, but they must be reviewed and evaluated by the designated QC technologist. QC software programs

78 SoftCopy Workstation QC- Weekly Assures consistency of brightness, contrast and image presentation on SoftCopy Workstation (this is guided by the manufacturer s recommendations) Weekly Tests: Display White Measurement Display Black Measurement Monthly: Quality Level Measurement Quarterly: Uniformity Measurement

79 Laser Printer QC: Weekly or Daily (based on manufacturer s recommendations) Assures consistency of printer performance Tests for gray scale visibility, uniformity and resolution characteristics. Print SMPTE (Society of Motion Picture and Television Engineers) Pattern Using densitometer, find density of: MD(40%) DD (40% - 10%) LD (90%) Plot these numbers on QC chart

80 Sample SMPTE Pattern

81 Artifact Evaluation- Weekly Assures the image is free of undesirable artifacts Image the 4 cm acrylic block (be sure it s clean) No compression paddle should be installed Manual exposure- MoRh or Rh/Ag Filter with various kvp and mas exposures Window /level to appropriate level Bring up Mag Box, and roam the image, looking for any artifacts Chart results

82 Artifact Evaluation, continued If artifacts are visible: Rotate acrylic block and repeat the test If the artifacts move with the block, the artifact is present in the acrylic, and does not present a problem with the system If the artifact persists: Ask a medical physicist to perform his/her artifact analysis test Artifacts must be eliminated prior to performing clinical patient exams

83 Signal to Noise/Contrast to Noise Measurements- Weekly Assures consistency of Digital Image Receptor Image ACR Phantom (with acrylic disk in place) Center phantom at chest wall Compression paddle just touching Auto Time exposure

84 SNR/CNR, continued Draw an ROI inside the acrylic disk record Mean Value Click on ROI Tool Drag the same ROI towards the chest wall, next to the disk, and record the Mean, std, and SNR First ROI Second ROI C H E S T W A L L

85 SNR/CNR, continued Logging the results: Plot the SNR value from beside the disk on the QC Chart To determine the CNR to plot on the chart: Subtract the Mean Value of the ROI BESIDE the disk from the Mean Value of the ROI OVER the disk (this is the Contrast) Divide the Contrast by the std from the ROI Beside the disk (this is the CNR) Plot the CNR on the QC Chart Some manufacturers have auto calculations.

86 SNR/CNR, continued Logging the results: Plot the SNR value from beside the disk on the QC Chart To determine the CNR to plot on the chart: Subtract the Mean Value of the ROI BESIDE the disk from the Mean Value of the ROI OVER the disk (this is the Contrast) Divide the Contrast by the std from the ROI Beside the disk (this is the CNR) Plot the CNR on the QC Chart Some manufacturers have auto calculations.

87 Phantom Image - Weekly The Phantom Image may be printed or scored on the softcopy workstation. Chart results. If printing the phantom: The same density rules apply to this printed Phantom as your normal film/screen Phantom

88 Detector Flat-Field Calibration Weekly To assure detector is calibrated properly Creates new, clean background for digital images. Follow on screen instructions Be SURE there is nothing but the acrylic on the detector during this procedure! Any additional object would get burned into the detector

89 Flat-Field Calibration, continued The system is adjusting the pixels to behave in the same manner Images are not being evaluated during this procedure

90 Additional QC Information ACR website for accreditation in digital mammography: MQSA links available QC charts for the different vendors tests and requirements For now, follow manufacturer s recommendations.

91 Connectivity DICOM Digital Imaging Communication of Medicine Standard used for transferring images and data among PACS devices PACS Picture Archiving Communication System Common storage/sending environment for images Communication between the HIS/RIS & Selenia Modality Work list, pre-fetching and routing prior studies

92 Connectivity CAD Computer Aided Diagnosis HL-7 How hospital systems communicate Admissions, discharges Lab, x-ray orders Scheduling Mainly patient data

93 Some DICOM Connectivity Options DICOM Receive DICOM Query / Retrieve DICOM Store DICOM Print Allows display of other DICOM images Ultrasound, MRI, CT, CR

94 Putting It All Together Workflow Manager DVD Archive Softcopy Workstation Approved DICOM Compatible Printer

95 Transition to Digital Your new best friend in Mammography is no longer the Processor Service Engineer. IT is everything! Complete dependence on IT/PACS for transfer and delivery of all images, scanned documents, patient reports, orders, etc. Mammography

96 The Future of Tomosynthesis

97 Tomosynthesis* 3-D Visualization of Breast Tissue Multiple views reconstructed into 3D image Helps solve tissue overlap problems Lower recall rates - Improved detection Normal Mammogram Tomosynthesis Slices * Works-in-progress, not approved for sale in the USA.

98 Why Tomosynthesis? Elimination of overlapping structures and shadows Clearer lesion margins Potential for reduced call-backs

99 Conventional 2-D Imaging Incident X-rays Objects being imaged Images superimposed on image 2-D image

100 Tomosynthesis Acquisition Image from multiple angles Incident X-rays Objects being imaged 2-D raw data images Exposure #1 Exposure #6 Exposure #11

101 Tomosynthesis Reconstruction Appropriate shifting and adding of raw data reinforces objects at specific height Height 1 Height 2

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