Prostate MRI: Not So Difficult
Neil M. Rofsky, MD, FACR, FSCBTMR, FISMRM
Dallas, TX
What is the biggest barrier to your practice incorporating prostate MRI?
• 1) I don’t know how to read the cases • 2) I don’t know how to report the cases • 3) The endorectal coil • 4) Limitations to data processing (DCE, DWI)
How many prostate MRI exams does your practice perform?
• 1) Zero • 2) ≤ 2/week • 3) 3-5/week • 4) 6-10/week • 5) > 10/week
Designate a Champion • Know your subject – Imaging Techniques – Clinical – Consider 1 wk training at program w/high volume
• Know the concerns of your referring MDs – Urology – Radiation Oncology – Medical Oncology
The MRI Tool Kit • Standard imaging – Axial
• T1W • T2W
– Coronal • T2W
• Dynamic contrast enhanced imaging – Axial
• Diffusion – Axial
• Spectroscopy
Plan the Exam: 45 min slot – start with a 1 hr slot
• Set-up (10 min) – ERC insertion – Glucagon injection – Positioning – Plan scan (inc sag T2)
• Standard imaging (15 min) – T1 weighted (4 minutes) – T2 weighted (11 minutes)
• Axial , Coronal • Diffusion (5 min)
– b values 0, 800-1000; • DCE imaging (10 min)
– T1 GRE – Facilitated with post-processing
Focus On Key Issues
• PSA / bx mismatch for staging – High PSA, low Gleason, low volume – Low PSA, high Gleason, any volume
• Rising PSA, repeat negative bx – Detect a focus for biopsy
Endorectal Coil MRI • Advantages – Higher spatial resolution for equivalent time
• Staging advantage – Faster imaging, all other parameters constant
• Disadvantages – Can be uncomfortable– Requires experience for optimal placement – Best with prep (enema) & glucagon – Patient and MD pre-conceptions
Interpretation tips • Detection – PZ is rarely classic (stranding) – Strongest evidence w/ multi-paramter +
• Low signal T2, w/o high signal T1 • DCE: Rapid uptake & washout • DWI: High signal on high B value, Low on ADC
• Staging – Read with high specificity
• Better with ERC • Better with 3T
DWI ADC map
Transverse/axial
Size Matters
Sagittal
Sosna, et al. Acad Radiol. 2003 Aug; 10(8):846-53 Bulman, et al. Radiology. 2012 Jan;262(1):144-51.
Report • Find reporting structure for key referents • Keep reporting structure consistent • Get familiar with PIRADS
Report • Technique (brief!) • Overall gland morphology – Report size & volume
• Use sagittal view: AP and CC • Use axial view: transverse • (Even better planimetry, but time consuming)
– Features of BPH – Describe delineation of PZ
Report: Abnormal Foci • Describe with degree of suspicion – T2, DCE and DWI congruent?
• CONSISTENT WITH
– 2 of 3 • Very suspicious
– 1 of 3 • “Some features suggestive of”
– Depends on how compelling that 1 is
Report- The Suspicious Foci • Describe Position
• Ax: Clock position, • CC: ÷ gland into 1/3’s • Radial: ÷ gland into 1/3’s
• Describe distance in touch with outer margin – Distinguish < vs. > 1.2 cm
• Describe contour with reference to lesion(s) • Describe neurovasc triangles – Clearly seen – Not well delineated – Infiltrated by tumor.
Report: Outside the Gland • Describe seminal vesicles – Symmetry – Visualization / atrophy – Multi-parametric features
• Describe LN’s – “using size criteria..”
• Describe Bones
76 y.o; PSA = 31; 3 prior neg bx rounds
2.5 x 1.6 cm REPORT: “An anterior mass is seen with uniform low signal intensity on T2WI’s, measuring 2.5 x 1.6cm, demonstrating abnormal contrast features, very suspicious for cancer. It is located at the mid- portion of gland (C-C dimension) from the 11:00 – 1:00 position (gland viewed from a lithotomy perspective). A biopsy targeted towards this area is expected to have a high positive yield. There is no definite evidence for extra-capsular extension.” IMPRESSION: “Anterior gland tumor as described above. Consider targeted biopsy.”
Establish & Maintain Credibility
• Under-promise, over-deliver • Follow-up on path – Communicate
• Seek 2nd opinions on difficult cases • Stay current with the literature – Ours and theirs!
Pt with progression on active surveillance
T2WI Diffusion MAP
ADC = 628 mm2/s.
Van As, et al. Eur Urol. 2009 Dec;56(6):981-7
Tumor ADC was a significant predictor of: 1) adverse repeat biopsy findings (p<0.0001; hazard ratio [HR]: 1.3; 95% CI: 1.1-1.6), 2) time to radical treatment (p<0.0001; HR: 1.5; 95% CI: 1.2-1.8)
Conclusions • Prostate MRI offers value to pts & MDs • Requires a champion • Use standard techniques • � Buy-in w/dialogue�