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�