Diagnostic Ultrasound - Abdomen and Pelvis

Prostatic Carcinoma
TERMINOLOGY
Abbreviations
• Prostate carcinoma (PCa)
Synonyms
• Prostate adenocarcinoma
IMAGING
General Features
• Best diagnostic clue
○ MR: Peripheral zone (PZ): T2 dark lesion with restricted
diffusion; central gland: "Erased charcoal" sign on T2WI
• Location
○ PZ 70-80%, transition zone (TZ) 20-25%, central zone
(CZ) 1-5%
• Targeted MR-guided and MR/ultrasound fusion-guided
biopsy is promising for increasing detection of high-risk
prostate cancer while reducing detection of low-risk cancer
compared with standard biopsy
Ultrasonographic Findings
• Grayscale ultrasound
○ Transrectal ultrasound (TRUS) is imaging modality of
choice to guide biopsy but performs poorly in cancer
detection and staging; also used to guide focal therapies
– TRUS-guided biopsy considered "blind" or "random"
since it is usually not targeted to specific abnormality
○ Traditional description of PCa is hypoechoic PZ lesion;
difficult to identify central gland tumors due to
heterogeneity from benign prostatic hyperplasia (BPH)
– Now with earlier cancer detection with PSA, studies
have shown that hypoechoic lesions are not
pathognomonic for cancer, as was once thought
– PCa can appear as hypoechoic (60-70%),
isoechoic/invisible (30-40%), rarely hyperechoic ±
asymmetric capsular bulging or irregularity
– Probability of hypoechoic lesion being PCa is 17-57%
• Color Doppler
○ PCa may be hypervascular; however, absence does not
exclude Ca, and other benign entities (e.g., prostatitis)
may also be hypervascular
• Power Doppler
○ No advantages over color Doppler
CT Findings
• Not accurate in detection of cancer within prostate
• Glazer et al showed mass-like PZ enhancement is predictive
of higher-grade (≥ Gleason 4 + 3) cancer
• Evaluate local/distant staging only among patients with
intermediate- or high-risk disease
○ Clinical stage ≥ T2b vs. 3 (differing guidelines), Gleason ≥
8, PSA > 10 vs. 20, or chance of lymph node involvement
> 20% (based on nomograms)
MR Findings
• MR is most sensitive imaging technique for prostate cancer
diagnosis and staging: Prostate Imaging and Reporting and
Data System (PI-RADS) 1-5
• Prostatic cancer is best seen on T2WI and DWI
○ Abnormal low T2 signal in normally high signal PZ with
corresponding reduced diffusion
– Differential for T2 dark lesion in PZ: Biopsy-related
hemorrhage, changes from hormone therapy,
prostatitis, atrophy, fibrosis
○ "Erased charcoal" sign in TZ: Focal, homogeneous low T2
signal lesion with ill-defined margins
• T1WI: Precontrast: Evaluate for post-biopsy hemorrhage;
dynamic postcontrast: Hypervascular lesion corresponding
to T2/DWI abnormality
• MR useful for staging
○ T stage: Organ confined (≤ T2 disease) vs. extending
beyond gland (≥ T3 disease); signs of extraprostatic
extension: Bulging prostatic contour, irregular or
spiculated margin, obliteration of rectoprostatic angle,
asymmetry or invasion of neurovascular bundle, seminal
vesicle or bladder wall invasion
○ Pelvic and retroperitoneal lymph nodes
○ Osteoblastic bone metastases: Low signal intensity on
both T1WI and T2WI
• Post-biopsy changes (e.g., hemorrhage, inflammation) may
complicate interpretation of prostate MR for staging; at
least 6 weeks interval between biopsy and MR should be
considered for staging
Nuclear Medicine Findings
• Bone scan
○ Tc-99m MDP planar bone scan is standard imaging
modality for diagnosis of bone metastases: Sensitivity
62-89%, specificity 57%; reflects osteoblastic response in
cortex, misses early marrow disease
○ Should only be performed in patients with high-risk
disease or symptoms of bony involvement: Clinical stage
≥ T2c vs. 3 (differing guidelines), Gleason ≥ 8, PSA > 10 vs.
20, or bony symptoms
○ Tc-99m MDP SPECT (single-photon emission CT)
improves sensitivity (92%) and specificity (82%)
• PET/CT
○ Main role of PET/CT is in primary staging and evaluation
for biochemically recurrent disease; not helpful in
diagnosis or T staging
○ 18F-FDG PET/CT: Limited utility due to relatively low
glucose metabolism of most PCa
○ 18F-NaF PET/CT: For bone metastases; higher diagnostic
accuracy, but arguably more expensive than bone scan +
SPECT
○ 11C-choline PET/CT: Limited accessibility, requires on site
cyclotron; may detect disease in nonenlarged nodes and
early marrow involvement; evaluation for suspected
recurrent disease
Imaging Recommendations
• Best imaging tool
○ MR is most sensitive imaging technique for prostate
cancer diagnosis and staging
○ TRUS is imaging modality of choice for prostate biopsy
DIFFERENTIAL DIAGNOSIS
Benign Prostatic Hyperplasia
• Hyperplasia of TZ and periurethral glands; heterogeneous,
nodular enlargement ± cystic degeneration, calcification
Prostatitis
• Acute and chronic prostatitis can mimic prostate cancer
Diagnoses: Urinary Tract
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