Prostate cancer generally refers to adenocarcinoma of the prostate, which accounts for more than 98% of all prostate cancers. Less common prostatic malignancies include neuroendocrine tumors, squamous tumors, sarcomas, and transitional cell carcinomas.The only established risk factors for prostate cancer are age, race/ethinicity, and family history of prostate cancer.
In the axial plane, the prostate is divided into four zones: (a)the anterior fibromuscular stroma, which contains no glandular tissue; (b) the transition zone surrounding the urethra, which contains 5% of the glandular tissue; (c)the central zone, which contains 20% of the glandular tissue; and (d)the outer peripheral zone, which contains 70%–80% of the glandular tissue.
The prostate is supplied by branches from the inferior vesical, middle rectal and internal pedendal arteries. Rich plexus of vein are present to the side and base of prostate which communicates freely with internal pudendal and vertebral venous plexus, these ate valveless veins.
At the base of bladder: The anterior fibromuscular stroma (arrow) consists of nonglandular tissue and appears dark. Note the symmetric homogeneous muscular stroma layer (arrowheads) in the posterior prostate baseMidprostate level : Homogeneously bright peripheral zone (arrowheads) surrounding the central gland (white arrows). The central gland is composed of the transition zone and central zone, which cannot be resolved at imaging. Therefore, they are referred to jointly as the central gland. Note theneurovascular bundles at the 5-o’clock and 7-o’clock positions (black arrows).At prostate apex : The homogeneous peripheral zone (arrowheads) surrounding the urethra (U). Note that the volume of the peripheral zone increases from thebase to the apex.
Benign tissues in theperipheral zone show hyperintense signals in T2 weightedimaging, whereas malignant changes show hypointensesignals, of which the reason could be the cellular density aswell as the malfunction of the gland when the malignantchange had occurred
MR spectroscopic spectrum, obtained at 1.5 T shows a high citrate (Ci)peak (resonance at 2.6 ppm) and a low choline (Ch)peak (resonance at 3.2 ppm), characteristics of benign tissue. The choline and creatine (Cr)peaks are overlapping.At 3 T : Good separation of the choline (Cho)and creatine (Cr)peaks at higher magnetic field strength. The spectrum is normal, with a high concentration of citrate (Ci)and low concentration of choline.
MR IMAGING IN PROSTATE CANCERA REVIEW OF DEPARTMENTAL CASES Sarbesh Tiwari
INTRODUCTION2nd most common malignant tumor in male.95% are adenocarcinomaHigher incidence in African Americans, incidenceraising in IndiaAge : 6th to 7th decade.Symptoms: Dysuria, hematuria, urgency+/‐frequency of micturition, bone painDiagnosis: Combination of DRE & PSA.Confirmation of diagnosis-Transrectal biopsy under Ultrasound guidance
ZONAL DISTRIBUTION OF PROSTATE CANCER 70 % prostate CA ------ In Peripheral Zone of Prostate 20 % prostate CA ------ In Transitional Zone of Prostate 10 % prostate CA ------ In Transitional Zone of Prostate
NORMAL MRI APPEARANCE OF PROSTATENormal prostate has homogenous low signalon T1WIZonal anatomy is best demonstrated on T2WIComprise of low signal central zone andhigher signal peripheral zoneTZ and CZ appears similar in SI and looselytermed the central gland
MR IMAGING IN PROSTATE CA INDICATION – To stage the extent of prostate cancer once the diagnosis is established To identify the presence of recurrent disease following treatment Persistent raised PSA with repeated negative TRUS biopsies.MRI is not used in the primary diagnosis of prostatecancer. This is usually established following biopsy atTRUS
MR IMAGING PROTOCOLMRI is usually performed on 1.5T or 3T MRI using endorectal and pelvic phase array coil.Standard Sequences : 1. Axial T1WI of pelvis 2. Axial + Sagittal + Coronal T2WI 3. MR Spectroscopy of selected volume of prostateOthers, 4. Diffusion Weighted Imaging 5. Dynamic contrast enhanced MRI.
CONVENTIONAL MRI FINDINGSTIWI : Tumor is isointense relative to glandT2WI : Tumor appears as a region of low signalintensity within normal high signal peripheralzoneDetection of extra capsular extension: 1. Asymmetry into neurovascular bundle 2. Obliteration of recto-prostatic angle 3. Irregular bulging or breech of prostate capsule 4. Invasion of bladder / rectum / seminal vesicle.
MRI FINDINGS CONTD…Diffusion Weighted Imaging : Restricted diffusion with reduced ADC value. : Increased cellularity of malignant lesions, with reduction of the extracellular space and restriction of the motion of a larger portion of water molecules to the intracellular spaceDynamic contrast enhanced MRI : Early, rapid, and intense enhancement with quick washout of contrast material : Increased tumor neovascularsation and thus increased micro vascular density as compared to normal prostate.
MR SPECTROSCOPY OF PROSTATENORMAL METABOLITE OF PROSTATE Citrate : Produced by normal epithelial cells of prostate Normal Peak at 2.6 ppm Choline : Precursor of phospholipids cell membrane Normal Peak at 3.2 ppm Creatine : Involved in cellular energy Normal peak at 3 ppm
MR SPECTROSCOPY OF PROSTATEClassic spectral signature of prostate cancerconsists of increased choline and decreased citrateRatio of (Choline + creatine)/ Citrate is usuallymeasured.Normal range : 0.22 +/- 0.013, range upto 0.5.Lower values for the Cho+cr /Cit ratio in theperipheral areas than in the central glands.Choline / creatine to citrate ratios: > 0.5 : suspicious > 1 : very suspicious > 2 : abnormal
DIAGNOSIS Prostate ca arising from the peripheral zone with extra capsular extension into left posterolateral periprostatic fat with infiltration of anterior rectal wall. Associated secondary deposits noted in sacrum and lumbar vertebra
CASE 362 yrs old male presenting with urgency and increased frequency ofmicturition with pain in left hip joint T2WI : Axial
DIAGNOSIS BENIGN PROSTATIC HYPERPLASIA WITH NORMAL SPECTROSCOPIC FINDINGS. UNILATERAL PAGETS DISEASE OF LEFT ILLIAC BONE.
CONCLUSIONMRI serves as a powerful modality forlocalization and staging of prostate cancerNon ionizing and non invasive.Excellent soft tissue resolution, allows betterdelineation of primary tumor and nearbyextension.Combination MR + MRS: Sensitivity 91% Specificity 95%
REFERANCE1. David Bonekamp, Michael A. Jacobs et.al Advancements in MR Imaging of the Prostate: From Diagnosis to Interventions. RadioGraphics 2011;31:677–7032. Textbook of radiology and imaging . Volume 2 David Sutton 7th edition.