MR IMAGING IN PROSTATE CANCER A REVIEW OF DEPARTMENTAL CASES

Sarbesh Tiwari

INTRODUCTION

2nd most common malignant tumor in male.

95% are adenocarcinoma

Higher incidence in African Americans, incidence raising in India

Age : 6th to 7th decade.

Symptoms: Dysuria, hematuria, urgency+/‐ frequency of micturition, bone pain

Diagnosis: Combination of DRE & PSA. 

Confirmation of diagnosis-Transrectal biopsy under Ultrasound guidance

ZONAL ANATOMY OF PROSTATEMC NEAL 1968

70 % prostate CA ------ In Peripheral Zone of Prostate

20 % prostate CA ------ In Transitional Zone of Prostate

10 % prostate CA ------ In Transitional Zone of Prostate

ZONAL DISTRIBUTION OF PROSTATE CANCER

NORMAL MRI APPEARANCE OF PROSTATE

Normal prostate has homogenous low signal on T1WI

Zonal anatomy is best demonstrated on T2WI

Comprise of low signal central zone and higher signal peripheral zone

TZ and CZ appears similar in SI and loosely termed the central gland

NORMAL T2 APPEARANCE OF PROSTATE

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 prostate cancer. This is usually established following biopsy at TRUS

MR IMAGING PROTOCOL

MRI 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 prostate

Others,

4. Diffusion Weighted Imaging

5. Dynamic contrast enhanced MRI.

CONVENTIONAL MRI FINDINGS

TIWI : Tumor is isointense relative to gland

T2WI : Tumor appears as a region of low signal intensity within normal high signal peripheral zone

Detection 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.

Explanation: 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 space

Dynamic contrast enhanced MRI :

Early, rapid, and intense enhancement with quick washout of contrast material

Explanation: Increased tumor neovascularsation and thus increased micro vascular density as compared to normal prostate.

MR SPECTROSCOPY OF PROSTATE

NORMAL 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

NORMAL MR SPECTROSCOPY

At 1.5 T At 3 T

MR SPECTROSCOPY OF PROSTATE

Classic spectral signature of prostate cancer consists of increased choline and decreased citrate

Ratio of (Choline + creatine)/ Citrate is usually measured.

Normal range : 0.22 +/- 0.013, range upto 0.5.

Lower values for the Cho+cr /Cit ratio in the peripheral areas than in the central glands.

Choline / creatine to citrate ratios:

> 0.5 : suspicious

> 1 : very suspicious

> 2 : abnormal

DEPARTMENTAL CASES

Case 1:Clinical Detail : A 69 yrs old patient with post TURP status and biopsy proven adenocarcinoma, presented for MR evaluation and staging of the disease.

T1WI Axial T1WI Sagittal

T2WI Axial

T2WI Axial T2WI Sagittal

DWI MR Spectroscopy

Spectroscopy : Results Table

DIAGNOSIS

PROSTATIC CA WITH EXTRACAPSULAR EXTENSION INTO LEFT SEMINAL VESICAL WITHOUT ANY LYMPHADENOPATHY.

BLADDER WALL HYPERTROPHY DUE TO PREVIOUS BOO.

CASE 2

T2WI - Axial

T2WI - Axial T2WI - Axial

•56 yrs old male presenting with difficulty in micturition, poor urinary stream and back pain

• Raised serum PSA- 20ng/ml

T1WI

T1WI-post contrast

MR Spectroscopy

Spectroscopy : Results Table

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 3

T2WI : Axial

62 yrs old male presenting with urgency and increased frequency of micturition with pain in left hip joint

DIAGNOSIS

BENIGN PROSTATIC HYPERPLASIA WITH NORMAL SPECTROSCOPIC FINDINGS.

UNILATERAL PAGETS DISEASE OF LEFT ILLIAC BONE.

CONCLUSION

MRI serves as a powerful modality for localization and staging of prostate cancer

Non ionizing and non invasive.

Excellent soft tissue resolution, allows better delineation of primary tumor and nearby extension.

Combination MR + MRS: Sensitivity 91% 

Specificity 95%

REFERANCE

1. David Bonekamp, Michael A. Jacobs et.al Advancements in MR Imaging of the Prostate: From Diagnosis to Interventions. RadioGraphics 2011;31:677–703

2. Textbook of radiology and imaging . Volume 2 David Sutton 7th edition.