MRI is superior to CT in imaging the kidneys & urinary bladder owing to the superior soft-tissue contrast. It depicts the renal anatomy much better and is able to provide urographic images even without the use of intravenous contrast. Additionally its ability to differentiate fat, mucin, water, and blood products aids in better characterization of a lesion for early detection and local staging, better than any other modality. Imaging the renal vessels (non-contrast angiography) is possible with special MR angiographic sequences. In addition, Dynamic triple-phase contrast acquisition can provide an exquisite display of vascular anatomy crucial to surgical planning in seconds while undertaking a routine post-Gd contrast study.
MRI is the imaging modality of choice for imaging prostate in males, uterus, cervix and ovarian lesions in females, anorectal lesions, imaging of the anorectal sphincter and pelvic floor. (Prostate has been dealt in a separate section in this handbook)
Correlative FDG-PET offers a true synergy, enhancing detectability and characterization of MR identified lesions and MR providing not only an anatomical correlate but also characterizing the PET detected lesions.
For clarity, we have divided the Genito-Urinary system into three sub-parts which include:
66 year old male with a left renal mass.
T2 Coronal(A), T2 Axial (B), PET MR fused(C) reveals a large FDG avid heterogeneous signal intensity mass arising from the lower pole of left kidney and involving the renal pelvis. The mass is supplied by the segmental lower pole branches of the left renal artery (red arrow in D) and is seen extending into the renal vein (white arrow in E) on Coronal MIP reformats of the triple-phase post-contrast VIBE images s/o RENAL CELL CARCINOMA WITH RENAL VEIN INVASION
91 year old female with recurrent hematuria and right side hydronephrosis on ultrasound with deranged renal function.
Coronal T2W (A) and PET/MRI fused images in Sagittal (B) and Coronal (C) sections showing mildly FDG avid lesion in the right renal pelvicalyceal system involving the PUJ and the upper ureter with proximal moderate hydronephrosis (arrows). Corresponding non-contrast MR Urography MIP image (D) showing right PUJ obstruction with moderate hydronephrosis.Coronal PET MIP image showing tracer accumulation in the right renal pelvis due to PUJ obstruction (red arrow) s/o TRANSITIONAL CELL CARCINOMA.
60 year old male with carcinoma of the urinary bladder underwent staging whole-body PET /MRI
WB PET/MRI revealed a polypoidal intravesical lesion seen appearing hypointense (dark) against the hyperintense (bright) signal of urine on T2 axial (B) bright on DWI (A) along the right posterolateral wall of the urinary bladder with possible full-thickness wall involvement and no demonstrable transmural extension, showing enhancement on post-contrast VIBE sequences(C) with increased FDG uptake on PET MR fused images (D).
74 year old male, follow up case of Ca urinary bladder, Post TURBT status. Presented with recurrent hematuria. Underwent WB PET/MRI for further evaluation.
Post-contrast VIBE (B, C) reveals focal enhancing thickening of bilateral posterolateral bladder wall including right VUJ and focal enhancing thickening along the left anterolateral bladder wall. Delayed FDG PET (D) and PET/MRI fused images (A) reveal increased FDG uptake corresponding to the enhancing wall thickening suggesting RECURRENCE.
74 year old female with carcinoma of the urinary bladder. Post TURBT / RT IN 2015. On follow up. Presented with an episode of hematuria. Was referred for re-evaluation to rule out disease recurrence in the urinary bladder. A whole-body FDG PET MRI was done.
The urinary bladder was well distended with normal wall thickness and no demonstrable enhancing or FDG avid lesion in the bladder wall to suggest disease recurrence. However, there was evidence of altered fluid collection in the endometrial canal appearing hyperintense on T1 W images (B) suggesting subacute blood (normally fluid appears hypointense on T1 W images and hyperintense on T2W). Cervix and vagina were otherwise unremarkable. The gynecological examination was unremarkable.
Axial STIR(A), T1W(B), Post-contrast VIBE(C), T2W(D) showing dilated endometrial canal (Endometrial thickness =8 mm) with altered fluid within bright on STIR and T2 (A, D) bright on T1W(B) and low signal and non enhancing on post contrast VIBE(C) suggesting altered blood products.
Axial post-contrast subtracted image (A), Sagittal (B) and Axial PET MR fused image(C) showing well distended urinary bladder with no demonstrable enhancement or FDG avidity along the walls suggesting no apparent local recurrence and the cause of hematuria being of uterine origin and not related to the primary malignancy of concern.
62 year old female operated for Ca Ovary with a history of treated Ca Breast presented for restaging.
Axial T2 HASTE image of the abdomen (A) showing an incidental hyperintense lesion in the lower pole of the right kidney with no apparent distortion of the renal contour (arrow). It showed minimal peripheral enhancement (B) and reported as a BOSNIAK category III cyst. However, there is no focal FDG uptake in the lesion (C).
Follow up scan after one year showed increase in the size of the lesion on T2 HASTE (A) with internal enhancing septae (B, C) and diffusion restriction (D, E) (yellow arrows) however nonavid on FDG PET (F) HPE proven Renal Cell Carcinoma.
66 year old female with pyrexia of unknown origin and deranged renal function.
The left kidney is diffusely enlarged with altered intensity, effaced calyces, perinephric stranding and loss of normal corticomedullary differentiation on T2W images (A, F). There is associated mild diffusion restriction on DWI(B) and ADC map( C) and diffuse relatively increased FDG uptake on PET (D) and PET MR fused (E). No demonstrable mass / hydronephrosis seen. MR appearance is suggestive of Acute Pyelonephritis of the left Kidney.
This short PET-MRI Scan case was compiled by Dr. Sangeeta Taneja and Dr. Amarnath Jena (Nuclear Medicine Physician at PET-Suite @ Indraprastha Apollo Hospital, Sarita Vihar).
Read More about PET-MRI Scan at House Of Diagnostics in Delhi and NCR.
The Simultaneous PET-MRI Scan is currently offered at PET-Suite at Apollo Hospital, Sarita Vihar.