Prostate MRI has become an increasingly common adjunctive procedure in the detection of prostate cancer. The procedure of choice is multiparametric MRI, a combination of high-resolution T2- weighted (T2w) morphological sequences and the multiparametric techniques of diffusion-weighted MRI (DWI), dynamic contrast-enhanced MRI (DCE-MRI), and proton MR spectroscopy (1H-MRS) and a structured reporting scheme (PI-RADS) similar to BIRADS classification for the breast.
Recently, a 68Gallium-labeled ligand of the prostate-specific membrane antigen (68Ga-PSMA) has been introduced in PET-imaging of prostate cancer with first promising results.
Together with the novel development of combined PET/MRI, the combination of excellent morphological detail, multiparametric functional information, and molecular PET data might lead to a significant improvement in detection, staging, and restaging of prostate cancer.
A combination of different parameters, e.g., as PSMA- expression, cellularity, and contrast media kinetics (e.g., permeability, influx, or plasma leakage), provides ancillary information for tumor characterization. This can facilitate biopsy targeting, prediction/monitoring of tumor aggressiveness (esp. for active surveillance) or for radiation therapy planning (e.g., boost on a dominant intraprostatic lesion).
Prostate-specific membrane antigen (PSMA) is a zinc-dependent peptidase, highly expressed by all prostate cancers and its expression increases with tumor aggressiveness, metastatic disease and disease recurrence. It is increasingly being recognized as a novel target for the PET imaging of prostate cancer (PCa) and 68Ga-DKFZ-11 (68Ga – PSMA ) has been suggested as a novel tracer for detection of PCa relapses and metastasis.
First human studies of PSMA PET/CT imaging have demonstrated high tracer uptake at the sites of the primary tumor and lymph node and bone metastasis in direct correlation with aggressiveness and Gleason cores. It seems to be a highly accurate imaging tool for the restaging of prostate cancer patients with biochemical recurrence and may be used in order to develop a treatment strategy for recurrent disease even in patients with low PSA levels. As a theranostic approach, its counterpart Lu-177 labeled ligands have a potential role for the treatment of castration-resistant prostate cancer.
Given below is a table depicting the positivity rate with PSMA and the serum PSA levels:
A 69-year-old male presented with raised Serum PSA level of 14.2 ng/ml on routine screening. TRUS Biopsy HPE: Adenocarcinoma Gleason’s 4+3=7, PET/MRI for staging workup.
Multi-parametric imaging of the prostate: Axial T2W (A) images showing moderate diffuse T2 hypointensity involving the bilateral peripheral zones of the prostate (Right>Left) with diffuse capsular bulge and involvement of the right neurovascular bundle (arrow). The area shows diffusion restriction (B, C) with early enhancement on dynamic contrast-enhanced imaging (D) and increased perfusion (E): PIRADS 5.Corresponding MR Spectroscopy image (F) showing elevated Cho+ Cr: Ci ratio(arrowhead).
As seen on the last set of images on the previous page: PET image at the level of the prostate gland (A) showing focal Ga 68 PSMA uptake. Axial T2W sections of the pelvis (B, C) showing normal-sized lymph nodes in bilateral external iliac groups. Corresponding PET/MRI fusion images (D-F) show Ga68 PSMA uptake within the prostatic lesion and in the bilateral otherwise non- suspicious external iliac lymph nodes (arrows).
As seen on the Whole Body Coronal PET MIP image (on the right) showing focal Ga-68 PSMA uptake in the bilateral common iliac nodes (red arrows).
A 66-year-old male presented with incidentally detected raised Serum PSA level of 13.56 ng/ml on routine screening.
Axial (A) and Coronal (B) T2W images of the Prostate gland showing focal T2 hypointense lesions in bilateral peripheral zones. The lesions show differential increased permeability (C) with diffusion restriction (D, E) PIRADS 5. Corresponding PET/MRI fused image (F) showing focal increased PSMA avidity(white arrows).
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.