A 65-year-old patient with prostate cancer was referred to MR for clinical staging of the disease. The PSA level was 25 µg/l and the biopsy of the prostate had shown a Gleason grade 5.
• A prototype of an endorectal coil and interface for 3T (Medrad, Pittsburgh, USA) was used for signal reception. The body coil was used for signal excitation.
• Multislice axial T2-weighted TSE sequence: 15 axial slices, TR 4490 ms, TE 153 ms, turbo factor 17, FoV 200 x 100 mm, matrix 768 x 384, slice thickness 2.5 mm. Hyperechoes were used to decrease SAR.
• Multislice coronal T2-weighted TSE sequence: 13 coronal slices, TR 4000 ms, TE 116 ms, turbo factor 17, FoV 180 x 90 mm, matrix 512 x 256, slice thickness 4 mm. Hyperechoes were used to decrease SAR.
• T1-weighted 3D sequence: Axial reconstruction of 32 partitions, TR 8.6 ms, TE 4.0 ms, flip angle 15 degrees, FoV 130 x 65 x 48 mm, matrix 256 x 128 x 32, slice thickness 2.5 mm.
• MAGNETOM Trio, software syngo MR 2004A
Fig. 1 T2-weighted axial images of the prostate of a 65-year-old patient with prostate cancer. The complete prostate is visualized from apex to base. The large tumor is visible in the right base of the prostate extending into the seminal vesicles (arrows).
Fig. 2 Four out of 13 T2-weighted coronal images of the prostate. As the images move towards the endorectal coil (from ventral to dorsal) the SNR of the images increases. Again the tumor with seminal vesicle invasion is indicated with the arrows.
Fig. 3 T1-weighted images of the base of the prostate and the seminal vesicles after contrast administration. The lesion of figure 1 is indicated with the arrows as enhancing tissue.
Fig. 4 Histopathology of four cuts through the base of the resected prostate. The tumor is indicated with a blue line. Extra capsular extension is indicated as CP+ and CP++, seminal vesicle invasion is indicated as VS++.
Results and Discussions
On axial and coronal T2-weighted imaging (Fig. 1 and 2) a large hypo-intense region is visible on the right side in the base of the prostate, extending into the seminal vesicles. After contrast agent administration this lesion, including seminal vesicle invasion, enhances on T1-weighted images (Fig. 3). Based on these findings the diagnosis is stage T3b. The histopathological analysis of biopsy material from the seminal vesicles confirmed the presence of cancer with Gleason grade 3+4. After a negative lymph node dissection the prostate was resected. The resected prostate was cut, stained and studied (Fig. 4), confirming the clinical stage of the disease: T3b. Because of medication before the prostatectomy the Gleason score was difficult to assess.
This is an example of accurate prostate cancer staging. The combination of an endorectal coil and a magnetic field strength of 3T provides enough SNR for high resolution imaging of the complete prostate. In this case the MRI findings made the urologist decide to take biopsies from the seminal vesicles. Since these were positive for cancer, lymph nodes around the prostate were dissected. With no signs of cancer in the lymph nodes, the next step was to resect the prostate itself.