Different types of MRI for Prostate Cancer
When it comes to technique, morphologic and functional sequences must be found. Morphologic sequences are T1 and T2. T2 needs to be high resolution, with 3 mm cuts and no separation between them. T1 should have a wide field of view in order to assess the whole pelvis and diagnose extraprostatic disease, while a narrow FOV is useful to view the prostate only.
The functional sequence consists of diffusion and dynamic contrast enhanced sequence. Diffusion refers to molecular movement in a specific site, a higher restriction appears hyperintense, the opposite means less cellularity. Higher B levels mean a higher cellularity, improving sensibility and specificity.
The ADC map (apparent diffusion coefficient) is useful to see if a lesion is suspicious once the water component seen in T2 has been removed. Finally we have the contrasted phases, which can be as much as 10.
We know that in high PIRADS scores, up to 50% of lesions detected are benign, so other tools in order to make differential diagnosis are always useful. For example, the ECHO gradient helps to distinguish the presence of blood.
Talking about equipment, there are 1.5 and 3 Tesla devices. Older 1.5T may need an endorectal coil to better define images, but more recent 1.5 T and 3T equipments do not need coils because there is no improvement in sensibility or specificity with it, it can even alter the sensibility in the periferic zone if it has air in it. An advantage of endorectal coils is a better definition of the fibroglandular stroma.
MRI has a high false positive rate, this has improved with technology, rising its specificity.
Presented by: Sara Vazquez, MD
Written by: Paulina Bueno Garcia Reyes, MD, medical writer for UroToday.com and Ashish Kamat, MD, Professor of Urology and Director of Urologic Oncology Fellowship at M.D. Anderson Cancer Center, at the Mexican Urologic Oncology Association Meeting - July 26 - 28, 2018