Multiparametric mri

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Dr. Peter Pinto at the NIH has been one of the leaders in pushing prostate MRI innovation. He coined the term, "The Manogram." 

The strength of the magnet can affect the image resolution. Most centers use 1.5 Tesla or 3.0 Tesla magnet. The strength of the magnet is not the only factor which affects quality - the array, the number of channels, the modernity of the coil, the protocol, and other factors can all contribute. An endorectal balloon can also be placed which acts like an antenna to boost the signal and reduce noise.This can be uncomfortable and is usually not necessary. 

Multiparametric refers to different sequences that are done which provide information that taken together can help assess prostate size and morphology, the presence of absence of significant cancer, the stage of a cancer, lymph nodes, and the presence of inguinal hernias. 

T2-weighted imaging

This is the main sequence which provides the most detailed anatomic picture. Normal prostate tissue usually has a bright signal whereas tumor is dark. This sequence also can determine whether the prostate capsule (e.g. orange peel) is intact or breached by a tumor. The seminal vesicles can be evaluated fairly well with this. 

Diffuse weight imaging and ADC map

Prostate tissue is made up of glands like little donuts. Normally, water can pass around these clusters of cells easily. Prostate cancer results in higher cellular density and as the grade increases fusion of glands (i.e. cribriforming) and mutation into dense sheets of cells. Water cannot pass as easily through these cancerous areas and thus diffusion is "restricted." The higher the grade the cancer the more diffusion restriction. This can be quantified with a measure of how dark the pixel is called the Apparent Diffusion Coefficient (ADC value). Normal prostate tissue has an ADC usually >1200 whereas cancer is usually <1000. This is inversely proportional to tumor grade such that the higher the grade the cancer the low ADC value. Intermediate risk cancers are usually in the 800-1000 range where as ADC values < 600 is usually associated with Gleason 8-10.

Dynamic contrast enhancement (DCE)

When gadolinium is given through the IV into the bloodstream, this passes through the prostate which takes up the contrast. Cancerous tissue usually has more blood supply to support it's abnormal growth and lights up earlier and brighter than normal tissue. This can be quantified with numeric parameters like Ktrans and Kep which are not commonly used clinically.  

After focal therapy there should be an absence of enhancement in the area that was treated. This is one of the key measures of radiographic success. 

T1 

T1 weighted imaging can be briefly checked to ensure there is no hemorrhage which is bright on T1. An upfront MRI can avoid this. If you have alreadt had a prostate biopsy then you need to wait 8 weeks for the blood to clear otherwise it can obfuscate the scan. 

Diffusion tensor imaging

This is an uncommon technique which can visualize nerves.