Читать книгу Anti-Aging Therapeutics Volume XIII - A4M American Academy - Страница 11

There are several MRI formats for examining the prostate. Each has its own characteristics and can refine the diagnosis. MRI routinely refers to the image of signal intensity in the gland with the patient in the tube of the unit. Three primary MRI formats have proven useful for prostate examination: EC-MRI uses an endorectal coil (EC) to improve resolution in the prostate; S-MRI (spectroscopic-MRI) involves analysis of the chemical composition of the prostate tissues, with emphasis on the compound choline; DCE-MRI (dynamic contrast enhanced-MRI) is the most useful format to complement 3-D Doppler for a complete diagnosis. DCE-MRI uses the injection of a contrast agent (gadolinium) that reveals the blood flow within tumorous prostatic tissue.⁴

MRI shows cancer as a loss or decrease of the normal glandular prostatic tissue signal, however, other benign pathologies, such as calculi, hemorrhage (bleeding from recent biopsy), stones, benign prostatic hyperplasia (BPH), and inflammation, may also produce this effect. Some infiltrating types of cancer will not produce any visible changes. The data from the 2009 American Roentgen Ray Meeting shows a 75% sensitivity (25% false negatives) and 95% specificity (5% false positives). MRI was originally used to stage the spread of cancer outside the prostate gland also denoted as ECE (extra capsular extension). The data showed ECE medium specificity (74%) and sensitivity (71%).

Each MRI format has a unique purpose:

•EC-MRI: By using the endorectal coil inflated as a balloon, EC-MRI was designed to better define the capsule of the gland and the seminal vesicles.

•S-MRI: This format was designed to detect intraglandular cancer and shows the aggression. The spectroscopic chemical analysis of cancer shows higher levels of choline and citrate than in normal prostatic tissues. The analyzed sections of the prostate are divided into a grid pattern of such a size that small cancers could be missed. While this technique appeared useful for larger tumors, a 2010 article noted an overall sensitivity of 56% for tumor detection. Currently, S-MRI is practiced at few medical centers in the US and is losing popularity at many international academic facilities. A 2008 presentation by Dr. O. Rouviere from Lyon, France at the French Radiology Meeting highlighted the problem that S-MRI was not effective in analyzing tumor extension into the fatty tissues adjacent to the prostate gland.

•DCE-MRI: This format is widely used and has improved specificity by about 80% according to the 2008 RADIOLOGY article by Drs. J. Futterer and J. Barentsz and sponsored by the Dutch Cancer Society. DCE-MRI provides noninvasive analysis of prostate vascularization as well as tumor angiogenesis and capillary permeability characteristics in PCa's. (This group has also developed a 3-D S-MRI system that improves the overall accuracy of standard S-MRI.)

A fourth MRI type takes a different approach:

•DWI-MRI: DWI-MRI (diffusion weighting imaging-MRI) is a process that shows molecular motion inside a tumor. The more motion, the more likely a lesion is benign, as in a fluid filled cyst. Several articles now assert that this technology may be used to predict Gleason scores.