الفهرس 
Anatomy Of The Prostate GlandOnly 14 pages are availabe for public view
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Abstract
Prostate cancer is considered one of the most common malignancies in elderly men.
Its diagnosis is based mostly on the results of ultrasonography (US)- guided transrectal biopsy. However, because of the low accuracy of US for prostate cancer detection and localization, a random biopsy is usually performed, which subsequently has several disadvantages, e.g. (a) it may lead to an increase in complications because of the unnecessary sampling of normal prostate tissue, (b) moreover, cancer located outside the routine biopsy site may be missed, (c) additionally, there may be difficulty in determining the site of a previous biopsy when repeating biopsy in a patient with a previous negative result and continuously high prostate-specific antigen levels.
For these reasons, an imaging modality like MRI is needed that permits the accurate detection and localization of prostate cancer as well as its proper staging, including local, nodal and distant metastatic invasion, contrary to trans-rectal ultrasound which is restricted only to local staging. Moreover MRI is also valuable for guidance of biopsy, and adequate follow- up after treatment.
Although T2-weighted MRI has been used widely for the pretreatment work up of prostate cancer on the basis of its excellent soft tissue resolution, yet its accuracy for the detection and localization of prostate cancer is unsatisfactory as T2-weighted imaging has significant limitations for depicting cancer in different sites, as well as overlap of MRI features of prostate cancer with many non-cancerous benign conditions.
Recently, investigators have applied, MR spectroscopy (MRS), diffusion weighted imaging (DWI) MRI and dynamic contrast enhanced (DCE) MRI in order to improve the diagnostic performance of MRI prostate cancer detection, staging, guidance of biopsy, better treatment selection, more accurate image-guided therapies, and finally monitoring of treatment effect. Currently, the majority of basic and clinical researches of prostate cancer are shifting to these functional MR imaging techniques.
MR spectroscopy is a non-invasive technique which depicts a higher ratio of choline and creatine to citrate in cancerous tissue than in normal tissue. Integration of MRS into routine prostate MRI has improved tumor detection rates and allows detection of prostate cancer in the transitional zone. It can be used also to predict the aggressiveness of prostate cancer and may be useful in evaluating low-risk prostate cancer which only needs watchful waiting with no need for intervention. Moreover, MRS has been used to help detection of recurrence after therapy. However, it is frequently affected by artifacts.
DWI MRI is potentially useful in diagnosis of prostate cancer for detection and localization, monitoring, biopsy, treatment planning and staging as well as potentially for response assessment. It may also aid in evaluation of more difficult cases such as disease in the transitional zone or when there is hemorrhage. The strengths of this technique are its short imaging time and relatively simple post-processing requirements. DWI and ADC show an inverse relationship to Gleason grades non-invasively. A high discriminatory performance is achieved in the differentiation of low, intermediate, and high grade cancer.
Dynamic contrast enhanced MR imaging allows an assessment of parameters that are useful for differentiating cancer from normal tissue. The advantages of this technique include the direct depiction of tumor vascularity, DCE MRI is helpful for the detection and localization of prostate cancer. Moreover, DCE MRI has been shown to provide a high accuracy for determining the extracapsular extension of prostate cancer and detecting local recurrence after a radical prostatectomy.
Optimization and standardization of the various technical parameters should help to render it as a robust adjunct to the conventional MR imaging of the prostate gland. Thus, a comprehensive evaluation in which both functional and anatomic MRI techniques are used (with proper understanding of their particular advantages and disadvantages) may help to improve the accuracy of MRI.