الفهرس 
ANATOMYOnly 14 pages are availabe for public view
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Abstract
Carcinoma of the prostate remains the most common malignant neoplasm and the second cause of cancer-specific death among men. Because early disease is usually asymptomatic, the need for reliable diagnostic modalities to identify patients with early-stage prostate cancer is essential for effective therapy .
Detection and treatment of prostate cancer are based on digital rectal examination, serum prostate specific antigen (PSA), and transrectal ultrasound scanning (TRUS) combined with ultrasound-guided biopsies.
Years of experience have shown that TRUS-directed biopsy, while very useful, has several limitations. Prospective TRUS imaging data have demonstrated that conventional gray-scale TRUS guided biopsy is slightly superior to random chance in detecting prostate cancer. The present trend is to increase the number of biopsies in order to compensate for the limitations of imaging alone.
However, conventional grey scale TRUS is not reliable for exclusion of prostate cancer or guiding biopsies and the false negative biopsy rate remains unacceptably high. This shortcoming has lead to the introduction of improved scanning modalities such as color Doppler (CD) and color power (CP) ultrasound scanning which enable visualization of blood vessel architecture and assessment of blood flow within the prostate, particularly the abnormal vascularisation associated with prostate carcinomas .
However, the utility of CD and CP are restricted by limitations in the sensitivity of ultrasound equipment, especially with respect to flow in small vessels with low moving blood volume and low velocity flow.
Using new encapsulated microbubble small than red blood cells ie, levovist increase the echoes from small vessels and overcome these problems.
Applications of ultrasound contrast agents can be performed at fundamental imaging using only the fundamental frequency of the probe, second harmonic or intermittent imaging combined with gray scale or Doppler. Color Doppler images have higher intensity. The duration of enhancement with the contrast agent is 15 to 20 minutes. However, a strong increase in this scattered signal can produce artifacts. They can be avoided by using a slow continuous infusion rate or multiple small boluses as well as by adjusting the Doppler gain. This injection mode is also recommended to provide prolonged and uniform enhancement of Doppler signals and improved image quality
Contrast enhanced color Doppler endorectal sonography increases the detection of prostate cancer. Improvement in sensitivity was high, while the difference in specificity was not as pertinent. It is accurate when using a common and routine application ultrasound unit. This technique is easy to perform and not time-consuming. Obtaining additional biopsy cores of suspicious enhancing foci significantly improves the detection rate of cancer.
Using a quantitative approach, it is possible to derive two types of index, one relating to the amount of signal enhancement broadly reflecting the vascular volume, and the other relating to the timing of the enhancement. In particular, the echo enhancement in individuals undergoing hormone treatment for prostate cancer was markedly less than those individuals not receiving treatment, and that the time to peak enhancement was also shorter in untreated patients.
Contrast enhanced CD or CP TRUS could be used to more precisely define the changes in blood flow within lesions and perhaps allow early detection of non-responders or escape from androgen deprivation therapy.
In conclusion , contrast enhanced transrectal ultrasonography increase the detection of cancer prostate and improve targeted biopsy ,however improvement in sensitivity is high there is no improvement in specificity .
contrast enhanced transrectal ultrasonography provide also a mean of monitoring cancer prostate patients who undergo hormonal therapy and help in early detection of non-responders patients .
There are still certain limitations of contrast enhanced transrectal ultrasonography such as the additional examination time. It is relatively more expensive than standard TRUS imaging , it is also not helpful for detecting cancers within the transitional zone portion of the gland due to the intense normal heterogeneous enhancement associated with benign prostatic hyperplasia. Prostatitis has been described as a cause of false-positive results.