ABSTRACT
All of these advances suggest that rapid coregistration of images from a variety of sources will be possible to compile a very detailed composite about an individual tumor biology. Coregistration superimposes radiographic images to further define specific anatomic areas of interest. As currently used in treatment planning and dosimetric assessment for radiotherapy, coregistration of computed tomography (CT) and MRI has shown superiority over use of pelvic bony reference marks.7 The addition of functional imaging to anatomic information from CT and ultrasound is now being utilized for intraprostatic dose escalation strategies and for confirmation of 3D energy delivery.8 This combination of functional and anatomic imaging with MRI and MR spectroscopic imaging (MRSI) to provide high-resolution spatiovascular information in prostate cancer is also under review.9,10 Furthermore, coregistration of radiolabeled monoclonal antibody scans with both CT and MRI have improved specificity for both newlydiagnosed prostate cancer and recurrent disease.11,12
Established clinical applications of gray-scale TRUS in prostate cancer include biopsy guidance, placement of radioactive seeds, and assessment of response to therapy. Despite the advantages of a relatively inexpensive, fast, and minimally invasive imaging technology, TRUS has shown very limited benefit for detection and staging of prostate cancer and is not recommended for screening. It has a relatively low sensitivity and specificity because most hypoechoic peripheral zone lesions are not malignant, and up to 56% of carcinomas are isoechoic.13 Likewise, TRUS is not very sensitive for detection of seminal vesicle invasion and is more suited as a guide for biopsy in those cases suspected of seminal vesicle involvement.14
