<b>Specific Organ Imaging</b>

Prim Care 1992 Dec;19(4):677-713
<b>Diagnostic imaging in cancer. </b>
Berman CG, Clark RA.   Department of Radiology, University of South Florida, Tampa. 

Screening chest radiographs do not reduce mortality from lung cancer. Should an incidental noncalcified pulmonary parenchymal nodule be discovered, chest CT will demonstrate one third of such patients to, in fact, have the multiple nodules of metastatic disease. CT is very helpful to guide fine needle aspiration biopsy of lung lesions and to assist in evaluation for resectability. MR can be helpful in special circumstances, including the definition of the extent of paravertebral, superior sulcus, and diaphragmatic lesions. Endorectal ultrasound is not sensitive enough to function as a screening tool for prostate cancer but is used routinely to guide biopsies. CT and MR are rarely helpful in staging this disease. Given the highly characteristic trait of bone metastasis in prostate cancer, a bone scan is mandatory in all patients. Double contrast barium enema can be used as an adjunct or alternative to sigmoidoscopy for colorectal cancer screening, in the preoperative evaluation of patients, and in postoperative surveillance. CT and MR can detect macroscopic adenopathy and liver metastases; CT is generally the preferred study. Screening mammography can have a major impact in reducing breast cancer mortality. It is recommended that a baseline study be obtained at age 35. Annual or biannual examinations should commence at age 40. Any palpable lesion, whether or not it is demonstrated mammographically, must be subjected to biopsy. Ultrasound is the most useful initial imaging study for evaluating pelvic masses. MR will, on occasion, identify the origin of a mass not determinable from ultrasound scan. MR is particularly valuable to identify parametrial spread (inoperability) of cervical cancer, and has been underused for this purpose. Surgery remains the mainstay for the staging of ovarian and endometrial cancer, although CT can be helpful to identify macroscopic relapse, ascites, or liver metastases. Bone scan and liver CT remain the standard procedures for detecting metastases in these respective organ systems. MR can be invaluable in the imaging of epidural metastasis and spinal cord compression in patients with vertebral metastatic disease. Contrast-enhanced MR is more sensitive than contrast-enhanced CT for detecting brain metastases, but the latter remains a useful tool. Chest CT can improve the detection of pulmonary metastases when this is of crucial importance. &&url PMID: 1465483 


<b>Liver/Spleen/Kidney</b>
Ultrasound, CT scan, and MRI can all visualize these organs well.  Preoperatively, MRI is probably preferred.

<b>Female Organs</b>
Ultrasound is a good first choice.  Then CT or MRI.  MRI will sometimes show pelvic pathology that the CT missed.

<b>Pelvis</b>
Pelvis and abdominal and chest walls can be shown well by Ultrasound, perhaps CT, but sometimes lesions show up best on MRI.

<b>Extremity</b>
MRI scans are best for delineation of any abnormality.  Ultrasound will sometimes show the presence of a metastasis within muscle.

<b>Lungs</b>
Chest X-rays are good for lung lesions, but CT scans are excellent.  MRI might be useful for adjacent soft tissues of the mediastinem, chest wall, and in and around the spine and head and neck. 

<b>Brain</b>
MRI scans are best for picking up brain lesions.

<b>Bone</b>

Imaging Techniques:
The main imaging techniques used to diagnose bone tumors are conventional radiography, CT, MRI, and isotope bone scan. Angiography is rarely used, but is helpful when a preoperative selective embolization is needed, or when complex vertebral surgery or vascular surgery is planned.

X-rays:  Lytic lesions appear as dark 'holes' in bones.  For a lytic lesion to show on X-ray, 50% of the bone matrix must be destroyed.  X-rays will not show early stage disease.  Conventional radiography is the screening examination of choice and is sufficient in several benign lesions not requiring treatment. Supplementary imaging studies are usually needed when radiographic findings are questionable and/or the lesion requires treatment. 

Bone Isotope Scan: will show areas of increased bone activity-including inflammation, arthritis, and infection. It can be thus useful to depict lesion quiescence or activity and to stage any tumor that can metastasize to the skeleton. Bone scan is also helpful to show bone lesions when they are not visible on plain radiographs and can indicate the tumor response to preoperative chemotherapy. High grade lesions show up best on bone isotope scans.

MRI scan:  MRI is the scan of choice for depicting any bone tumor.  MRI beautifully shows the different tissues and compartments and it is particularly sensitive in depicting fat. Moreover, it can be repeated many times, even in pregnant women, because it needs no ionizing radiations and iodinated contrast; it is also free of artifacts in the patients with orthopedic devices that are usually nonferromagnetic. However, the execution of an adequate MRI requires experience and knowledge of bone pathologic conditions. 
While Bone Isotope Scans and PET scans are useful adjuncts to indicate strong suspicious of metastases to bone, it is the MRI which is the definitive examination to give clear delineation of the bone tumor and its extent.  No imaging method is without its difficulties, however, and sometimes the MRI cannot distinguish between different types of lesions; one notable situation is between a hemangioma [a noncancerous tumor of twisted blood vessels] and some neoplasms [often also highly vascular].  [Repeatedly on the LMS ACOR List, the MRI has shown the bone mets, despite negative X-rays and negative bone scans.  The scan of choice for detecting bone tumors is MRI.  Ed.]

PET scan:  will show areas of increased metabolic rate, in bone and other organs, including inflammation, arthritis, and infection.  It is a new technique, and its specificity and reliability are still open to interpretation.  This technique is also best for finding high grade tumors.  

By CT scan: CT best shows mineralized tissues and pulmonary metastases. It is also frequently used as a guide for needle biopsies. Not a good choice for bone studies. 



<b>Compiled by doctordee, with the help of Roger, Neil, Glenn, Ro, Lynette, Jim, Dick and Richard.</b>
<b>last updated January 2004</b>