Radiologic Imaging Advancements in Patients with Colorectal Carcinoma
Kamyar Ilkhanipour, M.D.
Assistant Professor of Radiologic Sciences, Drexel University College of Medicine

There have been a number of exciting recent advances in radiologic imaging and treatment for patients with colorectal carcinoma. These advances have been primarily in the areas of diagnosis and screening, as well as radiologically guided therapy.

Computed tomography (CT) and magnetic resonance imaging (MRI) are the mainstays in the staging and follow-up of colorectal carcinoma. CT is a costeffective, safe and widely available modality used to evaluate the whole body for metastatic disease in patients with colorectal carcinoma. One of the most exciting advancements in the field of CT scanning is the introduction of multidetector scanners (MDCT). These machines can scan a patient’s chest, abdomen and pelvis in 30 to 45 seconds. Enhanced resolution and improved patient comfort are two obvious advantages of MDCT. The newer software accompanying these scanners allows faster reconstruction of images in multiple planes. This is often useful to the clinician in planning appropriate therapy, i.e. the surgical approach. CT angiography (CTA) can also be performed, giving the surgeon valuable vascular anatomic information. CT scanning continues to play the primary role in imaging guided biopsies, and lesions as small as 1 cm are now accessible for percutaneous fine needle aspiration. Another new CT technique is termed CT colonography. This study is used to evaluate the colon for polyps, which can eventually become cancers. There is considerable ongoing research to establish the role of CT colonography as a tool in screening patients for colorectal carcinoma. MRI is a complimentary modality to CT and can be useful to further characterize indeterminate abnormalities detected by CT. This is particularly evident in the liver, where occasionally CT cannot differentiate between benign and malignant lesions. MRI has recently been shown to accurately assess the stage of rectal carcinomas, therefore this technique provides valuable preoperative information on the local extent of disease.

Follow-up and staging patients with colorectal carcinoma can also be done with positron emission tomography (PET). This technique utilizes radioactively labeled markers that are injected intravenously and are concentrated in certain types of cancer. This modality can accurately differentiate benign from malignant tumors based on the amount of radiotracer uptake. When used
in conjunction with CT, the ability to detect and characterize metastases is synergistically increased. The most advanced form of this type of imaging is termed “fusion imaging”, where CT and PET scans are obtained at the same time. Although not as widely available as CT or MRI, PET imaging is fast becoming an integral part of the imaging workup of cancer patients. Lastly, there have been recent advances in the radiologically guided therapeutic options for patients with colorectal carcinoma. CT and ultrasound have been used to guide the placement of radiofrequency (RF) probes into liver metastases. RF probes are used to ablate these liver tumors using high-intensity radio waves. These probes can be placed into liver metastases intraoperatively or with CT guidance in an outpatient setting. This reflects the current trend in medicine toward minimally invasive procedures. Angiographically performed chemoembolization is another therapeutic procedure utilized in patients with liver metastases. Using intra-arterial catheters, chemotherapeutic agents can be delivered directly into the blood vessels that feed these tumors while sparing the nonaffected areas in the liver.

At Allegheny General Hospital, we have two MDCT scanners and three high-field MRI scanners performing state-of-the-art imaging studies. We have a third CT scanner with CT fluoroscopy, which is utilized for precision imaging-guided biopsies and RF tumor ablation procedures. The Interventional Radiology section is equipped with three angiography suites, and PET imaging is also available. We have a dedicated staff of physicians with subspecialty training and expertise in the fields of thoraco-abdominal imaging, interventional radiology, neuroimaging and nuclear medicine. The radiological options now available to the physicians that care for patients with colorectal carcinoma are greater now than they have ever been and are constantly evolving with advances in technology.