CT colonography method reduces radiation risk

May 07, 2003

Results of a recent study reconfirm previously published data, suggesting that CT colonography (CTC) can be performed with decreased radiography exposure to patients, says Michael Zalis, MD, of Massachusetts General Hospital and lead author of the study.

"Standard CTC is performed with approximately 100 mA, and the dose in our study was approximately 50% of this," says Dr. Zalis.

To evaluate the performance of this low-dose CTC technique as a way to reduce radiation risk for non-invasive colon cancer screening, Dr. Zalis and colleagues compared the studies of 100 patients at moderate risk for development of colorectal cancer who underwent CTC and video assisted conventional colonoscopy. Dr. Zalis says, "Moderate risk usually refers to ages 50-70, without history of inflammatory bowel disease, prior colon carcinoma, or familiar polyposis syndrome."

Reduced-dose CTC examinations were performed following polyethylene-glycol electrolyte preparation (the traditional bowel prep used for colonoscopy) and patient-controlled self-insufflation (the administration of air into the colon) on a multidetector CT. The size of lesions and the evaluation times of two readers were compared on a per-polyp basis to conventional colonoscopy, which was performed following each CTC, the same day.

Reader 1 demonstrated sensitivity of 90% for lesions 10 mm or larger, 67% for 5-10 mm lesions, and 50% for lesions that were 0-5 mm. Reader 2 also demonstrated sensitivity of 90% for lesions 10 mm or larger, but sensitivity of 58% for 5-10 mm lesions and 44% for 0-5 mm lesions. Dr Zalis says both readers took an average of 9-10 minutes to read the scans.

Dr. Zalis says, "We found no statistically significant difference in terms of detecting polyps using the low-dose technique. However, the low-dose technique will make subtle differentiation of extracolonic soft tissues more limited." He notes that the main point of CTC is to screen the colon, and even with low-dose technique, it is still feasible to detect gross extracolonic findings such as masses and lymphadenopathy.

Dr. Zalis recommends using the low-dose technique for asymptomatic screening, but says, "For patients with active symptoms, it may be useful for them to receive a more standard dose, as this might help characterize subtle extracolonic lesions." However, Dr. Zalis emphasizes that dosage difference for symptomatic patients has not been proven.

Dr. Zalis points out that radiation dosage depends on a patient's weight, and says, "new technology will allow the scanner to adjust the dose per slice based on the patient's cross sectional thickness, permitting even further reduction of dose."

The study will be presented May 7, during the American Roentgen Ray Society Annual Meeting in San Diego.
Contact: Danica Laub, 703-858-4332
Keri Sperry, 703-858-4306
Press Room: 619-525-6536

American College of Radiology

Related Colonoscopy Articles from Brightsurf:

Using robotic assistance to make colonoscopy kinder and easier
Scientists have made a breakthrough in their work to develop semi-autonomous colonoscopy, using a robot to guide a medical device into the body.

Nearly 1 in 8 patients receive unexpected out-of-network bills after colonoscopy
Nearly 1 in 8 commercially insured patients nationwide who underwent an elective colonoscopy between 2012 and 2017 performed by an in-network provider received potential 'surprise' bills for out-of-network expenses, often totaling hundreds of dollars or more.

Swallowing this colonoscopy-like bacteria grabber could reveal secrets about your health
Your gut bacteria could say a lot about you, such as why you're diabetic or how you respond to certain drugs.

Examining association between older age, risk of complications after colonoscopy
This observational study looked at the risk of complications after an outpatient colonoscopy among patients age 75 and older compared to younger patients.

Bowel cancer rates after colonoscopy vary by provider
A colonoscopy is the main test used to detect bowel cancer, but like most tests, it is not always 100% accurate and cancers can be missed.

Will disposable colonoscopy devices replace reusables?
As a disposable version of the instrument used in one of the most common medical procedures in the United States inches closer to widespread availability, a team of Johns Hopkins data researchers is studying the economic and safety implications associated with the devices used to perform colonoscopies.

Sedation method does not affect colonoscopy detection rate
Colon cancer is the second leading cause of cancer death in the United States and colonoscopy is the most-used screening tool to detect it.

Blue dye tablet helps identify polyps during colonoscopy
Ingestion of a blue dye tablet during bowel prep for colonoscopy could be a significant advance in the early detection of colorectal cancer (CRC).

Low complication rates after screening colonoscopy
During colonoscopy screening for bowel cancer and in the four weeks after the procedure, the risk for complications to develop is low.

Patients with positive fecal screening test, sooner is better for colonoscopy
The risk of colorectal cancer increased significantly when colonoscopy was delayed by more than nine months following a positive fecal screening test, according to a large Kaiser Permanente study published today in the Journal of the American Medical Association.

Read More: Colonoscopy News and Colonoscopy Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.