February 2010

Start Page: 14

Other Perspectives On Alternative Imaging Modalities

Michelle Butterworth, DPM, FACFAS, will not use standard CT scans to evaluate infection, including osteomyelitis. She prefers to use magnetic resonance imaging (MRI) if she needs an imaging study beyond radiographs. Dr. Butterworth says MRI has proven to be the most specific imaging study available for the evaluation of osteomyelitis and the patient does not receive a radiation dose.

In the future, however, Dr. Butterworth predicts newer CT scanning techniques, such as the FDG-PET/CT scan, may become more readily available and may prove to be more specific for evaluating osteomyelitis.

When it comes to infection, Molly Judge, DPM, FACFAS, says nuclear medicine technology (via indium labeled leukocyte imaging) provides more specific information about the nature and extent of infection than MRI since MRI cannot discriminate between infectious and benign inflammation, and often overestimates the site of involvement.

As Dr. Judge notes, one can use CT or MRI to evaluate osteochondral lesions. She notes that with the help of radiologists, she will get a MRI to evaluate adjacent sites of stress and strain due to compensatory mechanics. However, if she is working with facilities using traveling (mobile) MRI units, she will stick with the CT for osteochondral lesions.


Studies Suggest Possible Link Between CT Scans And Cancer

By Brian McCurdy, Senior Editor

   In recent years, computed tomography (CT) has gained wider usage among podiatrists as a diagnostic tool. However, recently published studies in the Archives of Internal Medicine sound a warning about a potential link between CT scans and cancer.

   In the first study, researchers estimated that about 29,000 future cancers could be related to CT scans performed in 2007.

   In the second retrospective study, researchers assessed the 11 most common types of diagnostic CT studies performed on 1,119 consecutive adults in 2008. The overall median effective radiation doses ranged from 2 millisieverts (mSv) for a routine head CT scan to 31 mSv for a multiphase abdomen and pelvis CT scan, according to the study.

   Researchers also estimated that one in 270 women who underwent CT coronary angiography at age 40 will develop cancer from a CT scan in comparison with an estimated one in 8,100 women who had a routine head CT scan at the same age.

   The study authors conclude that radiation doses from CT scans may be higher and more variable than generally known. Accordingly, they emphasize the necessity of more standardization across institutions.

CT Scans In The Lower Extremity: What You Should Know

   How much radiation do patients get from a lower extremity CT scan? Molly Judge, DPM, notes that a CT from the hip to the toes is equivalent to a single view chest X-ray. She says when it comes to the lower extremity, CT in general provides a low radiation dose.

   Dr. Judge will use a CT scan for a patient with a bone problem involving complex fracture and dislocations. If the problem is more vague and there is generalized bone and joint pain, Dr. Judge will opt for a triphase bone scan to “localize the pathology” and will consider other imaging modalities once she has honed in on the location.

   Dr. Judge, a Fellow of the American College of Foot and Ankle Surgeons, says the radiation dose of the triphase bone scan is equivalent to a two-view chest X-ray.

    “We tend to use this scanning modality liberally to reduce radiation exposure while obtaining a very good screening tool to determine if another form of ancillary imaging is necessary,” explains Dr. Judge, who is a certified nuclear medicine technologist.

   Michelle Butterworth, DPM, agrees about the need for standardization of radiation levels. She concurs with Dr. Judge that lower extremity CT scans seem to have a lower risk.

    “If the scan will aid in your diagnosis and guide your treatment plan, I think the benefit of the scan outweighs the risk regardless of sex or age,” maintains Dr. Butterworth, a Fellow of the American College of Foot and Ankle Surgeons.

   Dr. Butterworth most often uses CT scans to evaluate trauma patients. She says the scans can be helpful in assessing ankle fractures, calcaneal fractures and Lisfranc’s fractures. She orders CT scans for most complex midfoot and hindfoot fractures as well as some forefoot fractures. Dr. Butterworth adds that pursuing 3D reconstructions can also help facilitate better evaluation of the fractures.

   Dr. Butterworth says the CT scan permits a better overall view of the fragmentation and alignment of the fractures with much greater detail than standard radiographs.

    “I cannot give you one instance where a podiatrist can go wrong with a CT scan unless he or she is completely off the mark about standard indications and what pathology it can educate the physician about,” notes Dr. Judge, who is in private practice in Toledo and Port Clinton, Ohio. “I would not have suspected that overuse would have been an issue in our specialty of medicine.”

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