Determining the value, efficacy and utility of any advanced imaging study represents a mighty challenge. And advanced imaging technologies are under the gun as public and private payors attempt to rein in inappropriate imaging studies.
Professional societies are closing in (and narrowing) on definitions of appropriate imaging. Take for example, the American College of Physicians (ACP) revised recommendations for low back pain imaging, which assert that routine x-ray, CT and MRI studies should be to limited selected higher-risk patients with severe or progressive neurologic deficits, suspected serious or specific underlying conditions or candidates for invasive interventions. Similarly, a study published in the Journal of Pediatrics on Jan. 11 questioned the need for CT among pediatric patients with bleeding disorders after blunt head trauma.
While reimbursement policies, clinical studies and updated guidelines chip away at these and other common indications for advanced imaging, other studies are clearly defining the value of and appropriate roles for advanced imaging.
In the February issue of Radiology, Ohno et al started to clarify the value of quantitative first-pass 320-detector row perfusion CT. The researchers selected a tricky clinical situation—the differentiation of benign from malignant pulmonary nodules. The protocol is tricky from a number of perspectives. Not only are standard methods of assessment prone to both false positives and false negatives, surgical follow-up can be problematic as thoracotomy and biopsy can be especially difficult for patients with compromised lung function. Highly accurate imaging results may offer an improved paradigm.
And indeed perfusion CT indexes—perfusion, blood volume and extraction fraction—appear to provide essential utility, improving on the specificity and accuracy of PET/CT in the differentiation of malignant and benign pulmonary nodules. The approach also may play a role in management of pulmonary nodules.
CT also improves on another notoriously unclear imaging situation, according to a study published in the February issue of the Journal of Nuclear Medicine. Swiss researchers sought to determine if the addition of CT attenuation correction (which also provides calcium scoring capabilities) could improve the prognostic utility of SPECT myocardial perfusion imaging evaluation of patients with known or suspected coronary artery disease.
Researchers found that with attenuation correction prognostically relevant summed stress scores shifted to lower values, helping to better risk stratify patients and adding incremental prognostic value. In addition because the new model reduces false positive findings it could trim unnecessary downstream imaging.
Both studies indicate the value of CT, providing specific instances in which advanced imaging improves diagnostic accuracy and may facilitate better use of healthcare resources.
My prognosis? The data will continue to accrue for both sides of the imaging equation, showing that some types of studies are overutilized and inappropriate, while others are very appropriate, providing critical diagnostic data and setting the stage for more judicious use of downstream imaging and medical resources.
Editor of Health Imaging & IT