HM17 session summary: CT to PET scans – What every hospitalist needs to know



Timothy Kasprzak, MD, MBA

Session summary

“What imaging study should I order for this patient?” is a question that comes up frequently in the hospital. Dr. Kasprzak, the director of abdominopelvic and oncologic imaging at Case Western MetroHealth, Cleveland, offered some practical advice for inpatient clinicians during a rapid-fire session at HM17.

Dr. Raj Sehgal

Dr. Raj Sehgal

Regarding the choice of imaging modality, Dr. Kasprzak recommended the use of appropriateness criteria, such as one offered by the American College of Radiology (ACR) . The ACR not only provides recommendations for the most appropriate testing for various conditions but also evidence tables and literature searches for those interested in examining the data further.

The session also touched on the risks and benefits of contrast media for CT scans and MRIs. As with other tests and treatments in medicine, the use of contrast is always a “risk-benefit.” The main benefit of both forms of contrast is to improve the “conspicuity” of findings on imaging studies – many diagnoses that are visible with contrast (such as vascular lesions, solid organ lesions, or extravasations) are invisible without it.

The risks of both CT and MRI contrast have been re-evaluated over the past several years. More recent evidence is suggesting the prevalence of contrast-induced nephropathy is lower than previously thought, especially with newer non-ionic contrast. Conversely, there is some recent evidence that CT contrast might accentuate radiation-related DNA damage. Regarding MRIs, gadolinium has been associated with nephrogenic systemic fibrosis, particularly in patients with end-stage renal disease. This appears to be less prevalent with newer gadolinium agents. There are, however, recent reports of gadolinium deposition in the basal ganglia of patients. The clinical significance of this imaging finding is still unknown.

Lastly, Dr. Kasprzak offered advice on the use of PET scans on inpatients. While there are a few indications that would warrant inpatient use (such as evaluation in fever of unknown origin), most PET scans are done for oncologic reasons that do not warrant urgent inpatient use. In addition, some insurance companies don’t reimburse for inpatient PET studies.

Key takeaways for HM

• Utilize appropriate use criteria (such as offered by the ACR) for choosing the most worthwhile imaging study.

• Give relevant clinical history in your order to help the radiologist narrow the differential (and to help prevent the “clinically correlate” phrase as much as possible).

• Consider the risk/benefit of contrast use for all patients getting CT or MRI studies.

• Avoid the use of inpatient PET scans, except for very specific indications (such as obscure infections).

Dr. Sehgal is a hospitalist at the South Texas Veterans Health Care System in San Antonio, an associate professor of medicine at University of Texas Health-San Antonio, and a an editorial board member of The Hospitalist.

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