An Approach for Balancing Diagnostic Image Quality with Cancer Risk: Application to Pediatric Diagnostic Imaging of ^99mTc-Dimercaptosuccinic Acid

Abstract

A recent survey of pediatric hospitals showed a large variability in the activity administered for diagnostic nuclear medicine imaging of children. Imaging guidelines, especially for pediatric patients, must balance the risks associated with radiation exposure with the need to obtain the high-quality images necessary to derive the benefits of an accurate clinical diagnosis. Methods Pharmacokinetic modeling and a pediatric series of nonuniform rational B-spline–based phantoms have been used to simulate 99mTc-dimercaptosuccinic acid SPECT images. Images were generated for several different administered activities and for several lesions with different target-to-background activity concentration ratios; the phantoms were also used to calculate organ S values for 99mTc. Channelized Hotelling observer methodology was used in a receiver-operating-characteristic analysis of the diagnostic quality of images with different modeled administered activities (i.e., count densities) for anthropomorphic reference phantoms representing two 10-y-old girls with equal weights but different body morphometry. S value–based dosimetry was used to calculate the mean organ-absorbed doses to the 2 pediatric patients. Using BEIR VII age- and sex-specific risk factors, we converted absorbed doses to excess risk of cancer incidence and used them to directly assess the risk of the procedure. Results Combined, these data provided information about the tradeoff between cancer risk and diagnostic image quality for 2 phantoms having the same weight but different body morphometry. The tradeoff was different for the 2 phantoms, illustrating that weight alone may not be sufficient for optimally scaling administered activity in pediatric patients. Conclusion The study illustrates implementation of a rigorous approach for balancing the benefits of adequate image quality against the radiation risks and also demonstrates that weight-based adjustment to the administered activity is suboptimal. Extension of this methodology to other radiopharmaceuticals would yield the data required to generate objective and well-founded administered activity guidelines for pediatric and other patients.

Biokinetics, dosimetry, and radiation risk in infants after 99mTc-MAG3 scans

“…Despite a high uncertainty in the individual risk estimation (90%), this information might assist in the establishment of more accurate recommendations for this high-risk group of pediatric patients for keeping the balance between sufficient imaging quality at the lowest possible patient radiation exposure [14].…”

Standardization of Administered Activities in Pediatric Nuclear Medicine: A Report of the First Nuclear Medicine Global Initiative Project, Part 1—Statement of the Issue and a Review of Available Resources

“…In 2011, Sgouros et al reported on an approach for balancing diagnostic image quality with cancer risk for 99m Tc-DMSA (35). The authors used pharmacokinetic modeling and a pediatric series of nonuniform phantoms for simulating 99m Tc-DMSA SPECT images.…”

Virtual Reality for Dose Optimization in Pediatric Nuclear Medicine: Better Than the Real Thing: FIGURE 1.

“…With persisting concerns regarding radiation risks of diagnostic imaging procedures, the virtual-reality approach of Sgouros et al (11) can yield computationally validated "isoradiation risk"-administered activity guidelines for pediatric and other patients that account for differences in body morphometry and body mass among patients-all while circumventing the burdens and limitations of traditional clinical trials. With the rigor achieved in the current study, virtual reality is indeed better than the real thing.…”

“…Given the possibility of performing such suboptimal procedures in the interest of dose reduction, rigorous validation of diagnostic protocols designed to reduce patient exposure are therefore required before they are recommended for standard practice. In the current virtual-reality study by Sgouros et al (11), such validation was accomplished by remarkably realistic computer simulation of SPECT studies over a range of administered activities in combination with comparison of diagnostic information content of the resulting images using receiver operating characteristics. Alternatively, such an analysis could be performed empirically-that is, in the context of a traditional clinical trial in which different patient strata are administered different activities of a radiopharmaceutical and the diagnostic accuracy correlated with the administered activity.…”