WE‐C‐144‐01: The Management of Imaging Procedure Dose 2: Nuclear Medicine
Authors: Bolch W , Fahey F 
Published: July 2013

Wesley Bolch: Nuclear Medicine Dose Indices

A main clinical application of nuclear medicine is that of functional imaging of normal and diseased tissue, and the localization of malignant tissue and its potential metastatic spread. In these applications, the amount of administered activity is such that the absorbed dose to both imaged and non‐imaged tissues are typically very low and thus stochastic risks of cancer induction are greatly outweighed by the diagnostic benefit of the imaging procedure. Nevertheless, these tissues doses and their stochastic risks should be quantified for each patient, and placed in context of both their cumulative values received over multiple imaging sessions, and of doses and risks received by other diagnostic imaging procedures they may have (fluoroscopy and computed tomography, for example). The role of internal dosimetry in diagnostic nuclear medicine is thus to provide the basis for stochastic risk quantification. Once this risk is quantified, it may be used to optimize the amount of administered activity in order to maximize image quality while minimizing patient risk. This optimization process is of particular importance for pediatric patients owing to their enhanced organ radiosensitivities and years over which any stochastic effects may become manifest. This optimization should consider, as much as possible, patient age, gender, and body morphometry, and pharmacokinetics, along with all available image acquisition and processing techniques. Unlike other forms of diagnostic imaging, for which dose indices are readily measured, only the administered radioactivity is typically available for “dose tracking”. In this course, we will review data sources for organ and effective dose per unit administered activity for the more common molecular imaging radiopharmaceuticals. Particular attention will be given to sources of individual variability in both organ and effective dose attributed to both physiological and anatomical variations among patients.

Learning Objectives:

1. Identify the more common radiopharmaceuticals used in functional imaging of normal and diseased tissues.

2. Demonstrate understanding of the parameters needed to estimate tissue dose during nuclear medicine imaging and therapy.

3. Identify fundamental data sources for organ and effective dose per unit administered activity.

4. Demonstrate understanding of the physiological and anatomic sources of individual variability in organ and effective dose per unit administered activity.

5. Identify key features of new generation anatomical models that can reduce dose uncertainties through improved matching of patient body morphometry.

Fred Fahey: Tracking Doses in the Pediatric Population

A review of methods for estimating patient dose from pediatric nuclear medicine procedures is presented. Included is a discussion of hybrid imaging and factors that affect radiation dose from CT in PET/CT procedures. Consideration for choice of radionuclide and administered activity for various procedures are detailed, with a focus on the pediatric population. Technological advances allowing the further reduction in radiation dose is also discussed.

Learning Objectives:

1. List three considerations in estimating the radiation dose from pediatric nuclear medicine.

2. Discuss three factors that affect the radiation dose from the CT component of hybrid imaging.

3. Describe three factors that can affect the appropriate choice of administered activity for a nuclear medicine study.

4. List 2 advances that may lead to further reduction in the administered activity in pediatric nuclear medicine.