Approach to Pediatric Imaging

Approach to Pediatric Imaging

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Pediatric imaging in nuclear medicine encompasses imaging of a broad spectrum of developmental and pathologic entities. Some of these entities are unique to children and young adults while others are seen in both adults and young patients. There are several unique considerations when imaging a child or young adult.

Radiopharmaceutical Dosing

Unlike with adult patients in whom a fixed dose of radiopharmaceutical is more commonly used, pediatric radiopharmaceutical dosing is typically weight-based. The longstanding approach to determine pediatric dosing was to divide the child’s weight in kilograms by an idealized adult weight of 70 kg and multiply that by the standard radiopharmaceutical dose administered to an adult patient (child’s weight in kg/70)*(adult dose). More recently, consensus guidelines have standardized administered activity for pediatric patients. Differences exist between the North American Consensus Guidelines and the European Association of Nuclear Medicine dosage card, but efforts to harmonize those guidelines continue. Dosing according to either guideline as well as altering administered activities based on the clinical indication is acceptable.

Appropriate Application of Correlative Imaging

Other than the administered radiopharmaceutical, the other source of medical radiation exposure in nuclear medicine is correlative imaging, chiefly CT. In general, it is appropriate to limit the use of CT and the CT exposure parameters in pediatric patients to maintain dose from the CT component at ALARA while still obtaining the necessary diagnostic information.

For PET/CT, CT optimization means tailoring the CT parameters to the clinical question, which can range from attenuation correction only (lowest dose), to bone detail CT, localization CT, or diagnostic CT. CT parameters in each of these categories should be adjusted to patient size.

For SPECT/CT, CT parameters should similarly be tailored to the clinical question. More importantly, it may be that CT is not needed for every SPECT examination. In some settings, a negative SPECT is sufficient to rule out abnormality, and in other settings, correlation to anatomic imaging can be achieved through review of previously performed diagnostic imaging or post-hoc fusion. If CT is used, consider limiting coverage to the anatomic area of interest.

Need for Distraction or Sedation/Anesthesia

In general, pediatric patients have more difficulty holding still for imaging procedures than adult patients do. This can be particularly problematic in nuclear medicine in which both static and tomographic images may require several minutes to obtain. Many examinations can be achieved in pediatric patients without sedation or anesthesia through the application of coaching, distraction techniques (video goggles, etc.), and imaging technique (posterior positioning of the camera head). Sedation or general anesthesia may be required for some patients undergoing some examinations to obtain good quality images and answer the clinical questions (e.g., very young patients undergoing F-18 FDG PET/CT or I-123 MIBG exams). Sedation and anesthesia can be administered for most nuclear medicine studies without compromising the study itself. F-18 FDG PET/CT is one exception where sedation can impact the distribution of radiotracer, particularly in the brain. As such, for F-18 FDG PET/CT exams, sedation/anesthetic induction should be held until 30-45 minutes into the uptake period.

May 7, 2023 | Posted by in CARDIOVASCULAR IMAGING | Comments Off on Approach to Pediatric Imaging
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