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Beyond current guidelines: reduction in minimum administered radiopharmaceutical activity with preserved diagnostic
Frederic Fahey1, Katherine Zukotynski, David Zurakowski
1Division of Nuclear Medicine and Molecular Imaging, Boston Children's Hospital, Harvard Medical School, 300 Longwood Ave, Boston, MA, 02115, USA, frederic.fahey@childrens.harvard.edu.
Insights
Hepatobiliary scintigraphy in infants can use reduced radiopharmaceutical activity without compromising image quality. Enhanced planar processing (EPP) allows for significant activity reduction, potentially over 75%, while maintaining diagnostic interpretability.
Area of Science:
- Nuclear Medicine
- Pediatric Imaging
- Radiopharmaceutical Dosimetry
Background:
- Hepatobiliary scintigraphy is crucial for diagnosing pediatric liver and biliary tract conditions.
- Current guidelines recommend a minimum radiopharmaceutical activity (18.5 MBq) for infant studies.
- Reducing administered activity is desirable to minimize radiation exposure in infants.
Purpose of the Study:
- To evaluate if reduced radiopharmaceutical activity in infant hepatobiliary scintigraphy affects diagnostic image quality.
- To assess the efficacy of enhanced planar processing (EPP) in maintaining image quality with reduced activity.
Main Methods:
- 40 infants (10-270 days old) underwent hepatobiliary scintigraphy with (99m)Tc-mebrofenin or (99m)Tc-disofenin.
- Studies were performed with the minimum 18.5 MBq activity; simulated reduced activities (50%, 25%, weight-based) were created.
- Six nuclear medicine physicians assessed image quality (acceptability for clinical interpretation) with and without EPP.
Main Results:
- Full-activity studies (98%) were deemed acceptable.
- 50% reduced activity studies were acceptable with or without EPP, showing no significant difference from full activity.
- 25% reduced activity studies were unacceptable without EPP but became acceptable with EPP (P = 0.482).
Conclusions:
- Substantially reduced radiopharmaceutical activity is feasible for clinically interpretable infant hepatobiliary scintigraphy.
- EPP enables acceptable image quality with up to 75% activity reduction, significantly lowering radiation dose.
- These findings support revised activity guidelines for pediatric hepatobiliary scintigraphy.
Purpose:
To determine if the minimum administered radiopharmaceutical activity for hepatobiliary scintigraphy can be reduced while preserving diagnostic image quality using enhanced planar processing (EPP).
Methods:
A total of 40 infants between 10 and 270 days old (body mass 2.2 - 6.5 kg) had hepatobiliary scintigraphy during the period 2004 - 2010 following the intravenous administration of either (99m)Tc-mebrofenin (18 patients) or (99m)Tc-disofenin (22 patients). Due to the small size of these patients, they all received the minimum administered activity of 18.5 MBq consistent with the North American Consensus Guidelines. Six nuclear medicine physicians subjectively graded the acceptability of the image quality for clinical interpretation using a four-point scale (not acceptable, fair, good, excellent). Each physician independently graded seven image sets including the original study (full activity) and simulated reduced activity studies using binomial subsampling (50% of full activity, 25% of full activity and activity reduced by weight), with and without EPP.
Results:
For full-activity studies, 98% were deemed acceptable by the six physicians for clinical interpretation. The percentages of acceptable 50% reduced activity studies with and without EPP were not significantly different from the percentage of acceptable full-activity studies (P = 0.193 and P = 0.998, respectively). The percentage of acceptable 25% reduced activity studies without EPP was significantly different from the percentage of acceptable full-activity studies (P < 0.001); however, this difference vanished when EPP was applied (P = 0.482). The activity reduced by weight ranged from 1.85 to 4.81 MBq (10% to 26% of full dose) and the percentages of acceptable studies with and without EPP were significantly different from the percentage of acceptable full-activity studies (P < 0.001 and P = 0.02, respectively).
Conclusion:
Clinically interpretable hepatobiliary scintigraphy images can be obtained in infants when the minimum administered activity is substantially reduced. Without EPP, clinically acceptable images may be produced with a reduction of 50%, and with EPP, a reduction of 75% or more may be possible.
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