A practical method of I-131 thyroid cancer therapy dose optimization using estimated effective renal clearance.

In thyroid cancer patients with renal impairment or other complicating factors, it is important to maximize I-131 therapy efficacy while minimizing bone marrow and lung damage. We developed a web-based calculator based on a modified Benua and Leeper method to calculate the maximum I-131 dose to reduce the risk of these toxicities, based on the effective renal clearance of I-123 as measured from two whole-body I-123 scans, performed at 0 and 24 h post-administration.

Difference in appearance between prone and supine myocardial perfusion images obtained on a high-efficiency cadmium zinc telluride SPECT camera.

OBJECTIVE: The recent introduction of high-efficiency solid-state gamma cameras for myocardial perfusion single photon emission computed tomography has enabled lower patient radiation dose, faster imaging, and improved image quality. However, artifacts still complicate interpretation. Prone imaging is a common maneuver to reduce artifacts and increase accuracy for detection of coronary artery disease, but its effect on imaging relative to supine imaging has not been fully characterized in these new systems. METHODS: In this IRB-approved, HIPAA-compliant retrospective study, 30 patients were reviewed, who underwent prone and supine imaging on the GE 530c multipinhole cadmium zinc telluride camera under both rest and stress conditions. Informed consent was waived. Perfusion was scored visually by two readers on a five-point scale according to the 17-segment model. Differences were assessed for significance using a multivariate linear effects model and restricted maximum likelihood method. RESULTS: Prone positioning resulted in increased activity in the basal inferior (P<0.001), basal inferolateral (P=0.009), basal inferoseptal (P<0.001), and mid-inferior (P<0.001) segments when taking into account factors such as stress versus rest, perfusion scores of other segments, and reader. CONCLUSION: Prone imaging on the GE 530c camera increases measured tracer activity in the basal inferior, basal inferolateral, basal inferoseptal, and mid-inferior segments. Caution is advised when diagnosing myocardial ischemia in these territories, particularly if clinical data are unavailable.