RESUMO
BACKGROUND: Cardiac imaging with bone-avid tracers for the diagnosis of ATTR cardiac amyloidosis employs only limited quantification, but SPECT/CT acquisition can provide volumetric assessment with quantification of tracer uptake. Tafamidis is routinely used in the treatment of cardiac amyloidosis but there is scant data on changes in imaging results during therapy. The purpose of this study was to perform longitudinal assessment of Tc-99m-PYP imaging to determine if tafamidis therapy results in any change in quantitative measures of tracer uptake. METHODS: A prospective, single-center study of ATTR patients being treated with tafamidis using Tc-99m-PYP SPECT/CT to quantify cardiac tracer uptake in the whole heart and left ventricle. Standardized uptake values (SUVs) were adjusted for blood pool activity. Comparison of baseline activity was made to values obtained approximately every 6 months during treatment. RESULTS: Twenty-two patients (77.0 ± 7.5 years old, 86.4% male) were on tafamidis for 15.3 ± 4.0 months with an average time between baseline and final follow-up study of 16.8 ± 4.7 months. Thirteen (59.1%) had multiple follow-up amyloid studies. Statistically significant reductions in total SUVs, SUV volume, and percentage of injected dose were seen. Adjusted for the maximal aortic SUV, the total SUV's in the left ventricle decreased by 36.9%, the SUV volume by 38.7%, and the percentage of injected dose decreased by 34.9% (all p-values ≤0.0001). Over the study duration there was a decrease of 7.7%/month in the measured metrics. CONCLUSION: The quantitative SUV measurements from Tc-99m-PYP SPECT/CT revealed an overall decrease in scintographic amyloid burden during the course of tafamidis therapy, but additional work is needed to determine the optimal metrics and improve the reproducibility of the quantification.
RESUMO
BACKGROUND AND PURPOSE: To assess benefits of hybrid (single photon emission computerized tomography [SPECT]/computed tomography [CT]) imaging over SPECT imaging only in the management of young athletes with low back pain (LBP) due to suspected pars interarticularis fracture. METHODS: Retrospectively reviewed medical records of 163 consecutive patients who had radionuclide SPECT imaging for evaluation of LBP between January 1, 2010 and December 30, 2015. All enrolled patients were divided into two groups (group 1: patients with radionuclide SPECT imaging only and group 2: patients with radionuclide hybrid imaging). Radiation dose, cost benefits, and mean duration of delay in complete diagnosis were assessed and compared using Fisher's exact test. RESULTS: A total of 91 patients were enrolled after applying inclusion and exclusion criteria. The volume CT dose index and dose length product (DLP) estimated for a scan length of 10 cm (DLP 10) were significantly lower for patients in group II (CTDIvol ) (P = .001 and P = .001). Although, there was no significant difference in actual DLP (P = .52). There was a median delay of 7 days (interquartile range 2-10 days) for complete diagnosis in group I patients. Least expensive imaging for early definitive diagnosis required for the treatment decisions was in patients who had a radionuclide Technetium-99m methylene diphosphonate bone scan with limited lumbar spine planar and SPECT imaging followed by a thin slice, limited CT performed only when SPECT imaging was positive for an active pars interarticularis fracture. No significant difference in the management of patients between the groups (P = .47). CONCLUSION: Hybrid imaging should be preferred over SPECT only imaging for initial evaluation of suspected pars interarticularis fracture in young athletes with LBP.