Cardiac DPD-uptake time dependency in ATTR patients verified by quantitative SPECT/CT and semiquantitative planar parameters

Abstract

Background: Bone scintigraphy plays an important role in the diagnosis of cardiac Transthyretin-Related Amyloidosis (ATTR). The mechanism of myocardial tracer accumulation and its dependence over time are not fully understood. Recently, a scintigraphic quantification of the cardiac amyloid deposition has been discussed. Nevertheless, little is known regarding the right time of quantitative imaging.

Methods: The geometrical mean of decay corrected total counts over the heart and the heart/whole-body ratio (H/WB) were evaluated in 23 patients undergoing DPD-bone scan with planar whole-body images 1 and 3 hours post injection (p.i.). Myocardial standard uptake values (SUV)peak were assessed in another 15 patients with quantitative SPECT/CT imaging 1 hours and 3 hours p.i..

Results: Total counts over the heart (1 hours p.i.: 81,676 cts, range 69,887 to 93,091 cts and 3 hours p.i.: 64,819 cts, range 52,048 to 86,123 cts, P = .0005) and H/WB ratio (1 hours p.i.:0.076 ± 0.020 and 3 hours p.i. 0.070 ± 0.022; P = .0003) were significantly increased 1 hours p.i.. Furthermore median myocardial SUVpeak (1 hours p.i.:12.2, range 9.6 to 18.9 and 3 hours p.i.: 9.6, range 8.2 to 15.0, P = 0.0012) was also significantly higher after 1 hours p.i. compared to 3 hours p.i..

Conclusion: Cardiac DPD activity and myocardial SUVpeak are time-dependent, which should be considered when using quantitative bone scintigraphy in ATTR patients.

Keywords: ATTR; Amyloidosis; SPECT/CT; SUV; quantification; therapy monitoring.

Figure 1

Time-dependent DPD tracer uptake kinetics of the heart using planar imaging. A The decay corrected geometric mean of the myocardial total counts was significantly reduced 3 hours p.i. compared to 1 hours p.i. (1 hours p.i: 81,676 cts, range 69,887 to 93,091 cts and 3 hours p.i.: 64,819 cts, range 52,048 to 86,123 cts, *P = .0005). B For the H/CL 1 hours and 3 hours p.i., no significant difference could be observed between 1 and 3 hours p.i. (1 hours p.i: 2.2 ± 0.44 and 3 hours p.i 2.25 ± 0.57, P = .24). C The H/WB was significantly increased 1 hours p.i. compared to 3 hours p.i. (1 hours p.i.: 0.076 ± 0.020 and 3 hours p.i.: 0.070 ± 0.022; **P = .0003)

Figure 2

Time-dependent DPD tracer uptake kinetics using quantitative SPECT analysis. A Myocardial SUV peak was significantly increased 1 hours p.i. compared to 3 hours p.i. (1 hours p.i.: median SUVpeak: 12.2, range 9.6 to 18.9 and 3 hours p.i.: median SUVpeak: 9.6, range 8.2 to 15.0, ***P = 0.0012). B However, bone SUVpeak was significantly increased 3 hours p.i. compared to 1 hours p.i. (1 hours p.i.: median SUVpeak: 3.8, range 3.6 to 4.5 and 3 hours p.i.: median SUVpeak: 5.6, range 4.7 to 6.4; ****P = 0.0007). C Retention index similar to myocardial SUVpeak was significantly increased 1 hours p.i. compared to 3 hours p.i. (1 hours p.i.: 4.6, range 2.6 to 5.0 and 3 hours p.i.: 3.0, range 1.9 to 3.7; *****P = 0.04)

Figure 3

Example images of a patient with increased myocardial uptake 1 hours p.i. compared to 3 hours p.i. Anterior and posterior planar DPD-bone scintigraphy 1 hours and 3 hours p.i. of a patient with strong myocardial and soft tissue (decay corrected geometric mean of the total counts over the heart: 61,922 cts, H/CL ratio: 2.07, H/WB-ratio: 0.053), and mild bone uptake graded as Perugini score 3 1 hours p.i.. (left side). The same patient with moderate myocardial (myocardial SUVpeak 7.7; decay corrected geometric mean of the total counts over the heart: 37,217 cts, H/CL ratio 1.82, H/WB 0.043), reduced soft tissue and mild bone tracer uptake graded as Perugini grade 2 3 hours p.i. (right side)