A Routine PET/CT Protocol with Streamlined Calculations for Assessing Cardiac Amyloidosis Using (18)F-Florbetapir

Abstract

Introduction: Cardiac amyloidosis is a rare condition characterized by the deposition of well-structured protein fibrils, proteoglycans, and serum proteins as amyloid. Recent work has shown that it may be possible to use (18)F-Florbetapir to image cardiac amyloidosis. Current methods for assessment include invasive biopsy techniques. This work enhances foundational work by Dorbala et al. by developing a routine imaging and analysis protocol using (18)F-Florbetapir for cardiac amyloid assessment.

Methods: Eleven patients, three healthy controls and eight myloid positive patients, were imaged using (18)F-Florbetapir to assess cardiac amyloid burden. Four of the patients were also imaged using (82)Rb-Chloride to evaluate possible (18)F-Florbetapir retention because of reduced myocardial blood flow. Quantitative methods using modeling, SUVs and SUV ratios were used to define a new streamlined clinical imaging protocol that could be used routinely and provide patient stratification.

Results: Quantitative analysis of (18)F-Florbetapir cardiac amyloid data were compiled from a 20-min listmode protocol with data histogrammed into two static images at 0-5, 10-15, or 15-20 min. Data analysis indicated the use of SUVs or ratios of SUVs calculated from regions draw in the septal wall were adequate in identification of all healthy controls from amyloid positive patients in this small cohort. Additionally, we found that it may be possible to use this method to differentiate patients suffering from AL vs. TTR amyloid.

Conclusion: This work builds on the seminal work by Dorbala et al. by describing a short (18)F-Florbetapir imaging protocol that is suitable for routine clinical use and uses a simple method for quantitative analysis of cardiac amyloid disease.

Keywords: Florbetapir; PET/CT; amyloid; amyloidosis; cardiac.

Figures

Figure 1

Shows a 20-min acquisition of healthy (A) and amyloid positive (B) patients. Both images were acquired at 1 h post injection.

Figure 2

Shows average myocardial TACs for healthy and amyloid positive populations.

Figure 3

Shows boxplots of SUV ratios for all healthy and amyloid positive patient groups.

Figure 4

Shows liver TACs for average values of healthy control and amyloid positive groups.

Figure 5

Shows a comparison of liver uptake in healthy and diseased populations. These images show that using the liver as a reference point for quantitative measurements is risky as significant uptake is seen even in healthy controls. This is further exacerbated as TAC comparisons between TTR and controls are nearly indistinguishable.

Figure 6

Shows control and amyloid positive patient data imaged from three of the initial 0–80 min acquisitions. Each image from left to right shows the progression of time at approximately 5, 10, 30, and 60 min intervals.