Transthyretin cardiac amyloidosis (ATTR-CA) is traditionally diagnosed using planar bone scintigraphy with a Perugini visual score ≥ 2. Fast cardiac CZT-SPECT will be evaluated for its ability to reproduce this classification and provide reproducible quantitative myocardial uptake metrics.

Transthyretin cardiac amyloidosis (ATTR-CA) has emerged as a major cause of infiltrative cardiomyopathy, and early diagnosis is associated with improved prognosis. ATTR is now recognized far more frequently than in the past, owing to increased clinical awareness and advances in non-invasive imaging strategies, including planar bone scintigraphy.

In the absence of monoclonal gammopathy, a Perugini grade ≥ 2 on planar bone scintigraphy constitutes a highly specific diagnostic criterion for ATTR-CA, obviating in most cases the need for endomyocardial biopsy. Consequently, planar bone scintigraphy acquired with conventional Anger cameras has become the reference method in this setting.

In recent years, full-ring cadmium-zinc-telluride (CZT) single-photon emission computed tomography (SPECT) whole-body cameras have rapidly emerged. These systems offer enhanced image quality and count sensitivity, mainly due to the high intrinsic detection efficiency of CZT detectors and a dedicated full-ring geometry that optimizes photon collection over the patient's body or specific organs of interest. They have enabled the development of ultrafast three-dimensional acquisitions combined with SUV-based image scaling, thereby improving patient comfort and throughput, while also allowing lesion quantification.

However, the ability of rapid CZT-SPECT/CT acquisitions to accurately replicate the ATTR-CA diagnostic information obtained from standard planar imaging remains insufficiently documented. Furthermore, although CZT-SPECT/CT technology allows for precise quantification, it has not yet been established whether Standard Uptake Value (SUV) based parameters can serve as reliable and reproducible imaging biomarkers for ATTR-CA Therefore, the aim of this retrospective study will be to (i) evaluate whether fast CZT-SPECT recordings can reproduce the diagnosis of ATTR-CA obtained using Perugini scoring on standard planar images, either by applying Perugini scoring to planar projections or by using quantitative parameters, and (ii) compare the reproducibility of these approaches.

Inclusion Criteria:

• Patients who were routinely referred for bone scintigraphy for suspected transthyretin cardiac amyloidosis (ATTR-CA) between April 2024 and April 2025.

Exclusion Criteria:

• Patients who object to the use of their data

Retrospectively enrolled patients routinely referred for bone scintigraphy for suspected transthyretin cardiac amyloidosis (ATTR-CA) . During this period, a rapid three-dimensional CZT-SPECT cardiac acquisition was systematically attempted in addition to conventional planar imaging, depending on camera availability, for diagnostic purposes, particularly for identifying blood-pool activity and other extracardiac confounding uptake areas