Related Experiment Video
Updated: May 18, 2026
Retrospective Cardiac Gating with A Prototype Small-Animal X-ray Computed Tomograph
Published on: February 21, 2025
Approximate CT-free patient specific attenuation correction method for cardiac-dedicated pinhole CZT system: a
Michel Hesse1, Florian Dupont2, Véronique Roelants2
1Nuclear Medicine Department, Cliniques Universitaires Saint-Luc, 10 Avenue Hippocrate, 1200, Brussels, Belgium. michel.hesse@uclouvain.be.
Background:
Multi-pinhole cardiac-dedicated CZT gamma cameras improve clinical workflow by reducing acquisition duration and/or injected activities. As most of these systems lack integrated CT scanner, attenuation artifacts may appear in the reconstructed image depending on patient morphology. External CT-based attenuation correction is possible but requires manual SPECT-CT registration and increases patient absorbed dose. The aim of the present study was to develop an approach to estimate patient-specific attenuation maps directly from emission data acquired on a pinhole cardiac CZT camera.
Methods:
Two anthropomorphic torso phantoms were used. Their heart wall (with or without defects), liver insert and background cavity were filled with 99mTc solutions to simulate clinical activities. Reference acquisitions were obtained using a CZT SPECT/CT system. For each phantom, two acquisitions were performed on a pinhole cardiac CZT camera: a standard cardiac acquisition and a second acquisition with detectors radially moved away. Combination of both acquisitions enabled delineation of the body contour and segmentation of soft-tissue and lung regions. From this segmentation, a CT-free attenuation map was generated and imported into the manufacturer's reconstruction software to produce attenuation corrected (AC) images. These CT-free AC images were semi-quantitatively compared, using 17-segment polar maps, to (1) images corrected using a registered external CT, (2) AC images from the CZT SPECT/CT system, and (3) the true activity distribution in the phantoms. A three-dimensional voxel-wise comparison was also performed between CT-free AC and CT-based AC images of the pinhole CZT camera.
Results:
CT-free attenuation maps produced tracer distribution and 17-segment polar maps closely matching those obtained with CT-based attenuation correction. Heart wall defects in the anterior and inferior areas remained clearly visible except for half-obstructive defects. Differences relative to CZT SPECT/CT images were mainly attributable to camera geometry and reconstruction algorithm.
Conclusions:
The novel CT-free patient-specific attenuation correction method yields images comparable to CT-based AC images and shows good agreement with AC images from a CZT SPECT/CT system. This approach could enhance the diagnostic performance of current cardiac pinhole CZT cameras without requiring additional CT acquisitions.
