Advances in technical aspects of myocardial perfusion SPECT imaging

Abstract

Although myocardial perfusion SPECT (MPS) imaging is widely used in current clinical practice, it suffers from some fundamental limitations including long image acquisition, low image resolution, and patient radiation dose. In the last two decades, MPS was performed most commonly by standard dual-head scintillation cameras with parallel-hole collimators, typically configured in a 90°detector geometry and image reconstruction based on standard filtered-back projection algorithms. The required scan times were as along as 15-20 minutes for each stress and rest MPS acquisition to provide adequate imaging statistics, resulting in long overall test times and frequent artifacts caused by patient motion during the scan as well as compromised patient comfort. Recently, it has become very important to address these limitations, since MPS has new competitors in the non-invasive imaging arena most notably coronary CT angiography (CCTA), which allow diagnostic imaging in a very short time. In addition, a practice of combining MPS with other modalities such as CCTA for better diagnostic certainty 1 has intensified concerns regarding total radiation dose delivered to the patient. 2 The radiation dose and acquisition time are intrinsically linked with each other, as longer acquisition times could be used with lower injected doses and higher doses could be used to shorten acquisition times.There have been significant recent efforts by industry and academia to develop new imaging systems with increased sensitivity and new methods of image reconstruction optimizing image quality, which will simultaneously allow higher photon sensitivity and improve both image quality and resolution. These efforts address the main limitations of MPS by combining several approaches such as changing the detector geometry and optimizing tomographic sampling of the field of view for myocardial imaging, improving the detector material and collimator design, and optimizing the image reconstruction algorithms. In this review article we summarize these developments. NEW HARDWARE FOR OPTIMIZED MPS IMAGINGSeveral new dedicated hardware camera systems with optimized acquisition geometry, collimator design, and associated reconstruction software have been recently introduced by various vendors. Innovative designs of the gantry and detectors have been proposed which allow increased sampling of the myocardial region, and thus allow better local sensitivity. These systems combine an improvement in spatial resolution and sensitivity. By faster imaging times due to increased sensitivity and by eliminating the need to position the patient's arms above the head by imaging in an upright or reclining position, patient comfort is dramatically improved. As a consequence of faster imaging times and more comfortable patient positioning, these systems have the additional benefit of reducing patient motion during a scan. Furthermore, claustrophobic effects are reduced and the floor space requirements are more flexible since the new detectors and the associated mechanical are ...

Nuclear myocardial perfusion imaging using thallium-201 with a novel multifocal collimator SPECT/CT: IQ-SPECT versus conventional protocols in normal subjects

“…Several types of gamma cameras have recently been introduced with semiconductor material instead of the conventional sodium iodine crystals [5]. This improvement is achieved by means of a multifocal collimator that rotates around the patient in a cardio-centric orbit resulting in a four-fold magnification of the heart while keeping the entire torso in the field of view.…”

“…Multifocal collimators with dedicated reconstruction software have been introduced [4][5]. This IQ-SPECT system with 99m Tc agents reportedly shortens scan times and considered to be clinically applicable in diagnosing patients with coronary artery disease [4].…”

Optimization of iterative reconstruction parameters with attenuation correction, scatter correction and resolution recovery in myocardial perfusion SPECT/CT

“…The latest iterative reconstruction technologies (5,6) are commercially available as Flash 3D (Siemens Medical Solutions, Erlangen, Germany) (7)(8)(9), Astonish (Philips Medical Systems, Milpitas, CA, USA) (10)(11)(12), Evolution for Cardiac (GE Healthcare, Waukesha, WI, USA) (13) and wide beam reconstruction (UltraSPECT, Haifa, Israel) (13,14). Since noise reduction algorithm is incorporated into the latest iterative reconstruction processing as well as AC, SC and RR, half time cardiac SPECT imaging became feasible (11,(13)(14)(15)(16).…”

Dedicated cardiac cameras: a new option for nuclear myocardial perfusion imaging

“…Nevertheless, MPI is still affected by several drawbacks that are inherent to any nuclear technique with low photon flux, like attenuation due to non-uniform tissue, motion artefacts due to time-consuming scan and radiation exposure [2]. Therefore, shortening scan acquisition and reducing radiation dose without decreasing image quality are of the utmost importance for nuclear MPI in maintaining its central role in the management of patients with suspected or known CAD, especially in an era of impressive advances in coronary computed tomography (CT), cardiac magnetic resonance and ultrasound imaging.…”

“…Moreover, various new dedicated hardware camera systems with optimized acquisition geometry, collimator design and associated reconstruction software have been recently introduced by several manufacturers [2,[4][5][6][7]. These cameras vary in the number and type of scanning or stationary detectors and in whether NaI or cadmium zinc telluride (CZT) solid-state detectors are employed.…”