S. James Cullom

Multicenter Clinical Trial to Evaluate the Efficacy of Correction for Photon Attenuation and Scatter in SPECT Myocardial Perfusion Imaging

BACKGROUND Soft tissue attenuation is a prominent cause of single-photon emission computed tomography (SPECT) imaging artifacts, which may result in reduced diagnostic accuracy of myocardial perfusion imaging. A method incorporating simultaneously acquired transmission data permits nonuniform attenuation correction and when incorporating scatter correction and resolution compensation may substantially reduce interpretive errors. METHODS AND RESULTS A prospective multicenter trial was performed recruiting patients with angiographically documented coronary disease (n=96) and group of subjects with a low likelihood of disease (n=88). The uncorrected and attenuation/scatter corrected images were read independently, without knowledge of the patients clinical data. The detection of >/=50% stenosis was similar using uncorrected perfusion data or with attenuation/scatter correction and resolution compensation (visual or visual plus quantitative analysis), 76% versus 75% versus 78%, respectively (P=NS). The normalcy rate, however, was significantly improved with this new methodology, using either the corrected images (86% vs 96%; P=0.011) or with the corrected data and quantitative analysis (86% vs 97%; P=0.007). The receiver operator characteristic curves were also found to be marginally but not significantly higher with attenuation/scatter correction than with tradition SPECT imaging. However, the ability to detect multivessel disease was reduced with attenuation/scatter correction. Regional differences were also noted, with reduced sensitivity but improved specificity for right coronary lesions using attenuation/scatter correction methodology. CONCLUSIONS This multicenter trial demonstrates the initial clinical results of a new SPECT perfusion imaging modality incorporating attenuation and scatter correction in conjunction with 99mTc sestamibi perfusion imaging. Significant improvements in the normalcy rate were noted without a decline in overall sensitivity but with a reduction in detection of extensive coronary disease.

The value and practice of attenuation correction for myocardial perfusion SPECT imaging: A joint position statement from the American Society of Nuclear Cardiology and the Society of Nuclear Medicine

ConclusionDespite advancements in technologies, non-uniform soft tissue attenuation still affects the diagnostic accuracy of single photon emission computed tomography (SPECT) myocardial perfusion imaging. A variety of indirect measures have been used to reduce the impact of attenuation, most notably electrocardiography-gated SPECT imaging. However, all available techniques have limitations, making interpretation in the presence of attenuation difficult. The ultimate solution, similar to positron emission tomography imaging, is to use hardware/software algorithms to eliminate attenuation and provide images that are more uniform and easier to interpret. Several attenuation correction solutions are currently available and more will be available soon. The value of these solutions has been varied, particularly with clinical applications. Guidelines and standards clearly are necessary.In recognition of the importance of this issue, the American Society of Nuclear Cardiology and the Society of Nuclear Medicine convened a joint task force to develop a position statement on attenuation correction. It is being published concurrently in the Journal of Nuclear Cardiology and The Journal of Nuclear Medicine, a first for these societies.The purpose of this position statement is to clarify the role of attenuation correction in SPECT procedures, to provide guidelines for its clinical use, and to provide a basis for the evaluation of published validation. It is hoped that this position statement will provide an important and useful road map to the widespread adoption of attenuation correction into clinical practice.

Patient-Centered Imaging: Shared Decision Making for Cardiac Imaging Procedures With Exposure to Ionizing Radiation

The current paper details the recommendations arising from an NIH-NHLBI/NCI-sponsored symposium held in November 2012, aiming to identify key components of a radiation accountability framework fostering patient-centered imaging and shared decision-making in cardiac imaging. Symposium participants, working in 3 tracks, identified key components of a framework to target critical radiation safety issues for the patient, the laboratory, and the larger population of patients with known or suspected cardiovascular disease. The use of ionizing radiation during an imaging procedure should be disclosed to all patients by the ordering provider at the time of ordering, and reinforced by the performing provider team. An imaging protocol with effective dose ≤3 mSv is considered very low risk, not warranting extensive discussion or written informed consent. However, a protocol effective dose >20 mSv was proposed as a level requiring particular attention in terms of shared decision-making and either formal discussion or written informed consent. Laboratory reporting of radiation dosimetry is a critical component of creating a quality laboratory fostering a patient-centered environment with transparent procedural methodology. Efforts should be directed to avoiding testing involving radiation, in patients with inappropriate indications. Standardized reporting and diagnostic reference levels for computed tomography and nuclear cardiology are important for the goal of public reporting of laboratory radiation dose levels in conjunction with diagnostic performance. The development of cardiac imaging technologies revolutionized cardiology practice by allowing routine, noninvasive assessment of myocardial perfusion and anatomy. It is now incumbent upon the imaging community to create an accountability framework to safely drive appropriate imaging utilization.

Electrocardiographically gated myocardial perfusion SPECT: Technical principles and quality control considerations

ConclusionGated SPECT studies provide important information about cardiac function that is independent of perfusion data. This is permitted by the generalization of the nongated SPECT study to sample the data temporally. The benefits of this approach are accompanied by new technical and clinical challenges related largely to interaction of varying rates of sinus rhythm and the response of the computer system. Identification of potential technical limitations is important, as is recognizing for which patients gated SPECT acquisition may not be suitable. These considerations should be part of a quality program to assure the highest quality of gated SPECT images and optimize the clinical utility of this important new method of acquiring SPECT images.

An introduction to attenuation correction

SummaryAttenuation correction techniques have demonstrated improved diagnostic accuracy and quality of myocardial perfusion SPECT images in limited studies. The future success of these methods relies largely on understanding the characteristics of the images and their interpretative meaning, as well as their limitations. It will be important to define the impact on patient management decisions, quantitation, laboratory efficiency, physician confidence, and communication of important findings. Advances in these areas will help position nuclear cardiology to compete with other imaging modalities. As this technology matures, the technologist has an essential role in ensuring efficient use of these techniques and maximizing the quality of this promising new way to image patients.

Attenuation and scatter compensation in myocardial perfusion SPECT.

Nonuniform attenuation, Compton scatter, and limited, spatially varying resolution degrade both the qualitative and quantitative nature of myocardial perfusion SPECT. Physicians must recognize and understand the effects of these factors on myocardial perfusion SPECT for optimal interpretation and use of this important imaging technique. Recent developments in the design and implementation of compensation algorithms and transmission-based imaging promise to provide clinically realistic solutions to these effects and provide the framework for truly quantitative imaging. This achievement should improve the diagnostic accuracy and cost-effectiveness of myocardial perfusion SPECT.

PROSPECTIVE STUDY OF ULTRA-LOW DOSE STRESS-ONLY SOLID-STATE SPECT: COMPARISON OF EFFICIENCY, DOSIMETRY AND OUTCOMES VERSUS TRADITIONAL-DOSE ATTENUATION-CORRECTED STRESS-ONLY ANGER SPECT (NCT01373944)

Stress-only (SO) SPECT is increasingly being used in symptomatic low-intermediate risk patients in order to minimize ionizing radiation. We tested whether ultra-low dose Tc-99m sestamibi (MIBI) utilizing new CZT-SPECT instrumentation might be as effective as usual-dose MIBI using Anger cameras with