Gated SPECT
Encyclopedia
Gated SPECT - A nuclear medicine
imaging SPECT
(Single Photon Emission Computed Tomography) procedure where the ECG
(Electrocardiogram) guides the acquisition so that the resulting set of SPECT images shows the heart as it contracts over the interval from one R wave to the next.
The acquisition computer defines the number of time bins or frames to divide the R to R interval of the patient's electrocardiogram. A "window" may be set which discards data from R to R intervals which deviate from some amount from the patient's average R to R wave duration. This discards preventricular contractions and arrhythmias from the acquisition and improves the quality of the resulting study.
The camera will take a series of pictures around the patient, dividing each 'step' of the camera head's motion into the predetermined number of 'frames.' The details of this acquisition vary with single-headed, double-headed, or triple-headed cameras—but a single-headed camera typically acquires 32 'steps' over an arc of 180 degrees around the patient.
When the acquisition is completed, the technician must process the images (SPECT) to create a data set which represents the volume of tracer as seen by the camera during the study acquisition. In Gated SPECT, this process is performed for each of the time bins defined by the acquisition protocol. When viewed by the physician for interpretation, the heart can be watched as it contracts and expands from Diastole to Systole.
The computer can calculate for the physician the patient's ejection fraction
, end diastolic volume, wall motion, end systolic volume, myocardial thickening, shortening, and contractility. However, one is viewing an average of all collected heart beats over the image acquisition. Noise on the ECG, patient motion, artifacts, or a change in the heart rate during acquisition can degrade the quality of the resulting gated image dataset.
Nuclear medicine
In nuclear medicine procedures, elemental radionuclides are combined with other elements to form chemical compounds, or else combined with existing pharmaceutical compounds, to form radiopharmaceuticals. These radiopharmaceuticals, once administered to the patient, can localize to specific organs...
imaging SPECT
Single photon emission computed tomography
Single-photon emission computed tomography is a nuclear medicine tomographic imaging technique using gamma rays. It is very similar to conventional nuclear medicine planar imaging using a gamma camera. However, it is able to provide true 3D information...
(Single Photon Emission Computed Tomography) procedure where the ECG
Electrocardiogram
Electrocardiography is a transthoracic interpretation of the electrical activity of the heart over a period of time, as detected by electrodes attached to the outer surface of the skin and recorded by a device external to the body...
(Electrocardiogram) guides the acquisition so that the resulting set of SPECT images shows the heart as it contracts over the interval from one R wave to the next.
The acquisition computer defines the number of time bins or frames to divide the R to R interval of the patient's electrocardiogram. A "window" may be set which discards data from R to R intervals which deviate from some amount from the patient's average R to R wave duration. This discards preventricular contractions and arrhythmias from the acquisition and improves the quality of the resulting study.
The camera will take a series of pictures around the patient, dividing each 'step' of the camera head's motion into the predetermined number of 'frames.' The details of this acquisition vary with single-headed, double-headed, or triple-headed cameras—but a single-headed camera typically acquires 32 'steps' over an arc of 180 degrees around the patient.
When the acquisition is completed, the technician must process the images (SPECT) to create a data set which represents the volume of tracer as seen by the camera during the study acquisition. In Gated SPECT, this process is performed for each of the time bins defined by the acquisition protocol. When viewed by the physician for interpretation, the heart can be watched as it contracts and expands from Diastole to Systole.
The computer can calculate for the physician the patient's ejection fraction
Ejection fraction
In cardiovascular physiology, ejection fraction is the fraction of Blood pumped out of the Right Ventricle of the heart to the Pulmonary Circulation and Left Ventricle of the heart to the Systemic Circulation with each Heart beat or Cardiac cycle...
, end diastolic volume, wall motion, end systolic volume, myocardial thickening, shortening, and contractility. However, one is viewing an average of all collected heart beats over the image acquisition. Noise on the ECG, patient motion, artifacts, or a change in the heart rate during acquisition can degrade the quality of the resulting gated image dataset.