EANM procedural guidelines for myocardial perfusion scintigraphy using cardiac-centered gamma cameras

Abstract

An increasing number of Nuclear Medicine sites in Europe are using cardiac-centered gamma cameras for myocardial perfusion scintigraphy (MPS). Three cardiac-centered gamma cameras are currently the most frequently used in Europe: the D-SPECT (Spectrum Dynamics), the Alcyone (Discovery NM 530c and Discovery NM/CT 570c; General Electric Medical Systems), and the IQ-SPECT (Siemens Healthcare). The increased myocardial count sensitivity of these three cardiac-centered systems has allowed for a decrease in the activities of radiopharmaceuticals injected to patients for myocardial perfusion imaging and, consequently, radiation exposure of patients. When setting up protocols for MPS, the overall objective should be to maintain high diagnostic accuracy of MPS, while injecting the lowest activities reasonably achievable to reduce the level of radiation exposure of patient and staff. These guidelines aim at providing recommendations for acquisition protocols and image interpretation using cardiac-centered cameras. As each imaging system has specific design and features for image acquisition and analysis, these guidelines have been separated into three sections for each gamma camera system. These recommendations have been written by the members of the Cardiovascular Committee of EANM and were based on their own experience with each of these systems and on the existing literature.

Keywords: CZT gamma camera; Cardiac SPECT; Myocardial perfusion scintigraphy; Procedural guidelines.

Fig. 1

Example of quality control screens of MPS acquisitions with the D-SPECT camera. a Before starting the tomographic acquisition, a scout view is acquired that lasts 20–40 s to confirm that the detector arm is well positioned in the vertical axis and is close enough from the heart. The images located in the first row show that the detectors are well positioned in the vertical axis and include the whole heart in the field of view (left and middle images). Nevertheless, the heart (red circle, right image) is too far from the optimal position (circle with gray dotted line). Acquisition with the heart in this position may result in poor image quality. Efforts should be made to bring the detector arm closer from the chest and the heart of the patient. The duration of this low-dose stress acquisition after injection of a ^99mTc-labeled perfusion tracer was calculated at 8 min 42 s to reach an estimated LV myocardial count set at 1 million in the region of interest placed on the cardiac region on the scout view. b After the acquisition, a sinogram allows for the identification of patient movements in the horizontal axis and two panograms (for the two parts of the acquisitions separated by a movement of all the detectors in the arm) for the detection of movements in the vertical axis. Note the presence of patient movements in the vertical axis during the second part of the acquisition. In addition, the histogram shows all R-R intervals during the acquisition. Note the presence of abnormal short and long R-R intervals corresponding to extrasystolic and post-extrasystolic cardiac cycles. At the end of the acquisition, abnormal R-R intervals can be excluded from the gated reconstruction using the two red lines

Fig. 2

Example of quality control screens of MPS acquisitions with the GE camera using the Alcyone technology. a Before starting the tomographic acquisition, a scout view is acquired that lasts 20–40 s to confirm that the patient is well positioned in the vertical axis. The images located in the first row shows that the detectors is well positioned in the three axes and includes the whole heart in the field of view. The yellow cross (right images, in the three axes) should be placed the closest to the center of the heart. The duration of this low-dose stress acquisition after injection of a ^99mTc-labeled perfusion tracer was calculated at 6 min to reach an estimated LV myocardial count set at 1 million in the region of interest placed on the cardiac region on the scout view. b During the acquisition, a histogram shows all R-R intervals included in the acquisition. Note the presence of abnormal short and long R-R intervals corresponding to extrasystolic and post-extrasystolic cardiac cycles. At the end of the acquisition, abnormal R-R intervals can be excluded from the gated reconstruction. The proportion of accepted cardiac cycles should be sufficient to preserve image quality of gated images and obtain reliable values for LVEF. c At the end of the acquisition, on the right of the screen, the final quality of the three transaxial axes should be evaluated

Fig. 3

Example of quality control screens of MPS acquisitions with IQ-SPECT. a Before starting the tomographic acquisition, the entire patient set-up adds just one additional step to identify the position of the heart on the touch screen patient positioning monitor. The patient is placed on the bed in either supine or prone position, arms up, and moved under the nuclear detectors until the heart is approximately centered in the axial direction. The center of the projection of the heart on each detector is marked on the patient positioning monitor, allowing for the calculation of the location of the patient’s heart in 3-dimensional space. This will become the center of the cardio-centric orbit. The acquisition can then be started. The best way to immediately assess the quality of an IQ-SPECT study data is to load the raw projection series into the syngo Viewing tab. The projection data from a patient that has been positioned correctly will show a magnified heart at the center of every image as in the above example labeled Raw Projection Series. b There is a simple method to determine whether sufficient counts have been collected to produce an acceptable result in the reconstructed images. Load the projection data into the syngo Viewing tab and advance through the images to view 18 as in the example image below. This is the projection which contains the LAO view of the heart. Under the tool’s drop-down menu choose Circle or Freehand. Draw an ROI over the lateral wall as shown in the image below. Image statistics within the ROI will be calculated. It is important that the mean counts in the ROI over the lateral wall be at least 9 counts. c Acquisitions acquired with SMARTZOOM collimators can only be corrected for motion using the dedicated automatic motion correction tool and mask method. The operator should first review the data and determine if motion correction is required. One important factor in successful motion correction is the placement of the mask. In cases of extreme motion, it is best to try and re-image the patient