Acquisition
One day protocol:
- Fifteen min after stress injection, perform gated spect from 45° RAO to LPO, 32 views each 40 sec over 180° and high resolution collimator. Use 8 frames per cardiac cycle.
See Radiotracer Administration.- Repeat same acquisition 3 h - 4 h later at resting condition, 1 h after radiotracer administration and mild meal ingestion to clear hepatobiliary activity.
- For viability assessment, administer sublingual nitrates. Use of 5-10 mg isosorbide mononitrate 10 min before resting phase or reinjection, . Alternatively 5 mg nitroglycerin can be employed. It must be used cautiously in patients on erectile dysfunction medications, those with severe anemia and in cases with aortic stenosis or other preload-dependant cardiac pathologies. Likewise, if the resting viability phase follows stress with dypiridamole. In all these cases, keep patient supine for 30 min after the final acquisition, check blood pressure and allow the patient to go to the standing position gradually, in order to prevent fainting.
- Give iv aminophylline 125 mg if patient complains of headache or nausea/vomitus after the test.
Two day protocol:
- Same radiotracer dose for stress and rest acquisitions.
- Timing similar to one day protocol for stress and rest studies.
Right after the end of stress spect, check the acquisition to detect patient motion, bowel superimposition over the heart and attenuation. In females in the anterior wall and in males in the inferior wall. If so, a prone spect acquisition is useful in males to make a differential diagnosis with an infarction (fixed defect), because attenuation artefact will disappear from supine to prone spect.
As far as gating, adequate electrode installation is essential. Look for a neat QRS complex and tall R wave. In arrythmia due to premature contractions, use 10% window to exclude them, but this may prolong the acquisition. In atrial fibrillation it is better to accept all beat lengths. Depending of the arrythmia effect it would be wiser to perform a nongated acquisition and obtain satisfactory perfusion images.
References:
1 Mut F. Diagnostico de la Enfermedad Coronaria and Gonzalez P et al. Viabilidad Miocardica, in Medicina Nuclear Aplicaciones Clínicas. Ignasi Carrio y Patricio González . Editorial Masson, Barcelona España, 2003, p 39-56 and 105-119, respectively.
2 Hesse B et al. EANM/ESC procedural guidelines for myocardial perfusion imaging in nuclear cardiology. Eur J Nucl Med Mol Imaging. 2005 Jul;32(7):855-97.