The 360-degree orbit is most often used in SPECT studies EXCEPT for scans of

Question

Quizplus · Accepted Answer

The theory of SPECT requires that the scintillation camera acquire enough images of the patient at different angles to obtain a complete description of the distribution of the radioactive tracer.Several projections over a 180-degree orbit would be satisfactory if there were no scatter or attenuation.Because this is not often the case, 360-degree orbits are used for most SPECT studies (the exception is cardiac SPECT).The heart is located forward and to one side of the center of the thorax, resulting in a great deal of attenuation when the camera is behind the patient.The angles chosen for the 180 degrees are those closest to the heart, from 45 degrees right anterior oblique (RAO) to 45 degrees left posterior oblique (LPO).These projections are affected least by attenuation, scatter, and detector response because they are the closest to the heart.Reconstructions from 180-degree acquisitions have higher resolution and contrast than those from 360-degree acquisitions.

The 360-Degree Orbit Is Most Often Used in SPECT Studies