Instrumentation

Gamma Camera

Gamma Camera is the most commonly used equipment for nuclear imaging. It consists of the following Fig.

1) A large sodium iodide crystal, which is a scintillation type of detector of gamma rays, which produces scintillations when gamma rays fall on it.

2) A large number of photomultiplier tubes, which amplify the light signal and convert it to electrical signal for further processing.

3) A collimator, a sheet of lead or tungsten between the crystal and the patient, achieves better resolution of images
 

4) A computer and electronics to process the signals and reconstruct the images.

Dual head gamma camera - Different collimators

Single and multi-crystal or double and triple detector cameras are available these days. Planar imaging gives typically three standard views anterior, left anterior oblique and left lateral. This is currently replaced by SPECT (single photon emission computerized tomography), which allows cut sections or slices of left ventricle walls in three planes transverse, sagittal and coronal. Gated SPECT is a further refined form of SPECT, where imaging is done with ECG gating.

PET

PET cameras can image positron emitting tracers. Each positron emits two gamma rays which are detected by a pair of detector systems. High count rate images obtained by PET are of superior quality and resolution. These are newer techniques used to image myocardial energy metabolism.