Biliary system (cholescintigraphy) Scintigraphy of the
biliary system is called
cholescintigraphy and is done to diagnose obstruction of the
bile ducts by a gallstone (
cholelithiasis), a tumor, or another cause. It can also diagnose
gallbladder diseases, e.g. bile leaks of
biliary fistulas. Many centres now routinely use
SPECT (single-photon emission computed tomography) rather than just planar imaging for V/Q scans; in a survey of Australia, Canada, France, Germany, and the United States, over
80 % of centres used SPECT for acute pulmonary embolism diagnosis, and in >70 % of those combined it with CT imaging. Less common indications include evaluation of
lung transplantation, preoperative evaluation, evaluation of
right-to-left shunts. In the ventilation phase of a ventilation/perfusion scan, a gaseous radionuclide
xenon or
technetium DTPA in an aerosol form (or ideally using Technegas, a radioaerosol invented in Australia by Dr Bill Burch and Dr Richard Fawdry) is inhaled by the patient through a mouthpiece or mask that covers the nose and mouth. The perfusion phase of the test involves the intravenous injection of radioactive technetium
macro aggregated albumin (Tc99m-MAA). A gamma camera acquires the images for both phases of the study.
Bone For example, the ligand
methylene-diphosphonate (MDP) can be preferentially taken up by bone. By chemically attaching
technetium-99m to MDP, radioactivity can be transported and attached to bone via the
hydroxyapatite for imaging. Any increased physiological function, such as a fracture in the bone, will usually mean increased concentration of the tracer.
Heart A
thallium stress test is a form of scintigraphy, where the amount of
thallium-201 detected in cardiac tissues correlates with tissue blood supply. Viable cardiac cells have normal
Na+/K+ ion exchange pumps. Thallium binds the K+ pumps and is transported into the cells. Exercise or
dipyridamole induces widening (
vasodilation) of normal coronary arteries. This produces coronary steal from areas of ischemia where arteries are already maximally dilated. Areas of infarct or
ischemic tissue will remain "cold". Pre- and post-stress thallium may indicate areas that will benefit from myocardial
revascularization. Redistribution indicates the existence of
coronary steal and the presence of ischemic
coronary artery disease.
Parathyroid Tc99m-
sestamibi is used to detect
parathyroid adenomas.
Thyroid To detect metastases/function of thyroid, the isotopes
technetium-99m or
iodine-123 are generally used, and for this purpose the iodide isotope does not need to be attached to another protein or molecule, because thyroid tissue takes up free iodide actively.
Renal and urinary systems Full body Examples are
gallium scans,
indium white blood cell scans,
iobenguane scan (MIBG) and
octreotide scans. The MIBG scan detects adrenergic tissue and thus can be used to identify the location of
tumors such as
pheochromocytomas and
neuroblastomas. ==Function tests==