Scintillation camera radionuclide imaging with low-energy isotopes (iodine-125, caesium-131)

Anger cameras are normally used in the energy range from 70 keV to 400 keV. The main reason for this limitation is because of the bad intrinsic resolution at lower energies. But there are some clinical applications for camera investigations with low-energy isotopes. The authors therefore modified their camera by increasing the Z-signal amplification. The resolution and sensitivity were measured by comparing an ultra-fine low-energy collimator and an X-ray antidiffusion grid. The improvement of sensitivity from the X-ray grid was about twentyfold, but a decrease of intrinsic resolution was measured (factor: 1.8 comparing 125I with 99Tcsup(m)). In clinical investigations the modified camera was used together with the X-ray grid as a special kind of collimator inserted into a collimator changing system. Twenty patients were examined by thrombo-scintigraphy (125I-fibrinogen); in 20 patients kidney studies (125I-hippuric acid), and in 10 patients calf-muscle scans (131Cs-chloride) were carried out. The advantages of this system are as follows: simple modification of the Anger camera, a high sensitivity and the possibility of dynamic studies. The use is limited to organs near the body surface because of absorption. Another possible application is the demonstration of 125I-contaminations. (author)