Scintillation gamma camera

In first instance, the spatial resolution of SPECT is determined by the gamma camera. The resolution of the scintillator-... 

Figure 9.13.C shows the gamma scintillation camera, gamma camera, originally developed by Anger. It consists of a two-dimensional array of 40 - 100 PMTs (often hexagonally formed for tight stacking) viewing a large flat Nal(Tl) crystal of 400 mm diameter and 5-10 mm thick, which is located behind a lead collimator containing numerous holes. Typical hole size is 2 - 3 mm diameter and 40 mm l gth. Collimator dimensions (Fig. 9.13.D) depend on the E for is 0.2 - 0.3 mm.

Bill recognized immediately the importance of the invention of the scintillation camera, and persuaded Professor Charles Doan, head of the Department of Internal Medicine at Ohio State, to place an order for the first commercial version. This camera was to be built by a new company. Nuclear Chicago, under the leadership of John Kuranz, President. The company was founded in 1947 by John Kuranz and others from the nuclear reactor laboratory of Em-ico Fermi at the University of Chicago. By the early 1970s, Ohio-Nudear of Solon, Ohio, as well as Picker Medical and General Electric, were also providing gamma cameras to hospitals. 

The scintillation camera is the primary imaging instrument used in nuclear medicine and is often referred to as a gamma camera The scintillation camera is a position-sensitive gamma ray imager. Although the entire field of view is available for detection, it processes one event at a time. The spatial resolution is approximately 10 mm and it yields a count rate of 200 to 300 cpm//iCi in the field of view (cpm = counts per minute). The field of view covers a large portion of the body and is typically 40 X 50 cm, although other sizes are available. 

Gamma camera performance is determined primarily by collimator design and the characteristics of the scintillation material. In the case of a parallel colhmator, the colhmator design parameters are the hole diameter, their number, the distance between the holes (hole pitch), and the collimator thickness. The specific combination of these affects the sensitivity and the spatial resolution of the camera. Likewise, thick scintillating material limits spatial resolution, whereas a thin scintillation crystal yields lower sensitivities. 

Instillation. Particles are instilled by bronchoscopy directly onto the tracheal epithelium. Radiolabeled particles can be measured by a gamma-camera (20-23) or by scintillation detectors (8,24-28). The motion of large particles has been measured directly using cinephotography (29) or radiography (30,31). 

Gamma (y) Sodium iodide doped with thallium iodide are used pSlal(Tl)] thallium, which is present at 0.1-0.4% of sodium emits 420 nm scintillations. This phosphor is very efficient in absorbing y-radiation because of high atomic number of iodine and high density of sodium iodide. Sodium iodide is hermetically sealed. It is normally used in well counters. A typical well counter used in laboratory and that used in cameras in nuclear medicine are show in Figs. 3 and 4. 

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