Physics and Radiobiology of Nuclear Medicine

186 13. Positron Emission Tomography ularly if the annihilation occurs at the edge of the FOV. This also adds to the timing reso ...

PET Scanners 187 Detector 1 Detector 2 A Pulse 1 Pulse 2 Pulse 1 1 2 Coincidence Detector 2 Detector 1 B Pulse 2 12 Coincidence ...

188 13. Positron Emission Tomography limit, and all other annihilation events overlapping in their time widths (Fig. 13.3C) will ...

PET/CT Scanners 189 PET/CT Scanners Parallel to SPECT/CT systems, PET/CT has been developed, in which func- tional PET images ar ...

photons in the patient do not interfere with the CT scan, because of the high intensity of the CT photon beam. Fusion of the two ...

Hybrid Gamma Cameras Conventional dual-head and triple-head gamma cameras (Fig. 12.2) can be utilized as PET cameras by connecti ...

Next, the four pulses (A, B, C, and D) are summed up to give a Zpulse, which is then checked by the PHA if its amplitude is with ...

and the angle of orientation (f) of the LOR (i.e., the angle between rand the vertical axis of the field). A matrix of an approp ...

Two-Dimensional Versus Three-Dimensional Data Acquisition Coincident counts detected by a detector pair are called the promptswh ...

spatial resolution as a trade-off. The overall sensitivity in 2-D acquisition is 2 to 3% at best. To improve further the sensiti ...

Image Reconstruction Image reconstruction of 2-D PET data is accomplished by the same filtered backprojection and iterative meth ...

(13.3) where Ameanis the mean of all pixel counts and Aiis the counts in the ith pixel. The observed count Ciin the ith pixel fr ...

transmission scan is performed before the emission scan to avoid interfer- ence of radiations from the administered radioactivit ...

photons of PET by applying a scaling factor defined by the ratio of mass attenuation coefficient of 511-keV photons to that of 7 ...

Scatter Coincidences Annihilation radiations may undergo Compton scattering while passing through the body tissue and, due to hi ...

detector. However, as can be seen from Figure 13.11, the use of a larger diameter of the ring improves this effect. Correction c ...

Detector size. In the absence of collimators, unlike in SPECT, the intrin- sic resolution Riis the predominant factor in spatial ...

Reconstruction method. If the filter backprojection method is used for reconstruction, the choice of filter with a selected cut- ...

The transaxial spatial resolution typically ranges from 5 mm to 7 mm at 10 cm and the axial spatial resolution from 5.4 mm to 6. ...

where T,S, and Rare the true, scatter, and random coincidences, respec- tively. It serves as a parameter to compare the performa ...