Computed tomography (CT) is a well-established aid in the preoperative assessment of the dimension of mandible and maxilla for endo-osseous implant installation. CT is a valuable tool for the measurement of the alveolar ridge and recognition of the course of the inferior alveolar nerve canal. In the present study, three different techniques were examined: normal CT images with coronal and sagittal slices, standard reconstructions based on axial slices, and multiplanar reconstruction and display (MPR/MPD), also based on axial slices. Six dissected human jaw bones were examined with these three techniques. Afterwards, these jaws were sawn, and the real values were measured. Comparing these scores with the radiological measurements, the standard reconstruction technique seemed the most reliable method in the preoperative examination of the jaw bone quality and bone proportion.

No abstract

With conventional photon therapy, radiographs are widely used for the verification of patient positioning. This method cannot be used with neutrons because of the poor sensitivity of standard films to neutrons compared with γ rays. In addition, there is little difference in energy absorption between bone and soft tissue for these neutron beams (Bewley et al, 1973; Catterall & Bewley, 1979). The problem can be solved by introducing into the collimator, at the target position, a diagnostic X-ray tube (Risler & Wootton, 1988). Another approach entails visualizing the neutron-induced activity within the patient using positron emission tomography (PET). At high neutron energies, shortlived positron emitters are produced (Kleck et al, 1988; Vynckier et al, 1988) with activities sufficiently high to be visualized; the dose-equivalent rate close to the patient as a result of this activation is ∼ 30 μSv h−1 immediately after irradiation (Tatcher et al, 1987). The same approach was reported recently for pion radiotherapy (Goodman et al, 1986).

No abstract

No abstract