Standard and low-dose cone beam computer tomography protocol for orthognatodontic diagnosis: a comparative evaluation.

Considering the diagnostic capability offered by cone-beam computed tomography (CBCT), nowadays orthodontists often use this exam for treatment planning, especially in cases of impacted teeth, maxillary ipoplasia, orthognathic surgery etc. The aim of this study was to compare the radiation doses related to a conventional CBCT setting and that of a low dose protocol, usable in orthodontic practice. The absorbed organ doses were measured using an anthropomorphic phantom loaded with thermo-luminescent dosimeters related to sensitive organs (brain, bone marrow, salivary glands, thyroid, esophagus, oral mucosa, extrathoracic airways, lymph nodes). The device used was a MyRay Hyperion X9-11x5. The standard setting of the apparatus was 90 Kv, 36 mAs, CTDI/Vol 4.09 mGy, instead the low dose one was 90 Kv, 27 mAs, CTDI/Vol 2.89 mGy. Equivalent and effective doses have been calculated; the measurement of the effective doses was based on the ICRP recommendations. For the assessment of image quality, five readers, independent and experienced orthodontists, were asked to state if the images were sufficient enough to perform an orthodontic diagnosis. The lowest organ dose (5.01 microSv) was received by the esophagus during low dose CBCT acquisition. The highest mean organ dose instead (1227.67 microSv) was received by the salivary glands during conventional setting CBCT acquisition. Image quality has been considered sufficient for orthodontic diagnostic needs for both CBCT protocols. CBCT low dose setting should be preferred over the standard one in orthodontic practice, because it provides a significant lower radiation dose to the patients ensuring a good image quality. However, further studies are necessary to evaluate the opportunity of CBCT exams in orthodontic treatment planning.

High-Dose Robotic Stereotactic Body Radiotherapy in the Treatment of Patients With Prostate Cancer: Preliminary Results in 26 Patients.

BACKGROUND: Stereotactic body radiotherapy (SBRT) can emulate high dose rate brachytherapy (HDR-BRT) dose fractionation. We report our preliminary results using SBRT in monotherapy or pre-external-beam radiotherapy (EBRT) boost in patients with localized prostate cancer (LpC). The primary end point was the evaluation of both acute and late toxicities; secondary end point was the observation of prostate-specific antigen (PSA) nadir. PATIENTS AND METHODS: Patients with LpC having prostate volume ≤90 cm(3) were enrolled in the present study. Patients were treated with SBRT alone or in combined modality (SBRT + EBRT). SBRT was performed using a CyberKnife System (Accuray Incorporated, Sunnyvale, California) and fiducial tracking system. RESULTS: From February 2008 to July 2013, 21 patients for monotherapy (38 Gy/4 fractions) and 5 for combined modality (9.5 Gy/2 fractions plus 46 Gy/23 fractions EBRT) were enrolled. Androgen deprivation therapy (ADT) was administered in 16 of the 26 patients. The median pretreatment PSA was 9.4 (range, 4.5-14.3) ng/mL. All patients completed the planned therapy. Acute Grade 1 toxicity was observed in 18 patients, genitourinary (GU) in 12 / 26 patients, and gastrointestinal (GI) in 6 / 26 patients. Acute Grade 2 GU toxicity was reported in 1 / 26 patients, and Grade 2 GI toxicity was observed in 2 / 26 patients. The median PSA nadir was 0.15 (range, 0.02 = 1.4) ng/mL. Late toxicities were observed in 5 / 26 patients: Grade 1 GU (3 of 26), Grade 2 GU (1 of 26), and Grade 1 GI (1 of 26). Median follow-up was 21.5 (range, 8-65) months. CONCLUSIONS: Our preliminary results of SBRT "simulating" HDR for LpC confirm a minimal toxicity and an optimal PSA response. The PSA nadirs appear comparable with HDR-BRT.

Absorbed dose from contaminant electrons inside and outside megavoltage photon beams.

Megavoltage photon beams interactions with any object on their path give rise to secondary photons and electrons. This fact is particularly important in Radiotherapy. These secondary particles produce an unwanted dose contribution both on beam path and outside the geometrical edges of the irradiation field. The goal of this report is to investigate the dose contribution due to secondary electrons. Ionization measurements were made in a polystyrene phantom by means of a Markus ionization chamber, with X-ray beams produced by a "SL5" Philips and by a "Saturne 43" GE CGR linear accelerators. Specific fields for nasopharynx treatment and for supra-diaphragmatic lymphatic chains treatment ("mantle" fields) were investigated. Both depth ionization values on beam path and depth and surface ionization values outside the geometrical edges of the field were obtained. These measurements were made with and without specific electron filters for 6, 15, 25 MV X-ray beams. The results obtained prove that, both on the beam path and outside the geometrical borders of the field, electron contamination reduction by means of specific filters is important only for lower energy X-ray beams. For this sort of beams, the percentage reduction of electron contamination was found. Moreover, the amount of electron contamination outside the field geometrical edge versus field size was evaluated.