PubMed · 5756881
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I Horven. 1968. Electronic tonometer calibration.. https://doi.org/10.1111/j.1755-3768.1968.tb05901.x
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BACKGROUND AND PURPOSE: Daily use of conventional electronic portal imaging devices (EPID) for organ tracking is limited due to the relatively high dose required for high quality image acquisition. We studied the use of a novel dose saving acquisition mode (RadMode) allowing to take images with one monitor unit per image in prostate cancer patients undergoing intensity-modulated radiotherapy (IMRT) and tracking of implanted fiducial gold markers. PATIENTS AND METHODS: Twenty five patients underwent implantation of three fiducial gold markers prior to the planning CT. Before each treatment of a course of 37 fractions, orthogonal localization images from the antero-posterior and from the lateral direction were acquired. Portal images of both the setup procedure and the five IMRT treatment beams were analyzed. RESULTS: On average, four localization images were needed for a correct patient setup, resulting in four monitor units extra dose per fraction. The mean extra dose delivered to the patient was thereby increased by 1.2%. The procedure was precise enough to reduce the mean displacements prior to treatment to < o =0.3 mm. CONCLUSIONS: The use of a new dose saving acquisition mode enables to perform daily EPID-based prostate tracking with a cumulative extra dose of below 1 Gy. This concept is efficiently used in IMRT-treated patients, where separation of setup beams from treatment beams is mandatory.
The responses of several insert earphones in the Etymotic 3A series were measured with the occluded ear simulator (IEC 60711) and the 2cc coupler (IEC 60126). Acoustic clicks following a 100 us rectangular voltage pulse were compared. The peak-to-peak equivalent sound pressure levels in the ear simulator were found to be 9.2 dB greater than those in the 2cc coupler. The difference was independent of type of earphone among those tested. Similar comparisons were made for tone pips (brief tones or tone bursts) and continuous tones. For a given drive voltage, differences in earphone output were almost the same as the corresponding differences in published RETSPLs for the occluded ear simulator and 2cc coupler (ISO 389-2).
AIM: To develop a precise and simple mounting model (MM) for evaluating apex locators and to compare the repeatability of the MM with a conventional visual method (VM). METHODOLOGY: Electronic working length determination was performed in 32 maxillary central incisors using two methods: (i) the MM method and (ii) a conventional VM. The MM utilizes a micrometer to determine the distance travelled by the measuring file during working length determination. In the VM, the length of the measuring file (representing the working length) is determined visually using a caliper and a microscope at 6x magnification. Each measurement was repeated once. The repeatability of each method was evaluated by calculating the coefficient of repeatability. RESULTS: The coefficient of repeatability, which includes 95% of the differences between repeated measurements, was 0.04 mm for MM compared with 0.9 mm for VM. The measurement error of MM was significantly lower than VM (0.02 and 0.4 mm respectively). There was a statistically significant difference between the means of absolute difference in repeated measurements: MM 0.01 mm (95% confidence interval (CI): 0.01; 0.02 mm) compared with VM 0.4 mm (95% CI: 0.3; 0.5 mm). CONCLUSION: The new MM had superior repeatability in comparison with the conventional method where visual interpretation is a source of inaccurate measurement.