Objectives: To evaluate the utility of the application of a thyroid shield in intraoral radiography when using rectangular collimation. Methods: Experimental data were obtained by measuring the absorbed dose at the position of the thyroid gland in a RANDO ® (The Phantom Laboratory, Salem, NY) male phantom with a dosemeter. Four protocols were tested: round collimation and rectangular collimation, both with and without thyroid shield. Five exposure positions were deployed: upper incisor (Isup), upper canine (Csup), upper premolar (Psup), upper molar (Msup) and posterior bitewing (BW). Exposures were made with 70 kV and 7 mA and were repeated 10 times. The exposure times were as recommended for the exposure positions for the respective collimator type by the manufacturer for digital imaging. The data were statistically analyzed with a three-way ANOVA test. Significance was set at p , 0.01. Results: The ANOVA test revealed that the differences between mean doses of all protocols and geometries were statistically significant, p , 0.001. For the Isup, thyroid dose levels were comparable with both collimators at a level indicating primary beam exposure. Thyroid shield reduced this dose with circa 75%. For the Csup position, round collimation also revealed primary beam exposure, and thyroid shield yield was 70%. In Csup with rectangular collimation, the thyroid dose was reduced with a factor 4 compared with round collimation and thyroid shield yielded an additional 42% dose reduction. The thyroid dose levels for the Csup, Psup, Msup and BW exposures were lower with rectangular collimation without thyroid shield than with round collimation with thyroid shield. With rectangular collimation, the thyroid shield in Psup, Msup and BW reduced the dose 10% or less, where dose levels were already low, implying no clinical significance. Conclusions: For the exposures in the upper anterior region, thyroid shield results in an important dose reduction for the thyroid. For the other exposures, thyroid shield augments little to the reduction achieved by rectangular collimation. The use of thyroid shield is to be advised, when performing upper anterior radiography.

Objectives: In paediatric cancer survivors treated with chemotherapy and radiotherapy therapy, late effects on dental development are quite common. Oral radiologists are not familiar with the radiographic images of these specific dental consequences of chemotherapy and radiotherapy. With the goal of educating colleagues, to raise awareness of the needs of survivors, and to identify directions for future research, we present dental radiographs of survivors treated for head and neck rhabdomyosarcoma with chemotherapy and radiotherapy. Also, based on the survivors reviewed, a radiographic inventory of commonly found late dental developmental effects seen in conjunction with treatment is presented. Methods: Panoramic radiographic findings of five illustrative cases are presented, from a group of 42 survivors of head and neck rhabdomyosarcoma treated at the Academic Medical Center Amsterdam, The Netherlands over the past 25 years. Results: Five cases showing dental developmental disorders are presented. These cases show an association of the location of the radiation field and the developmental stage of the teeth with the severity of the effect on dental development. We also report an inventory of severe and moderate effects of chemotherapy and radiotherapy on the development of molars and anterior teeth. Conclusions: This paper presents five cases and a radiographic inventory to illustrate disturbances of dental development associated with chemotherapy and radiotherapy in children. Medical and dental professionals involved in the treatment of cancer survivors are relatively unaware of the dental consequences of radiation therapy and the age dependency of specific regional effects. These effects can be severe, with great impact on quality of life. Further research in this area could help improve planning of radiation therapy for children, potentially preventing or limiting dental or maxillofacial sequelae.

Objectives: During a cone beam CT scan, the patient is in an upright or supine position. This position depends on the brand and type of the scanner. The aims of this study are: (1) to investigate if the head position has an effect on cephalometric evaluation of the soft-tissue facial profile, comparing the recordings in natural head position (NHP) and supine head position (SHP) and (2) to investigate if age, gender and body mass index (BMI) are contributing factors to the effect of the head position. Methods: 90 subjects were photographed in profile both in NHP and in SHP. 12 soft-tissue angular and linear cephalometric values were calculated. Two-way random intraclass correlation coefficients were calculated to determine observer reliability. Paired t-tests and linear regression analyses were performed to investigate the differences between the head positions and the influence of age, gender and BMI. Results: Intraobserver reliability was generally high. Paired t-tests showed significant changes as a result of head positioning (p , 0.0001) in 9 of the 12 measurements. These differences were small and clinically not relevant, except for the "lower face-throat angle". Regression analysis revealed no relevant influence of age, gender and BMI. Conclusions: Cephalometric soft-tissue evaluation from a recording in SHP is generally reliable, except for the throat-chin area where a clinically relevant difference was found. The contour of the submandibular tissues in SHP causes the chin to appear more prominently. This can cause incorrect orthodontic diagnosis and treatment planning.

Background: Hand-held (HH) X-ray devices are currently introduced for routine dentistry in some global areas. Safety issues are resolved but imaging quality aspects remain to be explored. Aim: To compare the aiming accuracy of two intraoral radiography devices: the portable Nomad Pro2 and the wall-mounted (WM) Planmeca Intra. Setting and design: In vitro experimentation involving radiologic mannequins and unbiased student operators. Methods and materials: 20 operators obtained intraoral radiographs of four regions (bitewing, upper molar, lower molar and upper anterior) in five mannequins, using HH and WM devices. Beam-aiming devices were fitted with metal cross-wires to project on image sensors. Deviation from ideal perpendicular incidence of beam was calculated, based on positions of cross-wires relative to gold-standard positions (i.e. average of 10-fold precise aiming by authors via WM system). Analytic models relied on Wilcoxon signed-rank test and mixed model analyses. Results: Mean deviations from perfect aim were 2.88˚ (± 1.80˚) for WM and 3.06˚ (± 1.90˚) for HH methods. The difference among all operators (HH vs WM) was 0.17˚ (± 2.48˚), which was not significant. Seven operators showed better aim by HH device (13 by WM system); and in one instance, this difference was significant. Conclusions: Aiming precision proved similar for HH and WM methods of intraoral radiography, although individual operators may perform better using one of these modalities. Aim is not an expected limiting factor for image quality in HH (vs WM) diagnostics.

Purpose Determination of intra-oral surface areas might contribute to our understanding of the physiology of the oral cavity and oral diseases. In previous studies, the intra-oral surface area was determined using a laborious and technically challenging method. Our aim was to develop an easy and non-invasive method to determine the intra-oral surface areas. Methods In this study, we used cone-beam computed tomography (CBCT) and digital analysis in 20 human cadavers to determine various intra-oral surface areas, based on digital segmentation. Next, we explored whether there was a relationship between various intra-oral surface areas and anthropometric measurements of the head using Pearson correlation coefficient. Results Using CBCT and digital analysis, it was possible to determine various intra-oral surface areas. On average, the total intra-oral surface area was 173 ± 19 cm 2. Moderate, statistical significant correlations were observed between (1) the length of the head and the palatal surface area, as well as (2) the depth of the head and the surface area of the tongue. These correlations suggest the feasibility of estimating intra-oral surface areas without relying on CBCT imaging. Conclusions This study presents a technique for measuring the intra-oral surface areas by CBCT imaging in combination with digital analysis. The results of this study suggest that anthropometric measurements of the head might be used to estimate the surface areas of the palate and tongue.

The use of just the CTP (Protocol 2) resulted in a 36.8% reduction of the ED of a lateral cephalogram. This was comparable to the classical TC (Protocol 4). A 58.8% reduction of the ED was obtained when combining CTP and ACC (Protocol 3). The dose to the radiosensitive thyroid gland was reduced by 85% in Protocols 2 and 3 and by 89% in Protocol 4.

The conversion factor established for scattered ambient radiation was 0.05 µSv per mAs at 1 meter. This factor is 3-fold lower than the conversion factors reported previously.

Objectives: To find a method that is suitable for providing an objective assessment of the cost effectiveness of a dose-reducing measure used for diagnostic dental X-ray exposures. Methods: Three cost-utility analysis (CUA) methods were evaluated by comparing their assessments of two dose-reduction measures, a rectangular collimator and the combination of two devices that reduce the radiation dose received during orthodontic lateral cephalography. The following CUA methods were used: (1) the alpha value (AV), a monetary valuation of dose reduction used in the nuclear industry; (2) the value of a statistical life for valuation of the reduction in stochastic adverse effects; and (3) the time-for-time method, based on the postulate that risk reduction is effective when the number of years of life gained is more than the years that an average worker must work to earn the costs of the risk-reducing measure. The CUA methods were used to determine the minimum number of uses that was required for the dose-reducing device to be cost effective. The methods were assessed for coherence (are comparable results achieved for comparable countries?) and adaptability (can the method be adjusted for age and gender of specific patient groups?). Results: The performance of the time-for-time method was superior to the other methods. Both types of dose-reduction devices tested were assessed as cost effective after a realistic number of uses with all three methods except low AVs. Conclusions: CUA for the methods of X-ray dose reduction can be performed to determine if investment in low dose reduction is cost effective. The time-for-time method proved to be a coherent and versatile method for performing CUA.