W.E.R. Berkhout

Detection of in vitro proximal caries in storage phosphor plate radiographs scanned with different resolutions

OBJECTIVES To investigate the effect of the scanning resolution of storage phosphor plate (SPP) radiographs on the detection of proximal caries lesions. METHODS 10 dentists evaluated 72 proximal surfaces of premolars with respect to caries from SPP radiographs scanned with theoretical spatial resolutions of: (1) the Digora FMX at 7.8 lp mm(-1); (2) the Digora Optime at both 7.8 lp mm(-1) and 12.5 lp mm(-1); and (3) the Dürr VistaScan at 10 lp mm(-1) and 20 lp mm(-1), respectively. The lesions were validated by histological examination. Receiver operating characteristic (ROC) analysis was employed. RESULTS The A(z) value for the radiographs scanned with the Dürr VistaScan at 10 lp mm(-1) is significantly lower than those for the other series of radiographs (P = 0.000). CONCLUSIONS For SPP radiographs, an increased theoretical spatial resolution per se is not related to an improved detection of proximal caries.

Detection of Proximal Caries in vitro Using Standard and Task-Specific Enhanced Images from a Storage Phosphor Plate System

Eight dentists evaluated 72 proximal surfaces of premolars with respect to all caries lesions and to lesions into dentine in digital images from a storage phosphor plate system. The images were processed in four different ways: (1) the default algorithm of the standard imaging system (DF); (2) an algorithm correcting for attenuation and visual response (AV), and two proprietary caries-specific enhancement algorithms (3) K1, and (4) K2, respectively. The lesions were validated by histological examination. There were no significant differences in the areas under the receiver operating characteristic curves between differently processed radiographs for the categories of all caries lesions and caries into dentine.

Dose reduction in orthodontic lateral cephalography: dosimetric evaluation of a novel cephalographic thyroid protector (CTP) and anatomical cranial collimation (ACC)

OBJECTIVES To test the dose-reducing capabilities of a novel thyroid protection device and a recently introduced cranial collimator to be used in orthodontic lateral cephalography. METHODS Cephalographic thyroid protector (CTP) was designed to shield the thyroid while leaving the cervical vertebrae depicted. Using a RANDO(®) head phantom (The Phantom Laboratory, Salem, NY) equipped with dosemeters and a Proline XC (Planmeca, Helsinki, Finland) cephalograph, lateral cephalograms were taken, and the effective dose (ED) was calculated for four protocols: (1) without shielding; (2) with CTP; (3) with CTP and anatomical cranial collimator (ACC); and (4) with a thyroid collar (TC). RESULTS The ED for the respective protocols was (1) 8.51; (2) 5.39; (3) 3.50; and (4) 4.97 µSv. The organ dose for the thyroid was reduced from 30.17 to 4.50 µSv in Protocols 2 and 3 and to 3.33 µSv in Protocol 4. CONCLUSIONS 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 value of thyroid shielding in intraoral radiography.

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.

Association between extra- and intracranial calcifications of the internal carotid artery: a CBCT imaging study

OBJECTIVES This study aimed to evaluate the association between the extracranial and intracranial calcification depiction of the internal carotid artery (ICA), incidentally found in CBCT examinations in adults, and to discuss the conspicuous clinical implications. METHODS Out of a series of 1085 CBCT examinations, 705 CBCT scans were selected according to pre-defined criteria. The extra- and intracranial calcifications depicted along the course of the ICA were documented according to a comprehensive set of descriptive criteria. RESULTS In total, 799 findings were detected, 60.1% (n = 480) were intracranially and 39.9% (n = 319) were extracranially allocated. The χ(2) test showed associations between all variables (p < 0.001). Also, most of the combinations of variables showed statistically significant results in the McNemars test (p < 0.001). CONCLUSIONS We found that a significant correlation exists between extra- and intracranial calcifications of the ICA. It is clear that in cases of the presence of a calcification in the ICA extracranially, the arterys intracranial portion has an increased risk of showing the same findings. CBCT imaging is widely used as a diagnostic tool, thus, our results contribute to the identification of a subgroup of patients who should undergo further medical evaluation of the atherosclerosis of the ICAs.

Anatomically shaped cranial collimation (ACC) for lateral cephalometric radiography: a technical report

Lateral cephalograms in orthodontic practice display an area cranial of the base of the skull that is not required for diagnostic evaluation. Attempts have been made to reduce the radiation dose to the patient using collimators combining the shielding of the areas above the base of the skull and below the mandible. These so-called “wedge-shaped” collimators have not become standard equipment in orthodontic offices, possibly because these collimators were not designed for todays combination panoramic–cephalometric imaging systems. It also may be that the anatomical variability of the area below the mandible makes this area unsuitable for standardized collimation. In addition, a wedge-shaped collimator shields the cervical vertebrae; therefore, assessment of skeletal maturation, which is based on the stage of development of the cervical vertebrae, cannot be performed. In this report, we describe our investigations into constructing a collimator to be attached to the cephalostat and shield the cranial area of the skull, while allowing the visualization of diagnostically relevant structures and markedly reducing the size of the irradiated area. The shape of the area shielded by this “anatomically shaped cranial collimator” (ACC) was based on mean measurements of cephalometric landmarks of 100 orthodontic patients. It appeared that this collimator reduced the area of irradiation by almost one-third without interfering with the imaging system or affecting the quality of the image. Further research is needed to validate the clinical efficacy of the collimator.

Validation of anatomically shaped cranial collimation (ACC) in orthodontic lateral cephalography

The use of an anatomically shaped cranial collimator (ACC) to reduce patient dose in orthodontic lateral cephalography was investigated in this study. The aim was to evaluate the potential interference of the ACC on landmark identification for orthodontic cephalometry. Consecutive orthodontic patients underwent a total of 100 cephalograms using an ACC mounted on a Veraviewepocs(®) 3D X550 (J. Morita Co., Kyoto, Japan) X-ray unit. 10 observers were asked whether the identification of 5 landmarks close to the collimated area was hindered or rendered impossible by the presence of the collimator. Of the 500 landmarks that were judged by the 10 observers, 496 (99.2%) were reported to lack hindrance. In three landmarks, a minority of the observers reported hindrance. In 1 landmark, 8 of the 10 observers reported hindrance by the collimator. In no instance did the observers state that the identification of landmarks was impossible as a result of the collimation. Application of the ACC on the cephalostat of the X-ray unit is a viable way of reducing patient dose, as it only marginally interferes with the diagnostic yield of the exposure. The need to retake images when the ACC is applied was found to be extremely low.

Reducing an already low dental diagnostic X-ray dose: does it make sense? Comparison of three cost-utility analysis methods used to assess two dental dose-reduction measures

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.

Assessment of random error in phantom dosimetry with the use of error simulation in statistical software

Objective. To investigate if software simulation is practical for quantifying random error (RE) in phantom dosimetry. Materials and Methods. We applied software error simulation to an existing dosimetry study. The specifications and the measurement values of this study were brought into the software (R version 3.0.2) together with the algorithm of the calculation of the effective dose (E). Four sources of RE were specified: (1) the calibration factor; (2) the background radiation correction; (3) the read-out process of the dosimeters; and (4) the fluctuation of the X-ray generator. Results. The amount of RE introduced by these sources was calculated on the basis of the experimental values and the mathematical rules of error propagation. The software repeated the calculations of E multiple times (n = 10,000) while attributing the applicable RE to the experimental values. A distribution of E emerged as a confidence interval around an expected value. Conclusions. Credible confidence intervals around E in phantom dose studies can be calculated by using software modelling of the experiment. With credible confidence intervals, the statistical significance of differences between protocols can be substantiated or rejected. This modelling software can also be used for a power analysis when planning phantom dose experiments.