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Objective The magnification and distortion of images made from scanning and nonscanning CCD cephalometric systems was evaluated. Study design Acrylic box and dry human skull phantoms were imaged using a conventional cephalostat, the nonscanning Kodak 8000C, the horizontally scanning GE/Instrumentarium OC100D, and the vertically scanning Sirona OrthophosDS. True linear and angular measurements of the phantoms were made using a coordinate measuring system and the Hitachi MercuRay cone beam system. The accuracy of linear and angular measurements was assessed, as were magnification and distortion, where appropriate. Results Statistically significant differences between linear and angular measurements were found for almost all measurements for both phantoms. In general, the conventional cephalostat and Sirona OrthophosDS systems produced the greatest magnification and distortion while the GE/Instrumentarium OC 100D and Kodak 8000C systems, the least. Conclusions Measurement differences related to the beam geometries of these systems could not be predicted a priori. Unaccounted for, these differences could result in clinically significant consequences.

This study compared digital and digitized panoramic radiographs to detect incipient periapical lesions using the digital subtraction radiography (DSR) technique. Bone defects were created in 77 apical sites of dried human mandibles through the application of 70% perchloric acid. Conventional and digital radiographs were obtained twice at time zero and 2, 4, and 6 hours after application of the acid solution. Conventional radiographs were digitized by using the same attributes than direct digital radiographs. The baseline images were subtracted of the negative control and experimental groups and assessed by an experienced and blinded observer who assigned score 0 (normal) or 1 (mineral loss) to each image. The sensitivity of both modalities was statistically different in relation to experimental times. The percentage of correct responses significantly increased regarding experimental times. The specificity was high both for digitized and digital images. DSR of panoramic images, both digitized and digital, allows for the diagnosis of incipient-simulated periapical lesions with no differences in their performance.

The aim of this study was to introduce a prototype cone-beam computed tomography system equipped with a flat panel detector (FPD-CT system) and measure its radiation dose and spatial and lowcontrast resolution.A patient was rotated in a sitting position, and cone beam data were acquired with the flat panel detector from a fixed X-ray tube. Absorbed dose, spatial and low-contrast resolution, and variation in the CT attenuation value were assessed quantitatively in the acrylic phantom. The visibility of normal blood vessels in clinical images of seven patients was analyzed qualitatively by five board-certified radiologists. These quantitative and qualitative data were compared between the FPD-CT system and multidetector row CT (MDCT).Minimal low-contrast sensitivity and a moderate spatial resolution were demonstrated in images of central lung fields acquired by FPD-CT. The absorbed dose in the FPD-CT system decreased to approximately 2.5% of the dose in the MDCT system.Considering crossover structures in normal blood vessels and bronchi in the central areas of lung fields, this result implies that fairly acceptable spatial resolution can be realized with FPD-CT for detection and frequent follow-up of pulmonary abnormalities in the central lung fields.

Cone-beam imaging has gained broad acceptance in dentistry in the last 5 years. The purpose of this review is to describe the use in dentistry and consider issues requiring further development. Cone-beam machines emit an x-ray beam shaped liked a cone rather than a fan as in conventional computed tomography (CT) machines. After this beam passes through the patient the remnant beam is captured on an amorphous silicon flat panel or image intensifier/charge-coupled device (CCD) detector. The beam diameter ranges from 4 to 30 cm and exposes the head in one pass around the patient capturing from 160 to 599 basis images. These images are used to compute a volume from which planar or curved reconstructions can be extracted in any orientation. Voxels are isotropic and can be as small as 0.125 mm. 3-D images of bone or soft tissue surfaces can also be generated. In dentistry the most common indications for cone-beam imaging are assessment of the jaws for placement of dental implants, evaluation of the temporomandibular joints for osseous degenerative changes, examination of teeth and facial structures for orthodontic treatment planning, evaluation of the proximity of lower wisdom teeth to the mandibular nerve prior to extraction, and evaluation of teeth and bone for signs of infections, cysts, or tumors. Cone-beam images have largely replaced conventional tomography for these tasks. The effective dose from cone-beam imaging ranges from 6 to 477 microSv. The cost of the equipment is relatively low, about $150,000 to $300,000. Issues to be considered are the training of individuals making and interpreting cone-beam images, as well as means to further reduce patient exposure.

OBJECTIVES The aim of the study was to evaluate the level of agreement between bitewing radiographs and oblique lateral radiographs for the diagnosis of dental caries extending into dentine, and to draw conclusions from the results as to which view is more useful. SAMPLE Radiographs were selected from patients attending an orthodontic assessment clinic: 53 patients, 52% male, 48% female, aged 6-18 years old. Total 105 bitewings and 105 oblique lateral radiographs. METHODS Contemporaneous bitewing and oblique radiographs taken over the period 1987-97 were independently assessed by two dentists for the presence of caries extending into dentine. RESULTS The agreement between the oblique lateral and the bitewing radiographs for the presence of approximal caries expressed in the form of Cohen's Kappa gave values of 0.64 for observer 1 and 0.53 for observer 2. For occlusal caries, values were 0.72 for observer 1 and 0.56 for observer 2. Kappa values for the level of agreement between observers and for the same observer on different occasions were within the range 0.5-0.95 for both types of film. CONCLUSION The Kappa values for the agreement between the two views as well as the intra- and inter-observer agreement and reproducibility of the oblique lateral view all fall in the range K = 0.5-0.75. Results suggested a fair to good agreement in diagnoses made using the two types of film. However, levels were lower than estimates of reproducibility reported for bitewing films alone.

The aims of this study were to compare film and digital radiography in assessing the radiopacities of root canal sealers and to establish the relation in aluminum equivalent values of different methods. Standard disks of 5 different sealers were exposed together with an aluminum step wedge by using occlusal films and storage phosphor plates. Optical density of the sealers was evaluated by transmission densitometry, and mean gray values were determined by digital analysis. The data were analyzed by using two-way analysis of variance (P = .05). Pairwise comparisons were made by using Tukey post hoc and paired t tests (P = .05). The order from the most radiopaque to the most radiolucent sealer was the same for both methods; however, aluminum equivalent values determined by transmission densitometry were significantly higher (P < .01). Aluminum equivalent values of the 2 radiographic methods were 7%-20% different. The International Standards Organization standard for the radiopacity of dental root canal sealing materials needs modifications for digital systems.

Objectives: To assess the accuracy of NewTom 9000 cone beam CT (CBCT) images for the detection and quantification of periodontal bone defects in three dimensions. Methods: A sample of 146 sites in 5 dry skulls provided the ground truth (GT). Half of the sample had bone loss of at least 3 mm. Two metal spheres at each site ensured correspondence between GT and CBCT measurements. Skulls were submerged in water and scanned with the NewTom QR-DVT-9000. A full mouth series (FMX) was obtained of each skull using photostimulable phosphor plates. Six observers measured the bone height of each site and rated the presence or absence of bone loss. Measurements were compared to GT and Az-values were calculated from receiver operating characteristic curves. Results: The Az-value for CBCT was 0.74 (standard deviation (SD) 5 0.14) and for FMX 0.48 (SD 5 0.09). The difference was significant (ANOVA: P , 0.01). The diagnostic accuracy of CBCT was lower for anterior teeth (Az 5 0.59) than for molars (Az 5 0.82) and premolars (Az 5 0.79) (Tukey’s HSD (honestly significant difference): P , 0.01). The mean absolute difference between CBCT and GT was 1.27 mm (SD 5 1.43) and between FMX and GT 1.49 mm (SE 5 1.24) (ANOVA: P , 0.01). Measurements in the anterior mandible were less accurate than in other areas (Tukey’s HSD: P , 0.01). Conclusion: The NewTom 9000 cone beam CT scanner provides better diagnostic and quantitative information on periodontal bone levels in three dimensions than conventional radiography. The accuracy in the anterior aspect of the jaws is limited. Dentomaxillofacial Radiology (2008) 37, 319–324. doi: 10.1259/dmfr/26475758

BACKGROUND AND PURPOSE: Since the introduction of flat panel detector–equipped C-arms, the use of flat panel detector CT (FPCT) in the neuroradiologic angiography suite has become more frequent. This examination implicates its own specific radiation exposure. We used the CT dose index (CTDI) concept and adapted it to the special FPCT geometry to provide a consistent comparison with multisection head CT (cCT). MATERIALS AND METHODS: Exposure data obtained for routine scanning during a period of 1 year were used to assess a specific dose of a total of 217 rotational scans performed in 105 patients. One hundred seventy-two scans were 3D digital subtraction angiography (DSA) scans. There were 45 scans that were performed to achieve high-quality, soft-tissue resolution. Dose measurements in cylindrical polymethylmethacrylate (PMMA) phantoms were used to determine the CTDI value and to compare it with the reference values for cCT. In addition, the dose-area product (DAP) was registered and correlated with the CTDI and corresponding dose-length product (DLP) values. Exposure data and dose values were compared with cCT. RESULTS: Mean-weighted CTDI value of 3D-DSA was approximately 9 mGy per scan. High-quality, soft-tissue resolution FPCT scans, comparable with cCT, revealed a mean dose value of 75 mGy (reference value for cCT, CTDI w ∼ 60 mGy). CONCLUSION: The high-speed scans used for 3D-DSA revealed a significantly lower CTDI w and DLP compared with clinical CT. The high-quality FPCT protocol resulted in a higher dose and should therefore be limited to acute cases, when patient transfer to a CT scanner is considered to be a disadvantage for patient management.

Background: Medical film digitizers play an important transitory role as digital–analogue bridges in radiology. Digitized mammograms require evaluation of performance to assure medical image quality. Purpose: To compare the diagnostic accuracy in the interpretation of breast masses using original screen-film mammograms versus digitized images. Material and Methods: A total of 72 female patients between 55 and 81 years of age suspected of having breast cancer were selected by two non-observing radiologists. Of these, 31 cases were benign lesions and 41 cases were cancer. The mammography films were digitized using a laser film digitizer. Three radiologists, each with more than 10 years of experience in mammography, interpreted the screen-film mammograms and digitized images respectively. The time interval was 4 weeks. A four-point malignancy scale was used, with 1 defined as definitely not malignant, 2 as probably not malignant, 3 as probably malignant, and 4 as definitely malignant. Receiver operating characteristic (ROC) curves, sensitivity, and specificity were compared. Results: The average area-under-the-curve (Az) value of the original screen-film mammograms was 0.921, and the average Az value of the digitized images was 0.859. This difference was not statistically significant ( P=0.131). The detection specificity of extremely dense breasts was lower than that for other breast compositions for both digitized images and screen-film mammograms. No statistical significance in sensitivity and specificity was observed between digitized images and mammograms for each breast composition. Original screen-film mammograms were observed to perform better than digitized images. Conclusion: Digitized images with a spatial resolution of 175 µm can be used instead of screen-film mammograms in the diagnosis of breast cancer.

Objective: To prospectively evaluate the use of minimum-intensity projection (minIP) imaging, high-resolution (HR) computed tomography (CT), and pulmonary function tests for quantifying emphysema with histopathologic examination. Methods: MinIP and HRCT imaging data (n = 23) were obtained, and relative areas of the lung with attenuation values below thresholds from −940 to −1000 Hounsfield units (HU) and first to 13th percentiles were calculated for both data. Pulmonary function tests were performed before lung resection. These parameters were compared with mean alveolar perimeters measured on resected samples. Results: Strongest correlations with mean alveolar perimeter were obtained at −990 HU and the fifth percentile by minIP, −1000 HU and the seventh percentile by HRCT, and diffusion capacity. The correlation between the mean alveolar perimeter and relative areas below −990 HU by minIP showed significantly higher extension (0%-51%) than those below −1000 HU by HRCT (1%-21%). Conclusions: MinIP imaging is more than 2½ times more predictive for quantifying emphysema than HRCT, although diffusion capacity of lung for carbon monoxide is also a valid index.

Current electron detectors are either unable to image in vivo or lack sufficient spatial resolution because of electron scattering in thick detector materials. This study was aimed at developing a sensitive high-resolution system capable of detecting electron-emitting isotopes in vivo. Methods: The system uses a lens-coupled charge-coupled-device camera to capture the scintillation light excited by an electron-emitting object near an ultrathin phosphor. The spatial resolution and sensitivity of the system were measured with a 3.7-kBq 90Y/90Sr β-source and a 70-μm resin bead labeled with 99mTc. Finally, we imaged the 99mTc-pertechnetate concentration in the mandibular gland of a mouse in vivo. Results: Useful images were obtained with only a few hundred emitted β particles from the 90Y/90Sr source or conversion electrons from the 99mTc bead source. The in vivo image showed a clear profile of the mandibular gland and many fine details with exposures of as low as 30 s. All measurements were consistent with a spatial resolution of about 50 μm, corresponding to 2.5 detector pixels with the current camera. Conclusion: Our new electron-imaging system can image electron-emitting isotope distributions at high resolution and sensitivity. The system is useful for in vivo imaging of small animals and small, exposed regions on humans. The ability to image β particles, positrons, and conversion electrons makes the system applicable to most isotopes.

The purpose of this investigation was to measure the patient and staff dose during routine interventional cardiology procedures for an image intensifier-based and a flat detector system using a water phantom. The Integris BH3000 image intensifier-based (Philips) and the Axiom Artis flat detector-based (Siemens) angiography units were used in this study. The accuracy of tubes potential and irradiation timers and also internal dosimeters were verified and confirmed. A water phantom with a thickness of 18 cm was used for patient and staff dose measurements. For the Philips system, phantom entrance dose rates were 2.77 and 38.97 microGym(2) s(-1) during fluoroscopy and cineangiography. The respective dose rates for the Siemens were 1.98 and 13.46 microGym(2) s(-1). Phantom entrance dose rate was 28.5 and 65% higher for the Philips system during fluoroscopy and cineangiography, respectively. Comparing the scattered dose rates at the operator location showed that the flat detector-based Siemens system delivers five times lower dose to the operator in comparison with the image intensifier-based Philips unit. The results suggest that the decrease in received dose of the patient and staff is achievable using the flat detector system. In addition, application of lead curtain and glass is recommended to lower the cardiologist dose especially for the image intensifier-based Philips system.

The advancement of digital imaging has prompted more medical institutions to go filmless. The computed radiography (CR) system is becoming an important tool not only in diagnostic imaging, but also in radiation oncology. A new CR system that was specially designed for the use in radiation oncology, Fuji IP cassette type PII has been introduced to the market in the middle of year 2006. This project aimed to study some basic physical characteristics of this new type of cassette and explore its application for performing quality assurance (QA) tests and portal imaging in radiotherapy. All the images were read by FCR 5000 Plus reader. The image was found to reach its saturation value of 1023 (due to the image was stored in 10 bits data) by depending on the sensitivity value being adjusted. The uniformity test gave the result of 0.12%. The cassette was used to perform the QA tests which were previously performed using film. All the results met the specification as stated in AAPM Task Group 40. The comparison for the portal images of PortalVisionTM contrastdetail phantom showed that the spatial resolution of the images obtained by CR system (Fujifilm Co., Ltd., Tokyo, Japan) were better than the EPID (Varian Medical Systems, Inc., Palo Alto, USA) and film system (Eastman Kodak Co., New York, USA). The IP cassette type PII was found to be suitable as an alternative QA test tool and portal imaging in radiotherapy.

To prospectively determine in a fetal pig model whether diagnostic performance comparable to that of high-detail screen-film imaging can be achieved with computed radiography for the detection of simulated classic metaphyseal lesions (CMLs), by using Faxitron digital images as the reference standard, and whether radiation dose reduction is possible.This study was granted exempt status by the institutional review board and the animal care and use committee. Fractures simulating the CML were produced in distal femurs of 20 deceased fetal pigs. Twenty normal femurs served as control femurs. Femurs were imaged with a standard single-side-read 100-microm pixel sampling imaging plate (IP), a high-resolution dual-side-read 50-microm pixel sampling IP, and a high-detail screen-film imaging system. Eight tube current-time product settings (0.5-10.0 mAs) and two tube voltage selections (56 and 70 kVp) were employed. Two pediatric radiologists evaluated 920 images for fracture by using a five-point Likert scale. Area under the receiver operating characteristic curve (A(z)) values for the imaging systems were compared by using nonparametric chi(2) tests (all P.05).For pooled rater data, performance of computed radiography was comparable to that of screen-film imaging, and superior performance (P = .04) was achieved with the more experienced rater. The A(z) value tended to increase as the tube current-time product setting was increased. Within each system, there was no significant difference in A(z) values for all images obtained at 56 and 70 kVp (dual-side-read IP, P = .63; single-side-read IP, P = .25; screen-film imaging system, P = .5). At 56 kVp, a dose reduction of up to 69% was achieved, and accuracy of computed radiography was comparable to that of screen-film imaging.Findings in this study suggest that computed radiography can replace screen-film imaging in the detection of CMLs and may permit dose reduction.

Objective: The aim of this study was to establish a preclinical mouse model to study metastases of paediatric rhabdomyosarcoma at the macroscopic and cellular levels, with different imaging methods. Experimental Design: The alveolar rhabdomyosarcoma cell line Rh30 was stably transfected with the red fluorescent protein (DsRed2) then was xenotransplanted (intravenous injection [n = 8], and footpad injection [n = 8]) into nude mice (NMRI nu/nu). Macroscopic imaging of metastases was performed using DsRed2‐fluorescence and flat‐panel volumetric computed tomography scan. In a further series of animals (n = 8), in vivo cell trafficking of rhabdomyosarcoma cells using cellular imaging with an Olympus OV100 variable‐magnification small‐animal imaging system was used. Results: Metastases in the pelvis, thoracic wall and skin were visualized by fluorescence imaging. Pelvic metastases were found after tail vein injection and at other metastatic sites after footpad injection. Flat‐panel volumetric computed tomography scan data allowed highly specific analysis of contrast between tumour and surrounding tissue. Correlation between fluorescence and flat‐panel volumetric computed tomography scan imaging data was observed. Single‐cell imaging visualized tumour cells in the vessels and demonstrated the arrest of tumour cells at vessel junctions followed by extravasation of the tumour cells. Conclusion: We established a model for visualization of experimental metastatic invasion and describe relevant tools for imaging childhood rhabdomyosarcoma metastases at the macroscopic and cellular levels. Imaging of cell trafficking visualized the behaviour of tumour cells and development of metastases by accumulation and extravasation of rhabdomyosarcoma cells.

Doses for a range of examinations and views using digital X-ray equipment with full-body linear slit scanning capabilities (Statscan) have been compared with those from other published studies. Entrance doses (free-in-air) were measured using a dosimeter, and effective doses were generated using a Monte Carlo simulator. Doses delivered by the linear slit scanning system were significantly lower than those from conventional X-ray equipment. Effective doses were between 9 and 75% of the United Nations Scientific Committee Report on the Effects of Ionising Radiation doses for standard examinations. This dose reduction can be explained by the properties of linear slit scanning technology, including low scatter, beam geometry, the use of a digital detector and the use of higher than usual tube voltages.

The aim of this study is to assess the physical properties of a recently installed digital fluoroscopy unit, Axiom Iconos R200 unit (Siemens, Germany), including image quality and patient dose. Image quality parameters and patient doses were measured at various fields of view (FOV) and frame rates. The entrance surface dose rate (ESDR) was measured using standard 30 x 30 cm2 polymethylmethacrylate (PMMA) phantom with different thicknesses. The ESDR was measured using a 20 cm PMMA and largest FOV ranged from 1.1 to 8.2 mGy min(-1) for different frame rates available. The low-contrast sensitivity varied from 1.8 to 6.6%, as the limiting spatial resolution changes from 1.25 to 2.24 ln mm(-1) for the different magnifications, frame rates and phantom thicknesses. This study shows the weak points of the standard quality control protocols. The additional image quality and dose assessments revealed the existing potential for optimisation of the system.

The aim of this study was to compare detection of non-cavitated approximal caries lesions in images from seven solid-state intraoral digital receptors, with particular focus on two task-specific enhancement filters. One hundred and sixty approximal non-cavitated surfaces were radiographed under standardized conditions using the following seven intraoral solid-state digital receptors: two CMOS systems, Schick CDR-APS, and Kodak RVGui; and five CCD systems: Visualix, VistaRay, Dixi2, Sidexis, and Dr. Suni Plus. The Kodak RVGui digital images were captured with two task-specific, predefined enhancement filters (“dento-enamel” and “periodontal”). Eight observers examined the digital images for the presence or absence of approximal carious lesions. The teeth were subsequently sectioned for histological analysis, which served as the “gold standard” for the radiographic examination and allowed for a calculation of sensitivity, specificity, and overall accuracy. Both RVG modalities obtained the highest sensitivity values, which were significantly higher than with Visualix, Sidexis, and VistaRay images (all P ≤ 0.03). The RVG “periodontal” images also had a higher accuracy than Dixi2, Dr. Suni Plus, and CDR-APS (P ≤ 0.05). The RVG modalities also showed the largest observer variation, and their high sensitivities were mainly due to one observer. The sensitivity for VistaRay images was the lowest of all modalities and significantly lower than almost all the other digital systems (P ≤ 0.02; except for Visualix). Besides, Visualix images had lower sensitivity than CDR-APS, Dixi2, and Dr. Suni Plus images (P ≤ 0.003). On the other hand, the two RVGui image types showed the lowest mean specificity values. For overall accuracy, the differences among the modalities were non-significant (P > 0.05).

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 Az 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.

This ex vivo study evaluated the quality of digital radiographic images obtained with the photostimulable phosphor plate system (Digora) according to the processing delay and maintenance of optical plates in either opaque (supplied with the system) or transparent protective plastic cases during this period. Five radiographs were obtained from the mandibular molar region of a dry human mandible using optical plates. These plates were placed in the protective plastic cases before obtaining the radiographs and were processed immediately or after processing delays of 5, 60 and 120 min, when the case was removed. The results revealed a reduction in image quality when processing was delay 120 min compared to the other times. The opaque case provided better protection to the sensor than the transparent case. In conclusion, a 120-min processing delay for the Digora system caused a reduction in image quality, yet without interfering with the quality of diagnosis. The opaque case supplied by the system's manufacturer provided better protection to the optical plate than the transparent case.

OBJECTIVES: To assess radiographic methods and diagnostically sufficient images used before removal of mandibular third molars among randomly selected general dental clinics. Furthermore, to assess factors predisposing for an additional radiographic examination.METHODS: 2 observers visited 18 randomly selected clinics in Denmark and studied patient files, including radiographs of patients who had their mandibular third molar(s) removed. The radiographic unit and type of receptor were registered. A diagnostically sufficient image was defined as the whole tooth and mandibular canal were displayed in the radiograph (yes/no). Overprojection between the tooth and mandibular canal (yes/no) and patient-reported inferior alveolar nerve sensory disturbances (yes/no) were recorded. Regression analyses tested if overprojection between the third molar and the mandibular canal and an insufficient intraoral image predisposed for additional radiographic examination(s).RESULTS: 1500 mandibular third molars had been removed; 1090 had intraoral, 468 had panoramic and 67 had CBCT examination. 1000 teeth were removed after an intraoral examination alone, 433 after panoramic examination and 67 after CBCT examination. 90 teeth had an additional examination after intraoral. Overprojection between the tooth and mandibular canal was a significant factor (p CONCLUSIONS: Most mandibular third molars were removed based on an intraoral examination although 36.3% were insufficient.

Proximal dental caries remains a prevalent disease with only modest detection rates by current diagnostic systems. Many new systems are available without controlled validation of diagnostic efficacy. The objective of this study was to evaluate the diagnostic efficacy of three potentially promising new imaging systems.This study evaluated the caries detection efficacy of Schick 33 (Sirona Dental, Salzburg, Austria) intraoral digital detector images employing an advanced sharpening filter, Planmeca ProMax(®) (Planmeca Inc., Helsinki, Finland) extraoral "panoramic bitewing" images and Sirona Orthophos XG3D (Sirona Dental) CBCT images with advanced artefact reduction. Conventional photostimulable phosphor images served as the control modality. An ex vivo study design using extracted human teeth, ten expert observers and micro-CT ground truth was employed.Receiver operating characteristic analysis indicated similar diagnostic efficacy of all systems (ANOVA p 0.05). The sensitivity of the Schick 33 images (0.48) was significantly lower than the other modalities (0.53-0.62). The specificity of the Planmeca images (0.86) was significantly lower than Schick 33 (0.96) and XG3D (0.97). The XG3D showed significantly better cavitation detection sensitivity (0.62) than the other modalities (0.48-0.57).The Schick 33 images demonstrated reduced caries sensitivity, whereas the Planmeca panoramic bitewing images demonstrated reduced specificity. XG3D with artefact reduction demonstrated elevated sensitivity and specificity for caries detection, improved depth accuracy and substantially improved cavitation detection. Care must be taken to recognize potential false-positive caries lesions with Planmeca panoramic bitewing images. Use of CBCT for caries detection must be carefully balanced with the presence of metal artefacts, time commitment, financial cost and radiation dose.

The correlation of image quality with the exposure index (EI) and the processing protocol was investigated in a Kodak computed radiography (CR) system using clinical radiographs and a water phantom containing an aluminium and a copper step-wedge. The phantom was exposed to different dose levels and the acquired images were processed using four clinical protocols. The quality of these images was evaluated in terms of image brightness, contrast and noise. In clinical radiographs, there was no straightforward correlation of image quality with EI. In phantom images, higher EI values improved contrast and reduced noise but after a point this improvement does not justify the implied increase in patient dose. Image brightness, contrast and noise were also strongly dependent on the processing protocol. To obtain the images of satisfactory quality with the Kodak CR system, a dose slightly higher than those used in 400 relative speed screen-film systems and a processing protocol designated for the specific radiographic examination are required.

This study was carried out to investigate whether the electronic portal imaging (EPI) acquisition process could be optimized, and as a result tolerance and action levels be set for the PIPSPro QC-3V phantom image quality assessment. The aim of the optimization process was to reduce the dose delivered to the patient while maintaining a clinically acceptable image quality. This is of interest when images are acquired in addition to the planned patient treatment, rather than images being acquired using the treatment field during a patient's treatment. A series of phantoms were used to assess image quality for different acquisition settings relative to the baseline values obtained following acceptance testing. Eight Varian aS500 EPID systems on four matched Varian 600C/D linacs and four matched Varian 2100C/D linacs were compared for consistency of performance and images were acquired at the four main orthogonal gantry angles. Images were acquired using a 6 MV beam operating at 100 MU min(-1) and the low-dose acquisition mode. Doses used in the comparison were measured using a Farmer ionization chamber placed at d(max) in solid water. The results demonstrated that the number of reset frames did not have any influence on the image contrast, but the number of frame averages did. The expected increase in noise with corresponding decrease in contrast was also observed when reducing the number of frame averages. The optimal settings for the low-dose acquisition mode with respect to image quality and dose were found to be one reset frame and three frame averages. All patients at the Northern Ireland Cancer Centre are now imaged using one reset frame and three frame averages in the 6 MV 100 MU min(-1) low-dose acquisition mode. Routine EPID QC contrast tolerance (+/-10) and action (+/-20) levels using the PIPSPro phantom based around expected values of 190 (Varian 600C/D) and 225 (Varian 2100C/D) have been introduced. The dose at dmax from electronic portal imaging has been reduced by approximately 28%, and while the image quality has been reduced, the images produced are still clinically acceptable.

Modern neonatal incubators incorporate an X-ray tray device into the mattress support structure to facilitate patient examination with minimal disturbance and distress. However, the usual method of examination is to place the image plate directly underneath the baby. Users often cite radiological reasons for not using X-ray trays but modern quantitative evidence is lacking. This work looks at the technical and clinical aspects of imaging neonates in incubators and the impact that these may have in determining the imaging protocol. A number of hospitals were surveyed to determine their current method of examination and the reasons for their preference. Experimental measurements of the radiological impact of using (or not using) the X-ray tray were performed for a range of neonatal incubators. The average dose to the image plate was 5.9 microGy (range 5.4-6.4 microGy) for the "plate on mattress" method and 3.0 microGy (2.0-3.8 microGy) when using the tray--a 49% reduction owing to the mattress support materials. However, when using a computed radiography (CR) imaging system, the image quality differences were marginal. Survey results indicated that nurses preferred to use the tray but that radiographers were reluctant. We conclude that incubator manufacturers could do much to improve the radiological performance of their equipment and we offer recommendations. We also conclude that, with appropriate nurse and radiographer training and the advent of CR imaging systems, use of X-ray tray facilities may optimize imaging of the neonate in the incubator.

BACKGROUND AND PURPOSE: The development of flat panel detectors (FPDs) has made cone-beam CT feasible for practical use in a clinical setting. Our purpose was to assess the usefulness of cone-beam CT using the FPD in conjunction with conventional digital subtraction angiography (DSA) for performing superselective intra-arterial chemotherapy for head and neck tumors. MATERIALS AND METHODS: Twenty-three consecutive patients (43 feeding arteries) were prospectively examined. All of the patients underwent intra-arterial rotational angiography using an FPD system, and the cone-beam CT was reconstructed from the volume dataset. Two radiologists evaluated the quality of the cone-beam CT and then evaluated whether the additional information provided by the cone-beam CT was useful for the interventional procedures. RESULTS: In 41 (95%) of 43 arteries, the extent of contrast material perfusion was sufficiently visualized on cone-beam CT. In 20 (47%) of 43 arteries, the DSA plus cone-beam CT was superior to the DSA alone regarding the precise understanding of vascular territory of each artery. This information was helpful for predicting the drug delivery for superselective intra-arterial chemotherapy, especially in deeply invasive tumors with multiple feeding arteries. CONCLUSION: In superselective intra-arterial chemotherapy for head and neck tumors, cone-beam CT with FPD provides useful additional information, which allows interventional radiologists to determine the feeders, as well as the dose of antitumor agent for each feeder.

Introduction: As orthodontic practice moves toward 3-dimensional cephalometric analyses, a solution is required to ensure sustained availability of well-established projected treatment outcomes based on 2-dimensional analyses. This ex-vivo study was conducted to compare the accuracy of linear measurements made on photostimulable phosphor cephalograms with 3 methods for simulating lateral cephalograms with cone-beam computed tomography (CBCT). Methods: The linear distances between anatomical landmarks on dentate dry human skulls were measured by observers using digital calipers for S-N, Ba-N, M-N, ANS-N, ANS-PNS, Pog-Go, Go-M, Po-Or, and Go-Co. The skulls were imaged with CBCT with a single 360° rotation, producing 306 basis images and achieving 0.4 mm isotrophic voxel resolution on volumetric reconstruction for making ray-sum reconstructed cephalograms. Two other cephalogram approaches were used with the CBCT system—a single transmission image generated as a scout image designed to check patient positioning before CBCT, and a single-frame lateral basis image. Conventional digital lateral cephalograms (LCs) were acquired with the photostimulable phosphor system. Images were imported into a cephalometric analysis program (Dolphin Imaging Cephalometric and Tracing Software, Chatsworth, Calif) to compute the included linear measurements. Analyses were repeated 3 times and statistically compared with measured anatomic truth with ANOVA ( P ≤.05). The intraclass correlation coefficient was determined as an index of intra- and interobserver reliability. Results: The intraclass correlation coefficient for the LCs was significantly less than for the measured anatomic truth and for all CBCT-derived images. CBCT images either produced with individual frames or reconstructed from the volumetric data set were accurate for all measurements except Pog-Go and Go-M. CBCT scout images had the second highest accuracy for all measurements except Pog-Go, Go-M, and Go-Co. Conventional LCs had the least accuracy; they were accurate only for Po-Or and ANS-N. Conclusions: CBCT-derived 2-dimensional LCs proved to be more accurate than LCs for most linear measurements calculated in the sagittal plane. No advantage was found over single-frame basis images in using ray-sum generated cephalograms from the CBCT volumetric data set.

Mini C-arm image intensifiers are used commonly in surgery of the upper limb. With relatively low doses of emitted ionising radiation, portability and superior quality of image, they are a useful aid to the operating surgeon. However, these benefits are not so often used outside the theatre setting. This paper examines the use of a mini C-arm image intensifier in the out-patient clinic and presents an audit of 100 consecutive out-patients. We reviewed the potential benefits and effects on their care pathway. We also look at the specific radiation protection issues of the mini C-arm image intensifier in the out-patients clinic. We believe use of the mini C-arm image intensifier in the out-patient setting may speed treatment and reduce the cost of treatment.

In the optimization process of lumbar spine examinations, factorial experiments were performed addressing the question of whether the effective dose can be reduced and the image quality maintained by adjusting the image processing parameters. A 2k-factorial design was used which is a systematic and effective method of investigating the influence of many parameters on a result variable. Radiographic images of a Contrast Detail phantom were exposed using the default settings of the process parameters for lumbar spine examinations. The image was processed using different settings of the process parameters. The parameters studied were ROI density, gamma, detail contrast enhancement (DCE), noise compensation, unsharp masking and unsharp masking kernel (UMK). The images were computer analysed and an image quality figure (IQF) was calculated and used as a measurement of the image quality. The parameters with the largest influence on image quality were noise compensation, unsharp masking, unsharp masking kernel and detail contrast enhancement. There was an interaction between unsharp masking and kernel indicating that increasing the unsharp masking improved the image quality when combined with a large kernel size. Combined with a small kernel size however the unsharp masking had a deteriorating effect. Performing a factorial experiment gave an overview of how the image quality was influenced by image processing. By adjusting the level of noise compensation, unsharp masking and kernel, the IQF was improved to a 30% lower effective dose.

The introduction and extensive application of spectral shaping filters during fluoroscopic imaging procedures have decreased the patient skin entrance exposures (air kerma) dramatically while the image quality is optimized and maintained. The purpose of this article is to demonstrate and understand the functionality and operation of fluoroscopic automatic dose rate control logic installed on a modern cardiovascular angiography system, as seen from the equipment operation point of view. The fluoroscopic "patient" entrance exposure (air kerma) rate and the flat panel image receptor input exposure (air kerma) rate were obtained for reference and future application.

Magnification views are a common way to perform a secondary examination when suspicious abnormalities are found in a screening mammogram. The visibility of microcalcifications and breast lesions is restricted by the compromise between the image quality and the absorbed dose. In this study, image quality characteristics in magnification mammography were evaluated based on Monte Carlo techniques. A breast phantom was utilized, simulating a homogeneous mixture of adipose and glandular tissue in various percentages of glandularity, containing inhomogeneities of various sizes and compositions. The effect of the magnification degree, breast glandularity, tube voltage and anode/filter material combination on image quality characteristics was investigated in terms of a contrast-to-noise ratio (CNR). A performance index PI(nu) was introduced in order to study the overall performance of various anode/filter combinations under different exposure parameters. Results demonstrate that CNR is improved with the degree of magnification and degraded as the breast glandularity is increased. Degree of magnification 1.3 offers the best overall performance for most of the anode/filter combinations utilized. Under magnification conditions, the role of dose is demoted against the image quality, as magnification views are secondary, diagnostic examinations and not screening procedures oriented to non-symptomatic women. For decreased image quality weighting, some anode/filter combinations different from Mo/0.030 mmMo can be utilized as they offer a similar performance index. However, if the desired weighting for the image quality is high, the Mo/0.030 mmMo combination has the best overall performance.

Objective To compare experimentally the image quality of charged-coupled device (CCD)-based digital, flatbed scanner digitized, and dental film radiographs. Study design High-contrast standardized radiographs of an aluminum step wedge containing boreholes were obtained on dental radiographic film (F) and a CCD receptor (D). Digitization (S) was done with a flatbed scanner. Each radiograph was separated into 23 single images, 18 of which showed a dark spot. Thirty observers indicated their confidence on the visibility of the spots for a receiver operating characteristic (ROC) analysis. Results Mean Az values (area beneath the ROC curves) differed significantly (P < .05), being highest for D (Az = 0.76), followed by F (Az = 0.71) and S (Az = 0.60). Mean sensitivity of S (0.45) was significantly (P = .000) lower than for D (0.66) and F (0.67). Conclusion The difference between modality D and F was small. However, the inferior performance of S images, particularly in dark regions, could be clinically relevant.

Aim To compare the subjective quality of limited cone-beam computed tomography (LCBCT), storage phosphor plate (SPP) and F-speed film images for the evaluation of length and homogeneity of root fillings. Methodology Root canals of 17 extracted permanent mandibular incisor teeth were filled. With the teeth placed in their jaws, images were obtained with Accu-I-Tomo LCBCT, Digora® Optime image plate system and F-speed film using exposure parameters yielding ‘clinically’ acceptable density and contrast. Three radiologists and three endodontists independently rated the quality of all images in respect to homogeneity and the length of root fillings using a 3-graded scale. Evaluations were undertaken in two sessions. In the first, the coronal LCBCT images were not included. In the second, both coronal and sagittal LCBCT images were rated along with F-speed film and SPP images. Results were compared using the Friedman test (P

In modern X-ray computed tomography (CT) a trend to increased volume coverage by using multi-row detectors is apparent. Flat-panel detector CT (FPD-CT) systems provide an even larger field of measurement which, however, results in an increased scatter fraction. We investigated the scatter intensities registered in the case of FPD-CT. A hybrid model for the simulation of scatter combining deterministic and Monte Carlo methods was used for the scatter calculations. The influence of imaging parameters on the registered scatter intensity was examined both in single projections and reconstructed images. Scatter-to-primary ratios (SPRs) are given for various values of object thickness, field size, object-to-detector distance, incident energy and projection angle. For the simulations, homogeneous water phantoms and realistic patient data sets were used to produce scatter data representative for clinical situations. The SPR increases with object size, collimation and z-extent resulting in SPR>>1 and respective scatter artifacts in the reconstructed images. In contrary, the scatter intensity decreases non-linearly with the object-to-detector distance. The angular and spatial distributions of scatter form a flat function as compared to the distribution of the primary signal. Single scatter appears to determine the distribution and magnitude of the total-scatter intensity at the detector.

Background: Many departments have analog simulators and irradiation facilities (especially cobalt units) without electronic portal imaging. Import of the images into the R&V (Record & Verify) system is required. Material and Methods: Simulator images are grabbed while portal films scanned by using a laser scanner and both converted into DICOM RT (Digital Imaging and Communications in Medicine Radiotherapy) images. Results: Image intensifier output of a simulator and portal films are converted to DICOM RT images and used in clinical practice. The simulator software was developed in cooperation at the authors’ hospital. Conclusion: The digitalization of analog simulators is a valuable updating in clinical use replacing screen-film technique. Film scanning and digitalization permit the electronic archiving of films. Conversion into DICOM RT images is a precondition of importing to the R&V system.

We applied information theory to quantify information losses in assessing contrast-detail (C-D) analysis. Images of a C-D phantom were acquired with a flat panel detector (FPD) and a computed radiography (CR) by changing surface entrance doses. Six phantom radiographs (FPD: five images; CR: one image) were prepared for visual evaluations. Thirteen radiographers and two radiologists participated in the observation test. Detectability was defined as the shortest length of the cylinders of which border the observers could recognize from the background, and was recorded using row number. Information content was defined as the entropy summation operatorp(i)log(1/p(i)) with detection probabilities p(i), which were calculated from distribution of detection rate of the ith column. Information loss, in unit of bits, was calculated as the difference between information obtained and information content when all the columns were detected. The information losses decreased with the increase in cylinder diameters and with the increase in surface entrance dose. Because the information loss varies depending on distribution of detection rate, this method of using the information theory was expected to be more sensitive in evaluating the C-D image quality than using the averaged values of detectability.

The purpose of this study was to evaluate the performance and potential contribution of computer-aided detection (CAD) to independent double reading of paired screen-film and full-field digital screening mammograms.The cases of 3,683 women who underwent both screen-film mammography and full-field digital mammography (FFDM) with independent double reading for each technique were followed for 2 years to include cancers detected in the interval between screening rounds and cancers detected at the next screening round. Fifty-five biopsy-proven cancers were diagnosed. The baseline screening mammograms of the 55 cancers were defined as having positive findings if at least one of two independent readers scored it 2 or higher on a 5-point rating scale. The baseline mammograms of interval (n = 10) or secondround (n = 16) cancers were retrospectively classified as overlooked (n = 2), minimal sign actionable (n = 8), minimal sign nonactionable (n = 5), and normal (n = 11). The baseline mammograms of these cases of cancer were evaluated with a CAD system, and the CAD results were compared (McNemar's test for paired proportions) with the findings at prospective independent double reading of mammograms obtained with each technique.For FFDM, CAD sensitivity was 95% (37/39) compared with 64% (25/39) for double reading (p = 0.006), and for screen-film mammography, CAD sensitivity was 85% (33/39) compared with 77% (30/39) for prospective double reading (p = 0.57) of radiographically visible lesions in baseline mammograms. CAD correctly marked five (13%) of 39 cancers on screen-film mammography and 14 (36%) of 39 cancers on FFDM not detected at prospective independent double reading.CAD showed the potential to increase the cancer detection rate for FFDM and for screen-film mammography in breast cancer screening performed with independent double reading.

The aim of the work was to establish optimum ambient light conditions for viewing radiologic images of the wrist on liquid crystal display monitors.Five ambient light levels were investigated: 480, 100, 40, 25, and 7 lux. Seventy-nine experienced radiologists were asked to examine 30 posteroanterior wrist images and decide whether a fracture was present. All images were displayed on liquid crystal display monitors. Receiver operating characteristic analysis was performed, and the numbers of false-positive and false-negative findings were recorded.For all the radiologists, greater area under the receiver operating characteristic curve and lower numbers of false-positive and false-negative findings were recorded at 40 and 25 lux compared with 480 and 100 lux. At 7 lux, the results were generally similar to those at 480 and 100 lux. The experience and knowledge of radiologists specializing in imaging of musculoskeletal trauma appeared to compensate in part for inappropriate lighting levels.Typical office lighting and current recommendations on ambient lighting can reduce diagnostic efficacy compared with lower levels of ambient lighting. If, however, no light other than that of the monitor is used, results are similar to those with excessive levels of lighting. Careful control of ambient lighting is therefore required to ensure that diagnostic accuracy is maximized, particularly for clinicians not expert in interpreting posteroanterior wrist images.

The objective of our study was to compare the detection and distinguishability of microcalcifications on mammograms obtained with a digital direct flat-panel detector versus an analog system using an anthropomorphic breast phantom.Studies were performed with a digital mammography system (Selenia) and an analog mammography system (Mammomat 3). Sixty-five transparent films were used as test specimens. Randomly distributed round and heterogeneous silicate particles (diameter, 100-1,400 microm) and an anthropomorphic scatter body were applied to the films. All radiographs were taken at identical settings and exposures. Six radiologists rated the films and monitor-displayed images independently of each other in random order on a standardized electronic questionnaire.Interpretations based on monitor reading produced superior results over those based on digital image reading and analog film reading. In 41.1% (95% CI, 38.7-43.5%) of all the monitor readings, 20.2% (18.2-22.2%) of all digital images, and 19.6% (17.6-21.6%) of all analog films, the number of detectable microcalcifications agreed with the gold standard method. The diameter of visible microcalcifications was interpreted correctly in 35.6% (33.2-38.0%) of monitor readings, 19.0% (17.1-21.0%) of digital images, and 21.0% (18.9-23.0%) of analog films; and microcalcification shape was interpreted correctly in 53.8% (51.4-56.3%) of monitor readings, 28.2% (26.0-30.4%) of digital images, and 28.3% (26.0-30.5%) of analog films. Microcalcification number and size were underestimated more frequently than overestimated. Regardless of display medium, accuracy increased proportionately with the diameter of the simulated microcalcifications for all evaluation variables.Digital flat-panel mammography is superior to the analog screen-film method for the detection and morphologic characterization of microcalcifications larger than 200 microm in diameter when the display medium is a monitor.

The aim of the present study was to determine (1) the absorbed and the exit radiation doses for cephalometric exposures on a phantom head with various exposure settings and image receivers, and (2) the diagnostic image quality for various modalities assessed on cephalometric radiographs of patients.The dose measurements for lateral cephalometric radiographs were performed with a semiconductor detector, and also with thermoluminescent detectors and an Alderson phantom. Both the integral and the effective doses were determined. Two radiographs of each patient (n=119) were taken at two different times, one at a low tube potential setting, 75+/-5 kV, and one with a decreased dose. Film-screen systems with speed class 400 and one storage phosphor plate were used. Five observers assessed the radiographs for the visualization of six cephalometric reference points on a three-point scale with -1, 0 and 1. Twenty-seven image pairs were rescored to determine inter- and intrarater reliability. The statistical analysis was done using analysis of variance and Tukey's HSD (honestly significant difference) post hoc test.Increasing the tube potential setting led to an average dose reduction to 83% (integral dose) or to 87% (effective dose). Instead of taking the radiograph at a low tube potential setting (75 kV), a dose reduction of about 15% was feasible at a high tube potential setting (90 kV). A significant difference in reference point visibility existed between film radiographs at low tube potential settings (mean score 0.984) and at high tube potential settings (90 kV, mean score 0.958). For the storage phosphor plates, there was no significant difference to the film-screen combinations at low tube potential and halved milliampere seconds settings. In the second assessment, there was a high degree of agreement (96.6%) compared with the first assessment (unadjusted for random agreement).As there is only minimal dose reduction at increased tube potential settings, for a dose reduction, it seems to be more useful to use storage phosphor plates at unchanged tube potential and halved milliampere seconds settings compared with the film-screen combination.

Objectives The aim of this study was to compare the image performance of silicon-based flat-panel-detector-based volumetric computed tomography (fpVCT) to multislice spiral computed tomography (MSCT) for the visualization and detail detectability of skeletal structures in rodents of different development stages. Materials and Methods Rodents of different development stages were imaged with fpVCT (GE prototype with circular gantry with two 1024×1024, 200-μm pixel size, amorphous silicon/Cesium lodid (Csl) flat-panel detector) and eight-slice MSCT (LightSpeed Ultra). Imaging parameters (80 kVp, 100 mA) and the position of the rodents were identical in both techniques. Image quality, detail detectability, and contour of skeletal structures were judged by two observers in consensus using a 4-point scale (1=unsatisfactory…4=good). Findings were displayed and evaluated in axial slices, multiplanar reconstructions (MPR), maximum intensity projections (MIP) and volume rendering technique (VRT) in both modalities. Mean and standard of error of mean were calculated. Results In axial slices, visualization and detail detectability of very subtle skeletal structures, e.g., the basis of the skull was better in fpVCT than in MSCT (4 vs. 2 points). The MPRs of fpVCT showed less artifacts and more details than those of the MSCT. The MIPs and VRTs of the fpVCT demonstrated best image quality in all rodents of different development stages, whereas MSCT showed significant artifacts. Conclusion fpVCT outperformed MSCT in imaging of small rodents. Due to the truly isotropic volume data set with high spatial resolution, fpVCT is a powerful tool in evaluating detailed skeletal structures.

Objective: To compare diagnostic accuracy of tomograms obtained with film and three digital image receptor modalities for detection of morphological changes in the temporomandibular joint (TMJ). Methods: Lateral and frontal cross-sectional tomograms of 158 TMJs in 80 dry human skulls were obtained with four X-ray receptors: one conventional film (Agfa-Gevaert), two photostimulable phosphor (PSP) plates: VistaScan and Digora PCT and one charge-coupled device (CCD): ProMax. The film and the PSP plate tomograms were exposed in a Cranex Tome X-ray unit and the CCD tomograms in the ProMax X-ray unit. The tomograms were examined by three observers for the presence of morphological changes in the condyle, the mandibular fossa and the articular tubercle. Naked-eye inspection of the articular surfaces of the TMJs performed by the same three observers served as the gold standard for the true presence of morphological changes. Results: For examination of TMJ changes using lateral and frontal tomograms in combination and lateral tomograms separately, the ProMax modality obtained a significant lower diagnostic accuracy than the other three modalities, between which no significant differences were found. For morphological changes localized to the condyle in which the highest number of changes were present according to the gold standard, the same result was found. Conclusion: The ProMax modality was significantly less accurate than the film, VistaScan and Digora PCT modalities for the detection of overall TMJ morphological bone changes as well as condylar bone changes. Dentomaxillofacial Radiology (2007) 36, 12‐17. doi: 10.1259/dmfr/78486936

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.

New radiographic techniques have made it possible to color-code intra-oral digital radiographs. The purpose of the present study was to compare the accuracy and precision of marginal bone level measurements in digital radiographs with and without color coding.Periapical digital radiographs of 21 patients were processed with and without a color-coding algorithm. The patients had periodontal surgery immediately after exposure of radiographs, and vertical distances from the cemento-enamel junction (CEJ) to the most apical part of the marginal bone were measured clinically. The measured values were considered as a reference standard and subtracted from the corresponding radiographic vertical distance. Seven observers contributed to the radiographic measurements under the same viewing conditions.No statistically significant differences were found between absolute differences of vertical distances obtained from radiographs and their corresponding reference standards in the two types of radiograph. Intra- and inter-observer variability was not significant.Color-coded digital radiographs did not provide a more favorable accuracy when assessing marginal alveolar bone levels than black-and-white radiographs and thus did not improve measurement of such levels.

Purpose To prospectively evaluate a protocol for transit dosimetry on a patient population undergoing intensity modulated radiation therapy (IMRT) and to assess the issues in clinical implementation of electronic portal imaging devices (EPIDs) for treatment verification. Methods and Materials Fifty-eight patients were enrolled in the study. Amorphous silicon EPIDs were calibrated for dose and used to acquire images of delivered fields. Measured EPID dose maps were back-projected using the planning computed tomographic (CT) images to calculate dose at prespecified points within the patient and compared with treatment planning system dose offline using point dose difference and point γ analysis. The deviation of the results was used to inform future action levels. Results Two hundred twenty-five transit images were analyzed, composed of breast, prostate, and head and neck IMRT fields. Patient measurements demonstrated the potential of the dose verification protocol to model dose well under complex conditions: 83.8% of all delivered beams achieved the initial set tolerance level of Δ D of 0 ± 5 cGy or %Δ D of 0% ± 5%. Importantly, the protocol was also sensitive to anatomic changes and spotted that 3 patients from 20 measured prostate patients had undergone anatomic change in comparison with the planning CT. Patient data suggested an EPID-reconstructed versus treatment planning system dose difference action level of 0% ± 7% for breast fields. Asymmetric action levels were more appropriate for inversed IMRT fields, using absolute dose difference (−2 ± 5 cGy) or summed field percentage dose difference (−6% ± 7%). Conclusions The in vivo dose verification method was easy to use and simple to implement, and it could detect patient anatomic changes that impacted dose delivery. The system required no extra dose to the patient or treatment time delay and so could be used throughout the course of treatment to identify and limit systematic and random errors in dose delivery for patient groups.

X-ray phosphor-based detectors have enormously improved the quality of medical imaging examinations through the optimization of optical diffusion. In recent years, with the development of science and technology in the field of materials, improved powder phosphors require structural and optical properties that contribute to better optical signal propagation. The purpose of this paper was to provide a quantitative and qualitative understanding of the optical absorption characteristics in the assessment of powder phosphor-based detectors (from nano- scale up to micro-scale). Variations on the optical absorption parameters (i.e. the light extinction coefficient [Formula: see text] and the percentage probability of light absorption p%) were evaluated based on Mie calculations examining a wide range of light wavelengths, particle refractive indices and sizes. To model and assess the effects of the aforementioned parameters on optical diffusion, Monte Carlo simulation techniques were employed considering: (i) phosphors of different layer thickness, 100 μm (thin layer) and 300 μm (thick layer), respectively, (ii) light extinction coefficient values, 1, 3 and 6 μm(-1), and (iii) percentage probability of light absorption p% in the range 10(-4)-10(-2). Results showed that the [Formula: see text] coefficient is high for phosphor grains in the submicron scale and for low light wavelengths. At higher wavelengths (above 650 nm), optical quanta follow approximately similar depths until interaction for grain diameter 500 nm and 1 μm. Regarding the variability of the refractive index, high variations of the [Formula: see text] coefficient occurred above 1.6. Furthermore, results derived from Monte Carlo modeling showed that high spatial resolution phosphors can be accomplished by increasing the [Formula: see text] parameter. More specifically, the FWHM was found to decrease (i.e. higher resolution): (i) 4.8% at 100 μm and (ii) 9.5%, at 300 μm layer thickness. This study attempted to examine the role of the optical absorption parameters on optical diffusion studies. A significant outcome of the present investigation was that the improvement of phosphor spatial resolution without decreasing the light collection efficiency too much can be better achieved by increasing the parameter [Formula: see text] rather than the parameter p%.

Objective The purpose of the present study was to investigate the potential of using advanced external adaptive image processing for maintaining image quality while reducing exposure in dental panoramic storage phosphor plate (SPP) radiography. Materials and methods Thirty-seven SPP radiographs of a skull phantom were acquired using a Scanora panoramic X-ray machine with various tube load, tube voltage, SPP sensitivity and filtration settings. The radiographs were processed using General Operator Processor (GOP) technology. Fifteen dentists, all within the dental radiology field, compared the structural image quality of each radiograph with a reference image on a 5-point rating scale in a visual grading characteristics (VGC) study. The reference image was acquired with the acquisition parameters commonly used in daily operation (70 kVp, 150 mAs and sensitivity class 200) and processed using the standard process parameters supplied by the modality vendor. Results All GOP-processed images with similar (or higher) dose as the reference image resulted in higher image quality than the reference. All GOP-processed images with similar image quality as the reference image were acquired at a lower dose than the reference. This indicates that the external image processing improved the image quality compared with the standard processing. Regarding acquisition parameters, no strong dependency of the image quality on the radiation quality was seen and the image quality was mainly affected by the dose. Conclusions The present study indicates that advanced external adaptive image processing may be beneficial in panoramic radiography for increasing the image quality of SPP radiographs or for reducing the exposure while maintaining image quality.

As the use of diagnostic X-ray equipment with flat panel detectors (FPDs) has increased, so has the importance of proper management of FPD systems. To ensure quality control (QC) of FPD system, an easy method for evaluating FPD imaging performance for both stationary and moving objects is required. Until now, simple rotatable QC phantoms have not been available for the easy evaluation of the performance (spatial resolution and dynamic range) of FPD in imaging moving objects. We developed a QC phantom for this purpose. It consists of three thicknesses of copper and a rotatable test pattern of piano wires of various diameters. Initial tests confirmed its stable performance. Our moving phantom is very useful for QC of FPD images of moving objects because it enables visual evaluation of image performance (spatial resolution and dynamic range) easily.

Flat detectors (FD) have completely replaced image intensifiers in angiography. Due to this development not only the image quality of 2D digital subtraction angiography series (2-D-DSA) could be improved but also the acquisition of computed tomography (CT)-like cross-sectional images (FD-CT) within the angio suite became feasible. These techniques are now being used in daily clinical routine. Only little information about effective doses of these applications to patients has been published in the literature. We describe the effective patient dose of current applications in the field of angiography and demonstrate strategies to minimize the dose to the patient. In addition, we compare FD-CT applications to standard multislice CT applications.