Direct Digital System Research Articles

Radiopacity and Microleakage Evaluation of Different Intermediate Materials

Objective: The aim of this study is to compare the radiopacities of different types of materials with indications for application as a base under restorations and the microleakage of the final restorations with these materials applied as bases. Methods: Standart Class I cavities were prepared in 90 caries-free molar teeth. The cavities were randomly divided into 9 groups according to the type of intermediate material to be applied (n=10): 1. High flowable composite, 2. Low flowable composite, 3. Fiber reinforced composite, 4. Giomer, 5. Ormocer, 6. Alkasite, 7. Bioactive composite, 8. High viscosity glass ionomer, 9. Glass carbomer. The base materials in each group were applied to the cavity floor and restoration was completed using a nanohybrid composite resin and an universal adhesive system. To evaluate radiopacity, radiographic images were taken using direct digital system and mean gray values were measured with ImageJ software. To analyse microleakage, specimens were subjected to thermocycling, immersed in 2% methylene blue solution for 24 hours, sectioned buccolingually and leakage values observed on the half-piece surfaces were examined under a stereomicroscope and recorded. Data were analysed using One-way Analysis of Variance, Tukey HSD Test and Pearson Chi-Square with Bonferroni-corrected Z Test (p˂0.05). Results: In terms of radiopacity, while alkasite and low flowable composite showed the highest radiopacity, glass carbomer gave the lowest (p

Evaluation of mandibular trabecular and cortical structure by fractal analysis in hyperlipidemia and hypertension patients

IntroductionThis study aimed to evaluate the mandibular trabecular and cortical changes in patients with hyperlipidemia (HL) and/or hypertension (HT) using fractal dimension (FD) analysis, mandibular cortical width (MCW), panoramic mandibular index (PMI) and mandibular cortical index (MCI). Materials and methodsPanoramic radiographs of 100 patients were evaluated. FD measurement of three region of interest (ROI) including the angulus, corpus and interdental bone area were made. MCW, PMI and MCI were also measured and noted. ResultsAngulus, corpus and interdental FD values were significantly lower in three disease groups than the control group. Angulus, corpus, and interdental FD values were significantly lower in the HL+HT group than in the HL group and HT group. MCW value was significantly lower in the HL group, HT group, and HL+HT group than the control group. The cortical index C1 was more common in the control group while C2 was more common in the HT, HL and HL+HT group. ConclusionThe fact that FD was significantly lower in the HL+HT group compared to the HL and HT groups indicates the positive effect of their association on bone loss and quality. FD measurements on images obtained using a direct digital panoramic system can be used for treatment planning and follow-up of patients with HL and/or HT.

Macroscopic model and statistical model to characterize electromagnetic information of a digital coding metasurface.

A digital coding metasurface is a platform connecting the digital space and electromagnetic wave space, and has therefore gained much attention due to its intriguing value in reshaping wireless channels and realizing new communication architectures. Correspondingly, there is an urgent need for electromagnetic information theory that reveals the upper limit of communication capacity and supports the accurate design of metasurface-based communication systems. To this end, we propose a macroscopic model and a statistical model of the digital coding metasurface. The macroscopic model uniformly accommodates both digital and electromagnetic aspects of the meta-atoms and predicts all possible scattered fields of the digital coding metasurface based on a small number of simulations or measurements. Full-wave simulations and experimental results show that the macroscopic model is feasible and accurate. A statistical model is further proposed to correlate the mutual coupling between meta-atoms with covariance and to calculate the entropy of the equivalent currents of digital coding metasurface. These two models can help reconfigurable intelligent surfaces achieve more accurate beamforming and channel estimation, and thus improve signal power and coverage. Moreover, the models will encourage the creation of a precoding codebook in metasurface-based direct digital modulation systems, with the aim of approaching the upper limit of channel capacity. With these two models, the concepts of current space and current entropy, as well as the analysis of information loss from the coding space to wave space, is established for the first time, helping to bridge the gap between the digital world and the physical world, and advancing developments of electromagnetic information theory and new-architecture wireless systems.

Reduction of radiations exposure in endodontics: comparative analysis of direct (GX S-700, Gendex) and semidirect (VistaScan Mini View, Dürr) digital systems.

The importance of intraoral periapical radiography is crucial as it represents a fundamental mean of evaluation and diagnosis for supporting bone and teeth hard tissues diseases and pathologies. Even though conventional film technology is still widespread, presently there are many digital radiography alternatives. Direct digital systems are devices with an intraoral sensor wired or paired wireless with a computer. These devices do generate an image immediately during exposure and acquisition. The semi direct digital systems instead are based on phosphor image plates. Digital radiography offers many chances to improve our patient's healthcare standards reducing exposition to X-rays and the related stochastic radiation risk. Aim of this study is to compare the quality of images for endodontic purposes comparing three systems: conventional films, direct digital radiography and semidirect digital radiography.

Periapical radiographic technique errors made with digital sensors

Purpose: The objective of this study was to analyze the errors of technique in periapical radiographs as performed by fourth year students at the Dentistry School of the Pontifical Catholic University of Rio Grande do Sul, Brazil. Material and Methods: Fifteen students were randomly selected and each one performed a complete periapical examination in a mannequin. A Direct Digital X-Ray System equipped with a size 2 Sensor was used to obtain the radiographic images. A total of 210 periapical radiographs were evaluated and the images were classified according to the errors that were related to the radiographic technique. The students were also asked to report on their experience with the direct digital system. Results: The absence of a safety margin was the most frequent error on the radiographs that were performed by the students, while elongated image errors were not found. Regarding the radiographed regions, the highest frequency of errors was found in the upper canine region on the left side. Conclusion: The need for a greater training of the students of dentistry, in order to better perform the radiographic technique and to decrease the occurrence of technique errors in periapical radiographs when using a digital receptor, is emphasized. Keywords:Digital radiography, Diagnostic imaging, Learning, Students.

Viewpoint: COVID-19 and seed security response now and beyond

COVID-19 brings new challenges worldwide, including to smallholder farmers and their seed systems. In response, an escalating number of seed projects are being planned to deliver immediate aid or to alter current seed production programs. A Statement, prepared by diverse seed system experts, aims to steer both the immediate aid (next 1–2 seasons) and more developmental planning (next 1–3 years). The Statement includes 10 short-term and 4 medium-term recommendations, placing emphasis on all seed systems smallholders use: formal, informal, and integrated. It also looks beyond seed per se to the direct information and digital systems that shape remote assessments, data sharing and inclusive feedback. The Statement is prefaced by an introduction that helps contextualize the recommendations, reviews the history of humanitarian seed aid and summarizes the varied response forms that have unfolded over the last three decades.

An FPGA-based Direct Sampling and Digital Processing System for Wideband and Narrowband Radar Signal

This paper designs an integrated wideband and narrowband radar signal direct sampling and digital processing system based on FPGA. The system comprises a VPX case, a main board, a direct sampling board, a fiber board. It makes direct sampling of 1.8GHz-3.0GHz echo waves, with 3.2GHz sampling rate. The wideband and narrowband echo waves share the same ADC channel. After ADC sampling, both of wideband and narrowband data are exported to a mix-free digital quadrature demodulation module in FPGA. The narrowband data will be further processed by digital frequency down conversion. The wideband data will be further processed by digital de-chirp operation, with parallel DDS structure and multi-level decimation filters. Data rate of both the wideband and narrowband data after processing is decreased obviously. The designed sampling system cut down the analog radar signal processing operation, and decreases signal distortion. Besides, it integrated the reception, sampling and processing of wideband and narrowband signal, simplified the structure of radar system.

A survey on radiation exposure reduction methods including rectangular collimation for intraoral radiography by pediatric dentists in the United States

BackgroundThe authors conducted a survey of the American Academy of Pediatric Dentistry (AAPD) to determine awareness of the Image Gently Campaign in Dentistry (IGCD) and to ascertain radiologic practices, including radiation dose-reduction strategies such as rectangular collimation. MethodsAn institutional review board approved an electronic survey sent to 7,087 AAPD members covering practitioner demographic characteristics, radiographic techniques, and dose-reduction practices, including rectangular collimation. Responses were tabulated and analyzed using binomial tests, χ2 tests, and Fisher exact tests. ResultsA total of 1,124 pediatric dentists or residents in pediatric dentistry responded, (response rate 16%, margin of error ± 2.7%). The largest group (23.8%) graduated after 2010. More than 90% indicated that they followed American Dental Association (ADA)-AAPD radiation exposure guidelines, but only 33.5% were aware of IGCD. Almost all respondents used direct digital systems, storage phosphor plates, or both. Only 22.3% (n = 220) used rectangular collimation. Nonusers indicated that they were unfamiliar with collimation (33.3%) or concerned about potential for increased cone cuts (30.2%), 11.6% of respondents were unaware of any regulatory requirements for inspections of radiographic equipment recurring at regular intervals, and 4.1% of respondents considered use of lead aprons optional. ConclusionsAlthough the pediatric dentists surveyed believe they are in compliance with ADA-AAPD guidelines, most are unaware of IGCD recommendations. Use of digital radiography is almost ubiquitous, but use of rectangular collimation is limited. Practice ImplicationsDentists treating children should be familiar with ADA-AAPD radiation exposure guidelines and should consider using the dose-reduction strategies recommended by IGCD.

ВИСОКОЛІНІЙНІ БАЛАНСНІ ДВОТАКТНІ ПІДСИЛЮВАЧІ ПОСТІЙНОГО СТРУМУ ІЗ НИЗКОЮ ПОХИБКОЮ ЗСУВУ НУЛЯ

It is known that push-pull DC amplifiers (PPDA), as a rule, have a high linearity of the transfer characteristic, a wide passband (hundreds of MHz and GHz units) at the level of unity gain, and a significant rate of change in the output voltage (at least thousands of volts per microsecond). Serial models of such integrated PPDA are produced by Analog Devices, Texas Instruments, Linear Technology, National Semiconductor and others. Due to the presence of these characteristics, PPDA are widely used in current-voltage, current-current, ADC, DAC, direct digital synthesis systems and multi-channel digital systems for processing and recording analog signals. Despite the high indicated static and dynamic characteristics of the PPDAs built on bipolar transistors, which have a significant additive error in the form of an input zero bias current of hundreds of nA and μA units. Often this can degrade the static parameters of these devices and systems. When the input zero bias current appears, there are basic currents of bipolar transistors in the input stages of the amplifiers. To reduce their influence in single-cycle current amplifiers, some special circuit methods are used. Which allow an order of magnitude to reduce the input zero bias current of the differential stage without affecting the bias voltage or speed. To reduce the input zero bias current in the PPDA, it was proposed to apply basic current compensation in the input stages, as well as to build the input stages on Shiklai composite transistors, which will significantly improve the accuracy of the circuit as a whole.

Unified Open Hardware Platform for Digital X-Ray Devices; its Conceptual Model and First Implementation.

Background: Digital radiography devices are still the gold standard for diagnosis or therapy guidance in medicine. Despite the similarities between all direct digital x-ray systems, researchers and new companies face significant challenges during the development phase of innovative x-ray devices; each component is manufactured independently, guidance towards device integration from manufacturers is limited, global standards for device integration is lacking. Method: In scope of this study a plug-integrate-play (PIP) conceptual model for x-ray imaging system is introduced and implemented as an open hardware platform, SyncBox. The researchers are free to select each individual device component from different vendors based on their intended application and target performance are utilized in criteria. Result: As its first implementation, SyncBox and its platform a full body high resolution radiographic scanner that employs a novel TDI digital detector. Conclusion: We believe that SyncBox has a potential for introducing an open source hardware platform to x-ray equipment design.

Efficacy of digital radiographic systems in the quality assessment of intracanal materials used for primary teeth

Aim: To evaluate the performance of three digital radiographic systems in the analysis of root canal filling quality using different intracanal materials for primary teeth. Methods: Twenty-five bovine teeth were divided into 5 groups: Calen® combined with iodoform; Calen® combined with zinc oxide; zinc oxide and eugenol; UltraCal®XS, and 2% chlorhexidine combined with Ca(OH)2 + zinc oxide. Periapical radiographs were obtained with the VistaScan, Express, and SnapShot systems. The quality of the images was evaluated objectively (radiopacity) and subjectively (apical sealing and filling homogeneity). As the reference standard, the teeth were scanned with a micro-CT device. Results: Radiopacity differed among the radiographic systems and materials tested. In general, the greatest difference was observed between the Express and VistaScan systems; Calen® combined with iodoform resulted in the highest radiopacity. The radiographic systems did not differ in terms of homogeneity. However, Calen® combined with iodoform differed from the other materials and exhibited the best results. Regarding apical sealing, the SnapShot system and Calen® combined with zinc oxide provided the best results. Conclusion: Direct digital systems show better performance in evaluating the quality of endodontic treatment in primary teeth and should be preferred for this purpose.

Високолінійний двотактний підсилювач-маштабатор струму на біполярних транзисторах із заземленим навантаженням

Traditionally, the vast majority of electrical amplifying devices are based on voltage or current amplifiers with voltage output. They are used as elements in the ADC and DAC, as well as in information-measuring and recorded systems, signal generators in direct digital synthesis systems. This is due to the well-established theory and practice of designing such amplifiers. At the same time, in some cases it is more expedient to have operational amplifiers with current output, which can work with a grounded load. Mentioned modern devices and systems are built using integrated circuits. It should be born in mind that most of the parasitic parameters of these circuits are capacitances, and the voltage according to the second switching law cannot jump abruptly on the capacitance, then the speed of the amplifying devices can be greater if all operations on the signals are performed using current amplifiers rather than voltage amplifiers. Therefore, to maximize the use of the frequency properties of bipolar transistors, it should be used as a current amplifier. A controlled current generator can be quite easily obtained on the basis of an operational amplifier by including loads in the feedback circuit, but in this case it cannot be grounded, which narrows its capabilities. It is proposed that controlled current generators with a grounded load are to be constructed on the basis of a push-pull amplifier and current mirrors included in the negative feedback circle on bipolar transistors. However, this approach is new, almost not considered in the scientific and technical literature, therefore the topic of the article devoted to the creation of highly linear push-pull amplifiers — current scalers on bipolar transistors with a grounded load is relevant. A new method for constructing controlled current-to-current generators implemented on bipolar transistors is analyzed, in which negative feedback is based on the removal of current using current mirrors. Mathematical expressions are obtained that make it possible to set the values of current amplification factors and determine the output resistance of a DC amplifier. Computer simulation of the characteristics of a DC amplifier was carried out, the results of which confirm the possibility of their use in high-precision electronic circuits, in particular in multi-bit (n = 16…20) ADCs and DACs.

Imaging and Dosimetric Study on Direct Flat-Panel Detector-Based Digital Mammography System.

Introduction:Image quality of digital mammography system is generally defined by three primary physical parameters, namely, contrast, resolution, and noise. Quantification of these metrics can be done by measuring objective image quality parameters defined as contrast-to-noise ratio (CNR), modulation transfer function (MTF), and noise power spectra (NPS).Materials and Methods:In the present study, various imaging metrics such as CNR, contrast detail resolution, MTF, and NPS were evaluated for a direct flat-panel detector-based digital mammography system following the European Guidelines. Furthermore, system performance relating to both image quality and doses were evaluated using figure of merit (FOM) in terms of CNR2/mean glandular dose (MGD) under automatic exposure control (AEC) and clinically used OPDOSE operating mode.Results and Conclusion:Under AEC mode, FOM values for the 4.5 cm thick BARC polymethyl methacrylate (PMMA) phantom were found to be 15.02, 15.88, and 19.82 at Mo/Mo, Mo/Rh, and W/Rh target/filter (T/F), respectively. Under OPDOSE mode, FOM values were found to 65.32, 11.80, and 1.14 for the BARC PMMA phantom thickness of 2, 4.5, and 8 cm, respectively. Under OPDOSE mode, the calculated MGD values for three Computerized Imaging Reference Systems slab phantoms having total thickness of 7 cm were observed to be 3.03, 2.32, and 1.75 mGy with glandular/adipose tissue compositions of 70/30, 50/50, and 30/70, respectively, whereas for the 2–8-cm thick BARC PMMA phantom, the calculated MGDs were found to be in the range of 0.57–3.32 mGy. All the calculated MGDs values were found to be lower than the acceptable level of dose limits provided in European Guidelines.

Activation of TNF-α-AID axis and co-inhibitory signals in coordination with Th1-type immunity in a mouse model recapitulating hepatitis B

Hepatitis B virus (HBV) infection evokes host immune responses that primarily determine the outcome of HBV infection and the clinical features of HBV-associated liver disease. The precise mechanisms by which host factors restrict HBV replication, however, are poorly understood due to the lack of useful animal models that recapitulate immune responses to HBV. Here, we performed comprehensive immunologic gene expression profiling of the liver of a mouse model recapitulating anti-HBV immune response using a high sensitivity direct digital counting system. Anti-HBV cellular immunity with liver inflammation was elicited in mice hydrodynamically injected with a CpG-depleted plasmid encoding hepatitis B surface antigen (HBsAg) gene after preimmunization with HBsAg vaccine. Comprehensive expression analyses revealed the upregulation of Th1-associated genes including tumor necrosis factor (Tnf) and negative regulators of T cell function in the inflamed liver. Interestingly, activation-induced cytidine deaminase (Aicda, termed AID in humans), which reportedly suppresses HBV infection in vitro, was upregulated in hepatocytes in the course of anti-HBV immunity. Hepatocytic expression of Aicda in a Tnf-dependent manner was confirmed by the administration of Tnf antagonist into Aicda-tdTomato mice with anti-HBV immunity. Our findings suggest that activation of Tnf–Aicda axis and co-inhibitory signals to T cells in coordination with Th1-type immunity has critical roles in the immune response against HBV infection.

Mammographic density assessed on paired raw and processed digital images and on paired screen-film and digital images across three mammography systems.

BackgroundInter-women and intra-women comparisons of mammographic density (MD) are needed in research, clinical and screening applications; however, MD measurements are influenced by mammography modality (screen film/digital) and digital image format (raw/processed). We aimed to examine differences in MD assessed on these image types.MethodsWe obtained 1294 pairs of images saved in both raw and processed formats from Hologic and General Electric (GE) direct digital systems and a Fuji computed radiography (CR) system, and 128 screen-film and processed CR-digital pairs from consecutive screening rounds. Four readers performed Cumulus-based MD measurements (n = 3441), with each image pair read by the same reader. Multi-level models of square-root percent MD were fitted, with a random intercept for woman, to estimate processed–raw MD differences.ResultsBreast area did not differ in processed images compared with that in raw images, but the percent MD was higher, due to a larger dense area (median 28.5 and 25.4 cm2 respectively, mean √dense area difference 0.44 cm (95% CI: 0.36, 0.52)). This difference in √dense area was significant for direct digital systems (Hologic 0.50 cm (95% CI: 0.39, 0.61), GE 0.56 cm (95% CI: 0.42, 0.69)) but not for Fuji CR (0.06 cm (95% CI: −0.10, 0.23)). Additionally, within each system, reader-specific differences varied in magnitude and direction (p < 0.001). Conversion equations revealed differences converged to zero with increasing dense area. MD differences between screen-film and processed digital on the subsequent screening round were consistent with expected time-related MD declines.ConclusionsMD was slightly higher when measured on processed than on raw direct digital mammograms. Comparisons of MD on these image formats should ideally control for this non-constant and reader-specific difference.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-016-0787-0) contains supplementary material, which is available to authorized users.

Mean glandular dose in six digital mammography services in Santiago, Chile: preliminary reference levels.

The purpose of this paper was to estimate mean glandular dose levels (DG) in six digital mammography systems in Santiago, Chile, and to propose preliminary reference levels to execute mammography in Chile. The study was carried out assessing two direct digital systems and four computer-based radiography (CR) systems. Estimates of DG were calculated for different thicknesses of polymethyl methacrylate according to the quality control protocol in digital mammography of the Spanish Society of Medical Physics and NHSBSP Equipment Report 0604 Version 3. DG values ranged between 0.64 and 7.26 mGy for a range of 20- to 70-mm thickness, respectively. Thirty-six per cent of DG was higher than the acceptable dose level and 100 % of DG was higher than the desirable level. It is therefore necessary to optimise doses. The initial proposal to establish dose reference levels for DG would range between 0.90 and 6.40 mGy for a thickness range of 20 to 70 mm.

Interproximal Caries Detection Ability of Dental Practitioners Using Direct Digital System and Conventional Films

Corresponding Author: Leila Khojastepour Address: No. 232, between Molasadra and Felestin Avenue, Moadel Avenue, Shiraz,Iran Telephone: +989173158331 E-mail: khojastl@sums.ac.ir 1Assistant Professor, Department of Oral and Maxillofacial Radiology, Faculty of Dentistry, Shiraz University of Medial Science, Shiraz, Iran 2 Dental Practitioner The study aimed to compare the accuracy of proximal caries detection by dental practitioners using two different systems, direct digital system and conventional films, under routine environmental conditions. Materials and methods: Eleven extracted human posterior teeth were mounted on wax frames and were exposed using the direct digital system and conventional films. Seventy-four dental practitioners evaluated these images for proximal caries. No environmental conditions were dictated. The dental practitioners’ evaluations were compared with histopathological sections that were used as the gold standard. Results: There were no statistically significant differences in the dental practitioners’ ability to detect caries using the direct digital and conventional systems (P=0.548).No significant differences were found between groups based on the level of the dental practitioners’ work experience (P=0.167). Conclusion: Dental practitioners work well with both direct digital and conventional systems in the diagnosis of proximal caries, although the routine environmental condition is not the ideal one. Further, this ability is so basic that it is not influenced by the level of the dental practitioner’s experience. Therefore, we recommend that digital systems be considered for use in dental offices.

A Comparative Study of Different Radiographic Methods for Detecting Occlusal Caries Lesions

Objectives: The aim of this in vitro study was to compare the diagnostic accuracy of different radiographic imaging modalities in detecting occlusal caries lesions. Materials and Methods: Under standardized conditions, 125 extracted human permanent molar teeth with sound or occlusal caries lesions were radiographed using a conventional film system (F-speed), a direct digital imaging system (complementary metal oxide semiconductor sensor), an indirect digital imaging system (photostimulable phosphor plate) and a cone beam computed tomography system (CBCT). Two observers scored the resultant images for the presence or absence of caries. Then, the teeth were histologically prepared and a definite diagnosis was determined by stereomicroscopic assessment. The area under the receiver operating characteristic curve (A_z), sensitivity, specificity and accuracy of each imaging modality were calculated, as well as the intra- and interexaminer reproducibility. Results: For both thresholds, interexaminer agreement were higher for CBCT. For intraexaminer agreement, observers had different scores for both thresholds, but the scores were generally higher for CBCT. Similar A_z values were achieved with all imaging methods at a diagnostic D1 threshold. The A_z values of the CBCT system were found to be statistically higher than those of the other imaging modalities at a diagnostic D3 threshold (p > 0.05); no significant differences were found among the other imaging modalities. All radiographic methods showed similar sensitivities, specificities and accuracy in detecting D1 threshold. The CBCT system showed higher sensitivity and accuracy in detecting dentine lesions. Conclusions: Within the limitations of this study, CBCT exhibited better performance in detecting deep occlusal caries lesions than the other radiographic systems.

In vivo comparison of Kodak E-speed film and direct digital imaging system for assessment of interproximal bone loss

Aims: To evaluate the diagnostic accuracy of direct digital radiography as compared to a conventional radiographic film for the assessment of interproximal bone loss with intrasurgical measurements as the gold standard. Materials and Methods: A total of 100 patients, with untreated moderate-to-advanced periodontal disease, were included in the study. The presurgical radiographs were made using a Kodak E-speed film and a Dexis digital sensor simultaneously, for sites with interproximal bone loss. At the time of surgery, the distance from the cementoenamel junction to the bone defect (CEJ-BD) was measured for 331 interproximal defects. The radiographs were randomized and then linear measurements were taken for the same sites in both conventional and digital radiographs. Stastistical Analysis: Comparison between the conventional, digital, and intrasurgical measurements was done statistically using the Student's t-test. The agreement and correlation among the methods was assessed using the weighted Kappa measure of agreement and Pearson's correlation, respectively. Results: The results showed that the conventional (5.15 ± 2.19 mm) and digital analyzing techniques (5.13 ± 2.19 mm) underestimated the interproximal bone loss, as compared to the intrasurgical measurements (6.07 ± 2.05 mm) (p < 0.001). The difference between conventional and digital radiographic methods was found to be statistically insignificant (p = 0.92). Conclusion: Under normal clinical use, the alveolar bone levels revealed on intraoral direct digital radiographs and Kodak E speed film were almost same. Therefore, the digital radiographic system can be routinely used in clinical practice as an alternative to conventional film.

Validation of simulation of calcifications for observer studies in digital mammography

Studies using simulated calcifications can be performed to measure the effect of different imaging factors on calcification detection in digital mammography. The simulated calcifications must be inserted into clinical images with realistic contrast and sharpness. MoCa is a program which modifies the contrast and sharpness of simulated calcification clusters extracted from images of mastectomy specimens acquired on a digital specimen cabinet at high magnification for insertion into clinical mammography images. This work determines whether the use of MoCa results in simulated calcifications with the correct contrast and sharpness. Aluminium foils (thickness 0.1–0.4 mm) and 1.60 µm thick gold discs (diameter 0.13–0.8 mm) on 0.5 mm aluminium were imaged with a range of thicknesses of polymethyl methacrylate (PMMA) using an amorphous selenium direct digital (DR) system and a powder phosphor computed radiography (CR) system (real images). Simulated images of the tests objects were also generated using MoCa. The contrast of the aluminium squares and the degradation of the contrast of the gold discs as a function of disc diameter were compared in the real and simulated images. The average ratios of the simulated-to-real aluminium contrasts over all aluminium and PMMA thicknesses were 1.03±0.04 (two standard errors in the mean) and 0.99±0.03 for the DR and CR systems, respectively. The ratio of the simulated-to-real degradations of contrast averaged over all disc diameters and PMMA thicknesses were 1.007±0.008 and 1.002±0.013 for DR and CR, respectively. The use of MoCa was accurate within the experimental errors.