Radiographic features of COVID-19 based on an initial cohort of 96 patients in Singapore

INTRODUCTIONChest radiographs (CXRs) are widely used for the screening and management of COVID-19. This article describes the radiographic features of COVID-19 based on an initial national cohort of patients.METHODSThis is a retrospective review of swab-positive patients with COVID-19 who were admitted to four different hospitals in Singapore between 22 January and 9 March 2020. Initial and follow-up CXRs were reviewed by three experienced radiologists to identify the predominant pattern and distribution of lung parenchymal abnormalities.RESULTSIn total, 347 CXRs of 96 patients were reviewed. Initial CXRs were abnormal in 41 (42.7%) out of 96 patients. The mean time from onset of symptoms to CXR abnormality was 5.3 ± 4.7 days. The predominant pattern of lung abnormality was ground-glass opacity on initial CXRs (51.2%) and consolidation on follow-up CXRs (51.0%). Multifocal bilateral abnormalities in mixed central and peripheral distribution were observed in 63.4% and 59.2% of abnormal initial and follow-up CXRs, respectively. The lower zones were involved in 90.2% of initial CXRs and 93.9% of follow-up CXRs.CONCLUSIONIn a cohort of swab-positive patients, including those identified from contact tracing, we found a lower incidence of CXR abnormalities than was previously reported. The most common pattern was ground-glass opacity or consolidation, but mixed central and peripheral involvement was more common than peripheral involvement alone.     

上前牙内收过程中转矩控制的影像学研究

目的:研究上前牙内收过程中转矩控制与移动方式、内收与牙槽骨改建之间的关系.方法:选取111例拔牙患者治疗前、后的头颅侧位片,7例拔牙患者关闭间隙前、后的锥形束CT(CBCT),测量上前牙唇倾度,切缘、根尖水平和垂直向位移及牙槽骨厚度变化,采用SAS 8.02软件包分别对各测量项目进行t检验和x2检验.结果:上前牙控根内收者,唇倾度改变量小,切缘舌侧位移量小,根尖舌侧位移量大,内收后根尖牙槽骨总厚度减少,牙长度减少(P＜0.05);牙槽骨改建量少于牙移动量,成人与青少年无显著差异.结论:上前牙内收过程中,更多的转矩控制会引起较多的整体移动和部分控根的倾斜移动,以及较高的牙根吸收率.舌侧牙槽骨适应性改建量较小,过度舌侧移动会超过其改建能力,引起牙槽骨、牙体损伤.     

Reliability of pedicle screw assessment utilizing plain radiographs versus CT reconstruction

The position of 119 pedicle screws was assessed on plain antero-posterior and lateral radiographs taken immediately post-operatively and at 3 months' follow-up. The readings of five independent observers were compared with the gold standard of CT reconstructions. The position of only 41 % of implants (range 14%–56%) was assessed correctly on the plain radiographs (47% on follow-up films). Two-thirds of CT-detectable perforations were missed. As shown with perforations of the anterior cortex, delectability increased significantly with magnitude of perforation. No specifically difficult anatomic level or direction of malplacement could be identified. Interobserver variation was considerable. Plain radiographs were shown to be of limited use in assessing the position of pedicle screws.     

数字重建影像的重建算法

数字重建影像是2D-3D医学图像配准和放射治疗虚拟模拟的关键技术。本文使用光线跟踪算法,得到数字重建影像,并获得了满意的图像效果。     

Radiographic detection and assessment of the periodontal endosseous defects

AIMS: The aim of the present study was to investigate the potential of conventional radiography in detecting and accurately imaging periodontal endosseous (or osseous) defects when compared to surgical measurements. A further objective of the study was the selection of the most successful radiographic method for the assessment of endosseous defects. METHOD: Surgical measurements, during periodontal flap surgery, and radiographic measurements, from periapical and panoramic radiographs, were obtained from 5,072 proximal surfaces of 100 patients presenting with periodontitis. RESULTS: Statistical evaluation of the surgical and radiographic measurements revealed the following. (1) The ability of the radiographs to detect periodontal osseous defects was relatively low. (2) For periapical radiography, it depended, in descending order, on the depth and buccolingual width of the defect, the number of osseous walls and the jaw location. For panoramic radiography, it depended only on buccolingual width. (3) Osseous defects of small depth and/or small buccolingual width were the most difficult to detect radiographically. (4) Periapical radiography was more successful than panoramic in detecting osseous defects, and more accurate in assessing the defect dimensions (depth, mesiodistal width). (5) The difference in the defect detection ability between the 2 radiographic methods, the accuracy of the radiographic defect dimensions assessment as well as the degree of agreement between periapical and panoramic assessment depended on defect location and dimensions. CONCLUSIONS: Periapical radiography is superior to panoramic in detecting and accurately imaging periodontal osseous destruction.     

A semi‐automated computer‐assisted method for measuring bone loss adjacent to dental implants

The purpose of this study was to develop a repeatable method for measurement of bone support around root form and blade implants suitable for use in high-quality but unstandardized radiographs. 10 phantoms were fabricated to simulate progressive osseous defects around implants. Radiographs were taken in triplicate and digitized. Specialized software was written which placed a grid of known dimensions over the implant so that the top and the bottom of the grid were at the neck and the base of the implant, respectively. The investigators selected the edge of the bone at each point where the grid intersected the implant and the software automatically detected the implant edge. The software also outlined and displayed the defect on the computer monitor. Measurements were performed 5 times and the standard deviation was taken as a measure of the repeatability of the method. Repeatability for blades and root forms was 0.19 +/- 0.07 mm and 0.08 +/- 0.03 mm, respectively. There was no significant difference in the ability to measure bone loss in the blade versus the root form (p = 0.17, NS). These results indicate that this semi-automated computer-assisted method for measuring bone loss around implants is repeatable and may be of value for clinical trials using either root form or blade implants.     

Optimal exposure parameters for digital radiography of the infant skull: a pilot study

AIM: To determine optimal exposure parameters when performing digital skull radiographs in infants with suspected non-accidental injury (NAI). METHOD: Anteroposterior and lateral post-mortem skull radiographs of six consecutive infants with suspected NAI were made at six exposure levels for each projection. Entrance surface doses ranged from 75-351 microGy. Exposures were made with a Fuji 5000R computed radiography system onto a standard resolution imaging plate. In three patients exposures were repeated using a high-resolution imaging plate. Hard copy images with an edge-enhancement factor of 0.5 were produced. Six observers assessed and scored the radiographs from 1=poor to 5=excellent for visualization of five criteria. The criteria scored included outer table of skull vault, inner table of skull vault, suture margins, vascular markings and soft tissues of the scalp. Radiographs were then ranked in order of overall image quality. Film density and sensitivity values were recorded. Local research committee approval was obtained. RESULTS: Current parameters give an average entrance surface dose of 253 microGy and 246 microGy for anteroposterior and lateral radiographs, respectively. The study demonstrated no perceived improvement in image quality above an entrance surface dose of 200 microGy (80% of current dose) or by the use of a high-resolution imaging plate. CONCLUSION: The potential exists to reduce radiation exposure in infants. A study has commenced to determine the effects of dose reduction on diagnostic accuracy in suspected NAI.     

Radiographic outcomes among South African coal miners

Objectives: This study, the first to document the prevalence of pneumoconiosis among a living South African coal mining cohort, describes dose–response relationships between coal workers pneumoconiosis and respirable dust exposure, and relationships between pneumoconiosis and both lung function deterioration and respiratory symptoms. Methods: A total of 684 current miners and 188 ex-miners from three bituminous-coal mines in Mpumalanga, South Africa, was studied. Chest radiographs were read according to the International Labour Organization (ILO) classification by two experienced readers, one an accredited National Institute for Occupational Safety and Health (NIOSH) B reader. Interviews were conducted to assess symptoms, work histories (also obtained from company records), smoking, and other risk factors. Spirometry was performed by trained technicians. Cumulative respirable dust exposure (CDE) estimates were constructed from historical company-collected sampling and researcher-collected personal dust measurements. -Statistics compared the radiographic outcomes predicted by the two readers. An average profusion score was used in the analysis for the outcomes of interest. Because of possible confounding by employment status, most analyses were stratified on current and ex-miner status. Results: The overall prevalence of pneumoconiosis was low (2%–4%). The degree of agreement between the two readers for profusion was moderate to high (=0.58). A significant association (P<0.001) and trend (P<0.001) was seen for pneumoconiosis with increasing categories of CDE among current miners only. A significant (P<0.0001) additional 58 mg-years/m³ CDE was seen among those with pneumoconiosis compared to those without. CDE contributed to a statistically significant 0.19% and 0.11% greater decline in the percent predicted 1-second forced expiration volume (FEV₁) and forced vital capacity (FVC), respectively, among current miners with pneumoconiosis than among those without. Logistic regression models showed no significant relationships between pneumoconiosis and symptoms. Conclusions: The overall prevalence of pneumoconiosis, although significantly associated with CDE, was low. The presence of pneumoconiosis is associated with meaningful health effects, including deterioration in lung function. Intervention measures that control exposure are indicated, to reduce these functional effects.     

Detection of marginal defects of composite restorations with conventional and digital radiographs

The purpose of this study was to determine the validity of detecting approximal imperfections of composite fillings using three intraoral radiographic systems in vitro. Class II composite resin restorations (108) with three radiopacities (264, 306, 443% Al 99.5) of which 27 had marginal openings or overhangs, respectively, were conventionally (Ektaspeed plus) and digitally (Dexis, Digora) radiographed. Images were assessed by 10 observers for the presence of marginal gaps and overhangs, as well as for their need of restorative treatment according to a five-point confidence rating scale. The validity of the observations were expressed as areas under receiver operating characteristic (ROC) curves (Aroc). Repeated measures analysis of variance revealed significant effects of 'radiographic system' and 'diagnostic purpose'. Marginal overhangs (Aroc = 0.90) were significantly easier to diagnose than openings (Aroc = 0.63). Marginal gaps were better detected on conventional and Dexis radiographs than on Digora images. the range of sensitivities and specificities of the treatment decision was 0.53-0.56 and 0.87-0.88, respectively. It was concluded that the validity of detecting marginal defects of composite resin restorations based on radiographs was only slightly affected by the radiographic system being used. The diagnosis of marginal gaps frequently resulted in false-positive and false-negative decisions.     

Evaluation of periapical radiographs in the recognition of C-shaped mandibular second molars

AIM: The purpose of this study was to evaluate in a blind trial the efficacy of radiographs to recognize C-shaped mandibular second molars and to determine the incidence of this entity amongst second mandibular molars treated in the Department of Endodontology at the School of Dentistry of the University of Thessaloniki during a seven-year period (1989 - 95). METHODOLOGY: A total of 480 clinical records of root treated mandibular second molars were reviewed. The preoperative, working length, and final radiograph of each tooth alone and in combination were examined in groups as follows: group 1 (preoperative radiographs only), group 2 (working length radiographs), group 3 (final radiographs), group 4 (preoperative and working length radiographs), group 5 (preoperative and final radiographs) and group 6 (all three radiographs). The efficacy of each combination to identify the C-shaped cases was evaluated based on the interpretation of three experienced dentists looking simultaneously at each case. Films were examined on a viewer using a magnifying glass and allowing a two-week interval between groups. Results were compared with the clinical diagnoses stated on the patients' records (group 7). RESULTS: The review of clinical records revealed that 4.58% of second molars had C-shaped canals. Radiographic interpretation was overall more effective when based on film combinations (groups, 4, 5, and 6) than on single radiographs. Amongst the latter, working length radiographs were more helpful than the preoperative and final ones. Preoperative radiographs were the least effective in diagnosing C-shaped cases. CONCLUSIONS: Simultaneous interpretation of preoperative, working length and post-treatment radiographs is important when attempting to diagnose a C-shaped configuration.