Statistical analysis of kerf mark measurements in bone

Saw marks on bone have been routinely reported in dismemberment cases. When saw blade teeth contact bone and the bone is not completely sawed into two parts, bone fragments are removed forming a channel or kerf. Therefore, kerf width can approximate the thickness of the saw blade. The purpose of this study is to evaluate 100 saw kerf widths in bone produced by ten saw types to determine if a saw can be eliminated based on the kerf width. Five measurements were taken from each of the 100 saw kerfs to establish an average thickness for each kerf mark. Ten cuts were made on 10 sections of bovine bone, five with human-powered saws and five with mechanical-powered saws. The cuts were examined with a stereoscopic microscope utilizing digital camera measuring software. Two statistical cumulative logistic regression models were used to analyze the saw kerf data collected. In order to estimate the prediction error, repeated stratified cross-validation was applied in analyzing the kerf mark data. Based on the two statistical models used, 70–90% of the saws could be eliminated based on kerf width.     

Intra-class and inter-class tool discrimination through micro-CT analysis of false starts on bone

International Journal of Legal Medicine - Micro-CT has successfully been applied to the characterization of false starts (FSs) and, among several parameters, kerf width seems to correlate to the...     

Micro-computed tomography of false starts produced on bone by different hand-saws

The analysis of macro- and microscopic characteristics of saw marks on bones can provide useful information about the class of the tool utilized to produce the injury. The aim of the present study was to test micro-computed tomography (micro-CT) for the analysis of false starts experimentally produced on 32 human bone sections using 4 different hand-saws in order to verify the potential utility of micro-CT for distinguishing false starts produced by different saws and to correlate the morphology of the tool with that of the bone mark. Each sample was analysed through stereomicroscopy and micro-CT. Stereomicroscopic analysis allowed the identification of the false starts and the detection of the number of tool marks left by each saw. Micro-CT scans, through the integration of 3D renders and multiplanar reconstructions (MPR), allowed the identification of the shape of each false start correlating it to the injuring tool. Our results suggest that micro-CT could be a useful technique for assessing false starts produced by different classes of saws, providing accurate morphological profiles of the bone marks with all the advantages of high resolution 3D imaging (e.g., high accuracy, non-destructive analysis, preservation and documentation of evidence). However, further studies are necessary to integrate qualitative data with quantitative metrical analysis in order to further characterize the false start and the related injuring tool.     

Cutting crime: the analysis of the “uniqueness” of saw marks on bone

Witness marks produced on bone by the use of saws have traditionally been examined using stereomicroscopy. The marks are typically found on the kerf wall or floor and give important information about the implement that made them. This paper describes a new approach to the analysis of witness marks left on kerf walls and floors from crimes involving dismemberment. Previously, two types of marks have been identified: deep furrows formed during the pull stroke and fine striations formed on the push stroke. These types of striation allow the class of saw to be identified, but not an individual saw. With the advent of environmental scanning electron microscopy (ESEM), insulating materials can now be examined without the need for conductive coatings to be applied. This allows materials to be examined at higher magnifications than those available with stereomicroscopy. Here we report on a new, third type of striation that is visible at higher magnifications on ESEM images. These striations are formed from the imperfections on the cutting teeth of saws and give real possibilities of uniquely identifying whether or not a particular saw was used to cause the mark. In blind trials conducted on sawing of nylon 6.6, different individual saws could be successfully identified even if different people used the saw. We discuss ways in which these results can be extended to bone and how this may assist in the investigation of the act of dismemberment.     

Differentiation of serrated and non-serrated blades from stab marks in bone

Although evidence of sharp-force trauma on the human body, particularly the skeleton, can be extremely useful in providing information regarding the manner and context of death, there is still a lack of necessary detail available to the investigator. Using ribs, radii, scapulae, vertebrae and carpal bones, this study demonstrated that distinctions could be made between the stab marks left by serrated blades and those of non-serrated blades. Low power and scanning electron microscopy were used to record distinctive ‘T’-shaped stab marks from non-serrated blades and ‘Y’-shaped stab marks from serrated blades. In addition, elemental evidence of the presence of the blade in the stab-mark kerf was recoverable even when no metal fragment was visible.     

Characteristics and time-dependence of cut marks and blunt force fractures on costal cartilages: an experimental study

Purpose

The distinction between cut marks and blunt force injuries on costal cartilages is a crucial issue in the forensic field. Moreover, a correct distinction may further be complicated by decomposition, so the need arises to investigate the distinctive features of lesions on cartilage and their changes over time.

Methods

This study aimed to assess the stereomicroscopic features of cut marks (performed with six different knives) and blunt fractures (performed with a hammer and by means of manual bending) on 48 fragments of human costal cartilages. Moreover, in order to simulate decomposition, the cut and fractured surfaces were checked with stereomicroscopy and through casts after 1 and 2 days, 1 week, and 1, 2 and 4 months of drying in ambient air.

Results

In fresh samples, for single and unique cuts, striations were observed in between 44 and 88 % of cases when non-serrated blades were used, and between 77 and 88 % for serrated blades; in the case of “repeated” (back and forth movement) cuts, striations were detected in between 56 and 89 % of cases for non-serrated blades, and between 66 and 100 % for serrated blades. After only 1 week of decomposition the detection rates fell to percentages of between 28 and 39 % for serrated blades and between 17 and 33 % for non-serrated blades. Blunt force injuries showed non-specific characteristics, which, if properly assessed, may lead to a reliable distinction between different cut marks in fresh samples. The most evident alterations of the structure of the cartilage occurred in the first week of decomposition in ambient air. After one week of drying, the characteristics of cut marks were almost undetectable, thereby making it extremely challenging to distinguish between cut marks, blunt force fractures and taphonomic effects.

Conclusion

The study represents a contribution to the correct assessment and distinction of cut marks and blunt force injuries on cartilages, providing a glimpse on the modifications such lesions may undergo with decomposition.

     

Multiple neural network classification scheme for detection of colonic polyps in CT colonography data sets

RATIONALE AND OBJECTIVES: A new classification system for colonic polyp detection, designed to increase sensitivity and reduce the number of false-positive findings with computed tomographic colonography, was developed and tested in this study. MATERIALS AND METHODS: The system involves classification by a committee of neural networks (NNs), each using largely distinct subsets of features selected from a general set. Back-propagation NNs trained with the Levenberg-Marquardt algorithm were used as primary classifiers (committee members). The set of features included region density, Gaussian and mean curvature and sphericity, lesion size, colon wall thickness, and the means and standard deviations of all of these values. Subsets of variables were initially selected because of their effectiveness according to training and test sample misclassification rates. The final decision for each case is based on the majority vote across the networks and reflects the weighted votes of all networks. The authors also introduce a smoothed cross-validation method designed to improve estimation of the true misclassification rates by reducing bias and variance. RESULTS: This committee method reduced the false-positive rate by 36%, a clinically meaningful reduction, and improved sensitivity by an average of 6.9% compared with decisions made by any single NN. The overall sensitivity and specificity were 82.9% and 95.3%, respectively, when sensitivity was estimated by means of smoothed cross-validation. CONCLUSION: The proposed method of using multiple classifiers and majority voting is recommended for classification tasks with large sets of input features, particularly when selected feature subsets may not be equally effective and do not provide satisfactory true- and false-positive rates. This approach reduces variance in estimates of misclassification rates.     

Dental fracture and chocolate candies: Case report

A complaint by a customer to a food company claimed that the consumption of a chocolate candy fractured his anterior teeth, due to its hard consistency. Fragments of the fractured teeth and the chocolate candy that supposedly caused it were collected, examined and photographed. Fragments presented caries, large restorations, and suggested previous endodontic treatment. To evaluate causation, the food company requested a laboratory analysis, which simulated the human bite on chocolate candies of the same brand. Human teeth were assembled in a simulating device of masticatory functions of apprehension and incision. Teeth used were either sound or with non-restored endodontic accesses, to simulate previous conditions of the collected fragments. Twenty chocolate candies, cooled in a freezer to 0 °C for 2 h were used as test foods, and were positioned between the teeth of the device at the moment of the test. The set was put in a dynamometer, programmed to apply increasing forces (rate of advance of 5 mm/min), until rupture (either of the specimen or of the teeth). The applied force, in N, at the time of fracture was recorded and analyzed. The average force to fracture the test food was 233.23 N. No tooth was fractured in the experiment. Forces ranging from 191.3 to 275.2 N, applied to chocolate candies were not sufficient to neither fracture human teeth nor cause any structural damage. It was concluded that the dental fracture occurred because of previous oral health conditions of the customer.     

Scanning electron microscopy (SEM) and macroscopic analysis of immature human permanent molar immersion in hydrochloric acid (HCL, 38%)

Recent literature indicates the destruction of human remains using hydrochloric acid (HCl, 38%) is often attempted to obscure the identity of victims or as a disposal method. Dentition are informative in an investigation where acid is used as a means of body disposal, as teeth are more likely to survive intact. Importantly, researchers studying acid immersion have not observed immature dentition, nor have they analyzed immature acid-treated teeth using scanning electron microscopy (SEM). This study analyzes the effects of HCl on immature human molars, with two goals: understanding the timing and nature of physical changes to immature molars caused by HCl immersion, and aiding in the identification and age determination of dental tissues partially or nearly completely destroyed using HCl.Our results indicated that immature human molars immersed in HCl follow a pattern of physical changes and decrease in weight as they dissolve similar to mature molars, although the timing of dissolution is affected by their smaller size and incompletely developed roots in a predictable way. With less root material present and an open root tip, we observed that HCl can more quickly penetrate the pulp cavity of immature molars. The mobile SEM images indicated immature and mature molars immersed in HCl exhibit similar changes at the microscopic level. Immature molars treated with HCl for over 18 h exhibited cracking features similar to those visible on mature molars that were difficult to differentiate from similar features on untreated teeth (both mature and immature) when images were taken at 3,000x or less. The appearance of features such as peeling layers and lamination at high magnification (6000x) were visible on both acid-treated mature and immature molars, but were not visible on untreated molars at the same level of magnification.By observing changes in the enamel and pulp cavity, it was possible to determine whether third molars were immature until approximately 18 h immersed in acid. At 42 h, it was no longer possible to determine whether the molars were immature. However, they were still easily identifiable as human teeth. In situations where teeth may no longer be identifiable macroscopically, we found that the laminating and peeling features observed on high magnification SEM imagery can be useful in characterizing acid treatment even on very small fragments of dental remains, potentially allowing investigators to determine if acid was used as a disposal method.     

Functional magnetic resonance imaging using PROPELLER-EPI

Periodically rotated overlapping parallel lines with enhanced reconstruction-echo-planar imaging (PROPELLER-EPI) is a multishot technique that samples k-space by acquisition of narrow blades, which are subsequently rotated until the entire k-space is filled. It has the unique advantage that the center of k-space, and thus the area containing the majority of functional MRI signal changes, is sampled with each shot. This continuous refreshing of the k-space center by each acquired blade enables not only sliding-window but also keyhole reconstruction. Combining PROPELLER-EPI with a fast gradient-echo readout scheme allows for high spatial resolutions to be achieved while maintaining a temporal resolution, which is suitable for functional MRI experiments. Functional data acquired with a novel interlaced sequence that samples both single-shot EPI and blades in an alternating fashion suggest that PROPELLER-EPI can achieve comparable functional MRI results. PROPELLER-EPI, however, features different spatiotemporal characteristics than single-shot EPI, which not only enables keyhole reconstruction but also makes it an interesting alternative for many functional MRI applications.     

Comparison of racemization rates between vital and endodontically treated teeth for age estimation

Amino acid racemization of dentin (AAR) is among the most precise methods for age estimation in unidentified adult cadavers. Although vital teeth are generally used for this technique, cases often have endodontically treated (Endo) teeth only. Therefore, the aim of this preliminary pilot study was to determine the applicability of Endo teeth by comparing AAR rates between vital and Endo teeth. Thirty-six dentin samples from vital teeth and 18 dentin samples from Endo teeth were analyzed, including the maxillary first premolar, maxillary second molar, and mandibular second premolar. Standard calibration curves for the mandibular second premolar and maxillary second molar were compared among vital teeth, Endo teeth, and mixed vital/Endo teeth. Discrepancies between estimated and actual ages were assessed by analyzing the AAR rates for the maxillary first premolar between vital and Endo teeth. The AAR rates for Endo teeth were higher than those for vital teeth in both the mandibular second premolar and maxillary second molar, and the correlation of the standard calibration curve for vital teeth only was highest (r = 0.982836; r = 0.92011467), followed by mixed (r = 0.949579; r = 0.76158) and Endo teeth only (r = 0.896082; r = 0.744991). In the maxillary first premolar, discrepancies were more than 10 years for all 5 Endo teeth, based on the standard calibration curve of vital teeth. The present study suggests that the AAR rates for Endo teeth might be affected by variation in dentin structure between vital and Endo teeth.     

Dental age diagnostics by means of radiographical evaluation of the growth stages of lower wisdom teeth

The main criterion for dental age estimation in living adolescents and young adults is mineralization of third molars. A total of 1,260 orthopantomograms of 669 female and 591 male subjects aged between 15 and 22 years was examined. Of the orthopantomograms, 1,137 were from patients with Swiss citizenship and 123 were from other European countries. The mineralization status of lower third molars was evaluated based on Demirjian's classification of stages. For the statistical assessment of data, logistic regression and mean value testing were used. The findings show that completed growth in wisdom teeth is observable at ages less than 18. Male individuals were approximately 1 year ahead of females at stage H, and South East Europeans were approximately 6 months ahead of Swiss (Central Europe) at stage H. Mean values led to false conclusions regarding the question of the attained age of 18. Therefore, regression analysis should be used for the statistical assessment of data in dental age diagnostics.     

Pilot study to establish a nasal tip prediction method from unknown human skeletal remains for facial reconstruction and skull photo superimposition as applied to a Japanese male populations

Skull-photo superimposition is a technique used to identify the relationship between the skull and a photograph of a target person: and facial reconstruction reproduces antemortem facial features from an unknown human skull, or identifies the facial features of unknown human skeletal remains. These techniques are based on soft tissue thickness and the relationships between soft tissue and the skull, i.e., the position of the ear and external acoustic meatus, pupil and orbit, nose and nasal aperture, and lips and teeth. However, the ear and nose region are relatively difficult to identify because of their structure, as the soft tissues of these regions are lined with cartilage.We attempted to establish a more accurate method to determine the position of the nasal tip from the skull. We measured the height of the maxilla and mid-lower facial region in 55 Japanese men and generated a regression equation from the collected data. We obtained a result that was 2.0 ± 0.99 mm (mean ± SD) distant from the true nasal tip, when applied to a validation set consisting of another 12 Japanese men.     

Toward clinically usable CAD for lung cancer screening with computed tomography

Objectives

The purpose of this study was to define clinically appropriate, computer-aided lung nodule detection (CAD) requirements and protocols based on recent screening trials. In the following paper, we describe a CAD evaluation methodology based on a publically available, annotated computed tomography (CT) image data set, and demonstrate the evaluation of a new CAD system with the functionality and performance required for adoption in clinical practice.

Methods

A new automated lung nodule detection and measurement system was developed that incorporates intensity thresholding, a Euclidean Distance Transformation, and segmentation based on watersheds. System performance was evaluated against the Lung Imaging Database Consortium (LIDC) CT reference data set.

Results

The test set comprised thin-section CT scans from 108 LIDC subjects. The median (±IQR) sensitivity per subject was 100 (±37.5) for nodules?≥?4 mm and 100 (±8.33) for nodules?≥?8 mm. The corresponding false positive rates were 0 (±2.0) and 0 (±1.0), respectively. The concordance correlation coefficient between the CAD nodule diameter and the LIDC reference was 0.91, and for volume it was 0.90.

Conclusions

The new CAD system shows high nodule sensitivity with a low false positive rate. Automated volume measurements have strong agreement with the reference standard. Thus, it provides comprehensive, clinically-usable lung nodule detection and assessment functionality.

Key Points

? CAD requirements can be based on lung cancer screening trial results. ? CAD systems can be evaluated using publically available annotated CT image databases. ? A new CAD system was developed with a low false positive rate. ? The CAD system has reliable measurement tools needed for clinical use.     

Geographic Dispersion and Rural Versus Urban Utilization of CT Colonography in the United States

ObjectiveTo assess the geographic dispersion of CT colonography (CTC) as well as differences in CTC utilization in rural versus urban areas in individuals with commercial insurance.MethodsClaims data from approximately 18.5 million commercially insured individuals across the United States were used to determine CTC utilization based on geographic area. Geographic areas were defined as metropolitan statistical areas (MSAs) and statewide non-MSAs. Utilization rates per 100,000 covered person-years were calculated for each geographic area for both screening and diagnostic CTC using 2017 data (the most recent full-year data available). Differences in CTC utilization between MSAs (urban) and non-MSAs (rural) were evaluated using weighted multivariate logistic regression.ResultsCTC is widely dispersed across the United States with substantial geographic variability. Utilization of screening CTC was considerably lower among individuals residing in rural areas compared with those in urban areas (adjusted odds ratio = 0.353, P = .005). For individuals aged 50 to 64 years, screening CTC utilization was 2.38 per 100,000 in rural areas versus 6.67 per 100,000 in urban areas (P = .005). Utilization of diagnostic CTC was also lower in rural compared with urban areas, though this difference was not statistically significant (8.40 per 100,000 versus 13.11 per 100,000 respectively, P = .070).ConclusionsAlthough CTC is performed widely across the United States, utilization is generally low and varies substantially based on geographic region. CTC utilization is lower among individuals in rural compared with urban areas.     

Red fluorescence for assessing longitudinal tooth fractures

BackgroundThis study was designed to determine whether autofluorescence emitted from longitudinal tooth fractures (LTFs) differs between fracture types, with the aim of determining which clinical factors are related to red fluorescence at the fracture line.MethodsThirty-three extracted teeth were classified into cracked teeth, split teeth, and root fractures using LTF types according to the American Association of Endodontists classification. The types of LTFs were identified using an operating microscope. LTF autofluorescence was captured using a fluorescence technique. Clinical examinations were performed using the preoperative factors from clinical and radiographic findings.ResultsRed fluorescence was identified in 82% and 83% of cracked and split teeth, respectively. None of the vertical root fractures exhibited red fluorescence (p<0.001). When red fluorescence was identified on the outer tooth surface, it penetrated into the crack line, but fluorescence that was not red at the tooth surface did not penetrate the fracture line. Among the examined preoperative clinical factors, differences between the presence and absence of red fluorescence were identified for sinus tract formation (p = 0.021), and radiographic features (p = 0.027). Regression analysis revealed a significant factor related to the red fluorescence, with sinus tract formation having a negative effect on red fluorescence (odds ratio [OR]=0.09). The presence of comprehensive periradicular lesions in radiography had a positive effect on red fluorescence (OR=5.04).ConclusionsCracks originating from tooth crowns in certain types of LTFs were associated with red fluorescence, and cracks with red fluorescence were associated with extensive periodontal bone resorption around the teeth roots.     

Effect of Massed Versus Interleaved Teaching Method on Performance of Students in Radiology

PurposeRadiology instruction is based on the principle that grouped (or massed) repetition of an intellectual activity leads to expertise. The aim of this study was to test the hypothesis that the spaced (or interleaved) method of teaching chest x-ray interpretation is more effective than the massed method.MethodsAfter institutional review board approval was obtained, 40 first- and second-year medical students were randomized into two groups matched by age, gender, and education experience. Both groups saw six examples of 12 common chest radiographic patterns, one grouped, the other scrambled randomly without repeating strings. After a distraction, participants took a multiple-choice test consisting of two cases in each radiographic pattern, one previously shown, one new. Results were analyzed using two-tailed Student’s t test of proportion.ResultsComparing interleaved and massed groups, the average overall score was 57% versus 43% (P = .03), the recollection score was 61% versus 47% (P = .03), and the induction score was 53% versus 40% (P = 0.10), respectively. Comparing second- and first-year students, average scores were 67% and 39%, respectively (P < .01). First-year students in the interleaved and massed groups scored 55% and 36% (P = .02) in recall and 40% and 28% (P = .10) in induction. Second-year students in the interleaved and massed groups scored 71% and 63% (P = .36) in recall and 74% and 59% (P = .03) in induction.ConclusionsThe interleaved method of instruction leads to better results than the massed method across all levels of education. A higher level of medical education improves performance independent of method of instruction.     

A County-Level Analysis of the US Radiologist Workforce: Physician Supply and Subspecialty Characteristics

PurposeTo explore associations between county-level measures of radiologist supply and subspecialization and county structural and health-related characteristics.MethodsMedicare Physician and Other Supplier Public Use Files were used to subspecialty characterize 32,844 radiologists participating in Medicare between 2012 and 2014. Measures of radiologist supply and subspecialization were computed for 3,143 US counties. Additional county characteristics were identified using the 2014 County Health Rankings database. Mann-Whitney tests and Spearman correlations were performed.ResultsCounties with at least one (versus no) Medicare-participating radiologist had significantly (P < .001) larger populations (197,050 ± 457,056 versus 20,253 ± 23,689), lower rural percentages (39.5% ± 26.5% versus 74.6% ± 25.6%), higher household incomes ($47,608 ± $12,493 versus $42,510 ± $9,893), higher mammography screening rates (62.4% ± 7.0% versus 56.6% ± 15.3%), and lower premature deaths (7,581 ± 2,085 versus 7,784 ± 3,409 years of life lost). Counties’ radiologists per 100,000 population and percent of subspecialized radiologists showed moderate positive correlations with counties’ population (r = +0.505-+0.599) and moderate negative correlations with counties’ rural percentage (r = −0.434 to −0.523). Radiologist supply and degree of subspecialization both showed concurrent positive or negative weak associations with counties’ percent age 65+ (r = −0.256 to −0.271), percent Hispanic (r = +0.209-+0.234), and income (r = +0.230-+0.316). Radiologists per 100,000 population showed weak positive correlation with mammography screening (r = +0.214); percent of radiologists subspecialized showed weak negative correlation with premature death (r = −0.226).ConclusionGeographic disparities in radiologist supply at the community level are compounded by superimposed variation in the degree of subspecialization of those radiologists. The potential impact of such access disparities on county-level health warrants further investigation.     

SPECT imaging with off-set detector system: comparison of sampling angles 2, 4 and 6 degrees

PURPOSE: We evaluated an off set reconstruction method for single photon emission computed tomography (SPECT), and compared it with the conventional on set reconstruction method, using sampling angles of 2, 4, and 6 degrees. METHOD: A triple-detector system was used. In the off-set acquisition, sampling angles of the opposite detector were shifted 1/2 of the sampling angles of 2, 4, and 6 degrees. For example, when projection data were acquired every 6-degrees (sampling angle = 6 degrees), the projection angles were at 0 degrees, 6 degrees, 12 degrees, and 174 degrees with one detector, and 177 degrees, 183 degrees, 189 degrees, and 357 degrees with the other, opposite, detector. The conventional on set reconstruction images were compared with an off set reconstruction for a pool phantom of uniform concentration, a hot rods phantom, a myocardial phantom, and a human study. RESULTS: The off set reconstruction method was better at all three sampling angles. FWHM (mm) were 11.02 at off-set versus 11.17 at on-set (sampling angle 2 degrees), 11.13 at off-set versus 11.48 at on-set (sampling angle 4 degrees), and 11.24 at off-set versus 11.64 at on-set (sampling angle 6 degrees), respectively. In human myocardium SPECT, visualization of the interventricular septum and cardiac cavity was improved. CONCLUSION: Off set reconstruction by means of filtered back projection will be an efficient sampling mode, having a larger number of effective projection angles.