Forensic Imaging最新文献

Conventional photogrammetry faces challenges with non-textured, transparent, or reflective surfaces, affecting accurate 3D modeling, particularly in forensic documentation. This study evaluates improvements using lower exposure, exposure bracketing, and RAW format for better 3D modeling of non-textured surfaces. Two bodies were photographed under controlled conditions to assess techniques for non-textured surfaces, with a comparison set for textured surfaces. The experiments were conducted in an autopsy room with a Nikon D5500 camera, adjusting for low exposure, exposure bracketing, RAW format, and increased photo redundancy. Models with Meshroom (Alicevision). Our focus was on visual plausibility rather than quantitative metrics. Results indicated that using RAW format with exposure bracketing and low exposure significantly improved 3D models by reducing artificial edges seen with standard JPG images, despite some noise. A redundant series of RAW photos further reduced edge artifacts and noise, demonstrating the effectiveness of averaging photos to enhance model quality. However, these modifications showed marginal improvements on textured surfaces, underscoring their significant benefits primarily for non-textured surfaces. This study highlights the potential of modified photogrammetry techniques in forensic science, particularly for documenting challenging surfaces. It points out the need for further research, given its limitations in sample size and the absence of extensive parameter testing and quantitative analysis.

It is well known that skeletal characteristics vary among different populations. Sex dimorphic characteristics of the mandible have been reported from studies using either mandible bone or computer tomography (CT) scan images of the mandible to test its efficacy in estimating sex. Mandibular studies for estimating sex in any particular population group may not hold well for different populations owing to inherent geographical variations. With this background, we assessed the validity of mandible measurements from CT scan images to determine sex in the South Indian population. As a part of our study, 11 metric parameters and 1 angular parameter were measured and analyzed. The mean values of all the parameters were significantly higher for males as compared to females. Bigonial breadth indicated the best discriminatory ability of the study. Mandibular angle had the least predictive accuracy among all the discriminant functions studied. We further observed that a combination of parameters gave the best overall classification rate (92.3 %). When the same functions were tested on an independent testing data set, a combination of parameters and bigonial breadth gave the best classification rate (82.1 %) which was consistent. We concluded that the mandible has a high accuracy for sex estimation. All the parameters studied demonstrated statistically significant differences between the two sexes except the mandibular angle.

Objectives

We encountered a case in which an acute subdural hematoma (SDH) was observed on postmortem computed tomography (PMCT) but no hematoma was found under the dura mater during autopsy. Subsequent verification led to the conclusion that the SDH was pressing on the brain when PMCT was performed but was not observed because all the subdural blood drained out during craniotomy because the hematoma did not clot.

Materials and Methods

We examined 13 cases of SDH in which PMCT was performed before autopsy to determine the factors related to the presence or absence of blood clots in the SDH, and to determine whether PMCT before autopsy could determine the presence or absence of blood clots in the SDH.

Results

Blood clots were not found in the SDH of individuals with an estimated survival interval of 5 h or less or when the estimated survival interval was 1440 h or more. No particular trend was observed in the relationship between the presence or absence of clots in the SDH and HU values of the SDH.

Conclusion

Early death after injury and chronic SDH are thought not to contain SDH clots. In cases of early death after injury, the autopsy diagnosis of SDH should be made by careful observation of the fluid SDH during craniotomy, as SDH may not contain clots as an indicator of SDH at autopsy. Predicting the presence or absence of a clot within an SDH using PMCT is difficult.

Objectives

variations in the positions of organs and bones resulting from two different body positions during PMCT were investigated.

Methodology

Forty-four bodies were CT-scanned in two positions and compared using 18 landmarks and 27 distances.

Results and conclusion

Differences below 1 cm were observed for all measurements. The most significant variation was observed along the cranio-caudal plan (z). Awareness of these movements is important when using 3D models for visualization or 3D reconstructions.

Purpose

Since many intraoral radiographs are taken in mass disasters, it is important to reduce the finger irradiation dose to the operator and caregivers in intraoral radiography. However, there is not enough reporting on finger irradiation doses when the detector is placed in the oral cavity of a corpse. The objective of this study was to examine finger irradiation doses when using detector holders and protective gloves and to compare various reduction methods.

Methods

One type of disposable and two types of protective gloves were employed in this study. The average irradiation dose was calculated by dividing the accumulated dose by the number of irradiation events for intraoral imaging of the left mandibular molar; since the dosimeter detects a cumulative dose, irradiation was continued until the dose exceeded 100 μSv. Statistical analysis was performed using one-way analysis of variance, Bonferroni test, and multiple comparisons test (α = 0.05).

Results

A significant dose reduction was observed using protective gloves (maximum: 63%, mean: 59%; p<0.01). No significant difference in the irradiation dose to the finger was observed when disposable gloves were layered on protective gloves. When protective gloves were used with the detector holder held at the end position, the radiation dose reduced by approximately 91% compared to when the detector was held directly in the oral cavity. Implementing these radioprotective measures can reduce the risks of increased radiation exposure and contamination.

Conclusions

The combined use of detector holders and protective gloves was effective in reducing the radiation exposure to the operator's fingers.

Filtering is known to improve image quality of CT scans. Water immersion is one type of filtering that has been used for CT scanning dry (skeletonized) bones, and it has been suggested that this approach can increase measurement accuracy and improve fracture resolution. These tests have previously involved clinical CT scanners. Here we use an industrial micro-CT scanner and test whether water immersion and other x-ray filtering options increases fracture resolution in reconstructed scans of dry bones.

Eleven dry non-human bones were CT scanned using the same acquisition parameters, while varying filter options. Bones were scanned (1) in an unfiltered “dry” air environment, (2) using metal filters at the x-ray source, and (3) with the bones immersed in water. A small subset of bones (N = 3) was also scanned using the same parameters except increasing the number of projections acquired from 500 to 1500. Reconstructed scans were evaluated by the authors, in part using a Likert scale comparing filtered with unfiltered scans, to assess fracture resolution (overall appearance and extent).

Results showed that increasing the projections resulted in the greatest improvement in fracture resolution, followed by filtering at the x-ray source. Water immersion performed poorly overall, possibly due to movement artifacts that result from this type of scanning, in which the specimen rotates on a stage during the scan. When using this type of CT scanner, if increased fracture resolution is desired, water immersion is not recommended; increasing the number of projections or filtering at the x-ray source is suggested instead.

In forensic anthropology, the probable identification of an unknown individual is based on the presence of quantifiable phenotypic variations and the relationship of these variations to the individual's socio-cultural identity. This study aims to create sub-specific discriminate shape matrices to estimate socio-cultural identity among a modern black South African sample, with a particular emphasis on developing standards for predicting mid-facial variation within this population.

The sample consists of 191 adult South Africans representing nine modern black South African socio-cultural identity groups obtained from the Pretoria Bone Collection in the Department of Anatomy at the University of Pretoria. Three-dimensional (3D) modelling of the relevant anatomical area was performed using an EinScan H 3D scanner. The 3D anatomical extraction was performed by placing 37 standard craniometric landmarks and 388 sliding landmarks on 3D models.

The analysis of variance associated with the linear model “shape against socio-cultural identity” explained 95.5% of overall shape variation showed that variations in midfacial shape configurations were statistically significant (MANOVA: p= 0.001; 50-50 MANOVA: p <2e-16) for all shape configurations, including sub-specific discriminate shape matrices, separately. Additionally, cross-validated linear discriminant function analysis yielded an accuracy between 73.01% and 91.53% for all shape configurations and sub-specific discriminant shape matrices, reflecting the discriminative power of socio-cultural identity groups in the black South African population.

Our findings support the utilization of geometric morphometric methods (GMM) for socio-cultural identity estimation as they allow us to retain the objects' geometry and statistically analyze subtle structural differences.

Human identification forms an integral part of forensic and biological anthropology. For proper identification, a biological profile made up of biodata such as age, sex, ancestry, antemortem stature, and factors of individualization, is obtained and stored for use by anthropologists. A correct sex estimation can help unravel other anthropological parameters. South Africa has a multi-dimensionally high crime rate and its largest distinct population group (Black South Africans) is most affected by such crimes. Several authors have in the past used cranial measurements to carry out sex discrimination among South Africans, such attempts have largely been done using direct assessment of post-mortem specimens and on subjects of European Descent. This study, therefore, attempted to overcome these drawbacks by using a non-invasive method, the three-dimensional computed tomography (3DCT) to obtain population-specific data from a contemporary Black South African population group. It obtained measurements from cranial CT records of 350 Black South Africans (50 % sex ratio) housed in the Radiology Department of Charlotte Maxeke Johannesburg Academic Hospital. The Xiris and IntelliSpace software were used to reconstruct the images into three-dimensional forms from which measurements were taken. Evaluation of previously derived equations using data from the current study yielded low average classification accuracies which necessitated the formulation of new equations. Discriminant function analysis yielded acceptably high average classification accuracies for sex estimation which ranged from 78.3 % to 82.9 %.

Background and objectives

Postmortem examinations of fetuses play a crucial role in confirming abnormalities, especially vascular and cardiac malformations leading to fetal demise. This study aims at developing and assessing a method for acquiring Post-Mortem CT-Angiography (PMCTA) with the injection of a lipophilic contrast agent (CA) to better visualize the great vessels of the trunk and head.

Materials and methods

25 human fetuses (gestational age at death between 106 days and 28 weeks) were included. Examinations were performed using a dual-energy Multidetector Computed Tomography (MDCT) scanner. Three imaging sequences were acquired, before CA injection, after injection of 7mL of CA through umbilical artery (arterial phase), and after an injection of 15mL of CA through umbilical vein (venous phase). CA-induced vascular opacification was scored per-vessel in both phases as follows: 0 = none, 1 = partial, 2 = complete. Total opacification was defined as the sum of the per-vessel opacification scores.

Results

In 23/25 subjects, CA injection into the umbilical vessels was feasible manually using flexible catheters. After the first injection, at least a partial opacification of the arterial network was achieved in 15/23 (65%) subjects. After the second injection, a complete opacification of the venous network was achieved in 18/23 (78%) subjects. Failures occurred in 10/25 (40%) subjects and were mostly due to the preservation status.

Conclusion

PMCTA performed with a two-phase intra-umbilical injection of a lipophilic CA enabled to visualize the vascular network, even after a significant a postmortem interval. This protocol may help in detecting vascular malformations, improving clinical diagnoses and prenatal counselling.

Objectives

In quantitative postmortem computed tomography (qPMCT) the presence of putrefaction gas in tissues can obscure measurements such as bone mineral density (BMD). Quantitative CT analysis procedures adopted directly from clinical CT may not be designed to compensate for intracorporeal gas, which require additional measures for PM-imaging applications. Thus, a solid unbiased procedure for volumetric BMD analysis in PMCT of the deceased presenting with intracorporeal gas is desirable.

Materials and methods

We tested three different analysis procedures (AP1-3) for BMD analysis of the lumbar vertebrae (L1-3). Data in this retrospective study was based on synchronous PMCT acquisition with a solid five-phase Cann-Genant phantom from routine forensic examinations of 154 individuals distributed into three putrefaction groups: “None” (n = 95), “Mild” (n = 54), and “Moderate” (n = 10). AP1 was based on commercially available software (“Mindways”), which required the operator to subjectively place region of interest (ROIs) in areas without gas. The open-source software (“FIJI”) was used for AP2 and AP3 and enabled comparison of objectively placed ROIs with AP1. In AP3, threshold-filtering was applied to remove the signal from gas (in AP2 data) prior to BMD analysis.

Results

AP1 provided higher BMD values than AP2-3 due to subjective placement of ROIs in denser cortical areas. AP2 yielded the lowest BMD measurements with most variation, while AP3 yielded BMD measurements comparable to in vivo values published in clinical studies. AP3 provided greater interobserver correlation.

Conclusion

AP3 provided a simple open-source software-based approach to PMCT BMD analysis that allows for precise BMD measurements in PMCT.