Cartesian positioning system for localization of blast and ballistic fragments: a phantom-based pilot study.

Our purpose was to demonstrate the consistency of radiologists' three-dimensional measurements of simulated blast fragment locations in vitro in an effort to objectively localize retained fragments and wound paths. We designed a phantom consisting of 10 nail heads (simulating blast fragments) glued to wooden pegs that were randomly situated at distances from a reference point within a plastic tub. The x, y, and z coordinates of simulated fragments were recorded in Cartesian 3-space relative to the reference point. Computed tomography images of the phantom were acquired. Differences in x, y, and z positions as determined by three observers were summed for each fragment. Agreement between recordings of coordinates across readers was assessed using the intraclass correlation coefficient. Summed differences in coordinate positions as determined by readers ranged between 0.00 and 1.204 cm (mean: 0.732 cm). Across readers, the intraclass correlation coefficient for each dimension was >0.99. We found excellent agreement among readers with minimal discrepancy of measured locations of simulated fragments. Our results provide a foundation for trajectory analysis necessary to lead to automated organ damage reporting for immediate assessment in the emergency department and for forensic investigation and long-term epidemiological analysis.

Situs inversus totalis.

We present a case of situs inversus totalis. A 22-month-old infant presented with cyanosis, double-inlet left ventricle, severe pulmonary stenosis, and concern for underlying visceroatrial abnormalities. Chest (Fig. 1) and abdominal (Fig. 2) radiographs were obtained. Abdominal sonography was performed to clarify the presence of splenic tissue and further define the relationships of the inferior vena cava and abdominal aorta (Figs. 3-7). This case demonstrates typical radiographic and sonographic findings of situs inversus totalis and shows the utility of sonography.

Blast and ballistic trajectories in combat casualties: a preliminary analysis using a cartesian positioning system with MDCT.

OBJECTIVE: The purpose of this study is to determine the agreement with which radiologists identify wound paths in vivo on MDCT and calculate missile trajectories on the basis of Cartesian coordinates using a Cartesian positioning system (CPS). MATERIALS AND METHODS: Three radiologists retrospectively identified 25 trajectories on MDCT in 19 casualties who sustained penetrating trauma in Iraq. Trajectories were described qualitatively in terms of directional path descriptors and quantitatively as trajectory vectors. Directional descriptors, trajectory angles, and angles between trajectories were calculated based on Cartesian coordinates of entrance and terminus or exit recorded in x, y image and table space (z) using a Trajectory Calculator created using spreadsheet software. The consistency of qualitative descriptor determinations was assessed in terms of frequency of observer agreement and multirater kappa statistics. Consistency of trajectory vectors was evaluated in terms of distribution of magnitude of the angles between vectors and the differences between their paraaxial and parasagittal angles. RESULTS: In 68% of trajectories, the observers' visual assessment of qualitative descriptors was congruent. Calculated descriptors agreed across observers in 60% of the trajectories. Estimated kappa also showed good agreement (0.65-0.79, p < 0.001); 70% of calculated paraaxial and parasagittal angles were within 20° across observers, and 61.3% of angles between trajectory vectors were within 20° across observers. CONCLUSION: Results show agreement of visually assessed and calculated qualitative descriptors and trajectory angles among observers. The Trajectory Calculator describes trajectories qualitatively similar to radiologists' visual assessment, showing the potential feasibility of automated trajectory analysis.

CT-based ballistic wound path identification and trajectory analysis in anatomic ballistic phantoms.

PURPOSE: To evaluate the accuracy of computed tomography (CT)-based ballistic wound path identification in phantoms by determining the agreement between actual shooting angles and both trajectory angles measured with a picture archiving and communication system (PACS) angle tool and angles calculated from x, y, z coordinates of the entrance and exit points. MATERIALS AND METHODS: In this institutional review board-approved model study, two simulated legs were shot by a trained marksman from 50 yards at six clinometer-measured angles with a 0.30-06 rifle and then scanned at multidetector CT. Radiologists measured the wound path angles on paracoronal reformations by using a PACS angle tool. Observers determined the Cartesian coordinates of the entrance and exit points of the wound paths on axial CT images by using detailed instructions. Angles were calculated from these coordinates by using a computer arctangent function. Agreement between the angles was evaluated with Bland-Altman plots. Means, ranges, and standard deviations of the angles also were determined. RESULTS: Radiologists identified all six wound paths on the CT images. The PACS tool-based measured and coordinate-based calculated angles were within 5° of the shooting angles. Results indicated that in larger study populations, one can be 91% confident that future coordinate-based angle calculations will differ from the actual shooting angle by no more than 5° and 95% confident that PACS tool-based angle measurements will differ from the actual shooting angles by no more than 4.5°. One can be 95% confident that future coordinate-based angle calculations will differ from PACS angle measurements by no more than 4.02°. CONCLUSION: Study results demonstrated the feasibility of consistent wound path identification and the accuracy of trajectory angle determination in models with use of multidetector CT.