Elbow

thingiverse

This anatomical model contains a right elbow with a minor chip fracture of the coronoid process. Print Settings Printer Brand: LulzBot Printer: Mini Rafts: Yes Supports: Yes Resolution: .2 Infill: 20% Notes: If supports are not included, there may be some limited bone "matrix" inside the actual model; this might or might not be enough to support the structure. How I Designed This To convert a CT Scan (DICOM Images) to STL: DICOM images from a CT axial scan (bone window 2.0 B60s) were obtained and converted to STL using Slicer3D. Meshmixer was used to improve the quality of the scan and remove debris/artifact, unfortunately removing the fracture fragment. How does a Computed Tomography (CT/CAT) scanner work? A CT scanner contains an x-ray tube which rotates around the patient from within a circular, doughnut-shaped structure called a "gantry." The patient lies on a table, moving through the gantry, and the tube rotates around them in a helical pattern, increasing the speed of the scan. Opposite from the radiation source are multiple layers of detectors measuring the amount of radiation that passes through the patient and reaches the detectors. How does the computer process CT scan data? Radiation passing through the patient is partially attenuated or "absorbed" by various tissues, with bone absorbing more radiation than air. According to the Beer-Lambert law, the attenuation of energy relates to the properties of the material it passes through. We use these factors to identify different types of tissue on a CT scan. Hounsfield unit's (HU) are used to assign values to the amount of data received by each CT detector, comparing the known attenuation value of water to the amount of data received by each voxel. Water has an HU of 0; in comparison, air's value is -1000 and bone's value is +1000. From these values, we can identify what tissues the CT beam likely passed through. The computer reconstructs the image based on this data, arranging voxels into cross-sectional slices. Thinly sliced CT scans have a higher number of voxels, increasing spatial resolution. They are finer cross-sectional cuts, which increases radiation dose but decreases the risk of "missing" pathology. CT technologists and radiologists weigh the cost of radiation exposure against the need to see detail. Imagine slicing a loaf of raisin bread thinly if you want to count all the raisins; otherwise, you might miss some in larger slices. When asking for a CD of your CT scan from your medical provider, request thinly sliced cuts, as the original slices on the machine are sometimes thinner than those provided to the patient. The model has "stairs" because it is indicative of low resolution in the original CT, taken in 2012 with only 81 slices (in 2 mm thickness). You can see individual slices in the model near the actual joint.