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valchanov

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valchanov last won the day on October 14

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About valchanov

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  1. How many grams of polymer this thorax took (scaffold included)?
  2. Version 1.0.0

    0 downloads

    The skull from Full head HD set Prepared for 3D printing. Made from 0,7mm CT scan of a caucasian female in her 20-s. 5 parts model 14 5x2mm and 12 8x2mm neodymium magnets Printed on Prusa MK3Swith 3D Jake ecoPLA Glitter Silver1,5mm layer thickness4 perimeters, 30% gyroid infill Support on build plate only, 200C extrusion temperature (except the first layer, which is 210C)60 hours print, ~600g filament 80% of the anatomy curriculum.

    $60.00

  3. The shrinking is a major and complicated issue for all the 3D printing methods in general. I didn't cared about it, until I had to made really accurate, industrial-grade model, in which every micron matters. I'm not a material science engineer, but I have to address this issue even further, because my research group is planning to go in the direction of the temporary and permanent implants, in which even the slightest deviation can cause slow recovery, pain, inflammatory reaction or rejection. This is especially true for the 3d printed dentures and maxillofacial implants, in which even 50 micron deviation can cause significant problems for the patient. It's so good for me, that I'm not working for the dental medicine faculty, because for the bone implants deviation of 200 microns is perfectly acceptable. For the diagnostic models (presurgical, demonstration, teaching etc.) the acceptable deviation is even bigger - up to 500 microns. Every 3d printing method have some base shrinkage and warping, which is combined with the base deviation of the STL model itself and with the base shrinkage of the material. To make the issue even harder, the manufacturers didn't post the basic deviation of their materials, because this can ruin their trade secret. Every material in the market is not just a single polymer, but a composite of several polymers, with a lot of additives, which makes the issue even more complicated. There are several general rules: 1. Material Jetting > SLS > STL/DLP/FDM. From the termoplastic modalities, the material jetting is most accurate method, while STL/DLP/FDM are relatively equal in their accuracy. STL and DLP have better porstprocessing option than FDM, though. Overall, for the lower industrial segment, FDM is better in the printing of large objects (more than 10 cm), while STL and DLP are better in the smaller part printing. 2. Stiffer materials (high Young's modulus) are more accurate than the elastic materials. PLA (high stiffness) is more accurate than PETG or Nylon. This also depends on the 3d printing method. 3. Material with lower extrusion temperature are more accurate than materials with high extrusion temperature. PLA shrinks with 2-5% (depending on the manufacturer), while ABS ~8%. You can control this process even further by tuning the cooling fan. 4. Larger objects shrinks more than the smaller ones. It's better to cut your model into several attachable parts, printed individually, than to print it as a whole. 5. Enclosed system is more accurate than unenclosed one. The constant temperature in the enclosure will make the shrinkage more uniform in all the segments of the object, resulting on overall more accurate final product. The best practice is to start measuring your models. 1. When you're done with the model, reimport the stl again in the medical data program, used for segmentation, convert it into a label map and compare the geometry with the voxels of the source dataset. If you're using control points on the antropometric points (separate segmentation on the classical points of orientation in the human body, several voxels in size), every deviation will be visible and editable. If you're not, you'll have to compare it visually. 2. Use a professional CAD program (Fusion360, Solidworks) to measure the parts of the STL model. The digital simulations of those programs makes the quality control even better. 3. Use dicom viewer to measure the same distances in the DICOM dataset. 4. Use a caliper to measure the same distances on the 3d printed object. 5. 6-8 measurements per distance will be more than enough. 4-6 distances will be enough for a model. 6. Calculate average deviation at 90% confidence interval. 7. The resulting score will give you the accuracy of your model. 8. If you're not specifically targeting high accuracy or you're not a detail freak as myself, point 1 will be enough. You can check this guide, in which the issue is well explained. You can also check Form Lab's guide for dimensional accuracy, since you're regularly using Form2. For now, I can achieve without a problem 0,5 mm accuracy from CT scan to the 3D printed object (in some cases 0,2 mm), but I'm constantly fighting for every micron and I won't quit, until I achieve 0,2 mm on all of my models. I guess on some point I'll have to add a material science engineer to my research group. I'm also considering machine learning algorithm for quality control, but this is way over my head right now. To check how accurate are your models, you can use 3d printed tests. You can try the tolerance test and the all-in-one test. They work only for FDM, though.
  4. Bones The main advantage of the orthopedical presurgical 3d printed models is the possibility to create an accurate model, which can be used for metal osteosynthesis premodelling - the surgeons can prepare (bend, twist, accommodate) the implants prior the operation. After a sterilisation (autoclaving, UV-light, gamma-ray etc etc), those implants can be used in the planned surgery, which will decrease the overall surgery time (in some cases with more than an hour) with all it's advantages, including a dramatic decreasing of the complication rates, the X-ray exposure for the patient and for the surgeons, the cost and the recovery rates etc etc. For this purpose, you need a smooth bone model, with clearly recognizable and realistic landmarks, realistic measurements and physical properties, close to the real bone. Traditionally, the orthopedical surgeons in my institution used polystyrene models, made by hand, now they have access to 3d printed models and they are better in any way. Here are some tips how to print that thing. 1. Method - FDM. The bone models are the easiest and the most forgiving to print. You can make them with literally every printer you can find. FDM is a strong option here and, in my opinion, the best method on choice.2. Matherial - PLA - it's cheap, it's easy to print, it's the bread and butter for the bone printing. Cool extruding temperature (195-200C) decrease the stringing and increases the details in the models.3. Layer heigh - 0,150mm. This is the best compromise between the print time, the quality and the usability of the models.3. Perimeters (shell thickness) - 4 perimeters. One perimeter means one string of 3d printed material. It's width depends on the nozzle diameter and the layer thickness. For Prusa MK3 with 0,4mm nozzle 1 perimeter is ~0,4mm. To achieve a realistic cortical bone, use 4 perimeters (1,7mm). The surgeons loves to cut stuff, including the models, in some cases I have to print several models for training purposes. 4 perimeters PLA feels like a real bone.4. Infill - 15% 3d infill (gyroid, cuboid or 3d honey comb). The gyroid is the best - it looks and feels like a spongy bone. It's important to provide a realistic tactile sensation for the surgeons, especially the trainees. They have to be able to feel the moment, when they pass the cortical bone and rush into the spongiosa.5. Color - different colors for every fracture fragment. If the model is combined with a 3D visualization, which colors corresponds with the colors of the 3d print, this will make the premodelling work much easier for the surgeons. Also, it looks professional and appealing. 6. Postprocessing - a little sanding and a touch of a acrylic varnish will make the model much better.7. Support material - every slicer software can generate support, based on the angle between the building platform and the Z axis of the model. You can control this in details with support blockers and support enforcers, which for the bones is not necessary, but it's crucial for the vessels and the heart.Conclusions - the bone models are easy to make, they look marvelous and can really change the outcome of every orthopedical surgery.
  5. There are many challenging cases, in which the single segmentation is not enough. The paranasal sinuses and the congenital heart defects are notable examples. My usual workflow was to segment whatever I can as good as it's possible, to clean the unnecessary structures and the artefacts, to export the segmentation as stl 3d model and then to "CAD my way around". This is solid philosophy for simple, uncomplicated models, but for complex structures with a lot of small details and requirement from the client for the highest quality possible, this is just not good enough, especially for a professional anatomist like myself. Then I started to exploit the simple fact, that you're actually able to export the model as stl, to model it with your CAD software and then to reimport it back and convert it into label map again. I called this "back and forth technique". You can model the finest details on your model and then you can continue the segmentation right where you need it, catching even the slightest details of the morphology of the targeted structure. This technique, combined with my expertise, gives me the ability to produce the best possible details on some of the most challenging cases, including nasal cavity, heart valves, brain models etc. etc.To use this technique, just import the stl file, convert it into a label map (for 3D slicer - segmentation module/ export/import models and label maps). The main advantages of this technique are:1. You can combine the segmentation with the most advanced CAD functions of your favorite software. Two highly specialized programs are better than one "Jack of all trades" (cough cough Mimics cough cough)2. Advanced artefact removing.3. Advanced small detail segmentation and modelling.4. Combined with several markers (separate segmentations, several voxels in size) on the nearby anthropometric points, this technique increases the accuracy of the final product significantly. Without points of origin, the geometry of your model will go to hell, if you're not especially careful (yes, I'm talking about the 3D brushes in Slicer).5. You can easily compare the label map with the 3d model, converted back. Every deviation, produced during the CAD operations will be visible like a big, shining dot, which you can easily see and correct. This is one of the strongest quality control techniques.6. You can create advanced masks with all the geometrical forms you can possibly imagine, which you can use for advanced detail segmentation. Those masks will be linked with the spatial coordinates of the targeted structures - the stl file preserves the exact coordinates of every voxel, which was segmented.7. You can go back and forth multiple times, as many as you like.8. This technique is more powerful than the best AI, developed by now. It combines the best from the digital technologies with the prowess of the human visual cortex (the best video card up to date).The main disadvantages are:1. It's time consuming.2. It produces A LOT of junk files.3. Advanced expertise is needed for this technique. This is not some "prank modelling", but an actual morphological work. A specialized education and practical experience in the human anatomy, pathology and radiology will give you the best results, which this technique can offer. 4. You need highly developed visual cortex for this technique (dominant visual sense). This technique is not for the linguistic, spatial-motor, olphactory etc. types of brains. Recent studies confirms, that a part of the population have genetically determined bigger, more advanced visual cortex (The human connectome project, Prof. David Van Essen, Washington University in Saint Louis). Such individuals become really successful cinematographers, designers, photographers and medical imaging specialists. The same is true for all the other senses, but right now we're talking about visual modality and 3D intellect (I'm sorry, dear linguists, musicians, craftsmen and tasters). It's not a coincidence that I have so many visual artists in my family (which makes me the medical black sheep). But if you don't have this kind of brain, you can still use the technique for quality control and precise mask generation. Just let the treshould module or the AI to do the job for you in the coordinates, in which you want (You should really start using the Segment Editor module in Slicer 3D).5. You really need to love your work, if you're using this technique. For the usual 3D modelling you don't need so many details in your model and to "CAD your way around" is enough for the task.6. You should use only stl files. For some reason, the obj format can't preserve the spatial geometry as good as the stl format. Maybe because the stl is just a simple map of vertex coordinates and the obj contains much more sophisticated data. The simple, the better.On the picture - comparison of the semilunar valves, made by treshould segmentation at 250-450 Hounsfield units (in green) and modelled and reimported model (in red).
  6. Single versus multiple segmentation - Back and forth technique There are many challenging cases, in which the single segmentation is not enough. The paranasal sinuses and the congenital heart defects are notable examples. My usual workflow was to segment whatever I can as good as it's possible, to clean the unnecessary structures and the artefacts, to export the segmentation as stl 3d model and then to "CAD my way around". This is solid philosophy for simple, uncomplicated models, but for complex structures with a lot of small details and requirement from the client for the highest quality possible, this is just not good enough, especially for a professional anatomist like myself. Then I started to exploit the simple fact, that you're actually able to export the model as stl, to model it with your CAD software and then to reimport it back and convert it into label map again. I called this "back and forth technique". You can model the finest details on your model and then you can continue the segmentation right where you need it, catching even the slightest details of the morphology of the targeted structure. This technique, combined with my expertise, gives me the ability to produce the best possible details on some of the most challenging cases, including nasal cavity, heart valves, brain models etc. etc. To use this technique, just import the stl file, convert it into a label map (for 3D slicer - segmentation module/ export/import models and label maps). The main advantages of this technique are: 1. You can combine the segmentation with the most advanced CAD functions of your favorite software. Two highly specialized programs are better than one "Jack of all trades" (cough cough Mimics cough cough) 2. Advanced artefact removing. 3. Advanced small detail segmentation and modelling. 4. Combined with several markers (separate segmentations, several voxels in size) on the nearby anthropometric points, this technique increases the accuracy of the final product significantly. Without points of origin, the geometry of your model will go to hell, if you're not especially careful (yes, I'm talking about the 3D brushes in Slicer). 5. You can easily compare the label map with the 3d model, converted back. Every deviation, produced during the CAD operations will be visible like a big, shining dot, which you can easily see and correct. This is one of the strongest quality control techniques. 6. You can create advanced masks with all the geometrical forms you can possibly imagine, which you can use for advanced detail segmentation. Those masks will be linked with the spatial coordinates of the targeted structures - the stl file preserves the exact coordinates of every voxel, which was segmented. 7. You can go back and forth multiple times, as many as you like. 8. This technique is more powerful than the best AI, developed by now. It combines the best from the digital technologies with the prowess of the human visual cortex (the best video card up to date). The main disadvantages are: 1. It's time consuming. 2. It produces A LOT of junk files. 3. Advanced expertise is needed for this technique. This is not some "prank modelling", but an actual morphological work. A specialized education and practical experience in the human anatomy, pathology and radiology will give you the best results, which this technique can offer. 4. You need highly developed visual cortex for this technique (dominant visual sense). This technique is not for the linguistic, spatial-motor, olphactory etc. types of brains. Recent studies confirms, that a part of the population have genetically determined bigger, more advanced visual cortex (The human connectome project, Prof. David Van Essen, Washington University in Saint Louis). Such individuals become really successful cinematographers, designers, photographers and medical imaging specialists. The same is true for all the other senses, but right now we're talking about visual modality and 3D intellect (I'm sorry, dear linguists, musicians, craftsmen and tasters). It's not a coincidence that I have so many visual artists in my family (which makes me the medical black sheep). But if you don't have this kind of brain, you can still use the technique for quality control and precise mask generation. Just let the treshould module or the AI to do the job for you in the coordinates, in which you want (You should really start using the Segment Editor module in Slicer 3D). 5. You really need to love your work, if you're using this technique. For the usual 3D modelling you don't need so many details in your model and to "CAD your way around" is enough for the task. 6. You should use only stl files. For some reason, the obj format can't preserve the spatial geometry as good as the stl format. Maybe because the stl is just a simple map of vertex coordinates and the obj contains much more sophisticated data. The simple, the better. On the picture - comparison of the semilunar valves, made by treshould segmentation at 250-450 Hounsfield units (in green) and modelled and reimported model (in red).
    Excellent angio CT scan, very challenging modelling, quite interesting pathology. I'm almost done with the arterial segmentation and I'll start with the pulmonary artery, which will be hard to make. The quality of the scan made possible the modelling of the semilunar valves. I recommend this scan for tutorial and teaching purposes.
  7. If the models are for medical purposes - this is the webpage of the lab in my institution. You can check their equipment and find a similar service in your state. I'm also quite interested if anyone on this website is making such models.
  8. You want those crowns for a medical purposes or as a prank? Because the quality criteria for the dentures are quite high - even 50 microns deviation can cause unbearable pain for the patient. Usually a special dental 3D scanner is used for the model generation and a SLA or STL printer - for the dentures themself, with an expensive, FDA-approved polymer. There are specialized dental 3d printing labs, including in my institution. I'm definitely out of this league (yet).
  9. The heart is possible, but the valves will be a hard call, which depends on the skill of the radiologist and the 3D modeller. You can segment the cuspids on hand and hope for the best. Smaller slices, better result. The print will be also a hard call, unless you have a Polyjet on hand.
  10. Every plastic shrinks a bit when it's cooled down. This percentage is different for the different materials, but it's a good idea to scale up your model in the slicer with 0,05%. Also, some composites have minimal shrinkage and they should be on choice for prints, which requires high dimensional accuracy. I'm using Silk PLA (85% PLA, 15% Polyester, some other additives) with great success, because the shrinkage is lower than the natural PLA. On the graphic I measured a model of Aberrant arteria subclavia dextra - the CT scan with a dicom viewer, the model with Autodesk Fusion 360 and the printed model with vernier caliper. I calculated average deviation on 95% confidence interval and this is what I got. Note that the caliper was too tick and large for subclavia dextra, which resulted in the difference of the result (my tool is too large). I think those results are quite promising and I'm planing to close the circle - to measure cadaver, CT of the cadaver, generated 3D model and 3D printed model, when the ethical commission allow me to.
  11. Hello Can you give me some background information about the health condition of the patient? The set is excellent, but there is something really wrong with the anatomy of this heart. I want to model it properly.
  12. Version 1.0.0

    20 downloads

    This is a full High definition 3D model set of a head, made from 0,7mm CT scan. Caucasian female in her 20s. The set doesn't include the original dataset and the metadata for ethical reasons. I can provide the dataset as a personal request. The set includes: 1. Full head model of a head with the nasal cavity, paranasal sinuses, the pharynx and the superior part of the larynx. 2. Skull model with most of the foramens. The inner ear is NOT included in the set. 3. Mandibula model. 4. The first 6 cervical vertebrae. 5. The hyoid bone. The models are accurate, with proper geometry and measurements, in their raw format. They are also 3d printable. I can slice and dice them in whatever format you need, but I'll have to charge you additionally for that. anatomy, morphology, head, skull, vertebra, cervical, hyoid, set, atlas, axis, frontal, temporal, occipital, orbit, zygomatic, arch, mandible, angle, ramus, nasal, anterior, posterior, vertebral, foramen, mastoid, process, skin, bone, 3d, model, printable, .stl, maxillofacial, eye, lips, face, spinous, teeth, tooth, incisor, molar, premolar, canine, coronoid,

    $100.00

  13. I was thinking the same, until I found the Silk PLA. It's a composite - 85% PLA, 15% Polyester and it's dirt cheap. The advantages are: 1. In contrast to the natural PLA, the Silk one doesn't warp or deform during the cooling (or at least the deformation is minimal). 2. It prints really well. You can make the impossible possible with this material. 3. It looks amazing. The layer lines are almost invisible, the silk finishing is appealing, the colors are vivid. 4. The supports falls easily. You just have to pull them and they are done. Tried this on a heart, brain and aorta models. You don't even need increased retraction for this. 5. The stringing is minimal. No more "hairs". 6. It's cheap. 7. Because of those characteristics, this is material of choice for models with accurate morphological measurements. I'm using mostly this material, when I want to have an accurate model. So, check the local store for this material and try it yourself. You can thank me latter. P.S. For best results, print it at 200C.
  14. The whole time I was thinking that I'm doing something wrong, because it's impossible for a TAAA to be that big. This was beyond everything I ever saw for 22 years of medical education and experience. But yes, it's THAT big. I segmented the lumen, I added 2 cm margin around it to create a hollow shell, then I added the media of the aneurysmic sack and all the atherosclerotic plaques for extra realism. There was a part of the sack, which went into one of the perihepatic space, but I removed it, because my colleague asked me to. The result is marvelous model, bigger than my fist and I'm really proud with it.
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