CT or MRI of the knee
In case of knee injury, CT and MRI answer different questions: CT shows the bones in detail - fracture lines, depression of the articular surface, displacement of fragments, which determines the tactics of osteosynthesis; MRI - menisci, ligaments, cartilage and bone marrow edema. Therefore, for fractures, CT is performed (often before surgery), for injuries to ligaments and menisci, MRI is performed, and for metal structures and contraindications to MRI, only CT is performed. The study also identifies osteochondral bodies, cysts, tumors, and evaluates the limb axis.
Indications
- intra-articular fractures, complex displaced fractures, assessment of union;
- arthrosis with assessment of bone changes, cysts, necrosis of the femoral head;
- planning of endoprosthetics and osteosynthesis, monitoring of implants;
- tumors and tumor-like bone lesions;
- loose intra-articular bodies, developmental anomalies, hip dysplasia;
- inflammatory changes (osteomyelitis, arthritis) if MRI is not possible.
What is MSCT
Multislice computed tomography is a layer-by-layer X-ray study in which detectors receive dozens of sections up to 0.5–1 mm thick in one revolution of the tube, and a computer builds a three-dimensional image of the organ. MSCT is performed in 5-15 minutes, accurately shows bones, lungs, stones, hemorrhages, tumors and vessels (with contrast), and is often the method of choice for trauma and acute conditions when MRI is too long or contraindicated.
Preparation and contrast
Non-contrast MSCT does not require preparation. Before a study with intravenous contrast, a test for creatinine (kidney function) and the absence of an allergy to iodine are required; 4–6 hours without eating; When taking metformin, agree on a break with your doctor. Contrast (Unigexol) is administered using an automatic injector; a feeling of warmth for 1–2 minutes is normal. To examine the abdominal and pelvic organs, oral contrast is used, which is drunk 30–60 minutes before the scan. Remove metal objects from the examination area. The radiologist’s conclusion is completed within 1–2 hours, the images are issued on film and disk.
Radiation exposure and safety
Modern devices use low-dose protocols; the dose for one study is comparable to several months of natural background and does not accumulate dangerously when prescribed appropriately. MSCT is not performed on pregnant women (except for vital indications); for children - according to strict indications with a minimum dose. Iodine contrast is contraindicated in severe renal failure, iodine allergy and uncontrolled hyperthyroidism. Pacemaker and metal implants are not a contraindication, unlike MRI.
