Musculoskeletal system imaging
Ordinary X-ray is the main imaging modality regarding the skeletal system. This technique gives an excellent overview of the bony structures and joints and is used mainly to rule out fractures, pathological bone lesions and degenerative or inflammatory joint changes. X-ray is also used to characterise fractures, degree of mis-alignment of fractures and to visualise healing processes. For whole body screening purposes NM is preferred.
X-ray and NM are often combined with other modalities (CT and MRI) when a specific lesion is found in the skeletal system.
X-ray has very little place in soft-tissue imaging because of low inherent contrast and inability to differentiate between various structures. In these cases CT, ultrasound, and especially MRI will provide useful information.
Trauma
X-ray is used to detect or rule out fractures and luxations. In some areas, mainly in specific regions of the spine, skull, and sometimes in the hip and small bones of the hand and foot, fractures can initially be overlooked. If a fracture is clinically suspected, NM, CT or MRI will be performed. NM is particularly sensitive for the detection of stress fractures.
To detect significant soft-tissue damage (haematoma, contusions, partial or complete muscular rupture) ultrasound or MRI will give the answer.
Joints
X-ray will provide information about degenerative and inflammatory changes. High resolution sonography can detect synovial proliferation and hypervascularity due to rheumatoid arthritis or other inflammatory diseases. MRI can visualise articular cartilage, and is frequently used to examine shoulder, knee, wrist and other joints. MRI is also able to detect early pathological changes in the joints and surrounding capsula, ligaments and tendons.
Ultrasound is also used for shoulder-joint examinations, and for all practical purposes is equal to MRI in this location
Tumours of the skeletal system
X-ray is always performed, and in many cases is able to characterise a lesion whether this is benign or malignant. If the detected structural changes are uncertain or do not appear like a typical benign lesion, further imaging is mandatory. Sometimes CT or a nuclear scan is performed, but MRI will often give most information, especially regarding any soft-tissue involvement which is of great pre-operative importance.
Nuclear scans are often used to detect occult metastases
Soft tissue tumours
MRI is of great importance, and will not only give the precise extent of a tumour, but also valuable information about muscle, nerve and vessel invasion or entrapment in malignant tumours. CT is of limited use, and X-ray is just done to rule out coherent bone changes.
Osteomylitis
A 2-3 phase skeletal scintigram is more sensitive than X-ray in the early phase. However, findings are not specific and further specialised NM with alternative agents may be needed. Fat-suppressed MRI is becoming regarded as the optimal investigation. CT is used to identify sequestra.
GE Healthcare Glossary