Why musculoskeletal MRI is better at 3T
Musculoskeletal MRI is improved at 3T for several reasons:
- 3T has higher signal to noise and this makes MR imaging of the joints faster, more detailed (for trabecular detail) and higher in resolution.
- It is twice as sensitive to contrast enhancement
- Fat saturation of the joints is improved at 3T
The result is that when you combine fat saturation plus contrast you get more sensitive studies to areas of:
- Inflammation
- Tumors
- Healing
All of these have increased blood flow and enhancement which is easier to detect when using fat saturation. Most areas contiguous (and with thinner sections) can also be scanned, which means up to 30% more of the body can be scanned as compared to 1.5 T MRI. The images scanned in the extremities are often 512x512 matrix and 2mm thin.
More detail, more sensitivity
Being more sensitive to trabecular detail makes bony imaging very detailed and sensitivity to bone marrow tumours and subtle stress fractures much higher. This is important since the most common cause of bone pain is a subtle fracture. Whereas 1.5T scans may identify a bone bruise, with 3T the fracture line can be seen in most cases. Whenever the scan shows radiating linear edema in the bone this is definitely from a subtle fracture.
The ability to scan with thinner sections and higher resolution also directly impacts on being able to detect abnormalities. Being able to scan faster, thinner and with higher spatial resolution means very subtle injury or abnormality, such as small areas of arteriovenous shunting or subtle areas of inflammation or microtrauma, can be identified. Further, individual fibers of the anterior cruciate ligament of the knee or the subtle fibers of the calcaneofibular ligament in the ankle can be seen.
See the previously unseen
When you combine the higher resolution images with dynamic contrast enhanced imaging, tumors or diseases that simply could not see before can be observed.
Further, 3T scans of muscle trauma or even polymyositis allow the detection of abnormalities of the muscles that cannot otherwise be seen.
The combination of fat saturation and contrast allows areas of subtle inflammation to be observed which we could not seen previously. A 3T MRI of the foot and hand also allows us to scan with very small fields of view which basically is like being able to enlarge the area beind studied and see it with higher detail. When these capabilities are combined, the result is details of the bones and joints and wrist that were previously never seen except in pathological or autopsy specimens. Using 3T also allows non-invasive observation of the response to treatment to rheumatoid arthritis medication.