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MRI - dGEMRIC Evaluation of Cartilage

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Delayed gadolinium enhanced Magnetic Resonance Imaging of cartilage (dGEMRIC) is a recent technique where an MRI scan dedicated to detecting early cartilage breakdown is performed. GAG (glycosaminoglycan) molecules are vital to the integrity of cartilage, maintaining water molecules within cartilage and therefore the tensile strength, so that it may perform its day to day function of resisting forces imparted upon a joint.

Breakdown of GAG molecules due to wear and tear is one of the early steps leading to the gradual development of osteoarthritis. Importantly, GAG loss is potentially reversible in its early stages. By injecting MRI contrast (gadolinium) into a patient, gadolinium is delivered into a patient’s joints. As both GAG molecules and gadolinium are negatively charged, gadolinium will penetrate articular cartilage in an inversely proportional manner to the GAG concentration; that is to say, the lower the GAG concentration (lesser negative charge) the more the negatively charged gadolinium will penetrate the cartilage, relative to areas of higher GAG concentration.  The greater negative charge of normal cartilage (higher GAG concentration) will repel gadolinium penetration.

Fortunately, the penetration of gadolinium into the cartilage is readily measured on dedicated MRI scans. Areas of greater gadolinium penetration into cartilage and therefore increased cartilage breakdown (due to GAG loss) may be color coded, so it can be appreciated readily whether a joint is heading along the osteoarthritis pathway (figure 1). The advantage of dGEMRIC imaging is that it can detect cartilage changes before conventional MRI. Conventional MRI relies on a detecting a discrete cartilage tear reaching a sufficient size so that it is visible, however this is currently inadequate in patients who are considering joint preservation surgery, as irreversible osteoarthritis at this point has usually occurred and the joint is usually beyond salvage. dGEMRIC scans can reliably detect whether GAG loss has occurred even before visible cartilage breakdown. This may spare patients complex and extensive reconstructive surgery, as any such surgery is bound to fail should GAG concentration fall below a critical point. Conversely, normal GAG levels reliably predict surgical success.

dGEMRIC scans are therefore useful in the assessment of patients with:

  • femoroactebular impingement patients considering pelvic reconstruction (periacetabular osteotomy) (1) and other congenital or developmental joint disorders that require regular follow up, such as Perthe’s disease of the hip (2), or slipped upper capital femoral epiphysis (3)
  • surgically treated cartilage defects (such as microfracture and autologous chondrocyte implantation techniques) that require follow up (4)
  • an injured joint, such as after patellar dislocation (5) and cruciate ligament tears (6, 7)
  • suspected early arthritis prior to the development of established arthritis on conventional X-Rays and MRI scans (8).
MRI - dgemeric evaluation of cartilage

Figure 1A. Routine MRI evaluation of the left hip demonstrates relatively normal cartilage thickness overlying the femoral head (arrows), with no areas of discrete breakdown or defect formation.
Figure 1B. dGEMRIC images through the same hip however demonstrate areas of advanced GAG loss, as indicated by the presence by white and yellow pixels overlying the articular cartilage. Normal GAG cartilage levels are indicated by shades of red. The patient is not a candidate for joint preserving surgery.

References

  1. Cunningham T, Jessel R, eat al. Delayed gadolinium-enhanced magnetic resonance imaging of cartilage to predict early failure of Bernese periacetabular osteotomy for hip dysplasia. J Bone Joint Surg Am 88(7):1540-8, 2006
  2. Zilkens C, Holstein A, et al. Delayed gadolinium-enhanced magnetic resonance imaging of cartilage in the long-term follow-up after Perthes disease. J Pediatr Orthop 30(2):147-53, 2010
  3. Zilkens C, Miese F, et al. Delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC), after slipped capital femoral epiphysis. Eur J Radiol 2010 May 24 . [Epub ahead of print]
  4. Vasiliadis HS, Danielson B, et al. Autologous chondrocyte implantation in cartilage lesions of the knee: long-term evaluation with magnetic resonance imaging and delayed gadolinium-enhanced magnetic resonance imaging technique. Am J Sports Med 38(5):943-9, 2010
  5. Watanabe A, Obata T, et al. Degeneration of patellar cartilage in patients with recurrent patellar dislocation following conservative treatment: evaluation with delayed gadolinium-enhanced magnetic resonance imaging of cartilage. Osteoarthritis Cartilage 17(12):1546-53, 2009
  6. Fleming BC, Oksendahl HL, et al. Delayed Gadolinium-Enhanced MR Imaging of Cartilage (dGEMRIC) following ACL injury. Osteoarthritis Cartilage 18(5):662-7, 2010
  7. Young AA, Stanwell P, et al. Glycosaminoglycan content of knee cartilage following posterior cruciate ligament rupture demonstrated by delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC). A case report. J Bone Joint Surg Am 87(12):2763-7, 2005
  8. Williams A, Sharma L, et al. Delayed gadolinium-enhanced magnetic resonance imaging of cartilage in knee osteoarthritis: findings at different radiographic stages of disease and relationship to malalignment. Arthritis Rheum. 2005 Nov;52(11):3528-35.

AFL Medical Officers Association Cartilage Injury Forum 6th July 2010

Download PDF of Presentation MRI Evaluation of Cartilage - Presentation  July 2010
Dr George Koulouris


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Last Updated ( Tuesday, 05 April 2011 21:35 )  
 
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