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Normal and Ischemic Epiphysis of the Femur: Diffusion MR Imaging— Study in Piglets¹

¹ From the Department of Radiology, Massachusetts General Hospital and Harvard Medical School, 32 Fruit St, Boston, MA 02114 (D.J.); Departments of Radiology (S.A.C., S.V., R.L.R., P.S.D., R.V.M., A.H.) and Orthopaedic Surgery (F.S.), Children’s Hospital and Harvard Medical School, Boston, Mass; and Department of Radiology, Brigham and Women’s Hospital and Harvard Medical School, Boston, Mass (S.E.M.). Received October 12, 2001; revision requested January 8, 2002; revision received August 2; accepted September 26. Supported by a Children’s Hospital Research Council Award and by grant AR42396-05 from the National Institutes of Health. Address correspondence to D.J. (e-mail: djaramillo@partners.org).

View larger version (118K): [in a new window]   Figure 1a. Diffusion-weighted and gadolinium-enhanced MR images of the hip in a 3-week-old piglet. The hip is presumed to be normal. (a) Sagittal diffusion-weighted image (1,520/81.6, b = 5 and 500 sec/mm2) shows a clear differentiation between epiphysis (e), physis (p), and metaphysis (m). (b) Sagittal ADC map obtained with same parameters as for a shows that the regional anatomy is more difficult to distinguish, as the epiphyseal structures are nearly isointense. e = epiphysis. (c) Sagittal gadolinium-enhanced T1-weighted spin-echo MR image (600/10) obtained immediately after the line-scan diffusion image shows that there is normal enhancement of the epiphysis and physis. Slight irregularity in epiphyseal cartilage enhancement is due to the presence of vascular canals.

View larger version (149K): [in a new window]   Figure 1b. Diffusion-weighted and gadolinium-enhanced MR images of the hip in a 3-week-old piglet. The hip is presumed to be normal. (a) Sagittal diffusion-weighted image (1,520/81.6, b = 5 and 500 sec/mm2) shows a clear differentiation between epiphysis (e), physis (p), and metaphysis (m). (b) Sagittal ADC map obtained with same parameters as for a shows that the regional anatomy is more difficult to distinguish, as the epiphyseal structures are nearly isointense. e = epiphysis. (c) Sagittal gadolinium-enhanced T1-weighted spin-echo MR image (600/10) obtained immediately after the line-scan diffusion image shows that there is normal enhancement of the epiphysis and physis. Slight irregularity in epiphyseal cartilage enhancement is due to the presence of vascular canals.

View larger version (133K): [in a new window]   Figure 1c. Diffusion-weighted and gadolinium-enhanced MR images of the hip in a 3-week-old piglet. The hip is presumed to be normal. (a) Sagittal diffusion-weighted image (1,520/81.6, b = 5 and 500 sec/mm2) shows a clear differentiation between epiphysis (e), physis (p), and metaphysis (m). (b) Sagittal ADC map obtained with same parameters as for a shows that the regional anatomy is more difficult to distinguish, as the epiphyseal structures are nearly isointense. e = epiphysis. (c) Sagittal gadolinium-enhanced T1-weighted spin-echo MR image (600/10) obtained immediately after the line-scan diffusion image shows that there is normal enhancement of the epiphysis and physis. Slight irregularity in epiphyseal cartilage enhancement is due to the presence of vascular canals.

View larger version (69K): [in a new window]   Figure 2. Diffusion-weighted image (1,520/1.6, b = 5 and 500 sec/mm2) shows diffusion tensors in the distal femur of a 3-week-old piglet. Superimposed on the diffusion image are arrows indicating the direction of the tensors. The image shows the parallel pattern of diffusion of the physis and proximal metaphysis. The direction of the tensors is the same as that of the main axis of the bone. This is the same direction of the columns of the physis and metaphysis as seen on the histologic section at right.

View larger version (116K): [in a new window]   Figure 3a. Images show short-term ischemia of both femoral heads after 3 hours of maximal abduction in a 3-week-old piglet. (a) Coronal ADC map (1,520/81.6, b = 5 and 750 sec/mm2) shows the epiphyses to have uniform and symmetric signal intensity. However, ADC measurements showed that diffusion has been restricted by 12%. Arrows point to femoral heads. (b) Coronal gadolinium-enhanced T1-weighted spin-echo MR image (600/10) obtained immediately after the line-scan diffusion image shows patchy areas of decreased enhancement in the anterior cartilage of the femoral heads (arrows) and decreased enhancement in the epiphyseal marrow on the right, both of which are consistent with ischemia.

View larger version (121K): [in a new window]   Figure 3b. Images show short-term ischemia of both femoral heads after 3 hours of maximal abduction in a 3-week-old piglet. (a) Coronal ADC map (1,520/81.6, b = 5 and 750 sec/mm2) shows the epiphyses to have uniform and symmetric signal intensity. However, ADC measurements showed that diffusion has been restricted by 12%. Arrows point to femoral heads. (b) Coronal gadolinium-enhanced T1-weighted spin-echo MR image (600/10) obtained immediately after the line-scan diffusion image shows patchy areas of decreased enhancement in the anterior cartilage of the femoral heads (arrows) and decreased enhancement in the epiphyseal marrow on the right, both of which are consistent with ischemia.

View larger version (140K): [in a new window]   Figure 4a. Images show ischemia 6 hours after ligature of the femoral neck vessels of the contralateral hip in the piglet depicted in Figure 1. (a) Sagittal ADC map (1,520/81.6, b = 5 and 500 sec/mm2) of the side with surgery shows slight increase in the signal intensity of the epiphysis (e) compared with that of the contralateral side. ADC was measured to be 14% greater than it was on the side without surgery. (b) Sagittal gadolinium-enhanced T1-weighted spin-echo MR image (600/10) of the side with surgery obtained immediately after the line-scan diffusion image shows almost complete absence of enhancement of the femoral head, with only a small central enhancing area remaining.

View larger version (147K): [in a new window]   Figure 4b. Images show ischemia 6 hours after ligature of the femoral neck vessels of the contralateral hip in the piglet depicted in Figure 1. (a) Sagittal ADC map (1,520/81.6, b = 5 and 500 sec/mm2) of the side with surgery shows slight increase in the signal intensity of the epiphysis (e) compared with that of the contralateral side. ADC was measured to be 14% greater than it was on the side without surgery. (b) Sagittal gadolinium-enhanced T1-weighted spin-echo MR image (600/10) of the side with surgery obtained immediately after the line-scan diffusion image shows almost complete absence of enhancement of the femoral head, with only a small central enhancing area remaining.

View larger version (191K): [in a new window]   Figure 5a. Images show long-term ischemia 96 hours after ligature of the femoral neck vessels in a 3-week-old piglet. (a) Sagittal ADC map (1,520/81.6, b = 5 and 500 sec/mm2) of the side without surgery shows the epiphysis (e) and metaphysis (m) to be nearly isointense. (b) Sagittal gadolinium-enhanced T1-weighted spin-echo MR image (600/10) of the side without surgery obtained immediately after the line-scan diffusion image shows that there is normal enhancement of the epiphysis and physis (p). The center of the ossification normally has delayed enhancement because it is less vascular and has more fatty marrow. (c) Sagittal ADC map (1,520/81.6, b = 5 and 500 sec/mm2) of the side with surgery shows marked increase in the signal intensity of the epiphysis (e) compared with that of the contralateral side. ADC was measured to be 98% greater than it was on the side without surgery. (d) Sagittal gadolinium-enhanced T1-weighted spin-echo MR image (600/10) of the side with surgery obtained immediately after the line-scan diffusion image shows complete absence of enhancement of the femoral head. T2-weighted image (not shown) obtained concurrently was normal.

View larger version (147K): [in a new window]   Figure 5b. Images show long-term ischemia 96 hours after ligature of the femoral neck vessels in a 3-week-old piglet. (a) Sagittal ADC map (1,520/81.6, b = 5 and 500 sec/mm2) of the side without surgery shows the epiphysis (e) and metaphysis (m) to be nearly isointense. (b) Sagittal gadolinium-enhanced T1-weighted spin-echo MR image (600/10) of the side without surgery obtained immediately after the line-scan diffusion image shows that there is normal enhancement of the epiphysis and physis (p). The center of the ossification normally has delayed enhancement because it is less vascular and has more fatty marrow. (c) Sagittal ADC map (1,520/81.6, b = 5 and 500 sec/mm2) of the side with surgery shows marked increase in the signal intensity of the epiphysis (e) compared with that of the contralateral side. ADC was measured to be 98% greater than it was on the side without surgery. (d) Sagittal gadolinium-enhanced T1-weighted spin-echo MR image (600/10) of the side with surgery obtained immediately after the line-scan diffusion image shows complete absence of enhancement of the femoral head. T2-weighted image (not shown) obtained concurrently was normal.

View larger version (169K): [in a new window]   Figure 5c. Images show long-term ischemia 96 hours after ligature of the femoral neck vessels in a 3-week-old piglet. (a) Sagittal ADC map (1,520/81.6, b = 5 and 500 sec/mm2) of the side without surgery shows the epiphysis (e) and metaphysis (m) to be nearly isointense. (b) Sagittal gadolinium-enhanced T1-weighted spin-echo MR image (600/10) of the side without surgery obtained immediately after the line-scan diffusion image shows that there is normal enhancement of the epiphysis and physis (p). The center of the ossification normally has delayed enhancement because it is less vascular and has more fatty marrow. (c) Sagittal ADC map (1,520/81.6, b = 5 and 500 sec/mm2) of the side with surgery shows marked increase in the signal intensity of the epiphysis (e) compared with that of the contralateral side. ADC was measured to be 98% greater than it was on the side without surgery. (d) Sagittal gadolinium-enhanced T1-weighted spin-echo MR image (600/10) of the side with surgery obtained immediately after the line-scan diffusion image shows complete absence of enhancement of the femoral head. T2-weighted image (not shown) obtained concurrently was normal.

View larger version (163K): [in a new window]   Figure 5d. Images show long-term ischemia 96 hours after ligature of the femoral neck vessels in a 3-week-old piglet. (a) Sagittal ADC map (1,520/81.6, b = 5 and 500 sec/mm2) of the side without surgery shows the epiphysis (e) and metaphysis (m) to be nearly isointense. (b) Sagittal gadolinium-enhanced T1-weighted spin-echo MR image (600/10) of the side without surgery obtained immediately after the line-scan diffusion image shows that there is normal enhancement of the epiphysis and physis (p). The center of the ossification normally has delayed enhancement because it is less vascular and has more fatty marrow. (c) Sagittal ADC map (1,520/81.6, b = 5 and 500 sec/mm2) of the side with surgery shows marked increase in the signal intensity of the epiphysis (e) compared with that of the contralateral side. ADC was measured to be 98% greater than it was on the side without surgery. (d) Sagittal gadolinium-enhanced T1-weighted spin-echo MR image (600/10) of the side with surgery obtained immediately after the line-scan diffusion image shows complete absence of enhancement of the femoral head. T2-weighted image (not shown) obtained concurrently was normal.

View larger version (13K): [in a new window]   Figure 6. Graph of percentage change in ADC following 3 hours of abduction and 6 and 96 hours of femoral neck ligature. Diffusion is restricted with milder shorter ischemia, is mildly increased with short-term severe ischemia, and is markedly increased with long-term severe ischemia.