Bone marrow of the non-traumatic knee: Expected findings at MR imaging

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1 Bone marrow of the non-traumatic knee: Expected findings at MR imaging Poster No.: C-622 Congress: ECR 2009 Type: Educational Exhibit Topic: Musculoskeletal Authors: M. Castro, N. Silva, A. T. B. Almeida, B. Viamonte, A. Vieira ; Porto/PT, San Diego, CA/US Keywords: MRI, Knee, bone marrow DOI: /ecr2009/C-622 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 62

2 Learning objectives To understand the normal "maturation" of the knee marrow signal concerning to age. To identify normal variations of the knee medullary signal. To recognize the different pathologic non-traumatic changes of the knee medullary signal. Background The knee is the most frequent musculoskeletal MR study. In the MR evaluation of the knee we are frequently faced with focal or diffuse signal changes of the bone marrow that don't correspond to the common adult pattern(uniform high T1 signal, intermediate T2 signal and low STIR signal). These changes may be related to the expected red bone marrow in a child, reflect some kind of benign marrow heterogeneity or be associated with multiple differentpathologic processes. The different pathologic processes may be grouped into: Conversion abnormalities (chronic anaemia, increased oxygen demands, kidney or liverfailure ); Myeloid depletion (chemotherapy, aplastic anaemia, radiation therapy ); Marrow edema (trauma, infection, transient osteoporosis ); Marrow infiltration (leukemia, lymphoma, metastases, primary bone tumors ); Marrow ischemia. (steroids use, systemic erythematous lupus, sickle cell anaemia...). Images for this section: Fig. 1: Fig. 3. Normal bone marrow conversion(a) T1 coronal image of a 4-years-old girl shows high signal intensity yellow marrow in the ossified epiphysis and intermediate signal intensity red marrow in the metaphyseal, and diaphyseal marrow. (b) T1 coronal image of a 10-years-old boy presents predominantly increased signal intensity marrow in Page 2 of 62

3 the metaphysis and diaphysis. (c) T1 coronal image of a 16-years-old boy demonstrates some patchy subtle areas of intermediate signal red marrow in the metaphyseal, and diaphyseal marrow. (d) T1 coronal image of a forty-years-old woman shows the typical adult pattern of homogeneous high signal yellow marrow. Fig. 2: Scheme 1. Normal bone marrow conversion (T1-w appearance) in a schematic representation of the distal femur.distribution of the intermediate signal intensity (primarily red) marrow and of the high signal (predominantly yellow) marrow in the femur with increasing age as seen on MR images. Page 3 of 62

4 Fig. 3: Scheme 2. Sequence of reconversion (T1-w appearance) in a schematic representation of the distal femur.just the opposite of normal conversion. Yellow marrow (yellow). Red marrow (red). Fig. 4: Fig. 1. Normal yellow marrow appearanceforty years-old woman with complete conversion of the knee bone marrow to fatty marrow. (a) High signal in T1. (b) High signal on fast spin-echo T2. (c) Intermediate to low signal in gradient-echo. (d) Low signal on PD Fat Sat. Page 4 of 62

5 Fig. 5: Fig. 2. Normal red marrow appearanceten-years-old girl with normal red marrow in the diaphysis and metaphysis of the long bones. Red marrow presents with intermediate signal intensity on both T1 (a) and T2 (b); intermediate to low signal on gradient-echo (c) and higher signal than yellow marrow on PD Fat Sat (d). Page 5 of 62

6 Imaging findings OR Procedure details MR Imaging of Normal Bone Marrow Yellow marrow Yellow marrow is relatively inactive with regard to blood cell development and is composed of 80% fat with only 15% water and 5% protein. High signal intensity on T1-w images and intermediate signal intensity on T2-w images at spin-echo MR imaging reflects the predominance of fat. High signal intensity on fast spin-echo T2-w images. Low signal intensity on fat-suppressed sequences. On gradient-echo imaging its signal varies according to the amount of trabecular bone. Fig.: Fig. 1. Normal yellow marrow appearanceforty years-old woman with complete conversion of the knee bone marrow to fatty marrow. (a) High signal in T1. (b) High signal on fast spin-echo T2. (c) Intermediate to low signal in gradient-echo. (d) Low signal on PD Fat Sat. Hematopoietic marrow Marrow that is haematopoietically active is often referred to as red and is composed of approximately 40% water, 40% fat, and 20% protein. Intermediate signal intensity on both T1- and T2-w images reflecting its lower fat content and higher water content. Unless pathology is present, always have higher T1 intensity signal than muscle or normal intervertebral disks. Higher signal than yellow marrow on fat-suppressed sequences. On gradient-echo imaging its signal varies according to the sequence characteristics. Page 6 of 62

7 Fig.: Fig. 2. Normal red marrow appearanceten-years-old girl with normal red marrow in the diaphysis and metaphysis of the long bones. Red marrow presents with intermediate signal intensity on both T1 (a) and T2 (b); intermediate to low signal on gradient-echo (c) and higher signal than yellow marrow on PD Fat Sat (d). Normal Conversion Conversion of red to yellow marrow occurs during growth and has a predictable and orderly pattern. Virtually the entire fetal marrow space is dedicated to hematopoietic (red) marrow production at birth. Controversy exists about whether epiphyses and apophysesever contain red marrow. In the immediate postnatal period, conversion begins and is first evident in the extremities, specifically in the terminal phalanges of the hands and feet. This conversion progresses from peripheral (appendicular) toward central (axial) with respect to the skeleton as a whole. In individual long bones occurs first in epiphysis and apophysis, then in the diaphysis followed by the distal metaphysis. Page 7 of 62

8 Fig.: Scheme 1. Normal bone marrow conversion (T1-w appearance) in a schematic representation of the distal femur.distribution of the intermediate signal intensity (primarily red) marrow and of the high signal (predominantly yellow) marrow in the femur with increasing age as seen on MR images. Page 8 of 62

9 Fig.: Fig. 3. Normal bone marrow conversion(a) T1 coronal image of a 4-years-old girl shows high signal intensity yellow marrow in the ossified epiphysis and intermediate signal intensity red marrow in the metaphyseal, and diaphyseal marrow. (b) T1 coronal image of a 10-years-old boy presents predominantly increased signal intensity marrow in the metaphysis and diaphysis. (c) T1 coronal image of a 16-years-old boy demonstrates some patchy subtle areas of intermediate signal red marrow in the metaphyseal, and diaphyseal marrow. (d) T1 coronal image of a forty-years-old woman shows the typical adult pattern of homogeneous high signal yellow marrow. Normal Variations Small differences in the amount of red marrow from side to side are normal. Marked asymmetry is suspicious. May persist a curvilinear subchondral region of red marrow in the proximal humeral and femoral epiphyses but not in epiphyses of the knee. Heterogeneous patterns of red and yellow marrow distribution occur with isolated islands of red marrow on predominately yellow marrow or foci of yellow marrow inregions of predominately red marrow. Foci of red marrow are generally located around the periphery of the marrow space. Central foci of yellow marrow within islands of red marrow indicate a benignappearance. Page 9 of 62

10 Fig.: Fig. 4. Red marrow foci(a) T1 coronal. There is a low signal focus of red marrow (arrow) within the distal diaphysis of the femur. This is typically located in the periphery of the marrow space. Central foci of yellow marrow (arrowhead) within islands of red marrow indicate a benign appearance. b) STIR coronal. The red marrow island (arrow) presents with higher signal than the surrounding yellow marrow. Pathologic Processes Conversion Abnormalities Conversion to yellow marrow may be delayed such as in children and young adults with chronic illnesses (such as cyanotic heart disease or kidney or liver failure)or congenital anaemia's. If the demand for haematopoiesis exceeds the ability of existing red marrow to meet that demand, a conversion of yellow to red marrow is initiated. Causes of reconversion vary from anaemia to marrow replacement disorders (metastatic disease, myeloma, myelofibrosis, etc). The sequence of reconversion begins with the spine and flat bones followed by the extremities in a proximal to distal progression (just the reverse of primaryconversion). Page 10 of 62

11 Fig.: Scheme 2. Sequence of reconversion (T1-w appearance) in a schematic representation of the distal femur.just the opposite of normal conversion. Yellow marrow (yellow). Red marrow (red). This reconverted marrow is typically patchy rather than confluent. Reconverted marrow generally extends to but does not cross the physeal scar region. A patchy red marrow in the metaphyses of the long bones and in the flat bones of the pelvis of an adult is often described, as hyperplasic marrow. This is typicalin aerobically fit adults menstruating women, smokers and obese patients. Page 11 of 62

12 Fig.: Fig. 5. Marrow conversion abnormalities: MetrorrhagiasMarrow abnormality in a 45-years-old woman with severe metrorrhagias. Sagittal T1 (a) and gradient echo (b) MR images show extensive reconversion of marrow space to hematopoietic marrow (arrows). All marrow of distal femoral and proximal tibial metadiaphyses has been recruited. Despite the extensive reconversion the epiphyses retain yellow marrow (arrowheads) and have not undergone reconversion. Fig.: Fig. 6. Marrow conversion abnormalities: Thalassemia majort1 sagittal image. The red marrow in the distal femur and proximal tibia of this 26-years-old woman has normal signal, that is higher than muscle signal, but the distribution is abnormal for her age. The presence of red marrow in epiphyses is suggestive of chronic increased demand for hematopoiesis. Myeloid Depletion Page 12 of 62

13 Myeloid depletion occurs when the marrow space is completely devoid of hematopoietic elements. Occur as a consequence of chemotherapy, aplastic anaemia or radiation therapy. The involved marrow space demonstrates an MR signal pattern characteristic of fatty marrow, uniformly high signal intensity on T1-w images and low signal intensityon fatsuppressed images. Page 13 of 62

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15 Fig.: Scheme 3. Myeloid depletion (T1-w appearance) in a schematic representation of the distal femur.there is only fatty yellow marrow. Yellow marrow (yellow). Fig.: Fig. 7. Marrow depletion: Aplastic anemia(a) T1 sagittal image. There is high signal fatty marrow throughout the knee bone marrow. (b) PD Fat Sat image. There is a complete loss of signal of the bone marrow. Marrow Edema May be seen in a variety of settings such as trauma, adjacent to tumours, infection, arthritis or in transient osteoporosis. Marrow presents with low signal intensity on T1-w images and markedly high signal intensity on T2-w fat-suppressed and STIR images. Unlike reconversion marrow, it is much more intense on STIR images and does not respect boundaries such as the physeal scar. Page 15 of 62

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17 Fig.: Scheme 4. Marrow edema (T1-w appearance) in a schematic representation of the distal femur.low signal intensity on T1-w images that does not respect boundaries such as the physeal scar. Edema (black). Yellow marrow (yellow). Fig.: Fig. 8. Marrow edema: Patellar fractureforty-years-old woman with posttraumatic anterior knee pain. It is possible to see the fracture (arrows) of the lower third of the patella as a low signal line in T1 (b) that is surrounded by marrow edema (dots) that presents low signal in T1 (b) and high signal in PD Fat Sat (a). Fig.: Fig. 9. Marrow edema: Stress fracturefourteen-years-old boy who presented with knee pain. There is a horizontal low intensity fracture line (arrows) in the distal femoral Page 17 of 62

18 diaphysis surrounded by diffuse marrow edema (dots) that shows low signal in T1 (a) and high signal in PD Fat Sat (b). Fig.: Fig. 10. Marrow edema: Patellar dislocationin these axial MR images it is possible to see the typical "kissing" contusion (circles) of the medial side of the patella and of the anterior lateral femoral condyle that presents as "patchy" areas of low signal in T1 (a) and high signal in PD Fat Sat (b). This contusion pattern is virtually diagnostic of patellar dislocation. Fig.: Fig. 11. Marrow edema: Osgood-SchlatterEleven-years-old kid who presents with anterior knee pain. It is possible to see the typical high signal intensity within Page 18 of 62

19 the patellar tendon proximal to its insertion in the tuberosity (arrowheads) and the distention of the deep infrapatellar bursa (arrows). There is a reactive edema of the tibial tuberosity and proximal epiphysis marrow (dots) that presents as an area of low signal in T1 (a) and high signal in STIR (b). Page 19 of 62

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21 Fig.: Fig. 12. Marrow edema: Septic arthritis and OsteomyelitisFive-years-old boy with fever, knee pain and swelling. There is edema and inflammatory infiltration of the articular soft tissues and of the bone marrow of the lateral femoral condyle, which presents with low signal at T1 (a), high signal at STIR (b) and that enhances after contrast administration (c and d). Fig.: Fig. 13. Marrow edema: Peri-tumoral edema(a and b) Seventeen-years-old boy who presents with knee pain without traumatic history. It is possible to see a typical condroblastoma (arrows) in the proximal epiphyse of the tibia that is associated with a reactive zone of diffuse marrow edema (arrowheads) that presents as an area of low signal in T1 (a) and high signal in PD Fat Sat (b). (c) Eighteen-years-old boy that presents with pain in the proximal third of the leg. This coronal STIR image shows the typical osteoma osteoid nidus (arrowhead) in the cortical of the tibial diaphysis with reactive marrow edema (that presents as an high signal "patchy" area) (arrowhead). Page 21 of 62

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23 Fig.: Fig. 14. Marrow edema: Transient osteoporosissixty-two-years-old man who presents with knee pain without traumatic history. Coronal STIR image reveal high signal intensity corresponding to extensive marrow edema in both femoral condyle and in the adjacent soft tissues. This patient previously had transient osteoporosis of the hip. Marrow ischemia and infarction May be caused by trauma, medication (steroids), sickle cell anaemia, alcoholism, barotrauma, Gaucher disease, systemic erythematous lupus, pancreatitis, radiationtherapy, and idiopathic causes. Although the causes are varied, the pattern of injury and osseous response is predictable. The earliest manifestation is a non-specific focal area that looks like edema (intermediate signal intensity on T1-w images and high signal intensity on T2-wimages) in the typical locations for infarction (epiphyses and diametaphyses). A characteristic low signal intensity serpentine rim develops in over 90% of cases on both T1 and T2-w images representing the interface between living and deadbone. Page 23 of 62

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25 Fig.: Scheme 5. Marrow infarction (T1-w appearance) in a schematic representation of the distal femur.characteristic low signal intensity serpentine rim. Necrotic rim (black). Yellow marrow (yellow). In 80 % of the cases a high signal intensity line will be present on T2-w images just inside the low signal intensity serpentine line, called the"double-line sign". Fig.: Fig. 15. Marrow ischemia/infarction: Chronic corticotherapyt1 sagittal image. This is a 45-years-old man submitted to chronic corticotherapy after kidney transplant. MRI shows low signal serpentine lines (arrows) in the distal aspect of the medial femoral condyle and in the proximal aspect of the medial tibial plateau representing osteonecrosis. The adjacent bone marrow show low to intermediate signal intensity representing fibrosis (arrowheads). Page 25 of 62

26 Fig.: Fig. 16. Marrow ischemia/infarction: Systemic erythematosus lupus (SEL)Eighteen-years-old woman with SEL under corticotherapy who presents with knee pain. Sagittal (a) and coronal (b) T1 images shows low signal serpentine lines (arrows) in the distal aspect of both femoral condyles representing osteonecrosis. The intermediate bone marrow signal in the proximal femoral epiphysis (arrowheads) represents bone marrow edema. PD Fat Sat coronal image (c) from the same patient. The serpiginous lines of osteonecrosis become high signal (arrows) and the marrow edema presents with intermediate to high signal (arrowheads). Page 26 of 62

27 Fig.: Fig. 17. Marrow ischemia/infarction: Spontaneous osteonecrosis of the knee (SONK)Sixty-one-years-old man who presents with spontaneous knee pain. (a) Sagittal T1 image reveals a discrete area of subchondral decreased signal intensity (arrow) that reflects necrosis surrounded by intermediate signal (combination of fat and edema) (arrowhead). (b) PD Fat Sat coronal image shows the low signal intensity necrotic area (arrow) surrounded by diffuse increased signal intensity edema (arrowhead). Infiltration Marrow spaces may be filled as a result of acute inflammatory cells, neoplastic processes, or marrow-packing disorders such as Gaucher disease ormyeloproliferative disease. More often produce a focal lowering of marrow signal intensity on T1-w images (equal or lower than muscle or vertebral disks). Page 27 of 62

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29 Fig.: Scheme 6. Marrow infiltration (T1-w appearance) in a schematic representation of the distal femur.generally presents as focal areas of low marrow signal intensity on T1-w images. Infiltrative lesions (black). Yellow marrow (yellow). The pattern on T2-w images varies depending on the disease process, with certain disorders (primary tumours, metastatic lesions, infection) generally resulting inincreased signal intensity while others (leukemia, lymphoma, myelofibrosis, Gaucher disease) may remain low in signal intensity or show only minimal increase. Page 29 of 62

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31 Fig.: Fig. 18. Marrow infiltration: OsteosarcomaThirteen-years-old boy. T1 sagittal image shows the predominantly low and intermediate signal intensity of the mineralized osteoid in bone marrow. The posterior cortex shows destruction and there is extension of this tumor into the surrounding soft tissues. Distally, the tumor is bordered by the physis. Fig.: Fig. 19. Marrow infiltration: Breast metastasesfifty-one-years-old female with breast cancer. (a) T1 coronal image shows multiple low signal bone metastases that presents with a confluent appearance in the right femur and with a more focal involvement on the left femur. (b) STIR coronal image where those lesions presents with high signal. Page 31 of 62

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33 Fig.: Fig. 20. Marrow infiltration: Neuroblastoma metastasessix-years-old boy with neuroblastoma. (a) T1 coronal image shows multiple low signal bone metastases (arrows). Notice that the metastases presents with lower intensity signal than the muscle while the adjacent red marrow (arrowheads) keeps an intensity signal superior to the muscle signal. (b) STIR coronal image where those metastatic lesions presents with high signal (arrows). Page 33 of 62

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35 Fig.: Fig. 21. Marrow infiltration: LeukemiaSix-years-old boy with pain in proximal third of the leg. T1 coronal image that shows multiple focal areas (arrows) where marrow presents with signal equal or lower than the muscle signal. Page 35 of 62

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37 Fig.: Fig. 22. Marrow infiltration: Linfoma(a and b) Thirty-two-years-old female with abnormal bone scan. (a) T1 coronal image shows multiple focal areas of signal that is lower than the muscle signal. (b) PD Fat Sat sagittal image where those focal areas presents with high signal. (c and d) Ten-years-old boy with knee pain. (c) PD Fat Sat coronal image where is possible to see, in the distal femoral diaphysis, a "patchy" area of linfoma infiltration that presents with high signal. (d) T1 sagittal image. The infiltrative lesion becomes very low signal. Fig.: Fig. 23. Marrow infiltration: Gaucher diseaset1 coronal image. This is a 5-years old child with Gaucher disease prior to treatment with enzyme therapy. MR images demonstrate the patchy, intermediate signal intensity of a marrow space that has Page 37 of 62

38 been replaced by deposits of glucocerebrosides. Note the flaring of the distal femoral metaphyses. Opposed-phase imaging may be useful in the detection of fat within a lesion, thus helping distinguishing metastatic disease (with no fat in the tissue) fromhyperplasic marrow (in which fat is present). With out-of-phase imaging areas containing fat (eg, hyperplastic marrow) will become much lower in signal intensity, but areas containing metastatic disease remainintermediate in signal intensity. Images for this section: Page 38 of 62

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40 Fig. 1: Fig. 14. Marrow edema: Transient osteoporosissixty-two-years-old man who presents with knee pain without traumatic history. Coronal STIR image reveal high signal intensity corresponding to extensive marrow edema in both femoral condyle and in the adjacent soft tissues. This patient previously had transient osteoporosis of the hip. Page 40 of 62

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42 Fig. 2: Scheme 5. Marrow infarction (T1-w appearance) in a schematic representation of the distal femur.characteristic low signal intensity serpentine rim. Necrotic rim (black). Yellow marrow (yellow). Fig. 3: Fig. 16. Marrow ischemia/infarction: Systemic erythematosus lupus (SEL)Eighteen-years-old woman with SEL under corticotherapy who presents with knee pain. Sagittal (a) and coronal (b) T1 images shows low signal serpentine lines (arrows) in the distal aspect of both femoral condyles representing osteonecrosis. The intermediate bone marrow signal in the proximal femoral epiphysis (arrowheads) represents bone marrow edema. PD Fat Sat coronal image (c) from the same patient. The serpiginous Page 42 of 62

43 lines of osteonecrosis become high signal (arrows) and the marrow edema presents with intermediate to high signal (arrowheads). Page 43 of 62

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45 Fig. 4: Scheme 6. Marrow infiltration (T1-w appearance) in a schematic representation of the distal femur.generally presents as focal areas of low marrow signal intensity on T1-w images. Infiltrative lesions (black). Yellow marrow (yellow). Page 45 of 62

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47 Fig. 5: Fig. 20. Marrow infiltration: Neuroblastoma metastasessix-years-old boy with neuroblastoma. (a) T1 coronal image shows multiple low signal bone metastases (arrows). Notice that the metastases presents with lower intensity signal than the muscle while the adjacent red marrow (arrowheads) keeps an intensity signal superior to the muscle signal. (b) STIR coronal image where those metastatic lesions presents with high signal (arrows). Page 47 of 62

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49 Fig. 6: Fig. 21. Marrow infiltration: LeukemiaSix-years-old boy with pain in proximal third of the leg. T1 coronal image that shows multiple focal areas (arrows) where marrow presents with signal equal or lower than the muscle signal. Page 49 of 62

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51 Fig. 7: Fig. 22. Marrow infiltration: Linfoma(a and b) Thirty-two-years-old female with abnormal bone scan. (a) T1 coronal image shows multiple focal areas of signal that is lower than the muscle signal. (b) PD Fat Sat sagittal image where those focal areas presents with high signal. (c and d) Ten-years-old boy with knee pain. (c) PD Fat Sat coronal image where is possible to see, in the distal femoral diaphysis, a "patchy" area of linfoma infiltration that presents with high signal. (d) T1 sagittal image. The infiltrative lesion becomes very low signal. Fig. 8: Fig. 23. Marrow infiltration: Gaucher diseaset1 coronal image. This is a 5years old child with Gaucher disease prior to treatment with enzyme therapy. MR images demonstrate the patchy, intermediate signal intensity of a marrow space that has Page 51 of 62

52 been replaced by deposits of glucocerebrosides. Note the flaring of the distal femoral metaphyses. Fig. 9: Fig. 13. Marrow edema: Peri-tumoral edema(a and b) Seventeen-years-old boy who presents with knee pain without traumatic history. It is possible to see a typical condroblastoma (arrows) in the proximal epiphyse of the tibia that is associated with a reactive zone of diffuse marrow edema (arrowheads) that presents as an area of low signal in T1 (a) and high signal in PD Fat Sat (b). (c) Eighteen-years-old boy that presents with pain in the proximal third of the leg. This coronal STIR image shows the typical osteoma osteoid nidus (arrowhead) in the cortical of the tibial diaphysis with reactive marrow edema (that presents as an high signal "patchy" area) (arrowhead). Page 52 of 62

53 Fig. 10: Fig. 4. Red marrow foci(a) T1 coronal. There is a low signal focus of red marrow (arrow) within the distal diaphysis of the femur. This is typically located in the periphery of the marrow space. Central foci of yellow marrow (arrowhead) within islands of red marrow indicate a benign appearance. b) STIR coronal. The red marrow island (arrow) presents with higher signal than the surrounding yellow marrow. Page 53 of 62

54 Fig. 11: Fig. 5. Marrow conversion abnormalities: MetrorrhagiasMarrow abnormality in a 45-years-old woman with severe metrorrhagias. Sagittal T1 (a) and gradient echo (b) MR images show extensive reconversion of marrow space to hematopoietic marrow (arrows). All marrow of distal femoral and proximal tibial metadiaphyses has been recruited. Despite the extensive reconversion the epiphyses retain yellow marrow (arrowheads) and have not undergone reconversion. Page 54 of 62

55 Fig. 12: Fig. 6. Marrow conversion abnormalities: Thalassemia majort1 sagittal image. The red marrow in the distal femur and proximal tibia of this 26-years-old woman has normal signal, that is higher than muscle signal, but the distribution is abnormal for her age. The presence of red marrow in epiphyses is suggestive of chronic increased demand for hematopoiesis. Page 55 of 62

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57 Fig. 13: Scheme 3. Myeloid depletion (T1-w appearance) in a schematic representation of the distal femur.there is only fatty yellow marrow. Yellow marrow (yellow). Fig. 14: Fig. 10. Marrow edema: Patellar dislocationin these axial MR images it is possible to see the typical "kissing" contusion (circles) of the medial side of the patella and of the anterior lateral femoral condyle that presents as "patchy" areas of low signal in T1 (a) and high signal in PD Fat Sat (b). This contusion pattern is virtually diagnostic of patellar dislocation. Fig. 15: Fig. 9. Marrow edema: Stress fracturefourteen-years-old boy who presented with knee pain. There is a horizontal low intensity fracture line (arrows) in the distal femoral diaphysis surrounded by diffuse marrow edema (dots) that shows low signal in T1 (a) and high signal in PD Fat Sat (b). Page 57 of 62

58 Fig. 16: Fig. 8. Marrow edema: Patellar fractureforty-years-old woman with posttraumatic anterior knee pain. It is possible to see the fracture (arrows) of the lower third of the patella as a low signal line in T1 (b) that is surrounded by marrow edema (dots) that presents low signal in T1 (b) and high signal in PD Fat Sat (a). Page 58 of 62

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60 Fig. 17: Scheme 4. Marrow edema (T1-w appearance) in a schematic representation of the distal femur.low signal intensity on T1-w images that does not respect boundaries such as the physeal scar. Edema (black). Yellow marrow (yellow). Fig. 18: Fig. 7. Marrow depletion: Aplastic anemia(a) T1 sagittal image. There is high signal fatty marrow throughout the knee bone marrow. (b) PD Fat Sat image. There is a complete loss of signal of the bone marrow. Page 60 of 62

61 Conclusion Bone marrow should be evaluated on every MR examination performed. The normal and the expected abnormal bone marrow signal (in a specific clinicalcontext) should be recognized. Personal Information Miguel Castro miguelhcastro@gmail.com Hospital de São João do Porto, Portugal Radiology Department Directora: Isabel Ramos Phd References Berg, Bruno, et al. Classification and detection of bone marrow lesions with magnetic resonance imaging. Skeletal Radiology (1998) 27: Berg, Bruno, et al. Magnetic resonance imaging of the normal bone marrow. Skeletal Radiol (1998) 27: Kaplan, Phoebe, et al. (2001). Musculoskeletal MRI. Saunders Vogler, James B., Murphy, William A. Bone Marrow Imaging. Radiology (1998) 168: Jeffrey C. Weireb. MR Imaging of Bone Marrow: A Map Could Help. Radiology (1990); 177: Moore, Sheilla G., Dawson, Karen L., Red and Yellow Marrow in the femur: Age-related changes in Appearance at MR Imaging Radiology (1990); 175: Andrews, Carol L. From the RSNA Refresher Courses. Evaluation of the Marrow Space in the Adult Hip. Radiology (2000); 20: Mirowitz SA, Apicella P, Reinus WR, Hammerman AM. MR imaging of bone marrow lesions: relative conspicuousness on T1-weighted, fat-suppressed T2-weighted, and STIR images. AJR Am J Roentgenol (1994);162: Shellock FG, Morris E, Deutsch AL, Mink JH, Kerr R, Boden SD. Hematopoietic bone marrow hyperplasia: high prevalence on MR images of the knee in asymptomatic marathon runners. AJR Am J Roentgenol(1992); 158: Koo KH, Dussault R, Kaplan P, et al. Age-related marrow conversion in the proximal metaphysis of the femur: evaluation with T1-weighted MR imaging. Radiology (1998); 206: Jaramillo D, Laor T, Hoffer FA, et al. Epiphyseal marrow in infancy: MR imaging. Radiology (1991); 180: Meyers SP, Wiener SN. Magnetic resonance imaging features of fractures using the short tau inversion recovery (STIR) sequence: correlation with radiographic findings. Skeletal Radiology (1991); 20: Page 61 of 62

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