2014 SPR Postgraduate Course Answers, Rationales, References. Musculoskeletal Imaging: Focus on Oncology

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1 2014 SPR Postgraduate Course Answers, Rationales, References Musculoskeletal Imaging: Focus on Oncology 10-year-old girl with several months of increasing, intermittent right knee pain. Based on the appearance of the distal femur on T1-weighted images, which is the most likely diagnosis? A. Osteomyelitis B. Osteoid osteoma C. Ewing sarcoma D. Chondroblastoma E. Metastasis Moderators: Diego Jaramillo, MD, MPH John D. MacKenzie, MD Answer: D. Chondroblastoma Option A. Osteomyelitis is incorrect because there is little edema in the bone and none in the soft tissues. Brodie s abscess can have a well-defined margin and a fading halo, but it typically produces more sclerosis and tends to be smaller. Option B. Osteoid osteoma is incorrect because the lesion is central and does not produce surrounding bone sclerosis and cortical thickening. The core of the lesion (the nidus if it were an osteoid osteoma) is too large. Option C. Ewing sarcoma is incorrect because Ewing sarcoma is unlikely to be epiphyseal and is associated with a much larger mass. Ewing sarcomas usually destroy the cortex and have a soft tissue mass that often is larger than the intraosseous tumor. Option D. Chondroblastoma is correct because this is an epiphyseal lesion with a welldefined, low SI inner border and a halo of perilesional edema. Chondroblastomas are inflammatory lesions and result in pain and marrow edema. Option E. Metastasis is incorrect because most metastases are metaphyseal and multiple, typically based on the physis. Metastases would not be expected to have a well-defined marrow. REFERENCES: 1. Laor, T., Jaramillo, D. MR Imaging Insights into Skeletal Maturation: What is Normal? Radiology 2009; 250(1): Kellenberger, Christian J. "Pitfalls in paediatric musculoskeletal imaging. Pediatric radiology 2009; 39: Kaste SC.Imaging pediatric bone sarcomas.radiol Clin North Am Jul;49(4): Wyers MR.Evaluation of pediatric bone lesions.pediatr Radiol Apr;40(4): McCarville MB.The child with bone pain: malignancies and mimickers.cancer Imaging Oct 2;9 Spec No A:S Wootton-Gorges SL.MR imaging of primary bone tumors and tumor-like conditions in children.magn Reson Imaging Clin N Am Aug;17(3):

2 An 8-year-old male presented with limping and right thigh pain of 4- week duration. Patient also complains of fatigue for the last 2 weeks. Which of the follow is the MOST likely etiology? A. Brodie abscess B. Lymphoma/leukemia C. Ewing sarcoma D. Osteoid osteoma E. Eosinophilic granuloma (EG) Answer is E. Eosinophilic granuloma (EG) Radiograph shows a well-defined, lytic intramedullary lesion eccentrically located within the proximal right femur leading to minor cortical expansion. Low signal intensity on T1- weighted images and bright signal intensity on T2-weighted fat-suppressed images. Pathology showed sheets of Langerhan cells as well as histiocytes, eosinophils and giant cells most consistent with eosinophilic granuloma. Option A is unlikely because Brodie s abscess is usually a centrally located lytic lesion with significant surrounding sclerosis. Option B is unlikely because of the absence of soft tissue mass. Option C is unlikely because Ewing sarcoma usually has laminated periosteal reaction and heterogeneously high signal on T2-weighted images and is accompanied by a soft tissue mass. Option D is unlikely because besides the absence of nocturnal pain relieved by salicylates, there is no cortical thickening or appreciable nidus. Option E was the finding on open biopsy with intra-operative frozen section. See above. REFERENCES: 1. David R, Oria RA, Kumar R et-al. Radiologic features of eosinophilic granuloma of bone. AJR Am J Roentgenol. 1989;153 (5): Greis, PE and FM Hankin, Eosinophilic Cranuloma, Clinical Orthopaedics and Related Research, 257:204211, August, year-old boy presented with a forearm knot. The most likely diagnosis is: A. Chronic osteomyelitis B. Langerhans cell histiocystosis C. Ewing sarcoma D. Buckle fracture of the distal radial metadiaphysis 2

3 Correct answer is C. Ewing Sarcoma. The radiographic findings of a permeative pattern with ill-defined margins and a broad zone of transition within the radial diaphysis suggest an aggressive process. Additionally, there is a large soft tissue mass projecting along the medial mid forearm. Ewing sarcoma, a round cell tumor of bone, has radiographic features of an aggressive process, has a predilection for a diaphysis location in a long bone, and frequently has an associated soft tissue mass. Nearly 80% of patients with Ewing sarcoma are younger than 20 years of age. Incorrect answers: Option A. is incorrect. The radiographic appearance of chronic osteomyelitis usually is associated with bone sclerosis, may show a sequestrum, and is not associated with a large soft tissue mass. However, acute osteomyelitis can have an aggressive appearance, as in this patient, although a large soft tissue mass in the setting of presentation with a knot (i.e. soft tissue mass) rather than pain, swelling, and fever, would be unusual. Option B. is incorrect. Approximately 1/3 of patients with Langerhans cell histiocytosis of bone (eosinophilic granuloma) will have osseous involvement of a long bone. The radiographic appearance of bone involvement is variable. Early lesions can look aggressive with ill-defined borders and a permeated appearance, similar to this patient. Occasionally, there is associated cortical disruption and an adjacent soft tissue mass, however, a mass of this size is unusual. References: 1. Fletcher CDM, Bridge JA, Hogendoorn PCW, Mertens F (eds). WHO classification of tumours of soft tissue and bone. 4th edition. Internation Agency for Research on Cancer (IARC). Lyon, France Miller TT. Bone tumors and tumorlike conditions: analysis with conventional radiography. Radiology (3) Odgen JA. Skeletal injury in the child. 3rd edition. Springer-Verlag. New York. Radius and ulna Option C. is incorrect. The small concavity of the ulnar side of distal radial metaphysis is a normal variation and should not be confused for an acute buckle fracture. The marrow signal within the proximal femurs on this coronal T1-weighted image of a 16-year old girl best reflects: A. Multifocal bone infarcts B. Reconversion bone marrow C. Normal bone marrow D. Stress fractures Answer: B. Reconversion marrow. Marrow transformation occurs in a predictable pattern in the long bones. The first regions to undergo fatty transformation are the epiphyses. Fatty marrow conversion begins within 6 months of the radiological appearance of the secondary ossification center. This is followed by the diaphyses and then proceeds to the metaphyses. The normal marrow pattern of a 16-year old should be fatty marrow signal within the epiphyses with partially fatty marrow present in the diaphyses and metaphyses. On this T1-weighted image, there is homogenous, abnormal, decreased signal intensity of the proximal femurs suggesting hematopoietic marrow. The signal intensity of the proximal femurs is not as hypointense as muscle. This pattern best reflects reconversion marrow. Choice A is not correct as there are no focal increased regions of signal intensity typical of acute hemorrhage or serpiginous regions of low signal intensity as seen in subacute or chronic bone infarcts. Choice C is not correct. In a healthy 16-year old patient, the femoral heads should demonstrate fatty marrow signal, as would be depicted as increased signal intensity on T1-weighted imaging, not low signal intensity as seen on this image. Choice D is not correct. The marrow signal within the proximal femurs is diffusely abnormal, not typical of stress fractures that appear as linear, hypointense regions of signal abnormality surrounding by focal marrow edema, as demonstrated by hypointensity on T1-weighted imaging. 3

4 References Streak artifact is decreased from image 1 to image 2 by which of the following? 1. Laor T, Jaramillo D. MR Imaging Insights into Skeletal Maturation: What is Normal? Radiology 2009; 250(1): Daldrup-Link HE, Henning T, Link T. MR imaging of therapyinduced changes of bone marrow. Eur Radiol 2007; 17: Malkiewicz A, Dziedzic M. Bone marrow conversionimaging of physiological changes in bone marrow. Pol J Radiol 1012; 77(4): A. Switching to a lower kvp B. Switching to a soft tissue reconstruction C. Increasing pitch D. Reconstructing image without overlap Answer: B) Switching to a soft tissue reconstruction REFERENCE: Buckwalter KA. Optimizing imaging techniques in the postoperative patient. Semin Musculoskelet Radiol 2007;11: RATIONALE: Switching to a soft tissue reconstruction will minimize streak artifact. Increasing kvp, increasing ma, decreasing pitch, and creating reconstructed images with overlap will also minimize streak artifact. REFERENCE: Buckwalter KA. Optimizing imaging techniques in the postoperative patient. Semin Musculoskelet Radiol 2007;11:

5 11 y/o girl diagnosed with acute lymphoblastic leukemia underwent screening MR of the hips and knees upon completing her first phase of reinduction chemotherapy. Which of the following statements is TRUE? A. MR of the knees shown here is normal. B. The findings shown in these two images are expected to be transient. C. Findings shown here have been demonstrated only in adolescents who have reached skeletal maturity. D. The findings shown here are associated with rapid evolution to extensive osteonecrosis. E. The findings shown here have been shown to develop only in the knees. Coronal T1 Coronal STIR D. is the true statement and, thus, the correct answer. The findings indicated by the arrows shown above, have been found to herald rapid evolution of extensive osteonecrosis as shown in the follow-up images below. In contrast to the commonly described MR changes of osteonecrosis (well-defined, geographic lesions that characteristically are of decreased signal on T1- and increased signal on T2- weighted or STIR sequences), these earlier changes are less conspicuous, often poorly defined, and often demarcated by subtle edema. 6 month follow-up showing marked progression of osteonecrotic lesions that involve more than 30% of the articular surfaces of the distal femoral and proximal tibial articular surfaces (arrows). Coronal T1 Coronal STIR 6 month follow-up showing marked progression of osteonecrotic lesions that involve more than 30% of the articular surfaces of the distal femoral and proximal tibial articular surfaces (arrows). Coronal T1 2-y follow-up images show consolidation, contraction, retraction from the articular surface and further maturation of the osteonecrotic lesions involving the epiphyses of the knees. Coronal T1 Coronal STIR Coronal STIR 5

6 References: Statement A is false. Both knees have early MR changes of osteonecrosis (see arrowed images and additional explanations). Statement B is false. The findings on these two images herald the evolution of extensive osteonecrosis. They are not transient but represent the earliest MRdetectable changes reported thus far. Statement C is false. The described findings are not restricted to adolescents. In fact, they are notable to be seen in patients prior to skeletal maturity; a population at lesser risk for developing osteonecrosis than adolescents and young adults. Statement E is false. These early changes of osteonecrosis may be seen in any joint. Sansgiri RK, Neel MD, Soto-Fourier M, Kaste SC. Unique MRI findings as an early predictor of osteonecrosis in pediatric acute lymphoblastic leukemia. AJR Am J Roentgenol May;198(5):W doi: /AJR Karimova EJ, Wozniak A, Wu J, Neel MD, Kaste SC. How does osteonecrosis about the knee progress in young patients with leukemia?: a 2- to 7-year study.clin Orthop Relat Res Sep;468(9): doi: /s Epub 2010 Jun 26. Kadan-Lottick NS, Dinu I, Wasilewski-Masker K, Kaste S, Meacham LR, Mahajan A, Stovall M, Yasui Y, Robison LL, Sklar CA. Osteonecrosis in adult survivors of childhood cancer: a report from the childhood cancer survivor study. J Clin Oncol Jun 20;26(18): doi: /JCO Karimova EJ, Rai SN, Ingle D, Ralph AC, Deng X, Neel MD, Howard SC, Pui CH, Kaste SC. MRI of knee osteonecrosis in children with leukemia and lymphoma: Part 2, clinical and imaging patterns.ajr Am J Roentgenol Feb;186(2): Karimova EJ, Rai SN, Deng X, Ingle DJ, Ralph AC, Neel MD, Kaste SC. MRI of knee osteonecrosis in children with leukemia and lymphoma: Part 1, observer agreement AJR Am J Roentgenol Feb;186(2): Regarding imaging assessment by whole body diffusion weighted imaging (WB-DWI), which of the following anatomic areas are potential pitfalls (areas with the potential for false positives)? A. Spleen B. Waldeyer s ring C. Bone marrow D. Lung E. All of the above Best answer = E. All of the above. The spleen and Waldeyer s ring are structures with known high diffusivity. Bone marrow can exhibit variable diffusivity depending on the degree of red marrow present. Lung is also challenging due to the potential for motion artifact from respiration and cardiac motion. 6

7 References: 1. Takahara T, Imai Y, Yamashita T et al (2004) Diffusion weighted whole body imaging with background body signal suppression (DWIBS): technical improvement using free breathing, STIR and high resolution 3D display. Radiat Med 22: Kwee TC, Takahara T, Ochiai R et al (2008) Diffusion-weighted whole-body imaging with background body signal suppression (DWIBS): features and potential applications in oncology. Eur Radiol 18: Kwee TC, Takahara T, Vermoolen MA, et al (2010) Whole Body Diffusion Weighted Imaging for Staging Malignant Lymphoma in Children. Pediatr Radiol 40: Pre: Post: FSEIR DWI ADC Map ADC=2.5 ADC= year-old with proximal tibial osteosarcoma: pre- & post-chemotherapy. The response to therapy is best characterized as: A. No change B. Complete response C. Partial response D. Progressive disease E. Indeterminate 13-year-old with proximal tibial osteosarcoma: pre- & post-chemotherapy Pre: Post: FSEIR DWI ADC Map ADC=2.5 ADC=1.1 The response to therapy is best characterized as: A. No change B. Complete response C. Partial response D. Progressive disease E. Indeterminate Correct answer = D Although the soft tissue component has decreased, diffusion is more restricted and ADC values increased throughout the tumor. References: 1. Costa FM, Ferreira EC, Vianna EM. Diffusion-weighted MRI for the evaluation of musculoskeletal tumors. Magn Reson Imaging Clin N Am Feb; 19(1): Fayad LM, Jacobs MA, Wang X, Carrino JA, Bluemke DA. Musculoskeletal tumors: how to use anatomic, functional, and metabolic MR techniques. Radiology 2012 Nov; 265(2):

8 This image artifact can be reduced by which of the following? A. Switching to a gradient echo pulse sequence B. Decreasing the bandwidth C. Switching to a STIR pulse sequence D. Increasing the echo train length Answer: C) Switching to a STIR pulse sequence REFERENCE: White LM, Buckwalter KA. Technical considerations: CT and MR imaging in the postoperative orthopedic patient. Semin Musculoskelet Radiol 2002;6:5-17. RATIONALE: STIR is resistance to susceptibility artifacts produced by metallic hardware and is preferred for imaging around hardware when fat suppression is desired. Avoid gradient echo pulse sequences; they have considerable susceptibility artifact from lack of a refocusing pulse. Increasing the bandwidth and decreasing the echo train length will also decrease susceptibility artifact. 12-year-old girl with diffuse bone pain for the last two weeks. Based on the appearance of the distal femur on T1-weighted images, the most likely diagnosis is: REFERENCE: White LM, Buckwalter KA. Technical considerations: CT and MR imaging in the postoperative orthopedic patient. Semin Musculoskelet Radiol 2002;6:5-17. A. Sickle cell disease B. Osteosarcoma C. Leukemia D. Marrow reconversion E. Stress injury 8

9 Answer: C. Leukemia Option A. Sickle cell disease is incorrect because the involvement in sickle cell should be relatively symmetrical and uniformly diffuse. Infarcts are also often seen in association with diffuse marrow involvement. Option B. Osteosarcoma is incorrect because there is no evidence of bone destruction, tumor bone or soft tissue mass, all of which are characteristic of this tumor. Most osteogenic sarcomas have a sharp transition zone between normal and involved bone on T1-weighted images. Option C. Leukemia is correct because there is diffuse involvement of the left distal femur. At the age of the patient, both the epiphysis and metaphysis should contain primarily fatty marrow. Note that the cortex is preserved, the abnormal low SI in the marrow is homogeneous and there are no margins between involved and uninvolved bone, all of which are characteristic of acute lymphoblastic leukemia. Option D. Marrow reconversion is incorrect because there is no residual fatty marrow, which would always be seen even with severe reconversion. The appearance of the right femur could be consistent with hyperactive marrow. Marrow reconversion is also symmetrical. Option E. Stress injury is incorrect because most femoral stress injuries would affect the diaphysis and would not produce homogenous epiphyseal marrow abnormality. Stress injuries are often associated with soft tissue edema, although the edema is typically less prominent than that of the. REFERENCES: 1. Laor, T., Jaramillo, D. MR Imaging Insights into Skeletal Maturation: What is Normal? Radiology 2009; 250(1): Kellenberger, Christian J. "Pitfalls in paediatric musculoskeletal imaging. Pediatric radiology 2009; 39: Kaste SC.Imaging pediatric bone sarcomas.radiol Clin North Am Jul;49(4): Wyers MR.Evaluation of pediatric bone lesions.pediatr Radiol Apr;40(4): McCarville MB.The child with bone pain: malignancies and mimickers.cancer Imaging Oct 2;9 Spec No A:S Wootton-Gorges SL.MR imaging of primary bone tumors and tumor-like conditions in children.magn Reson Imaging Clin N Am Aug;17(3): The patchy, hyperintense signal intensity seen scattered throughout the bones of the mid- and hindfoot on this sagittal fluid-sensitive image of a 9-year old child best represents: A. Osteomyelitis B. Multiple stress fractures C. Erosions from juvenile idiopathic arthritis (JIA) D. Marrow changes from altered weight bearing Answer: D. Marrow changes from altered weight bearing. A speckled marrow appearance with patchy foci of increased signal intensity within the mid- and hindfoot is often seen in children who have altered weight bearing, frequently following trauma. It is believed that these foci represent perivascular regions of red marrow seen in the context of disuse osteopenia. Choice A is not correct as the changes are not a pattern of confluent osteitis, as typically seen in osteomyelitis. Choice B is not correct. There are no hypointense linear changes to suggest stress fractures. The hyperintense foci depicted are not the result of direct posttraumatic edema. Choice C is not correct. Bone erosions appear as focal areas of edema within the cortical bone. The signal changes in this patient demonstrate hyperintense fluid-sensitive signal within more central aspects of the bone. 9

10 Reference: 1. Laor T, Jaramillo D. MR Imaging Insights into Skeletal Maturation: What is Normal? Radiology 2009; 250(1): Which of the following radiographic appearance is highly characteristic of an aggressive bone process? A. Multiplicity of lesions B. Saucerization C. Mineralization D. Permeative pattern Correct answer is D. Permeative Pattern. A permeative pattern refers to illdefined, patchy small lucencies as a result of bone destruction. Although this pattern is associated with an aggressive process, it does not unequivocally imply malignancy. In addition to the small round blue cell lesions that often result in a permeative appearance, this pattern also can be seen with benign aggressive entities such as acute osteomyelitis and Langerhans cell histiocytosis. Incorrect answers: Option A. is incorrect. Multiplicity of lesions may be seen in both aggressive processes such as metastatic disease, or non-aggressive entities such as multiple enchondromatoses, fibrous dysplasia, non-ossifying fibromas, etc. Option B. is incorrect. Saucerization results from a process that begins on the outer surface of bone, such as within the periosteum or soft tissue and cause a relative excavation of the outer bony contour. It may be seen from a variety of causes, both non-aggressive and aggressive. Examples of etiologies that may produce saucerization of bone include soft tissue masses such as Ewing sarcoma or rhabdomyosarcoma, synovial processes such as pigmented villonodular synovitis, and benign lesions such as foreign body reaction or aneurysm. Option C. is incorrect. Mineralization refers to calcification of the matrix of a lesion. The matrix may be osteoid, chondral, fibrous, or adipose. The pattern and morphology of the mineralization can aid in the determination of matrix composition. Both aggressive and non-aggressive lesions may be mineralized. For example, mineralization of osteoid may be seen in osteosarcoma, however, it may also be seen in the setting of a healing fracture or osteoid osteoma response. References: 1. Fletcher CDM, Bridge JA, Hogendoorn PCW, Mertens F (eds). WHO classification of tumours of soft tissue and bone. 4th edition. Internation Agency for Research on Cancer (IARC). Lyon, France Miller TT. Bone tumors and tumorlike conditions: analysis with conventional radiography. Radiology (3) Odgen JA. Skeletal injury in the child. 3rd edition. Springer-Verlag. New York. Radius and ulna

11 dx 2: s/p 2 cycles rx 3: s/p rx change T2 fs DWI (outside hospital exam, no DWI) ADC 12-year-old with radiation induced, refractory tibial osteosarcoma. The response to therapy in scan 3 is best characterized as: A. Decreased tumor size B. Increased tumor size C. Decreased viable tumor D. Increased viable tumor E. No change 12-year-old with radiation induced, refractory tibial osteosarcoma dx 2: s/p 2 cycles rx 3: s/p rx change T2 fs (outside hospital exam, no DWI) DWI ADC The response to therapy in scan 3 is best characterized as: A. Decreased tumor size B. Increased tumor size C. Decreased viable tumor D. Increased viable tumor E. No change Correct answer = C Scan B: increase in tumor size and restricted diffusion despite therapy. Scan C: after rx change stable tumor size but markedly increased diffusion indicating tumor necrosis, decreased cellularity. References: 17 y/o girl diagnosed with lymphoblastic lymphoma. Coronal T1-weighted MR of her hips obtained approximately 4 months after the initiation of chemotherapy. What statement below is incorrect regarding osteonecrosis in this case? 1. Costa FM, Ferreira EC, Vianna EM. Diffusion-weighted MRI for the evaluation of musculoskeletal tumors. Magn Reson Imaging Clin N Am Feb; 19(1): Fayad LM, Jacobs MA, Wang X, Carrino JA, Bluemke DA. Musculoskeletal tumors: how to use anatomic, functional, and metabolic MR techniques. Radiology 2012 Nov; 265(2): A. Lymphoblastic lymphoma may be treated as per acute lymphoblastic leukemia. Patients thus receive large doses of glucocorticoids. B. Osteonecrosis can be considered a systemic toxicity in pediatric patients treated for acute lymphoblastic leukemia/lymphoma. C. Teenagers and young adult patients are at greater risk for developing treatment-induced osteonecrosis than pre-teens. D. Over time (years), this patient s femoral head lesions are expected to resolve. E. Bilaterality of involvement is common in the development of osteonecrosis in children treated for malignancies. 11

12 D is the false statement and is, thus, the correct answer. The bilateral femoral head osteonecrotic lesions in this patient involve nearly the entire articular surface of both femoral heads. Lesions involving > 30% of the articular surface in these patients are at great risk of progressing to collapse. Statement A is true. Exposure to high dose glucocorticoids such as those used in treating acute lymphoblastic leukemia/lymphoma is associated with the development of osteonecrosis. Statement B is true. Due to the systemic exposure of chemotherapy treatment, all joints are at risk for developing osteonecrosis. Thus, this toxicity can be considered as a result of systemic exposure in contrast to single-joint involvement that may occur from trauma. Statement C is true. Regardless of the quoted study, adolescents have repeatedly been shown to be at greater risk for developing glucocorticoid-induced osteonecrosis than preteens. The exact reasons have yet to be determined but suggested hypotheses include hormonal basis and changes in physeal patency and vascularity that occur with skeletal maturation. Statement E is true. Due to the systemic exposure of chemotherapy treatment, all joints are at risk for developing osteonecrosis. Bilateral involvement of joints is typical of treatment-related osteonecrosis. References: Kadan-Lottick NS, Dinu I, Wasilewski-Masker K, Kaste S, Meacham LR, Mahajan A, Stovall M, Yasui Y, Robison LL, Sklar CA. Osteonecrosis in adult survivors of childhood cancer: a report from the childhood cancer survivor study. J Clin Oncol Jun 20;26(18): doi: /JCO Karimova EJ, Rai SN, Howard SC, Neel M, Britton L, Pui CH, Kaste SC. Femoral head osteonecrosis in pediatric and young adult patients with leukemia or lymphoma. J Clin Oncol Apr 20;25(12): Mont MA, Zywiel MG, Marker DR, McGrath MS, Delanois RE. The natural history of untreated asymptomatic osteonecrosis of the femoral head: a systematic literature review. J Bone Joint Surg Am Sep 15;92(12): doi: /JBJS.I Mohammad Amin Kerachian, Chantal Séguin, Edward J. Harvey. Glucocorticoids in osteonecrosis of the femoral head: A new understanding of the mechanisms of action The Journal of Steroid Biochemistry and Molecular Biology, Volume 114, Issues 3 5, April 2009, Pages Janke LJ, Liu C, Vogel P, Kawedia J, Boyd KL, Funk AJ, Relling MV. Primary epiphyseal arteriopathy in a mouse model of steroid-induced osteonecrosis. Am J Pathol Jul;183(1): doi: /j.ajpath Epub 2013 May 11. A 7 year old male was referred to our clinic by his primary care provider for pain and swelling of his right proximal tibia of three months duration. Which of the following is the MOST likely etiology? A. Giant cell tumour of bone (GCT) B. Chondroblastoma C. Chondromyxoid fibroma D. Chondrosarcoma E. Non-ossifying fibroma Answer is C. Chondromyxoid fibroma Radiographs show an eccentrically placed Iytic lesion with well-defined and sclerotic margins in the proximal metaphysis of the right tibia. MRI shows homogeneously hypointense T1-weighted and hyperintense T2-weighted images. There are no fluid-fluid levels and there is smooth, thick periosteal reaction along the proximal tibia. Open biopsy with intra-operative frozen section was performed. Pathology showed spindled and stellate cells with eosinophilic cytoplasm, embedded within a chondromyxoid matrix, most consistent with CMF. Option A is unlikely because GCT occurs only with a closed growth plate, without surrounding sclerosis (80-85%) or periosteal reaction (70-90%). Option B is unlikely because chondroblastomas arise in the epiphysis or apophysis of long tubular bone in the skeletally immature. Option D is unlikely because chondrosarcomas are very rare in children and usually have intralesional calcifications (60-78%) with significant cortical remodeling, thickening and periosteal reaction and moth eaten appearance or permeative appearance in higher grade tumors. Option E is unlikely. Non ossifying fibromas are usually asymmetrical, cortically based and multiloculated; they have no associated periosteal reaction or cortical breach. 12

13 REFERENCES: 1. Choi, Yun S, et al. "A rare case of epiphyseal chondromyxoid fibroma of the proximal tibia." Korean Journal of Radiology 12.6 (2011): De Mattos, C.B., et al., Chondroblastoma and chondromyxoid fibroma. J Am Acad Orthop Surg, (4): p Lersundi, A., et al., Chondromyxoid fibroma: a rarely encountered and puzzling tumor. Clin Orthop Relat Res, : p Which of the following statements regarding whole body diffusion weighted imaging is FALSE: A. May increase the sensitivity of conventional (T1 and T2-weighted) whole body MRI alone. B. Is unable to discriminate between benign and malignant lymph nodes. C. Ideally performed with breath holding technique in the chest and abdomen. D. Improves detection of lymph nodes in the abdomen and pelvis. E. Adequate fat-suppression can be challenging at higher field strengths. References: Best answer = C. Ideally performed with breath holding technique in the chest and abdomen. Breath holding techniques, while decreasing respiratory motion, require greater slice thickness with lower signal to noise ratio. Recently developed free breathing diffusion weighted imaging techniques allow for thinner slices and multi-planar reformatting capabilities. 1. Takahara T, Imai Y, Yamashita T et al (2004) Diffusion weighted whole body imaging with background body signal suppression (DWIBS): technical improvement using free breathing, STIR and high resolution 3D display. Radiat Med 22: Kwee TC, Takahara T, Ochiai R et al (2008) Diffusion-weighted whole-body imaging with background body signal suppression (DWIBS): features and potential applications in oncology. Eur Radiol 18: Kwee TC, Takahara T, Vermoolen MA, et al (2010) Whole Body Diffusion Weighted Imaging for Staging Malignant Lymphoma in Children. Pediatr Radiol 40: