Bone Marrow Changes on MRI: Self-Assessment Module

Transcription

1 1.5 CME 1.0 SAM AJR Integrative Imaging LIFELONG LEARNING FOR RADIOLOGY Bone Marrow Changes on MRI: Self-Assessment Module Catherine C. Roberts 1, William B. Morrison 2, Laura W. Bancroft 3,4, Felix S. Chew 5 ABSTRACT Objective The educational objectives for this self-assessment module are for the participant to exercise, self-assess, and improve his or her understanding of the MRI evaluation of bone marrow. Conclusion The activities in this article guide the participant to understanding the key concepts of evaluating bone marrow signal changes with MRI. INTRODUCTION This self-assessment module on the MRI evaluation of the bone marrow has an educational component and a selfassessment component. The educational component consists of six required articles that the participant should read. The self-assessment component consists of 10 multiple-choice questions with solutions. All of these materials are available on the ARRS Website ( To claim CME and SAM credit, each participant must enter his or her responses to the questions online. EDUCATIONAL OBJECTIVES By completing this educational activity, the participant will exercise, self-assess, and improve his or her understanding of: A. MRI evaluation of normal red and yellow bone marrow. B. MRI of neoplastic bone marrow involvement. C. MRI of bone marrow necrosis. REQUIRED READING 1. Swartz PG, Roberts CC. Radiological reasoning: bone marrow changes on MRI. AJR 2009; 193[suppl]:S1 S4 2. Disler DG, McCauley TR, Ratner LM, Kesack CD, Cooper JA. In-phase and out-of-phase MR imaging of bone marrow: prediction of neoplasia based on the detection of coexistent fat and water. AJR 1997; 169: Poulton TB, Murphy WD, Duerk JL, Chapek CC, Feiglin DH. Bone marrow reconversion in adults who are smokers: MR imaging findings. AJR 1993; 161: 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 1992; 158: Waitches G, Zawin JK, Poznanski AK. Sequence and rate of bone marrow conversion in the femora of children as seen on MR imaging: are accepted standards accurate? AJR 1994; 162: Tang YM, Jeavons S, Stuckey S, Middleton H, Gill D. MRI features of bone marrow necrosis. AJR 2007; 188: INSTRUCTIONS 1. Complete the educational and self-assessment components included in this issue. 2. Visit and log in. 3. Select Self-Assessment Modules from the Lifelong Learning box in the lower left of the page. 4. Add the SAM to your shopping cart and order the online SAM as directed. (The SAM, including questions, must be ordered to be accessed even though the activity is free to ARRS members.) After purchasing the SAM, click on OK; you will be returned to the ARRS home page. 5. Click on the My Education tab at the top of the page, then on My Online Products. (Note: You must be logged in to access this personalized page.) 6. You can also access the purchased SAM by logging on to 7. Answer the questions online to obtain SAM credit. Keywords: bone marrow, chemical shift imaging, fibrosis, MRI, neoplasm, opposed-phase imaging, red marrow reconversion DOI: /AJR Received April 10, 2008; accepted after revision June 7, Department of Radiology, Mayo Clinic, 5777 E Mayo Blvd., Phoenix, AZ Address correspondence to C. C. Roberts (roberts.catherine@mayo.edu). 2 Department of Radiology, Thomas Jefferson University Hospital, Philadelphia, PA. 3 Department of Radiology, Mayo Clinic, Jacksonville, FL. 4 Present address: Department of Radiology, University of Central Florida, Orlando, FL. 5 Department of Radiology, University of Washington, Seattle, WA. AJR 2009;193:S5 S X/09/1933 S5 American Roentgen Ray Society S5

2 Roberts et al. QUESTION 1 Regarding MRI of the bone marrow, which sequence is LEAST helpful in differentiating neoplastic from nonneoplastic entities? A. Inversion recovery. B. T1-weighted. C. Conventional gradient-echo. D. Opposed-phase or chemical shift imaging. E. T2-weighted, fat-suppressed. QUESTION 2 Regarding red bone marrow, which of the following is TRUE? A. Red marrow can be focal and mass-like. B. Red marrow reconversion always progresses in a consistent, predictable pattern. C. Red marrow in adults typically persists in the hands and feet. D. Red marrow does not contain fat cells. E. Red marrow is easily differentiated from neoplasm on MRI. QUESTION 3 Which of the following characteristics of normal bone marrow is TRUE? A. Marrow in long-bone diaphyses matures last. B. Once red marrow has matured to yellow marrow, it cannot become hematopoietic. C. Yellow or fatty marrow consists entirely of fat. D. Macroscopic foci of fat in normal marrow can be visible on MRI. E. Red marrow begins converting to yellow marrow at 5 years of age. QUESTION 4 What are the typical MRI characteristics of neoplastic marrow involvement? A. Isointense to muscle on T1, lack of signal dropout B. Hyperintense to muscle on T1, lack of signal dropout C. Isointense to muscle on T1, signal dropout on outof-phase imaging. D. Hyperintense to muscle on T1, signal dropout on out-of-phase imaging. E. Hypointense to muscle on T2, lack of signal dropout QUESTION 5 All of the following can cause red marrow reconversion EXCEPT: A. Physiologic stress. B. Smoking. C. Aging. D. Marrow-stimulating medication. E. Living at high altitude. QUESTION 6 Regarding bone marrow necrosis, which statement is FALSE? A. Its MRI appearance can simulate extensive avascular necrosis. B. Bone marrow necrosis is the same pathologic entity as avascular necrosis. C. Bone marrow necrosis is typically associated with a poor prognosis. D. Bone marrow necrosis can be seen after chemotherapy. E. Bone marrow necrosis should initiate search for occult malignancy. QUESTION 7 In pediatric femora, the conversion of red to yellow marrow has all of the following characteristics EXCEPT: A. Earliest conversion in the proximal and distal epiphyses. B. Beginning as early as 6 months of age. C. Following a predictable sequence. D. Completion after the age of 10 years. QUESTION 8 Which of the following is TRUE regarding marrow imaging? A. The adult marrow imaging pattern is typically achieved by the age of 25 years. B. Red marrow contains no fat or protein content. C. The presence of red marrow in unexpected areas is always abnormal. D. Red marrow in the adult knee should be considered malignant until proven otherwise. E. Red marrow has a relatively short T1 because of its high percentage of fat. S6

3 MRI of Bone Marrow Changes QUESTION 9 In asymptomatic marathon runners, hematopoietic hyperplasia in bone marrow is attributable to all of the following EXCEPT: A. Hemolysis. B. Hematuria. C. Gastrointestinal bleeding. D. Increase in plasma volume. E. Stress fracture. Solution to Question 1 MRI is helpful for characterizing marrow abnormalities. A combination of characteristics seen on different imaging sequences can favor neoplastic or nonneoplastic changes. Fluid-sensitive sequences, including inversion recovery and T2-weighted fat-suppressed sequences, can accentuate areas of bone marrow that need additional assessment. Unfortunately, both red bone marrow reconversion and neoplasm can show increased signal on fluid-sensitive sequences. Options A and E are not the best responses. On T1-weighted images, neoplastic entities tend to have a signal intensity isointense or hypointense to skeletal muscle [1]. Nonneoplastic entities involving the bone marrow tend to have T1-weighted signal hyperintense to skeletal muscle [1]. Option B is not A conventional gradient-echo sequence is helpful in accentuating the bony trabeculae, which can be destroyed in neoplastic processes, but is probably the least helpful of the listed MR sequence options for differentiating neoplastic from nonneoplastic entities. Option C is Opposed-phase sequences show the presence or absence of fat in questioned areas of bone marrow. Neoplastic entities tend to lack fat, thus lacking signal dropout [2]. Nonneoplastic entities involving the bone marrow tend to preserve normal marrow fat cells and thus have signal dropout on out-ofphase images [2]. Option D is not Solution to Question 2 Red bone marrow has a variety of normal appearances. These appearances include smooth contiguous involvement of bones, focal mass-like lesions, and a fine-speckled appearance. This makes differentiating red bone marrow from neoplasm difficult in some cases. Option A is When red bone marrow reconverts from yellow marrow, it does not always progress in a predictable pattern. Certain areas of the body are more likely to be involved with red marrow reconversion, including the spine and pelvis, but the pattern in which red bone marrow reconverts can vary. Red bone marrow diffusely involves the skeleton at birth. The red marrow converts to mature yellow or fatty marrow, from peripheral to central [3]. Option B is not QUESTION 10 In the average adult, all portions of the skeleton contain hematopoietic marrow EXCEPT the: A. Pelvis. B. Femora. C. Ribs. D. Hands. E. Skull. The bones of the hands and feet tend to contain mature fatty marrow early in the maturation process, with red marrow usually not persisting in these regions. Option C is not Red bone marrow consists of hematopoietic cells containing water and fat cells. The combination of these two cell types in a single imaging voxel produces normal signal cancellation, or dropout, as seen on out-of-phase images when compared with in-phase chemical shift images [2]. Option D is not Although red bone marrow can be easily differentiated from neoplasm on MRI in some cases, there are many cases in which this differentiation is more problematic because of the inconsistent location and a sometimes masslike pattern of red marrow reconversion. Option E is not Solution to Question 3 Regarding maturation of red bone marrow in the long bones, the diaphyseal region matures to yellow marrow first [4]. The normal sequence of bone marrow maturation is from red, hematopoietic marrow to yellow, fatty marrow. Option A is not In times of stress, yellow marrow can reconvert to hematopoietic red bone marrow [4]. Option B is not Although yellow or fatty marrow is predominately composed of fat cells, the yellow marrow still contains some hematopoietic cells. Option C is not Normal bone marrow contains both microscopic and macroscopic foci of fat. The presence of macroscopic regions of marrow fat on MRI is reassuring for a benign process. Option D is Red bone marrow begins maturing to yellow bone marrow at a very early age. Classically, this maturation was thought to begin in late childhood, but studies using MRI have shown this maturation process to begin at less than 1 year of age [5]. Option E is not Solution to Question 4 MRI characteristics of neoplastic bone marrow involvement include its being isointense or hypointense to muscle on T1-weighted images [1]. Neoplastic bone marrow involvement S7

4 Roberts et al. also lacks normal signal dropout on out-of-phase imaging, due to the lack of remaining normal bone marrow fat. Option A is Red bone marrow is typically hyperintense to muscle on T1-weighted sequences [1]. Option B is not A bone marrow lesion isointense to muscle on T1-weighted images but showing signal dropout on out-of-phase imaging suggests continued presence of marrow fat, favoring a benign process. Option C is not Normal red bone marrow having hyperintense signal to muscle on T1-weighted images and signal dropout on out-of-phase imaging is described in option D. Option D is not Red bone marrow and neoplasm can be hyperintense to skeletal muscle on fluid-sensitive sequences. Option E is not Solution to Question 5 Mature, yellow bone marrow can reconvert to red, hematopoietic marrow for several different reasons. Physiologic stress, high athletic activity, marrow replacement disorders, living at high altitude, smoking cigarettes, and anemia are all causes of red bone marrow reconversion [3, 4]. Bone marrow stimulating medications that are often given with chemotherapy are intended to stimulate red marrow reconversion. Options A, B, D, and E are not the best responses. The normal aging process is not a typical cause of red bone marrow reconversion. Option C is Solution to Question 6 Despite the differences in pathology, the appearance of bone marrow necrosis on MRI can simulate extensive avascular necrosis [6]. Option A is true and not Bone marrow necrosis is a distinct clinicopathologic entity from avascular necrosis [6]. Necrosis of the bone marrow occurs without disruption of the bone marrow spicular architecture, differentiating it from avascular necrosis. Bone marrow necrosis tends to involve the bone marrow of the spine and pelvis diffusely, whereas avascular necrosis is typically periarticular and focal. Option B is false and is Patients with bone marrow necrosis often have a poor prognosis because this entity is associated with malignancy. Option C is true and not Bone marrow necrosis can occur before, during, and after chemotherapy. Option D is true and not If bone marrow necrosis is diagnosed without a known malignancy, a search for occult malignancy should be initiated because these two entities are associated [6]. Option E is true and not Solution to Question 7 Yellow marrow conversion occurs first in the proximal and distal epiphyses, and then in the diaphysis, distal metaphysic, and proximal metaphysis. Option A is true and not Yellow marrow in the femoral diaphysis can be seen with MRI in children as young as 6 months old [5]. Option B is true and not Conversion of red to yellow marrow in pediatric femora typically follows a predictable sequence and pattern, with some variability in the age of presentation of this phenomenon. Option C is true and not MRI documentation of yellow marrow conversion actually occurs earlier in childhood than previously realized. This reconversion has been documented in children less than 1 year old. Option D is false and is Solution to Question 8 The adult marrow imaging pattern is typically achieved by the age of 25 years. Option A is Red marrow contains fat, but to a lesser extent than yellow marrow. Red marrow is composed of approximately 40% water, 40% fat, and 20% protein [4]. Option B is not The presence of red marrow in unexpected areas is not necessarily abnormal but can represent absence of primary conversion or reconversion of marrow [4]. Option C is not Red marrow in the adult knee should not be considered malignant and can be a normal finding in heavy smokers, younger patients, and obese women who smoke heavily [4]. Option D is not Yellow marrow, not red marrow, has a relatively short T1 because of its high percentage of fat. Option E is not the best response. Solution to Question 9 Hematopoietic hyperplasia in the marrow of asymptomatic marathon runners is the result of sports anemia. This has been attributed to hemolysis, hematuria, gastrointestinal bleeding, excessive sweat loss, and increase in plasma volume [3]. Options A, B, C, and D are all true and are not the best responses. Stress fractures do not cause hematopoietic hyperplasia. Option E, which is not true, is Solution to Question 10 In the average adult, only the axial skeleton (pelvis, vertebrae, sternum, ribs, and skull) and proximal shafts of the humeri and femora contain hematopoietic marrow [4]. The remaining skeleton contains fatty marrow. Options A, B, C, and E are all true and not the best responses. The adult hands should not contain hematopoietic marrow. Any extreme causes of marrow reconversion could result in the presence of some red marrow in the hands and wrists that would be evident on MRI. Option D is false and is References 1. Swartz PG, Roberts CC. Radiological reasoning: bone marrow changes on MRI. AJR 2009; 193[suppl]:S1 S4 S8

5 MRI of Bone Marrow Changes 2. Disler DG, McCauley TR, Ratner LM, Kesack CD, Cooper JA. In-phase and out-of-phase MR imaging of bone marrow: prediction of neoplasia based on the detection of coexistent fat and water. AJR 1997; 169: 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 1992; 158: Poulton TB, Murphy WD, Duerk JL, Chapek CC, Feiglin DH. Bone marrow FOR YOUR INFORMATION reconversion in adults who are smokers: MR imaging findings. AJR 1993; 161: Waitches G, Zawin JK, Poznanski AK. Sequence and rate of bone marrow conversion in the femora of children as seen on MR imaging: are accepted standards accurate? AJR 1994; 162: Tang YM, Jeavons S, Stuckey S, Middleton H, Gill D. MRI features of bone marrow necrosis. AJR 2007; 188: The reader s attention is directed to the Radiological Reasoning article on which this SAM is based, which begins on page S1. S9