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Epitomes Important Advances in Clinical Medicine
Radiology The Scientific Board ofthe California Medical Association presents the following inventory of items ofprogress in radiology. Each item, in the judgment ofa panel of knowledgeable physicians, has recently become reasonablyfirmly established, both as to scientific fact and important clinical significance. The items are presented in simple epitome, and an authoritative reference, both to the item itselfand to the subject as a whole, is generally givenfor those who may be unfamiliar with a particular item. The purpose is to assist busy practitioners, students, researchers, or scholars to stay abreast ofthese items ofprogress in radiology that have recently achieved a substantial degree of authoritative acceptance, whether in their own field ofspecial interest or another. The items ofprogress listed below were selected by the Advisory Panel to the Section on Radiology ofthe California Medical Association, and the summaries were prepared under its direction. Reprint requests to Division of Scientific and Educational Activities, California Medical Association, PO Box 7690, San Francisco, CA 94120-7690
Magnetic Resonance Imaging of Musculoskeletal Tumors PRIMARY AND METASTATIC musculoskeletal tumors are comand potentially life-threatening. Although conventional radiographs are the primary means of detecting and diagnosing these tumors, plain films have two shortcomings-poor definition of tumor extension and poor detection of early osseous metastases. Magnetic resonance imaging (MRI), because it can produce images in multiple planes while displaying superior soft-tissue contrast resolution, has had a substantial effect on the description, preoperative staging, and postoperative follow-up of musculoskeletal tumors. Several MRI findings increase a physician's index of suspicion for malignant tumor: inhomogeneous signal intensity, irregular margination, osseous destruction, encasement of neurovascular structures, and disruption of more than one compartment of bone, joint, or muscle. As a general rule, osseous and soft-tissue tumors have low or intermediate signal intensity on TI-weighted images and a high signal on T2-weighted images. Osteoblastic lesions are often the exception; they have low signal intensity on both Ti- and T2weighted images. Tumor conspicuity and delineation are usually not improved by administering intravenous gadolinium-gadolinium enhancement actually may obscure tumor mon
ment and prognosis. In the case of osteogenic sarcoma, for example, MRI not only helps physicians plan an approach for biopsy and surgical procedures, it also helps them plan whether surgical intervention will consist of a limb-salvage procedure, an amputation, or a disarticulation. Another important contribution of MRI is the monitoring of a tumor's response to adjuvant therapy-both preoperatively and postoperatively. Tumors responding to radiation or chemotherapy generally become more sharply marginated and decrease in size and vascularity. Magnetic resonance imaging effectively helps characterize, stage, and follow musculoskeletal tumors and now is accepted as the imaging study of choice for such tumors. ROBERT D. BOUTIN, MD MICHAEL R. WILLIAMSON, MD Albuquerque, New Mexico REFERENCES Dalinka MK, Zlatkin MB, Chao P, Kricun ME, Kressel HY: The use of magnetic resonance imaging in the evaluation of bone and soft-tissue tumors. Radiol Clin North Am 1990; 28:461-470 Gold RI, Seeger LL, Bassett LW, Steckel RJ: An integrated approach to the evaluation of metastatic bone disease. Radiol Clin North Am 1990; 28:471-483 Manaster BJ, Ensign MF: Imaging of musculoskeletal tumors. Semin Oncol 1991; 18:140-149 Murphy WA: Imaging bone tumors in the 1990s. Cancer 1991; 67:1169-1176 Seeger LL, Widoff BE, Bassett LW, Rosen G, Eckardt JJ: Preoperative evaluation of osteosarcoma: Value of gadopentetate dimeglumine-enhanced MR imaging. AJR 1991; 157:347-351
margins.
The staging of musculoskeletal tumors requires determining the tumor extent, the histologic grade, and the presence or absence of metastases. A bone scan is the method of choice when screening the whole body for skeletal metastases, but its findings are notoriously nonspecific and its spatial resolution is so poor that precise preoperative planning is precluded. Computed tomography (CT), on the other hand, has good spatial resolution and effectively detects early cortical erosions, but its contrast resolution is inferior to that of MRI. The present consensus is that MRI is superior to CT for defining the infiltration of the tumor into bones, muscles, joints, and neurovascular structures. Tumor margins visualized by MRI have been shown to match closely those found by pathologic examination. At times, however, differentiating tumor from peritumoral edema is just as difficult with MRI as it is with other modalities, such as CT. Delineating tumor from healthy tissue is crucial for manage-
Vena Cava Filters WHILE MOST PATIENTS with deep vein thrombosis can be successfully treated with anticoagulation therapy alone, some require the placement of an inferior vena cava filter, either as an alternative form of treatment or as adjunctive treatment along with anticoagulation, for prevention of pulmonary embolism. Generally accepted indications for placement of a vena cava filter include: absolute contraindication to anticoagulation; a complication of anticoagulation (such as hemorrhage); a relative contraindication to anticoagulation, such as patients prone to falling; the presence of a large amount of free-floating clot; short-term contraindications to anticoagulation, such as brain biopsy; deep vein thrombosis with unsuspected pulmonary embolism diagnosed at presentation; and a massive pulmonary embolism with residual lower extremity deep vein thrombosis. Since placement of a
Epitomes Important Advances in Clinical Medicine
Radiology The Scientific Board ofthe California Medical Association presents the following inventory of items ofprogress in radiology. Each item, in the judgment ofa panel of knowledgeable physicians, has recently become reasonablyfirmly established, both as to scientific fact and important clinical significance. The items are presented in simple epitome, and an authoritative reference, both to the item itselfand to the subject as a whole, is generally givenfor those who may be unfamiliar with a particular item. The purpose is to assist busy practitioners, students, researchers, or scholars to stay abreast ofthese items ofprogress in radiology that have recently achieved a substantial degree of authoritative acceptance, whether in their own field ofspecial interest or another. The items ofprogress listed below were selected by the Advisory Panel to the Section on Radiology ofthe California Medical Association, and the summaries were prepared under its direction. Reprint requests to Division of Scientific and Educational Activities, California Medical Association, PO Box 7690, San Francisco, CA 94120-7690
Magnetic Resonance Imaging of Musculoskeletal Tumors PRIMARY AND METASTATIC musculoskeletal tumors are comand potentially life-threatening. Although conventional radiographs are the primary means of detecting and diagnosing these tumors, plain films have two shortcomings-poor definition of tumor extension and poor detection of early osseous metastases. Magnetic resonance imaging (MRI), because it can produce images in multiple planes while displaying superior soft-tissue contrast resolution, has had a substantial effect on the description, preoperative staging, and postoperative follow-up of musculoskeletal tumors. Several MRI findings increase a physician's index of suspicion for malignant tumor: inhomogeneous signal intensity, irregular margination, osseous destruction, encasement of neurovascular structures, and disruption of more than one compartment of bone, joint, or muscle. As a general rule, osseous and soft-tissue tumors have low or intermediate signal intensity on TI-weighted images and a high signal on T2-weighted images. Osteoblastic lesions are often the exception; they have low signal intensity on both Ti- and T2weighted images. Tumor conspicuity and delineation are usually not improved by administering intravenous gadolinium-gadolinium enhancement actually may obscure tumor mon
ment and prognosis. In the case of osteogenic sarcoma, for example, MRI not only helps physicians plan an approach for biopsy and surgical procedures, it also helps them plan whether surgical intervention will consist of a limb-salvage procedure, an amputation, or a disarticulation. Another important contribution of MRI is the monitoring of a tumor's response to adjuvant therapy-both preoperatively and postoperatively. Tumors responding to radiation or chemotherapy generally become more sharply marginated and decrease in size and vascularity. Magnetic resonance imaging effectively helps characterize, stage, and follow musculoskeletal tumors and now is accepted as the imaging study of choice for such tumors. ROBERT D. BOUTIN, MD MICHAEL R. WILLIAMSON, MD Albuquerque, New Mexico REFERENCES Dalinka MK, Zlatkin MB, Chao P, Kricun ME, Kressel HY: The use of magnetic resonance imaging in the evaluation of bone and soft-tissue tumors. Radiol Clin North Am 1990; 28:461-470 Gold RI, Seeger LL, Bassett LW, Steckel RJ: An integrated approach to the evaluation of metastatic bone disease. Radiol Clin North Am 1990; 28:471-483 Manaster BJ, Ensign MF: Imaging of musculoskeletal tumors. Semin Oncol 1991; 18:140-149 Murphy WA: Imaging bone tumors in the 1990s. Cancer 1991; 67:1169-1176 Seeger LL, Widoff BE, Bassett LW, Rosen G, Eckardt JJ: Preoperative evaluation of osteosarcoma: Value of gadopentetate dimeglumine-enhanced MR imaging. AJR 1991; 157:347-351
margins.
The staging of musculoskeletal tumors requires determining the tumor extent, the histologic grade, and the presence or absence of metastases. A bone scan is the method of choice when screening the whole body for skeletal metastases, but its findings are notoriously nonspecific and its spatial resolution is so poor that precise preoperative planning is precluded. Computed tomography (CT), on the other hand, has good spatial resolution and effectively detects early cortical erosions, but its contrast resolution is inferior to that of MRI. The present consensus is that MRI is superior to CT for defining the infiltration of the tumor into bones, muscles, joints, and neurovascular structures. Tumor margins visualized by MRI have been shown to match closely those found by pathologic examination. At times, however, differentiating tumor from peritumoral edema is just as difficult with MRI as it is with other modalities, such as CT. Delineating tumor from healthy tissue is crucial for manage-
Vena Cava Filters WHILE MOST PATIENTS with deep vein thrombosis can be successfully treated with anticoagulation therapy alone, some require the placement of an inferior vena cava filter, either as an alternative form of treatment or as adjunctive treatment along with anticoagulation, for prevention of pulmonary embolism. Generally accepted indications for placement of a vena cava filter include: absolute contraindication to anticoagulation; a complication of anticoagulation (such as hemorrhage); a relative contraindication to anticoagulation, such as patients prone to falling; the presence of a large amount of free-floating clot; short-term contraindications to anticoagulation, such as brain biopsy; deep vein thrombosis with unsuspected pulmonary embolism diagnosed at presentation; and a massive pulmonary embolism with residual lower extremity deep vein thrombosis. Since placement of a
