Magnetic resonance in the diagnosis and follow-up of soft-tissue sarcomas]

The authors analyze the advantages of MR imaging in the detection, staging and follow-up of malignant soft-tissue sarcomas. The role of MR imaging is retrospectively evaluated in 34 patients (16 men and 18 women) ranging in age from 3 to 82 years (mean: 38); 19 of them had a primary neoplasm, while the extant 15 patients were examined after surgery, and residual or recurrent tumors were present. Ten examinations were performed on an 0.5 T imager (CGR Magniscan 5000), and 27 were obtained with a 1.5 T system (Magnetom 42 SP Siemens). In all cases T1 and T2 sequences were acquired; in 3 patients T1-weighted sequences were performed after Gd-DTPA administration. In the 19 patients with primary tumors pathologic specimens were obtained. The value of MR imaging in the evaluation and characterization of soft-tissue sarcomas and its capabilities in detecting neurovascular encasement and bone involvement are discussed. Post-Gd-DTPA scans may help in the differentiation of necrotic areas from active tumors. MR diagnostic criteria of malignancy, including tissue heterogeneity and irregular margins, were not fulfilled in 3 of the studied cases.     

Osteosarcoma. A new diagnostic approach in presurgical loco-regional staging

The value of Magnetic Resonance (MR) imaging was examined in the anatomical staging of bone osteosarcomas. Eleven patients were studied--8 central and 3 parosteal osteosarcomas. The accuracy of MR imaging was compared to that of plain film, scintigraphy, CT, and angiography. MR imaging was superior to both CT and radionuclide scanning in defining intramedullary extension and in showing skip metastases. Cortical erosion in central osteosarcomas was demonstrated by MR imaging, CT, and plain film; in 1 case of parosteal osteosarcoma MR imaging was superior to CT in showing cortical penetration. In two cases MR imaging did not accurately demonstrate the relationship of the tumor to the major vessels; only angiography showed vascular involvement. MR imaging was useful in delineating extraosseous extension. The importance is stressed of a correct use of MR imaging towards an accurate diagnosis. In fact, intramedullary extension and skip metastases were better demonstrated on T1-weighted images with large fields, while T2-weighted images and small fields were needed for the best overall evaluation of extraosseous involvement. In conclusion, MR imaging should be used for preoperative staging of osteosarcomas in those cases where diagnosis was made on the basis of clinical, radiographic, and bioptic findings.     

Primary musculoskeletal tumors: examination with MR imaging compared with conventional modalities

In 176 cases of primary musculo-skeletal tumors, the informative value of magnetic resonance (MR) imaging was compared with that of plain radiographic examination, angiography, scintigraphy, and computed tomography (CT). In all patients the surgical and histopathologic results were known. For bone tumors confined to the bone, MR imaging was excellent for evaluation of intraosseous extent, but it could not be proved significantly better than CT or scintigraphy. MR imaging was inferior to plain radiography and CT for evaluation of calcification, ossification, cortical destruction, and endosteal/periosteal reaction. For soft-tissue tumors and bone tumors with soft-tissue extension, MR imaging was significantly better than the other modalities in all variables examined: delineation between tumor and muscle, tumor and vessel, tumor and fat, tumor and joint, and tumor and bone, as well as depicting intralesional necrosis and bleeding.     

Tumors of the osseous spine: staging with MR imaging versus CT

Twelve patients with tumors involving the osseous spine were evaluated with magnetic resonance (MR) imaging and computed tomography (CT), six with and six without intrathecal injection of contrast material. MR imaging was found to be superior to CT without contrast material and equal to CT with contrast material in delineating the anatomic relationships of the tumors, including bone involvement, spinal canal invasion, paraspinal soft-tissue extension, and vascular involvement. Since MR imaging can provide most of the anatomic information necessary for treatment planning, intrathecal injection of contrast material can be avoided in most instances when evaluating tumor involvement of the osseous spine. However, CT without contrast medium was superior to MR imaging in showing critical cortical bone destruction and calcified tumor matrix.     

MR imaging of the nasopharynx and floor of the middle cranial fossa. Part II. Malignant tumors

The intracranial extension of tumors of the nasopharynx and related spaces presents a difficult imaging problem. Unlike computed tomography (CT) scans, magnetic resonance (MR) images are not limited by beam-hardening artifacts from bone or dental amalgam. Forty-six patients with malignant tumors of the nasopharynx and related spaces affecting the skull base underwent MR imaging. MR images were obtained with a 0.3-T permanent-magnet imaging system in axial, sagittal, and coronal planes. MR findings were compared with clinical records, plain radiographs, CT scans, and pathologic correlates when available. MR imaging could demonstrate neoplastic invasion of the bone of the floor of the middle cranial fossa and the vital soft-tissue structures related to it as well as or better than CT. Tumor extension was viewed directly as a continuous mass or indirectly by marrow replacement or displacement of normal structures. Specific anatomic routes through which tumors extend from the nasopharynx to the middle cranial fossa were inferred from MR findings.     

Advanced magnetic resonance imaging techniques in the evaluation of musculoskeletal tumors

Magnetic resonance (MR) imaging is an important modality for the preoperative and posttreatment evaluation of musculoskeletal tumors. In some cases, MR imaging is unable to offer information about the extension of tumoral necrosis and the presence of viable cells. Advanced MR imaging techniques are now used in association with conventional MR imaging to improve the diagnostic accuracy and the evaluation of treatment response. This article discusses each advanced MR imaging technique with regard to the clinical applications of tumor detection and characterization, differentiation of benign from malignant tumors and tumor tissue from nontumor tissue, and assessment of treatment response.     

MR imaging of tumor and tumorlike lesions of bone and soft tissue

This review examines the role of MR imaging in the diagnosis and staging of tumors and tumorlike lesions of bone and soft tissue. For tumors of bone, the plain radiograph is not only the least expensive diagnostic test but is the most reliable predictor of the histologic nature of a given lesion. Consequently, it should be the first procedure performed and serve as the basis for determining the next step in the patient's evaluation. MR imaging is the examination of choice for staging bone tumors. CT is preferred to MR imaging only when the characteristics of the lesion are inadequately defined on plain radiographs, as may occur in flat bones. Although MR imaging is of limited value in predicting the histology of bone tumors, it is a useful tool for distinguishing round-cell tumors and metastases from stress fractures and medullary infarcts in symptomatic patients with normal radiographs. For depiction of soft-tissue masses, MR imaging is unrivaled. The histologic nature of a soft-tissue mass may, in some instances, be predicted on the basis of its MR appearance and multicentricity. Biopsy of bone and soft-tissue tumors should follow and not precede MR imaging. MR imaging reliably shows change in tumor volume after radiation or chemotherapy. It is less reliable in predicting the amount of tumor necrosis.     

Assessment of vascular invasion by musculoskeletal tumors of the limbs: use of contrast-enhanced MR angiography

PURPOSE: To prospectively evaluate the accuracy of contrast material-enhanced magnetic resonance (MR) angiography in the evaluation of vascular invasion by bone and soft-tissue tumors, with surgery serving as the reference standard. MATERIALS AND METHODS: This study was approved by the regional ethics committee, and all patients gave informed consent. Preoperative MR angiograms and MR images of 31 sites in 30 patients with bone or soft-tissue sarcomas (n = 21) or other tumors (n = 9) were assessed for features of vascular invasion. All images were prospectively evaluated by two musculoskeletal radiologists working in consensus. MR images were evaluated for the presence of a fat plane between the vessels and the tumor and partial or total encasement of vessels. MR angiograms were evaluated for the presence of vascular displacement, stenosis, or occlusion. MR imaging and MR angiographic features of vascular invasion were graded. Imaging findings were correlated with surgical findings and classified as negative if there was no vascular invasion and as positive if there was vascular invasion. RESULTS: Among the 31 cases, 20 were classified as negative and 11 were classified as positive at surgery. All but three cases with a gap between the tumor and the vessels on MR images were classified as free and without adhesions at surgery. All cases with arterial stenoses at MR angiography had tumoral adhesion or tumoral encasement at surgery. MR imaging had a sensitivity of 64%, a specificity of 95%, a positive predictive value of 88% a negative predictive value of 83%, and an accuracy of 84% in the detection of vascular invasion on the basis of findings of partial or total encasement. MR angiography had a sensitivity of 82%, a specificity of 85%, a positive predictive value of 75%, a negative predictive value of 90%, and an accuracy of 84% in the detection of vascular invasion on the basis of the findings of a stenosis. CONCLUSION: On contrast-enhanced MR angiograms, findings of stenosis were sensitive and specific in the detection of arterial invasion. MR imaging evidence of partial or total encasement is highly specific in the detection of vascular invasion, while MR imaging evidence of a gap between the tumor and the vessels excludes an arterial invasion.     

MR imaging of the knee. Part II. Chronic disorders

Sixty patients with symptoms of chronic disease of the knee joint were evaluated with high-resolution, thin-section magnetic resonance (MR) imaging. MR imaging depicted a wide variety of knee joint abnormalities including osteochondritis dissecans, medullary infarcts, epiphyseal osteonecrosis, intraarticular osteochondral fragments, synovial cysts, joint effusions, intraarticular soft-tissue tumors, synovial disease, leukemic infiltration of bone marrow, Osgood-Schlatter disease, and nonossifying fibroma. In two cases MR imaging depicted bone infarcts not seen on both radionuclide bone scans and standard radiographs. The highly detailed depiction of the articular cartilage was of particular importance in predicting arthroscopic findings in cases of osteochondritis dissecans. In two cases, a soft-tissue mass (pigmented villonodular synovitis) and a large osteochondral fragment undetected at arthroscopy were accurately localized with MR imaging. The results indicate that MR imaging is capable of providing information that might otherwise require multiple, sometimes invasive diagnostic procedures.     

Characterization of bone and soft-tissue tumors with in vivo 1H MR spectroscopy: initial results

PURPOSE: To determine if in vivo detection of choline by using hydrogen 1 (1H) magnetic resonance (MR) spectroscopy with dynamic contrast material-enhanced MR imaging can help differentiate between benign and malignant musculoskeletal tumors. MATERIALS AND METHODS: MR imaging was performed in 36 consecutive patients with bone and soft-tissue tumors larger than 1.5 cm in diameter. Examinations were performed at 1.5 T with a surface coil appropriate for the location of the lesions. Single-voxel 1H MR spectroscopy was performed by using a point-resolved spectroscopic sequence with echo times of 40, 135, and 270 msec. The volume of interest within lesions was positioned on the areas of early enhancement (<8 seconds after arterial enhancement) according to the findings of dynamic contrast-enhanced MR imaging with subtraction. The criterion for determining whether choline was present in a lesion was a clearly identifiable peak at 3.2 ppm in at least two of the three spectra acquired at echo times. MR spectroscopic results and histopathologic findings were determined in blinded fashion and compared with kappa statistics. P <.001 was considered to indicate a significant difference. RESULTS: Choline was detected in 18 of 19 patients with malignant tumors and in three of 17 patients with benign lesions. The three benign lesions included one perineurioma, one giant cell tumor, and one abscess. Choline was not detected in 14 patients with benign lesions nor in one patient with a densely ossifying low-grade parosteal osteosarcoma. In vivo 1H MR spectroscopy characterized bone and soft-tissue tumors, resulting in a sensitivity of 95%, specificity of 82%, and accuracy of 89% (P <.001). CONCLUSION: Choline can be reliably detected in large malignant bone and soft-tissue tumors by using a multiecho point-resolved spectroscopic protocol. 1H MR spectroscopy can help differentiate malignant from benign musculoskeletal tumors by revealing the presence or absence of water-soluble choline metabolites.     

Soft-tissue masses of the locomotor system: comparison of MR imaging with CT

Magnetic resonance (MR) images and computed tomographic (CT) scans of histologically characterized soft-tissue masses of the locomotor system in 35 patients were compared for image contrast, demonstration of bone destruction, and display of extent and anatomic relationships of the masses. Subjective criteria for predicting malignancy were tested. T1 measurements were made in a few cases. Intensities of masses relative to those of fat and muscle in spin-echo T1-weighted and highly T2-weighted images were evaluated for correlation with tissue type. Subjective value of using coronal and sagittal images was assessed. Because of its superior inherent image contrast and its ability to provide direct sagittal and coronal images, MR was better than CT in demonstrating size and extent of most tumors and their relationships to vascular and nonvascular structures. However, bone destruction was more difficult to see with MR. Except for fatty tumors, MR was not helpful in identifying tissue type. Subjective criteria were of limited value in distinguishing benign from malignant lesions. Moreover, there is currently no credible evidence that T1 or T2 measurements are helpful in this regard. Study results suggest that MR is superior to CT in evaluating soft-tissue masses of the locomotor system. If an MR examination is performed, CT may not be necessary in certain cases unless bone involvement is suspected.     

Use of MR imaging to assess results of chemotherapy for Ewing sarcoma

MR imaging was used to monitor the results of initial chemotherapy of primary Ewing sarcoma of bone. The signal intensities of the soft-tissue and marrow components of the tumor were evaluated on T2-weighted images obtained in 10 patients (nine with responsive tumors) at presentation and during and immediately after completion of two cycles of chemotherapy. MR evidence of marrow and soft-tissue involvement was seen in all tumors at presentation. After treatment, the bone-marrow component of the nine drug-sensitive tumors showed an increase in signal intensity that in eight cases became comparable to that of water. Changes in signal intensity of the soft-tissue component were variable, consisting of increases in two of the responsive lesions, no change in three, a decrease in two, and complete resolution of the soft-tissue mass in two. There was no increase in signal intensity of either the bone-marrow or the soft-tissue component of the single nonresponsive tumor. All of the responsive tumors showed advanced healing, and abundant bony sclerosis was apparent on CT. Bone-marrow examinations, performed in seven of the nine patients with responsive lesions, disclosed no evidence of tumor in four. Two patients had residual extramedullary tumor; the nonresponsive lesion contained sheets of tumor cells. The increase in marrow signal intensity on T2-weighted images was associated with replacement of marrow elements by a loose, hypocellular myxoid matrix containing modest amounts of collagen, consistent with response to chemotherapy and eradication of disease. Therefore, an increase in the T2-weighted signal intensity of the bone-marrow component of Ewing sarcoma of bone reflected a favorable response to chemotherapy. MR signal changes, however, were not predictive of resolution of malignant disease within adjacent soft tissue.     

Value and limits of CT in the preoperative assessment of primary malignant tumors of bone. Observations in 138 cases

To estimate the capabilities and limitations of CT in the preoperative evaluation of malignant primary bone neoplasms, 138 patients were examined with high resolution CT and subsequently underwent surgery. In all cases a pathologic examination of the surgical specimen was performed, whose results were compared to CT findings. CT appears to yield important diagnostic contribution to preoperative staging. As a matter of fact, CT shows the tumor extension and its relationship to the adjacent anatomical structures, particularly, it shows the involvement of the muscular and vascular bundles, and that of the articular cavity and medullary canal. These data are of primary importance for planning therapy. The commonest CT limitations are: overestimation of the tumor extension, false positives and false negatives when searching "skip" metastases, and, sometimes, inaccurate definition of the relationship between tumor and vascular bundles and/or articular cavities. These limitations may be overcome by using, when necessary, other techniques--i.e. angiography, bone scan and, above all, MR imaging.     

Trans-sphenoidal spread of rhinopharyngeal neoplasms. Correlations between computerized tomography and magnetic resonance

In 1957 Teoh observed, in an autopsic series of 31 patients with nasopharyngeal carcinoma, 3 cases of neoplastic spread through the marrow spaces of the base of the skull, without macroscopic bone alterations. In order to demonstrate in vivo this kind of neoplastic spread, CT and MR examinations of 35 patients with nasopharyngeal carcinoma were reviewed. In 3/26 cases the invasion of the marrow spaces of the clivus was demonstrated. In these cases CT showed only minimal alterations in spongiosa and cortices of the clivus, associated with intracranial soft-tissue tumoral components. MR imaging demonstrated, with great accuracy, the replacement of bone marrow in the clivus by neoplastic tissue of intermediate signal intensity on T1-weighted images. Tumor tissue was characterized by high signal intensity on T2-weighted images. The authors stress the greater utility of MR imaging in evaluating the permeative involvement of the base of the skull.     

MR imaging of primary bone and soft tissue tumors

MR imaging of 131 cases with pathologically confirmed primary bone and soft tissue tumors were studied. They included 44 bone tumors (25 benign tumors, 19 malignant tumors) and 87 soft tissue tumors (55 benign tumors, 32 malignant tumors). MR imaging was performed on 0.5T, superconductive magnet system. All tumors were evaluated with T1-weighted, T2-weighted and STIR images. In some cases, contrast enhanced MR imaging with Gd-DTPA was applied. MR imaging was proving to be a valuable technique in the evaluation of patients with primary bone and soft tissue tumors. MR imaging was superior to the other modalities in delineating the extent of the tumor and their relation to surrounding structures in all cases. However, plain radiography and CT were more useful for evaluation of calcification, ossification, cortical destruction and endosteal/periosteal reaction than MR imaging. Direct sagittal and coronal images from MR imaging added accurate assessment for the relation between the tumor and their adjacent structures. MR imaging was of limited value in distinguishing benign from malignant tumors with the demonstration of tumor structures only, especially soft tissue tumors. But in bone and soft tissue tumors which have specific morphologic features and intensity patterns, MR imaging was very useful for diagnosis.     

MR imaging of extraabdominal desmoids: differentiation from other neoplasms.

A retrospective review of MR images of 36 patients with histologically proved extraabdominal desmoids was done to define the MR characteristics of these tumors and to determine if MR could be used to differentiate desmoids from other benign and malignant soft-tissue neoplasms. The desmoids evaluated included eight primary and 30 recurrent lesions. Our study was conducted in parallel with another study in which the MR appearance of 95 benign and malignant soft-tissue masses was evaluated, and the MR images of these masses were compared with our findings. The four desmoids from that study are included in our data. The signal intensity of the tumor on T1- and T2-weighted images was graded relative to the intensities of muscle and fat. Homogeneity, margin, neurovascular and bone involvement, and fibrosis (low-signal regions within the tumor on both T1- and T2-weighted images) were evaluated. On MR imaging, the desmoids showed inhomogeneous signal (97%), poor margination (89%), neurovascular involvement (58%), and bone involvement (37%). Fibrosis was present in 88% of primary desmoids and 90% of recurrent ones, and intermediate signal (greater than that of muscle and less than that of fat) was present in 75% and 50% of these, respectively. Our results show that the MR features of desmoids have characteristics that are commonly found in malignant tumors (inhomogeneous signal, poor margination, and neurovascular involvement). MR features of desmoids that distinguish them from malignant neoplasms are the presence of fibrosis and intermediate signal in the regions of the tumor.     

PET evaluation of soft-tissue masses with fluorine-18 fluoro-2-deoxy-D-glucose.

Positron emission tomography (PET) with fluorine-18 fluoro-2-deoxy-D-glucose (FDG) was performed in 19 patients referred for clinical evaluation of soft-tissue masses. These patients had 20 different lesions and had been evaluated previously with computed tomography (CT) and/or magnetic resonance (MR) imaging. The diagnoses were subsequently confirmed with open biopsy or excision (19 lesions) or by clinical and radiographic follow-up (one lesion). Semiquantitative assessment of FDG accumulation (differential uptake ratio) within the suspected tumor helped correctly separate the 10 malignant tumors from the 10 benign lesions. In contrast, a simple ratio of FDG uptake within the suspected tumor to that within comparable normal soft tissue was less successful in helping make this distinction, with overlap in 12 of the 20 cases. Careful comparison with findings from other available imaging studies is essential for accurate interpretation of PET studies of soft-tissue masses, but in many cases, PET may be a useful adjunct in the preoperative evaluation of suspected soft-tissue tumors, yielding valuable information that is not provided with CT or MR imaging.     

Failure of MR imaging to detect reflex sympathetic dystrophy of the extremities

Reflex sympathetic dystrophy of the extremities is a disease with a wide spectrum of clinical manifestations. It is characterized by pain, hyperthermia, and cutaneous changes and has been linked to an abnormality of regional blood flow. The disease is associated with previous injury or trauma including surgery, but also has been found in association with myocardial infarctions and tumors. The final diagnosis can be made only on the basis of the clinical course, which is characterized either by regression without sequel or the appearance of aponeurotic and tendinous retractions including bony sclerosis in the affected region occurring over many months to years. The literature and our own results show that MR imaging has high sensitivity for diagnosing transient osteoporosis of the hip, which is generally thought to be a form of reflex sympathetic dystrophy. Therefore we investigated the usefulness of MR imaging for diagnosing sympathetic dystrophy of the extremities. Twenty-five patients underwent T1- and T2-weighted MR imaging of the affected body region. They were selected on the basis of the initial clinical findings and positive findings on scintigraphy, which is known to be a sensitive, but not very specific, imaging method for sympathetic dystrophy. The final diagnosis was established on the basis of the clinical course in 17 of the 25 patients. In 10 of these, findings on MR images were completely normal, in six the MR images showed only nonspecific soft-tissue changes or bone marrow sclerosis, and in one patient they showed changes in bone marrow signal. Of the remaining eight patients without a final diagnosis of sympathetic dystrophy, MR showed soft-tissue or bone marrow alterations in six. MR imaging appears to be of little value in establishing the diagnosis of sympathetic dystrophy, but it may improve diagnostic specificity when used in conjunction with scintigraphy.     

MR imaging characteristics in primary lymphoma of bone with emphasis on non-aggressive appearance

Purpose To assess the heterogeneity of magnetic resonance (MR) imaging characteristics in primary lymphoma of bone (PLB), in particular the non-aggressive appearance. Subjects and methods In a retrospective study, MR imaging features were analyzed in 29 patients with histologically proven PLB. The following parameters were evaluated: tumor size, bone marrow and extension into soft tissues, signal characteristics of bone marrow and soft-tissue components, including enhancement, and involvement of cortical bone (complete disruption, focal destruction, permeative destruction and cortical thickening). Results PLB presented with extension into the soft tissue in 22 (76%) of 29 patients, was only subtle in three of these 22 patients, and was absent in seven patients. Signal intensity (SI) of the soft-tissue part was most frequently homogeneously isointense with muscle on T1-weighted images (90%) and high on T2-weighted images (91%). Enhancement was predominantly homogeneous and diffuse (82%). In 93% of patients cortical bone appeared abnormal: among those patients complete cortical disruption was seen in 28%, with extension into soft tissues in all but one patient; a permeative pattern of destruction was present in 52% of patients, 66% of these had an associated soft-tissue mass. Two patients with normal-appearing cortical bone had no extension into soft tissues. In two patients focal cortical destruction was noticed; in one patient cortical bone was homogeneously thickened, and in one patient PLB was selectively localized within the cortical bone. SI of the bone marrow tumor component was more frequently heterogeneous (in 54%), compared with the soft-tissue component, being high on T2-weighted images in 89%, intermediate in 7% and low in 4%. Similarly, enhancement was heterogeneous in 59%. Conclusion The MR imaging appearance of PLB is variable. In 31% of PLB patients, the tumor was intra-osseous, with linear cortical signal abnormalities or even normal-appearing or thickened cortical bone without soft-tissue mass, and, as such, PLB may not infrequently look non-aggressive on MR imaging.     

Diseases of the musculoskeletal system in children: imaging with CT, sonography, and MR.

We reviewed the applications of CT, sonography, and MR imaging in diseases of the musculoskeletal system in children. Unique advantages of each technique are discussed, and common disease entities and practical applications of the three imaging methods are stressed. Evaluation of congenital dysplasia of the hip, hip effusion, and soft-tissue foreign bodies with sonography are emphasized. The role of CT in imaging patients with congenital dysplasia of the hip, tarsal coalition, osteomyelitis, and benign and malignant bone tumors is stressed. Common applications of MR that are emphasized include imaging of osteomyelitis, musculoskeletal tumors, normal bone marrow, and avascular necrosis. Innovations are briefly discussed, including evaluation of dermatomyositis with MR and imaging sternoclavicular dislocation, congenital vertical talus, and fractures and dislocations with sonography.