Spondylolysis, spondylolisthesis, and associated nerve root entrapment in the lumbosacral spine: MR evaluation.

Spondylolysis is defined as a bone defect in the pars interarticularis. Its cause is uncertain but is believed in most cases to be related to repeated stress, trauma, or both. Findings of spondylolysis on conventional radiographs and on CT scans have been well characterized. Although these imaging techniques remain effective for the diagnosis of this defect, MR imaging is increasingly used as the primary or sole imaging method in patients with lower back pain and radiculopathy. Therefore, because MR images of the lumbar spine may be interpreted in the absence of correlative CT scans or conventional radiographs, the MR features of spondylolysis and its associated findings must be recognized. This essay illustrates the MR findings of lumbosacral spondylolysis and associated entrapment and direct impingement of the spinal nerve root.     

MR imaging of diffuse bone marrow replacement in pediatric patients with cancer

In the magnetic resonance (MR) imaging examinations of three children with tumors (two neuroblastoma, one rhabdomyosarcoma) and three with leukemia, the marrow demonstrated a diffuse, uniform pattern of hypointensity on T1-weighted images and hyperintensity on T2-weighted images. The authors observed that this reversal ("flip-flop") of the usual MR characteristics of fatty marrow was seen in the epiphyses, metaphyses, and diaphyses. The purpose of this study was to establish the radiographic and clinicopathologic correlates of this MR finding on the basis of findings from plain radiographs, bone scans, and bone marrow aspirates. Plain radiographs and bone scans demonstrated either normal findings or changes limited to the metaphyses. In all patients, analysis of bone marrow aspirates demonstrated metastases. The authors concluded that even in the absence of evidence of discrete bone metastases on a plain radiograph or a bone scan, this diffuse and uniform "flip-flop" pattern reflects diffuse marrow replacement by tumor cells.     

Diagnostic evaluation of cancer patients with pelvic pain: comparison of scintigraphy, CT, and MR imaging

Pelvic pain in cancer patients can result from several causes. The most appropriate choice of imaging techniques for evaluating such patients has not been established. We evaluated 27 cancer patients with pelvic pain by using radionuclide bone scintigraphy (24 patients), abdominal CT (27 patients), and pelvic MR imaging (27 patients) and used the correlation between symptoms and imaging findings to compare these imaging methods. The study population included 11 patients with Ewing sarcoma, six with other sarcomas, five with colorectal cancers, and five with other tumors. All patients had pelvic pain, and eight had pain radiating to a leg. Twenty-three patients had soft-tissue masses, and 19 had bone metastases; 16 had both. Findings on bone scans explained the symptoms in 17 (71%) of 24 patients, findings on CT in 23 (85%) of 27 patients, and findings on MR imaging in 25 (93%) of 27 patients. The difference between bone scanning and CT or MR was statistically significant (p less than .05); however, the difference between CT and MR imaging was not significant (p greater than .05). MR imaging detected 41 (98%) of 42 relevant lesions, whereas CT detected 31 (74%) of 42, and bone scanning 17 (44%) of 39. We conclude that MR is superior to either bone scanning or CT in the initial evaluation of pelvic pain in cancer patients. Such information can be important in directing the treatment of these patients.     

Detection of brain metastases: comparison of contrast-enhanced MR with unenhanced MR and enhanced CT

Contrast-enhanced MR studies were compared with noncontrast MR and contrast-enhanced CT scans in the evaluation of intraparenchymal brain metastases. Fifty consecutive inpatients were studied with short and long repetition time (TR) sequences before and after the administration of gadopentetate dimeglumine. In addition, a delayed short TR sequence was performed. The contrast CT, noncontrast MR, immediate postcontrast short TR sequence, postcontrast long TR sequence, and delayed postcontrast short TR sequence were each read blindly and independently by two neuroradiologists. These results were then compared with a final interpretation, reached by all the neuroradiologists in the study, using all the clinical information and imaging findings. Postcontrast short TR scans proved to be superior to other sequences. They were particularly useful in the detection of metastases in the posterior fossa and cortex. The delayed postcontrast short TR scan held no definite advantage over the immediate postcontrast short TR scan, although metastases were sometimes seen slightly better after the delay. While long TR sequences were not always sensitive or specific, they often did provide ancillary information and were particularly useful in cases of hemorrhagic metastases. Because of these findings, we recommend that the evaluation of intraparenchymal metastases consist of a single postcontrast long TR scan followed by a single postcontrast short TR scan. While these sequences should be very accurate in the detection of metastases, we also generally perform a single precontrast short TR scan as well, since the question of hemorrhage or bone lesion may be clinically relevant.     

Radionuclide evaluation of skeletal metastases: Practical considerations

The indications for radionuclide bone scanning to evaluate possible metastatic disease are reviewed. The causes of false-positive and falsenegative interpretations are discussed and illustrated. Since breast cancer leads all malignant tumors in incidence of skeletal metastases found at autopsy, the efficacy of preoperative bone scans in patients with breast cancer is analyzed in detail. A routine preoperative bone scan for patients with Stage I breast cancer produces negligible immediate benefits, but may serve a useful purpose as a baseline to enhance the detection of subtle changes that could represent metastases in a subsequent scan. However, the clinical usefulness of this screening procedure for Stage I disease must be balanced with its cost. Clinical Stage II is a grey area and may include patients with large primary tumors and axillary nodal involvement, implying a greater chance for the occurrence of skeletal metastases and hence a significant yield in bone scans. Patients with clinical Stages III or IV disease have the greatest chance of harboring metastases and should have an extensive diagnostic evaluation including bone scans prior to definitive treatment. Selected radiographs of sites of abnormally increased radionuclide activity and an anteroposterior radiograph of the pelvis should be correlated with the scan to permit a single comprehensive diagnostic impression.Presented at the 11th Annual Meeting and Refresher Course of the International Skeletal Society, Philadelphia, Pennsylvania, USA, September 12–15, 1984     

Early MR demonstration of spinal metastases in patients with normal radiographs and CT and radionuclide bone scans

Forty patients with known primary tumor and progressive back pain, suspected of having spinal metastatic disease, underwent magnetic resonance (MR) examinations of the thoracic and lumbosacral spine. Conventional radiographs and CT scans of the spine were all normal. The radionuclide bone scans were equivocal. In 21 patients focal or diffuse vertebral MR abnormalities were detected. In nine patients the lesions were hypointense on T1 sequence, and the same lesions were demonstrated poorly or not at all on T2 and proton density sequences. In eight other patients the bone marrow metastases presented with strong signal intensity on T2 and were poorly or not at all demonstrated on T1 and proton density sequences. In three patients with multiple myeloma, the signal intensity pattern of the vertebrae was diffusely heterogeneous, with alternating small foci of strong and weak signals (a mosaic-like pattern). Following the MR studies, needle biopsy confirmed the malignancy in the 21 patients who had shown abnormalities. No correlation between the type of primary tumor and the signal intensity of the vertebral metastases was shown. Possibly the mosaic pattern shown in three of the multiple myeloma patients represents a special case.     

Trauma to the foot

Minor trauma to the foot may cause stress fracture, avulsion fracture or ligamentous and tendon injury. Plain radiographs are frequently normal. Radionuclide bone scan is a sensitive detector of early bone injury. A stress fracture may develop focal uptake or diffuse uptake throughout the bone involved. MR imaging is the most sensitive means of evaluating injury to the soft tissues. Acute edema, partial tear, complete tear, and chronic tendinitis have distinct features on T1- and T2-weighted images. Major trauma occurs most commonly as a result of falls from heights and from motor-vehicle accidents. Plain films are useful in the initial evaluation of the extent of trauma. CT is particularly useful in evaluating calcaneal fractures that involve the subtalar joint. Both MR imaging and CT scans are useful in detecting injured or entrapped tendons associated with fracture-dislocations.     

Suspected non-small cell lung cancer: incidence of occult brain and skeletal metastases and effectiveness of imaging for detection--pilot study

PURPOSE: To estimate the incidence of occult metastases to the brain and skeleton in patients suspected of having non-small cell lung cancer (NSCLC) (stage higher than T1Nomo) with surgically resectable disease, to assess the accuracy of screening magnetic resonance (MR) imaging and radionuclide bone scanning for help in identifying occult metastases, and to determine the effectiveness of a high dose of MR contrast material. MATERIALS AND METHODS: Twenty-nine patients suspected of having NSCLC localized to the lung or to the lung and regional nodes underwent preoperative MR imaging with contrast material enhancement and radionuclide bone scanning for detection of brain or skeletal metastases. Patients were followed up for 12 months to determine the incidence of clinical metastatic disease. RESULTS: Eight (28%) patients had occult metastatic disease to the brain or skeleton. Brain metastases were identified on MR images in five of six patients. Bone metastases were identified on MR images in four of five patients and on bone scans in three of five patients. MR imaging was no more accurate than bone scanning for skeletal evaluation. A high dose of MR contrast material allowed detection of more metastases and of small lesions. CONCLUSION: Contrast-enhanced MR imaging of the brain is indicated for the exclusion of brain metastases in patients with clinically operable known or possible NSCLC and a large (> 3-cm) lung mass. Skeletal imaging may be indicated if an isolated brain metastasis is detected.     

Paget disease: MR imaging findings

Magnetic resonance (MR) images of 13 patients with Paget disease were reviewed, and findings were correlated with those from computed tomographic (CT) scans, radiographs, and, in two patients, surgical biopsy. MR imaging findings correlated with CT and radiographic findings of cortical thickening, increased size of bone, and coarse thickened trabeculae. Focal or diffuse decreased signal intensity, representing dense bone, was seen on images obtained with short and long repetition times (TRs) and echo times (TEs); high-signal foci, representing fat collections, were seen on short TR/TE images; and high-signal foci, representing fibrovascular marrow in active Paget disease, were seen on long TR/TE images. Complications of Paget disease-including basilar invagination, spinal stenosis, and sarcoma--were well identified on MR images. Although MR imaging is not generally used in diagnosis of Paget disease, the disease will be encountered more frequently as more MR imaging examinations are performed. An awareness of the range of findings in Paget disease is useful in evaluating MR images of the musculoskeletal and other systems.     

Bone scans with one or two new abnormalities in cancer patients with no known metastases: reliability of interpretation of initial correlative radiographs

To determine the reliability of radiographs obtained for correlation with bone scans showing one or two new abnormalities in cancer patients without known metastases, a retrospective study of 306 scans showing such lesions was performed. Overall, 14% of the lesions proved to be malignant. The initial radiographic interpretation was normal for 43% of the new bone scan lesions; 17% of these lesions were metastases. A benign process was identified on radiographs for 38% of the abnormalities; only one (1%) was a metastasis. Twelve percent of new bone scan lesions correlated with radiographic abnormalities considered either suggestive of or consistent with metastasis, of which 24% and 71%, respectively, proved to be metastases. In cancer patients with one or two new bone scan abnormalities, correlative radiographs showing a benign abnormality are reliable. However, if the radiographs are either normal or show findings considered suggestive of or consistent with metastasis, further evaluation or follow-up is warranted.     

Insufficiency fractures of the tibial plateau

An insufficiency fracture of the tibial plateau may be the cause of knee pain in patients with osteoporosis. The diagnosis is usually not suspected until a bone scan is done, as initial radiographs are often negative or inconclusive and clinical findings are nonspecific and may simulate osteoarthritis or spontaneous. In five of 165 patients referred for bone scans due to nontraumatic knee pain, a characteristic pattern of intense augmented uptake of radionuclide confined to the tibial plateau led to a presumptive diagnosis of insufficiency fracture, later confirmed on radiographs.     

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.     

Comparative sensitivity of CT scans, radiographs and radionuclide bone scans in detecting metastatic calvarial lesions

CT scans of 100 patients with histologically diagnosed extracerebral neoplasms were reviewed and compared with either radionuclide bone images or skull radiographs. The results of this correlative study indicate that CT scans are more sensitive than skull radiographs in detecting corresponding calvarial lesions; conversely, radionuclide bone scans appear to be more sensitive than CT in detecting similar lesions.     

Factors influencing visualization of vertebral metastases on MR imaging versus bone scintigraphy

OBJECTIVE: The purpose of this study was to investigate whether the location and size of vertebral body metastases influence the difference in detection rates between MR imaging and bone scintigraphy. MATERIALS AND METHODS: We retrospectively evaluated the vertebral body lesions detected on MR imaging in 74 patients with known widely disseminated metastatic disease. Three radiologists independently reviewed the MR images and bone scintigraphs. MR imaging findings included lesion size and its spatial relationship to the bony cortex (intramedullary, subcortical, and transcortical) and results were correlated with those of planar technetium 99m bone scintigraphy. RESULTS: Findings on bone scans were negative for all intramedullary lesions without cortical involvement shown on MR imaging, regardless of their size. Findings on bone scans (71.3% for transcortical and 33.8% for subcortical) were frequently positive for lesions with cortical involvement (trans- or subcortical), and the probability of positive findings on bone scans was also influenced by the lesion size. Statistical analysis showed a positive correlation among cortical involvement, lesion size, and positive findings on bone scintigraphy (p < 0.0001). CONCLUSION: Location (the presence of cortical bone involvement on MR imaging) and size of the vertebral body metastases appear to be important contributing factors to the difference in detection rates between MR imaging and bone scintigraphy. Cortical involvement is likely the cause of positive findings on bone scans. Early vertebral metastases tend to be small and located in the medullary cavity without cortical involvement, and therefore, findings may be positive on MR images but negative on bone scans.     

Incidence of bone metastases in women with minimal and occult breast carcinoma.

A total of 42 women with proved minimal (14) or occult (28) breast carcinoma were evaluated for up to 48 months (mean = 28 months). Bone scans, radiographs, blood chemistries, enzyme levels, and operative findings demonstrated metastases only in those 6 patients (14%) who presented with symptomatic metastases from an unknown primary source. The other 36 women are free of metastases. Preoperative radionuclide bone scans may not be necessary for women with minimal and asymptomatic occult breast cancers.     

Leptomeningeal metastasis: MR imaging

Seven patients with central nervous system neoplasia and leptomeningeal metastases, proved either at initial diagnosis or on follow-up with contrast material-enhanced computed tomography (CT), were evaluated with magnetic resonance (MR) imaging. In two patients, diffuse sulcal enhancement on CT scans was inapparent on T1- or T2-weighted MR images. Likewise, in four patients diffuse cisternal enhancement on CT scans was not identifiable with MR. Nodular or focal cisternal masses were identified with both CT and MR imaging in three patients; in two, however, MR imaging provided less information. Ependymal and subependymal metastases identified with CT (two patients) were indistinguishable on MR images from periventricular abnormalities of radiation therapy and/or hydrocephalus. These findings suggest that leptomeningeal metastasis may be so subtle or inapparent as to be overlooked with MR imaging alone. Thus, CT and MR imaging should be considered complementary techniques for initial diagnosis and follow-up of tumors with a propensity for leptomeningeal metastasis.     

Detection of bone metastases in thyroid cancer patients: bone scintigraphy or 18F-FDG PET?

BACKGROUND: Similar to the situation in other tumour types, it is currently unclear whether fluorodeoxyglucose (FDG) positron emission tomography (PET) is adequate in the detection of bone metastases of thyroid cancer. The purpose of this retrospective study was to evaluate the performance of bone scans in comparison with FDG PET in the detection of bone metastases in patients with differentiated thyroid cancer (DTC). MATERIALS AND METHODS: Twenty-four patients had undergone both FDG PET and bone scans within 6 months because of suspected bone metastases. All scans were re-evaluated using all available additional imaging and clinical data for verification. Scan findings were scored as positive, negative or doubtful. RESULTS: Bone metastases were present in eight of 24 (33%) patients. Only bone scintigraphy but not FDG PET suggested the presence of bone metastases in three patients, all confirmed with magnetic resonance imaging (MRI)/X-ray. Five patients were identified with bone metastases on both bone scan and FDG PET, which was confirmed by computed tomography (CT)/MRI/X-ray in four. Five patients had doubtful findings on bone scans whereas FDG PET scans were negative. MRI showed degenerative disorders in two of five and was normal in two. Eleven patients had both a negative bone scan and FDG PET scan. CONCLUSION: In three of eight (38%) thyroid cancer patients bone metastases were only identified on bone scans. Therefore, bone scans are still valuable in detecting bone metastases in patients with DTC and can not be replaced by FDG PET.     

Intraparenchymal brain metastases: MR imaging versus contrast-enhanced CT

Prospective and retrospective studies of 75 patients were performed to assess the sensitivities of magnetic resonance (MR) imaging and computed tomography (CT) in the evaluation of suspected intraparenchymal brain metastases. The findings on MR images were equivalent to those on CT scans in 49 of the 75 patients; the remaining findings were discordant in 26 patients, and neither MR imaging nor CT was consistently superior. MR imaging demonstrated more metastases in nine of these 26 patients. However, contrast material-enhanced CT scans were superior in lesion depiction in eight of the 26 patients. Large enhanced lesions that were nearly isointense on MR images were seen well on CT scans. In several cases in which results were discordant, gadolinium-diethylenetriaminepentaacetic acid (DTPA)-enhanced MR images were obtained, and this agent behaved similarly to iodinated contrast agents. If indicated clinically, such as before surgery for a single metastasis, the authors perform both MR imaging and contrast-enhanced CT. Gd-DTPA-enhanced MR imaging may prove to be the method of choice for depiction of intraparenchymal metastases.     

Imaging manifestations of spinal fractures in ankylosing spondylitis

BACKGROUND AND PURPOSE: Spinal fractures in ankylosing spondylitis (AS) were difficult to diagnose before CT and MR imaging were available. The purpose of our investigation was to characterize spinal fractures and determine the value of different imaging modalities in AS. METHODS: Twelve successive cases of spinal fractures were identified in MR imaging files of AS patients. Conventional radiographs were available for 12, CT scans for 7, and 3D-CT scans for 4. We carefully reviewed clinical histories and imaging presentations. RESULTS: Fractures were found in the cervical spine in 3 patients and in the thoracolumbar spine in 9. The 3 columns of the spine were involved in 11 patients. A routine 4-mm axial CT was not enough to demonstrate all fractures and ligament tears. The sensitivities of 3D-CT scans for demonstration of the following problems were similar to that of MR imaging and were better than that of conventional radiographs: tearing of the posterior longitudinal ligament, the thoracic spinous process fracture, and the facet fracture. MR imaging depicted these following findings that usually were not shown on conventional radiographs or 3D-CT scans: cord deformity, soft tissue disruption, and ligament tears in the posterior column. MR imaging also showed avascular necrosis and occult fractures better than conventional radiographs or CT scans. CONCLUSIONS: MR imaging shows abnormalities in AS that may not be clear or even detectable by using other imaging methods. With the capability to show lesions in the posterior column, MR imaging can serve to evaluate AS patients with spinal fracture for the possibility of 3-column involvement.     

Bone scan update

The radionuclide bone scan is one of the most commonly performed pediatric nuclear medicine procedures. Bone scintigraphy is used as the diagnostic procedure of choice for diagnosis of bone and soft-tissue infection and can aid in the diagnosis of occult trauma without radiographic findings. There is a complimentary role for bone scintigraphy in the assessment of a child with suspected nonaccidental injury. The use of bone scan in a child with unexplained bone pain or limp may provide a diagnosis that could be related to trauma, tumor, or inflammation. A negative bone scan can help relieve concern for significant pathology. Bone scans in children require careful attention to technique to obtain high-quality diagnostic images. Routine whole-body imaging, magnification, additional views, and the use of single-photon emission computed tomography also are a routine part of this examination in children. Correlation with conventional radiographs is mandatory, and the judicious use of hybrid imaging with the addition of computed tomography may further improve diagnostic acumen, confidence and accuracy. New radiopharmaceuticals such as fluorine-18 may also play a role in changing techniques for pediatric bone scintigraphy.