Follow-up of musculoskeletal tumours 2. Metastatic disease

Both the prognosis and the morbidity of a patient with a primary malignant musculoskeletal tumour have improved over the past 25 years due to the advent of adjuvant chemotherapy and limb-sparing surgery. This has important implications for the role of imaging at the time of initial diagnosis and during follow-up. This pictorial essay reviews the imaging and pitfalls in the interpretation of musculoskeletal sarcoma metastases using a variety of radiological techniques. The optimal imaging strategy will be stressed. Received: 29 January 1998; Revision received: 13 May 1998; Accepted: 14 May 1998     

Recent advances in magnetic resonance imaging of musculoskeletal tumours

Magnetic resonance imaging (MRI) has become the method of choice, where available, for the evaluation of musculoskeletal neoplasms. Recently, there has been interest and development in a number of areas in this field: (a) gradient-echo (fast-scan) sequences, which may often be substituted for more time-consuming T2-weighted sequences, are useful as localizing sequences and play an important role in intravenous contrast-enhanced scanning; (b) magnetic resonance contrast agents (e.g., gadolinium) improve delineation of tumours on static imaging and may help in estimating tumour aggressiveness with dynamic imaging; (c) STIR (short inversion time inversion recovery) increases lesion conspicuity; (d) spectroscopy, still an investigational area, may help in evaluating tumour response to chemotherapy and radiotherapy.     

原发性骨肌肿瘤的PET/CT应用进展

PET/CT的融合成像对众多实性肿瘤的分期及治疗有重要价值。然而,该技术对骨肌恶性肿瘤的评估尚未实现常规临床应用。采用MR和CT的体层成像技术进行评估     

PET/CT in primary musculoskeletal tumours: a step forward

Hybrid imaging with combined positron emission tomography/computed tomography (PET/CT) plays an important role in the staging and management of a wide variety of solid tumours. However, its use in the evaluation of musculoskeletal malignancy has not yet entered routine clinical practice. Cross-sectional imaging with magnetic resonance imaging (MR) and computed tomography have well-established roles but there is increasing evidence for the selective use of PET/CT in the management of these patients. The aims of this article are to review the current evidence and clinical applications of PET/CT in primary musculoskeletal tumours and discuss potential future developments using novel PET tracers and integrated PET/MR.     

PET imaging of musculoskeletal tumours with fluorine-18 alpha-methyltyrosine: comparison with fluorine-18 fluorodeoxyglucose PET

Fluorine-18 labelled alpha-methyltyrosine (FMT) was developed for positron emission tomography (PET) imaging, and its potential for clinical application in patients with brain tumours has been demonstrated. This is the first trial to compare FMT with 18F-fluoro-2-deoxy-D-glucose (FDG) for the evaluation of musculoskeletal tumours. Seventy-five patients were examined with both FMT- and FDG-PET within a 2-week period. Imaging findings were visually inspected in conjunction with computed tomography and/or magnetic resonance imaging, and standardized uptake values (SUVs) for both FMT and FDG in lesions were also generated and compared with histological findings. A significant correlation between FMT and FDG SUVs was found for all lesions (r=0.769, P<0.0001), and mean values for malignant tumours were significantly higher than those for benign lesions in both FMT- and FDG-PET. The diagnostic sensitivities and specificities for malignancy were 72.7% and 84.9%, respectively, using FMT with a cut-off SUV of 1.2, and 72.7% and 66.0%, respectively, using FDG with a cut-off SUV of 1.9. The resultant accuracy with FMT was 81.3%, higher than that for FDG (68.0%), and the difference with respect to specificity was significant (chi2cal=5.0625, P<0.05). On the other hand, while a significant correlation was found between malignant tumour grade and SUV with both FMT- (rho=0.656) and FDG-PET (rho=0.815), only the latter demonstrated significant differences among grades I, II and III. FMT and FDG for PET appear equally effective at detecting musculoskeletal tumours. In evaluating musculoskeletal tumours, FMT may be superior to FDG in the differentiation between benign and malignant tumours, while FDG may be the better choice for non-invasive malignancy grading.     

Review of non-positron emission tomography functional imaging of primary musculoskeletal tumours: beyond the humble bone scan

Bone and soft tissue tumours are rare neoplasms. There are five major roles of imaging in the management of primary musculoskeletal tumours, that is, to differentiate between benignity and malignancy, to evaluate for local tumour extension, to screen for metastases, to judge the effect of chemotherapy, and to monitor for recurrence. To accomplish this, multiple modalities are required because no single examination is able to complete all these tasks. These modalities include plain radiography, CT, MRI, conventional nuclear medicine as well as positron emission tomography (PET) imaging. Elsewhere, PET imaging has been discussed at length, because it is likely to be superior in the assessment of bone and soft tissue tumours over conventional nuclear medicine procedures. However, conventional nuclear medicine may be of value when PET is unavailable. In this review, an overview of anatomical imaging will be given and the role of non-PET functional imaging will be discussed in detail. A variety of illustrative cases will be presented.     

99mTc-tetrofosmin scintigraphy in musculoskeletal tumours: the relationship between P-glycoprotein expression and tetrofosmin uptake in malignant lesions

The aims of this study were to assess the role of (99m)Tc-tetrofosmin scintigraphy in the diagnosis of malignant vs. benign musculoskeletal tumours and to determine the relationship between P-glycoprotein expression and tetrofosmin uptake in malignant lesions. Forty-six patients (32 malignant, 14 benign) with various musculoskeletal lesions were studied. Each patient underwent (99m)Tc-methylene diphosphonate three-phase bone scanning initially. At least 2 days later, dynamic and static (99m)Tc-tetrofosmin scans were obtained. The tetrofosmin scans were evaluated by visual and quantitative analysis. The count ratio of the lesion to the contralateral normal area (uptake ratio, UR) was calculated from the region of interest drawn on the tetrofosmin scan. The lesions were then resected by open biopsy to obtain a histopathological diagnosis. P-glycoprotein levels were determined immunohistochemically in 22 of 32 malignant lesions. A significant difference between the mean UR values of benign and malignant lesions was found (1.36 +/- 0.47 vs. 3.35 +/- 2.08, P = 0.000). Visual analysis showed an accuracy of 85%, and the accuracy of the quantitative analysis was 87% with the threshold level of UR as 1.76. When perfusion findings were added to the evaluation criteria, the accuracies of visual and quantitative analysis were increased to 87% and 89%, respectively. The relationship between the levels of P-glycoprotein and the UR values of tetrofosmin was not statistically significant (r = -0.235, P = 0.2). In addition, the mean UR value of the patients with P-glycoprotein expression was not statistically different from that of the patients without P-glycoprotein expression (3.01 +/- 1.48 vs. 4.27 +/- 2.90, P = 0.297). In conclusion, visually significant tetrofosmin uptake and increased perfusion in a musculoskeletal lesion strongly suggest that the lesion is malignant (positive predictive value, 96%). P-glycoprotein expression was not found to be a major factor interfering with 30 min tetrofosmin uptake in a malignant musculoskeletal lesion. However, the relatively high false-negative rate among negative results (28%) limits the value of (99m)Tc-tetrofosmin scintigraphy as a single diagnostic tool in differentiating between benign and malignant musculoskeletal tumours.     

The value of intratumoral heterogeneity of 18F-FDG uptake to differentiate between primary benign and malignant musculoskeletal tumours on PET/CT

Objective:

The cumulative standardized uptake value (SUV)–volume histogram (CSH) was reported to be a novel way to characterize heterogeneity in intratumoral tracer uptake. This study investigated the value of fluorine-18 fludeoxyglucose (¹⁸F-FDG) intratumoral heterogeneity in comparison with SUV to discriminate between primary benign and malignant musculoskeletal (MS) tumours.

Methods:

The subjects comprised 85 pathologically proven MS tumours. The area under the curve of CSH (AUC-CSH) was used as a heterogeneity index, with lower values corresponding with increased heterogeneity. As 22 tumours were indiscernible on ¹⁸F-FDG positron emission tomography, maximum standardized uptake value (SUV_max), mean standardized uptake value (SUV_mean) and AUC-CSH were obtained in 63 positive tumours. The Mann–Whitney U test and receiver operating characteristic (ROC) analysis were used for analyses.

Results:

The difference between benign (n = 35) and malignant tumours (n = 28) was significant in AUC-CSH (p = 0.004), but not in SUV_max (p = 0.168) and SUV_mean (p = 0.879). The sensitivity, specificity and accuracy for diagnosing malignancy were 61%, 66% and 64% for SUV_max (optical threshold value, >6.9), 54%, 60% and 57% for SUV_mean (optical threshold value, >3) and 61%, 86% and 75% for AUC-CSH (optical threshold value, ≤0.42), respectively. The area under the ROC curve was significantly higher in AUC-CSH (0.71) than SUV_max (0.60) (p = 0.018) and SUV_mean (0.51) (p = 0.005).

Conclusion:

The heterogeneity index, AUC-CSH, has a higher diagnostic accuracy than SUV analysis in differentiating between primary benign and malignant MS tumours, although it is not sufficiently high enough to obviate histological analysis.

Advances in knowledge:

AUC-CSH can assess the heterogeneity of ¹⁸F-FDG uptake in primary benign and malignant MS tumours, with significantly greater heterogeneity associated with malignant MS tumours. AUC-CSH is more diagnostically accurate than SUV analysis in differentiating between benign and malignant MS tumours.     

Imaging of musculoskeletal trauma

Many significant papers in the current literature on musculoskeletal trauma deal with new advances in MR imaging. The increasing role of MR imaging in the evaluation of traumatic lesions of the knee explains the number of papers dealing with the differentiation of true traumatic lesions from normal variants or clinically insignificant changes. Other contributions on musculoskeletal trauma deal with more conventional imaging techniques, such as arthrography, plain films, and even complex tomography.     

Staging of musculoskeletal neoplasms

This review reports the natural evolution of benign and malignant lesions of connective tissue derivation that led to the staging system, the system for both benign and malignant lesions, its articulation with surgical treatment and early experience with its use.From: Uhthoff HK (ed) Current concepts of diagnosis and treatment of bone and soft tissue tumors. Springer, Berlin Heidelberg New York Tokyo 1984, p 1     

Imaging of musculoskeletal infections

Imaging studies play a critical role in the diagnosis and management of musculoskeletal infections in children. Conventional radiography is usually the first imaging study performed with other imaging modalities as needed. Ultrasound is helpful in detecting joint effusions and fluid collections in the soft tissue and subperiosteal regions, and may guide localization for aspiration or drainage. CT can demonstrate osseous and soft tissue abnormalities and is ideal for detecting gas in soft tissues. Nuclear scintigraphy and MR imaging are valuable because of their high sensitivity. Scintigraphy is particularly useful in identifying multifocal involvement, which is an important consideration in neonatal osteomyelitis and CRMO. MR imaging provides accurate information on both the soft tissues and bones and is our imaging study of choice for evaluating the local extent of musculoskeletal infections.     

Low-field musculoskeletal MRI

Since it was first introduced in the field of medical imaging in the early 1980s, MRI has become essential for the diagnosis and treatment of musculoskeletal conditions. Most imaging in the United States is performed on high-field (>1.0T), whole-body scanners. However, for reasons discussed below, imaging at low (<0.5T) and medium (0.5-1.0T) field strengths using small, low-cost, easily installed scanners in imaging centers and physicians' offices is gaining increasing popularity. Such scanners can be very useful for imaging the upper and lower extremities, from the shoulder to the fingers and the hips to the toes. In this review we provide an overview of the different available extremity scanners and their advantages and disadvantages, briefly review the literature regarding their use, and discuss our experience in using low-field extremity scanners to evaluate joints.     

Unique musculoskeletal trauma

Pelvic and lower extremity insufficiency fracture in the osteoporotic individual, an approach to posttraumatic wrist instabilities, and certain upper and lower extremity pediatric fractures are discussed. The case material concentrates upon the clinical/radiographic recognition of subtle trauma and the multimodality approach to these unique traumatic musculoskeletal conditions. The impact that computed tomography has had on some of these traumatic conditions also is presented.     

Embolization of musculoskeletal tumors

Transarterial embolization should be considered in the treatment algorithm of primary or secondary bone tumors. Specific benefit is present where there is a high risk of bleeding at surgery, where there is spinal involvement and neural encroachment, where active bleeding is present, or in awkward surgical locations where prolonged surgery is anticipated.     

Image-guided musculoskeletal biopsy

Image guidance allows safe passage of needles, often into small and otherwise inaccessible lesions, and into the portions of the lesion most likely to yield useful samples, while avoiding damage to important structures. This article hopes to provide a useful guide to image-guided musculoskeletal biopsy for radiologists in practice and in training.     

Trauma musculoskeletal ultrasound

Musculoskeletal ultrasound has benefited from the recent exponential improvement in probe technology to the extent that it is now the imaging modality of choice for many peripheral soft tissue injuries. This article aims to highlight these areas and encourage the use of this modalilty in these scenarios rather than the currently more favoured magnetic resonance imaging scan.