In vivo proton spectroscopy of giant cell tumor of the bone

Quantitative Musculoskeletal Tumor Imaging

The role of quantitative magnetic resonance imaging (MRI) and positron emission tomography/computed tomography (PET/CT) techniques continues to grow and evolve in the evaluation of musculoskeletal tumors. In this review we discuss the MRI quantitative techniques of volumetric measurement, chemical shift imaging, diffusion-weighted imaging, elastography, spectroscopy, and dynamic contrast enhancement. We also review quantitative PET techniques in the evaluation of musculoskeletal tumors, as well as virtual surgical planning and three-dimensional printing.

Proton MR spectroscopy in characterization of focal bone lesions of peripheral skeleton

Background

The aim of our study was to determine the value of single-voxel proton MR spectroscopy (1HMRS) in distinguishing benign from malignant focal bone lesions in the peripheral skeleton. MRI and 1HMRS was performed in 50 focal lesions (> 1 cm size) detected on radiographs of peripheral skeleton.1HMRS was performed at 1.5 T with TE of 144 ms with automatic shimming and water suppression. Qualitative analysis for a discrete choline peak at 3.2 ppm was done. Significance of the presence of choline peak on 1HMRS in distinguishing benign from malignant lesions was calculated using histopathology as a gold standard. Chi-square test was used and p value < 0.05 was considered significant.

Results

Forty-one benign and 9 malignant lesions were confirmed by histopathological results. Amongst malignant lesions, choline peak was positive in all but 1 case of low-grade lymphoma. MR spectra of 11 benign lesions showed the presence of choline peak. All 7 benign giant cell tumors (GCT) were positive for choline peak. The sensitivity, specificity, PPV, NPV of proton MR spectroscopy in differentiating benign from malignant lesions were 87.5%,71%,38.8%, and 96.4% respectively. p value was significant (< 0.05).

Conclusion

1HMRS in focal bone lesions can help in the differentiation of malignant from benign musculoskeletal tumors. Although some benign lesions may show false-positive result, absence of choline peak is a reliable reassurance against malignancy. GCT is an exception amongst benign bone tumors as it consistently shows the presence of choline peak on 1HMRS.

MRI biomarkers in osseous tumors

Although radiography continues to play a critical role in osseous tumor assessment, there have been remarkable advances in cross-sectional imaging. MRI has taken a lead in this assessment due to high tissue contrast and spatial resolution, which are well suited for bone lesion assessment. More recently, although somewhat lagging other organ systems, quantitative parameters have shown promising potential as biomarkers for osseous tumors. Among these sequences are chemical shift imaging (CSI), apparent diffusion coefficient (ADC), and intravoxel incoherent motion (IVIM) from diffusion-weighted imaging (DWI), quantitative dynamic contrast enhanced (DCE)-MRI, and magnetic resonance spectroscopy (MRS). In this article, we review the background and recent roles of these quantitative MRI biomarkers for osseous tumors. Level of Evidence: 3 Technical Efficacy Stage: 3 J. MAGN. RESON. IMAGING 2019. J. Magn. Reson. Imaging 2019;50:702-718.

Characterisation of musculoskeletal tumours by multivoxel proton MR spectroscopy

OBJECTIVE

The purpose of this study is to evaluate the role of multi-voxel proton MR spectroscopy in differentiating benign and malignant musculoskeletal tumours in a more objective way and to correlate the MRS data parameters with histopathology.

METHODS AND MATERIALS

A hospital-based prospective study was carried out comprising 42 patients who underwent MRI examinations from 1 July 2013 to 30 June 2014. After routine sequences, single-slice multi-voxel proton MR spectroscopy was included at TE-135 using the PRESS sequence. The voxel with the maximum choline/Cr ratio was used for analysis of data in 32 patients. The strength of association between the MR spectroscopy findings and the nature of tumour and histopathological grading were assessed.

RESULTS

Of the 42 patients, the MR spectra were not of diagnostic quality in 10. In the remaining 32 patients, 12 (37.5%) had benign and 20 (62.5%) malignant tumours. The mean choline/Cr ratio was 6.97 ± 5.95 (SD) for benign tumours and 25.39 ± 17.72 (SD) for malignant tumours. In our study statistical significance was noted between the choline/Cr ratio and the histological nature of musculoskeletal tumours (p = 0.002) assessed by unpaired t-test. The choline/Cr ratio and histological grading were also found to be significant (p = 0.001) when assessed by one-way ANOVA test.

CONCLUSIONS

Multi-voxel MR spectroscopy showed a higher choline/Cr ratio in malignant musculoskeletal tumours than in benign ones (p = 0.002). The choline/Cr ratio and histological grading of musculoskeletal tumours also showed statistical significance (p = 0.001).

1H NMR metabolomic signatures related to giant cell tumor of the bone

¹H NMR metabolomic profiling for giant cell tumor of the bone.

The role of magnetic resonance imaging in the evaluation of bone tumours and tumour-like lesions

Bone tumours and tumour-like lesions are frequently encountered by radiologists. Although radiographs are the primary screening technique, magnetic resonance imaging (MRI) can help narrow the differential or make a specific diagnosis when a lesion is indeterminate or shows signs of aggressiveness. MRI can extend the diagnostic evaluation by demonstrating several tissue components. Even when a specific diagnosis cannot be made, the differential diagnosis can be narrowed. MRI is superior to the other imaging modalities in detecting bone marrow lesions and tumoral tissue (faint lytic/sclerotic bone lesions can be difficult to visualise using only radiographs). Contrast-enhanced MRI can reveal the most vascularised parts of the tumour and MRI guidance makes it possible to avoid biopsing necrotic areas. MRI is very helpful in local staging and surgical planning by assessing the degree of intramedullary extension and invasion of the adjacent physeal plates, joints, muscle compartments and neurovascular bundles. It can be used in assessing response to neoadjuvant therapy and further restaging. The post-therapeutic follow-up should also be done using MRI. Despite the high quality of MRI, there are a few pitfalls and limitations of which one should be aware. Applications of MRI in bone tumours will probably continue to grow as new sequences are further studied.

TEACHING POINTS

• When a lesion is indeterminate or shows signs of aggressiveness, MRI is indicated. • When MRI does not lead to a diagnosis, biopsy is indicated. • MRI is superior to the other imaging modalities in detecting bone marrow lesions. • MRI is very helpful in local staging and surgical planning. • MRI is used in assessing the response to neoadjuvant therapy, restaging and post-therapeutic follow-up.

Musculoskeletal tumors: how to use anatomic, functional, and metabolic MR techniques

Although the function of magnetic resonance (MR) imaging in the evaluation of musculoskeletal tumors has traditionally been to help identify the extent of disease prior to treatment, its role continues to evolve as new techniques emerge. Conventional pulse sequences remain heavily used and useful, but with the advent of chemical shift imaging, diffusion-weighted imaging, perfusion imaging and MR spectroscopy, additional quantitative metrics have become available that may help expand the role of MR imaging to include detection, characterization, and reliable assessment of treatment response. This review discusses a multiparametric approach to the evaluation of musculoskeletal tumors, with a focus on the utility and potential added value of various pulse sequences in helping establish a diagnosis, assess pretreatment extent, and evaluate a tumor in the posttreatment setting for recurrence and treatment response.

Imaging review of skeletal tumors of the pelvis--part I: benign tumors of the pelvis

The osseous pelvis is a well-recognized site of origin of numerous primary and secondary musculoskeletal tumors. The radiologic evaluation of a pelvic lesion often begins with the plain film and proceeds to computed tomography (CT), or magnetic resonance imaging (MRI) and possibly biopsy. Each of these modalities, with inherent advantages and disadvantages, has a role in the workup of pelvic osseous masses. Clinical history and imaging characteristics can significantly narrow the broad differential diagnosis for osseous pelvic lesions. The purpose of this review is to familiarize the radiologist with the presentation and appearance of some of the common benign neoplasms of the osseous pelvis and share our experience and approach in diagnosing these lesions.

Proton MR spectroscopy in metabolic assessment of musculoskeletal lesions

OBJECTIVE

The purposes of this review are to describe the principles and method of MR spectroscopy, summarize current published data on musculoskeletal lesions, and report additional cases that have been analyzed with recently developed quantitative methods.

CONCLUSION

Proton MR spectroscopy can be used to identify key tissue metabolites and may serve as a useful adjunct to radiographic evaluation of musculoskeletal lesions. A pooled analysis of 122 musculoskeletal tumors revealed that a discrete choline peak has a sensitivity of 88% and specificity of 68% in the detection of malignancy. Modest improvements in diagnostic accuracy in 22 of 122 cases when absolute choline quantification was used encourage the pursuit of development of choline quantification methods.

In vivo 1H MRS for musculoskeletal lesion characterization: which factors affect diagnostic accuracy?

In vivo (1)H MRS is a noninvasive imaging technique for the identification of malignancy. Musculoskeletal lesions vary in their composition, causing field inhomogeneity and magnetic susceptibility effects which may be technical and diagnostic challenges for MRS. This study investigated the factors that affect diagnostic accuracy in the use of MRS for the characterization of musculoskeletal neoplasms. During a 7-year period, 210 consecutive patients with musculoskeletal lesions larger than 1.5 cm in diameter were examined. MRS of a single-voxel point-resolved spectroscopy sequence with TE = 135 ms was undertaken using a 1.5-T scanner. Lesions with a choline signal-to-noise ratio larger than 3.0 were considered to be malignant tumors. The diagnostic accuracy was calculated for all lesions and for subgroups on the basis of lesion type (bone and soft tissue), lesion composition (mixed and solid nonsclerotic), lesion size (≤4, >4-10 and >10 cm), MR scanner (MR scanner 1 and 2) and selected voxel size (≤3, >3-8 and >8 cm(3)). Multivariate logistic regressions were performed to estimate the associations between each factor and diagnostic accuracy. The diagnostic accuracy was 73.3% for all lesions. The accuracy was 54.4% for mixed lesions and 80.4% for solid nonsclerotic lesions (p < 0.001). The diagnostic accuracy was lower for larger lesions [86.8% for lesions of ≤4 cm, 71.6% for lesions of >4-10 cm (p = 0.04) and 63.6% for lesions of >10 cm (p = 0.007)]. There was no difference in diagnostic accuracy for bone versus soft-tissue lesions or as a function of MR scanner or voxel size. By the use of multivariate logistic regression, a solid nonsclerotic lesion was 3.15 times (95% confidence interval, 1.59-6.27) more likely than a mixed lesion to have a diagnosis (p = 0.001). MRS can be used to characterize musculoskeletal lesions, particularly solid nonsclerotic lesions.

Study of single voxel 1H MR spectroscopy of bone tumors: differentiation of benign from malignant tumors

OBJECTIVE

To evaluate the clinical application of single voxel (1)H MRS in the discrimination of benign and malignant bone tumors.

MATERIALS AND METHODS

Eighty-three patients (64 male, 19 female), presenting with a bone tumor, were examined on a 1.5 T MRI scanner. Using pathological results as a gold standard, there were 34 benign and 49 malignant tumors. After plain MRI scans, a 3D fast SPGR sequence was used for dynamic contrast-enhanced scanning. Dynamic images were transferred to the workstation, where the region of maximal enhancement was identified for prescription of the (1)H MRS sequence. Single-voxel (1)H MRS was then performed with the probe-p sequence, TR/TE = 1500/110 ms, VOI ranging from 14.4 mm × 7.3mm × 20.2mm to 27.9 mm × 25.5 mm × 20.1 mm, automatic shimming and water suppression, 15 min post-contrast. For control purposes, the 3rd lumbar spine vertebral body of six patients having lumbar disc herniation (LDH) without systemic disease was examined with (1)H MRS of normal bone marrow. The static contrast enhancement scan was used for these LDH patients. Conversion of raw MR signal to an MR spectrum was performed using SAGE 7. Cho/Lip (choline/lipids) peak height ratios were calculated. ROC curve analysis was used to determine the cut-off of Cho/Lip ratio for discrimination.

RESULTS

For malignant tumors, one resonance at 3.30-3.19 ppm attributed to choline and another at 1.14-1.55 ppm attributed to lipid were detected. With normal bone marrow and most benign tumors, no choline signal was detected. Choline was only found in six benign lesions. With a threshold for Cho/Lip peak height ratio of 0.2, the area under ROC curve was 0.819. The corresponding sensitivity and specificity of (1)H MRS were 76% and 88%.

CONCLUSIONS

Single voxel (1)H MRS can help in discriminating benign and malignant bone tumors.

A feasibility study of quantitative molecular characterization of musculoskeletal lesions by proton MR spectroscopy at 3 T

OBJECTIVE

The purpose of this study is to establish the feasibility and potential value of measuring the concentration of choline-containing compounds by proton MR spectroscopy (MRS) in musculoskeletal lesions at 3 T.

SUBJECTS AND METHODS

Thirty-three subjects with 34 musculoskeletal lesions (four histologically proven malignant, 13 histologically proven benign or proven benign by follow-up analysis, and 17 posttreatment fibrosis with documented stability for 6-36 months) underwent single-voxel 3-T MRS studies. In each case, both water-suppressed and water-unsuppressed scans were obtained. The quality of the scans was recorded as excellent, adequate, or nondiagnostic, and the choline concentration was measured using water as the internal reference. The choline concentrations of benign and malignant lesions were compared using the Mann-Whitney test.

RESULTS

Spectral quality was excellent in 26 cases, adequate in four cases, and nondiagnostic in four cases. For malignant lesions (three sarcomas), the choline concentrations were 1.5, 2.9, and 3.8 mmol/kg, respectively. For five benign lesions (two neurofibromas, two schwannomas, and one enchondroma), the choline concentrations were 0.11, 0.28, 0.13, 0.8, and 1.2 mmol/kg, respectively. For seven benign lesions (two hematomas, two bone cysts, one lipoma, one giant cell tumor, and one pigmented villonodular synovitis), the spectra showed negligible choline content. For three posttreatment fibrosis cases, the choline concentration range was 0.2-0.4 mmol/kg. For the remaining 12 posttreatment fibrosis cases, the spectra showed negligible choline content. Average choline concentrations were different for malignant and benign lesions (2.7 vs 0.5 mmol/kg; p = 0.01).

CONCLUSION

The measurement of choline concentration within musculoskeletal lesions by MRS is feasible using an internal water-referencing method at 3 T and has potential for characterizing lesions for malignancy.

Quantification of muscle choline concentrations by proton MR spectroscopy at 3 T: technical feasibility

OBJECTIVE

The quantification of choline in musculoskeletal tissues has several potential uses, including characterizing malignancy, but has not been previously achievable. We present a method of measuring the absolute concentration of choline by proton MR spectroscopy (MRS) in skeletal muscle at 3 T.

MATERIALS AND METHODS

At 3 T, choline measurements were performed in phantoms and healthy volunteers using proton MRS (point-resolved spectroscopy sequence [PRESS]; TR/TE, 2,000/135). In vitro choline concentrations were measured in three phantom solutions (10, 5, 1.25 mmol). Choline T1 and T2 relaxation times were measured in the muscles of five healthy subjects. In vivo choline concentrations were measured using water as an internal reference and average T1 and T2 relaxation times in 20 muscle locations (quadriceps, hamstring, adductor) of seven healthy subjects (four men, three women). Descriptive statistics are reported.

RESULTS

In vitro, the average measured choline concentrations of the 10-, 5-, and 1.25-mmol solutions were 9.91, 5.03, and 1.22 mmol, respectively. In vivo, the average T1 and T2 relaxation times of choline were 1,372+/-57 (SD) and 134+/-11 milliseconds, respectively. The average choline concentrations in the quadriceps and hamstring muscles were 10.0+/-0.4 (SD) and 8.0+/-2.9 mmol/kg. Interindividual variation existed in the choline concentrations (quadriceps range, 6.7-13 mmol/kg), but there was little variation by patient sex.

CONCLUSION

In the musculoskeletal system, the measurement of choline concentration by proton MRS at 3 T is feasible using water as an internal reference. These data provide a quantitative basis for future investigations of metabolite concentrations in normal and diseased musculoskeletal tissues.