Correlating metabolic activity on 18F-FDG PET/CT with histopathologic characteristics of osseous and soft-tissue sarcomas: a retrospective review of 136 patients

Molecular Imaging in Soft-tissue Sarcoma: Evolving Role of FDG PET

Soft tissue sarcomas are a rare and heterogenous group of tumors that account for 2% of all cancer-related deaths. Molecular imaging with FDG PET can offer valuable metabolic information to help inform clinical management of soft tissue sarcomas that is unique and complementary to conventional diagnostic imaging techniques. FDG PET imaging often correlates with tumor grade, can help guide biopsy, and frequently detects additional sites of disease compared to conventional imaging in patients being considered for definitive or salvage therapy. Traditional size-based evaluation of treatment response is often inadequate in soft tissue sarcoma and changes in metabolic activity can add significant value to interim and end of treatment imaging for high-grade sarcomas. FDG PET can be used for detection of recurrence or malignant transformation and thus play a vital role in surveillance. This article reviews the evolving role of FDG PET in initial diagnosis, staging, treatment response assessment, and restaging. Further studies on the use of FDG PET in soft sarcoma are needed, particularly for rare histopathologic subtypes.

Positron Emission Tomography/Computed Tomography Transformation of Oncology: Musculoskeletal Cancers

The past 25 years have seen significant growth in the role of positron emission tomography/computed tomography (PET/CT) in musculoskeletal oncology. Substantiative advances in technical capability and image quality have been paralleled by increasingly widespread clinical adoption and implementation. It is now recognized that PET/CT is useful in diagnosis, staging, prognostication, response assessment, and surveillance of bone and soft tissue sarcomas, often providing critical information in addition to conventional imaging assessment. As individualized, precision medicine continues to evolve for patients with sarcoma, PET/CT is uniquely positioned to offer additional insight into the biology and management of these tumors.

Tata Memorial Centre Evidence Based Use of Nuclear medicine diagnostic and treatment modalities in cancer

ABSTRACT

PET/CT and radioisotope therapy are diagnostic and therapeutic arms of Nuclear Medicine, respectively. With the emergence of better technology, PET/CT has become an accessible modality. Diagnostic tracers exploring disease-specific targets has led the clinicians to look beyond FDG PET. Moreover, with the emergence of theranostic pairs of radiopharmaceuticals, radioisotope therapy is gradually making it's way into treatment algorithm of common cancers in India. We therefore would like to discuss in detail the updates in PET/CT imaging and radionuclide therapy and generate a consensus-driven evidence based document which would guide the practitioners of Oncology.

Skin Malignancies: Imaging Review with Radiologic-Histopathologic Correlation

Skin malignancies are commonly encountered as primary or incidental findings. Neoplasms that affect the skin include primary (basal cell carcinoma, squamous cell carcinoma, melanoma, and Merkel cell carcinoma) and secondary (mesenchymal neoplasms, lymphoma, and metastases) tumors. Imaging provides valuable anatomic information (tumor size, depth of involvement, presence of distant metastasis, and data for guiding biopsy) and functional information (metabolic activity and sentinel node mapping data). This information, in addition to biopsy results, improves the histopathologic characterization of tumors and treatment planning. Various histopathologic types of the same entity exhibit different biologic behavior and have different imaging features. Familiarity with the multimodality imaging features, histopathologic characteristics, and various modes of dissemination (direct invasion; perineural, lymphatic, and hematogenous spread) of the most common skin malignancies helps radiologists narrow the differential diagnosis in clinical practice. ©RSNA, 2023 Supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center.

Progressive abdominal pain with acute exacerbation due to retroperitoneal follicular dendritic cell sarcoma: a case report with targeted genomic sequencing analysis

BACKGROUND

Follicular dendritic cell sarcoma (FDCS) is a rare malignancy that arises from follicular dendritic cells and typically presents as a slow-growing painless mass without specific symptoms. Here we report an unusual case of a 55-year-old female with retroperitoneal FDCS who presented with progressive abdominal pain onset and acute exacerbation.

METHODS

On CTA, a middle-upper abdominal mass (58*40 mm) was shown with multiple enlarged lymph nodes. After en-bloc resection of the tumor, the patient recovered completely from her symptoms and was discharged without complication. One month later, the patient returned for follow-up and the relevant tests were completed.

RESULTS

In this case, CA724 elevated significantly and seemed to be associated with tumor progression. The results of positron emission tomography/computed tomography (PET/CT) and radiological examinations, including magnetic resonance imaging (MRI) and computed tomography angiography (CTA), were discussed to improve our understanding of diagnostic tools on FDCS. Targeted genomic sequencing analysis revealed three novel gene mutations, EPHA3 (nonsense mutation), DDR2 (SNV), and BIRC3 (InDel).

CONCLUSION

We reported an unusual case of retroperitoneal FDCS with acute exacerbated abdominal pain. The interpretations of CA724, PET/CT, as well as imaging results deserve further investigation in FDCS. Genomic sequencing revealed three novel gene mutations in FDCS, including EPHA3 (nonsense mutation), DDR2 (SNV), and BIRC3 (InDel).

Biology and Management of High-Grade Myxofibrosarcoma: State of the Art and Future Perspectives

Myxofibrosarcoma (MFS) is one of the most common adult soft tissue sarcomas, typically arising in the extremities. Histologically, MFS is classified into three grades: low, intermediate, and high. Histological grades correlate with distant metastases and tumor-associated mortality. The diagnosis of MFS is challenging due to a lack of well-characterized immunohistochemical markers. High-grade MFS displays highly complex karyotypes with multiple copy number alterations. Recent integrated genomic studies have shown the predominance of somatic copy number aberrations. However, the molecular pathogenesis of high-grade MFS remains poorly understood. The standard treatment for localized MFS is surgical resection. The systemic treatment options for advanced disease are limited. This review provides an updated overview of the clinical and imaging features, pathogenesis, histopathology, and treatment of high-grade MFS.

Fibroblast Activation Protein Inhibitor (FAPI)-PET Imaging in Sarcoma

Advances in histopathologic and molecular genetic subtyping of sarcoma will potentially allow identification of novel diagnostic and therapeutic targets for specific subtypes, but a "pan-sarcoma" target is needed. This article provides an overview on expression of one potential candidate, fibroblast activation protein alpha in soft tissue and bone sarcoma, and the resulting application of 68Ga-FAPI as novel imaging probes in these rare tumor entities. Current preclinical and clinical data on 68Ga-FAPI-PET/CT in sarcomas are summarized. 68Ga-FAPI-PET-CT potentially offers important complementary information to be used in diagnostic work-up, assessment of therapy response, and prognostication of soft tissue and bone sarcomas.

Comparing Apparent Diffusion Coefficient and FNCLCC Grading to Improve Pretreatment Grading of Soft Tissue Sarcoma-A Translational Feasibility Study on Fusion Imaging

Simple Summary

Histological subtype and grading are essential for the planning of soft tissue sarcoma. Pretherapeutic grading based on core needle biopsies is frequently not reliable due to intratumoral heterogeneity. This pilot study assessed the ability of functional radiological imaging to improve histopathological grading. Multiple biopsies were taken from the sarcoma specimens during tumor resection and radiopaque markers were placed. Subsequently, fusion of preoperative magnetic resonance imaging and postoperative computed tomography of the specimen allowed for comparison of histopathological grading and diffusion-weighted imaging. The apparent diffusion coefficient appears to correlate with FNCLCC criteria and may supplement pretreatment assessment and multimodal treatment allocation in soft tissue sarcoma.

Abstract

Histological subtype and grading are cornerstones of treatment decisions in soft tissue sarcoma (STS). Due to intratumoral heterogeneity, pretreatment grading assessment is frequently unreliable and may be improved through functional imaging. In this pilot study, 12 patients with histologically confirmed STS were included. Preoperative functional magnetic resonance imaging was fused with a computed tomography scan of the resected specimen after collecting core needle biopsies and placing radiopaque markers at distinct tumor sites. The Fédération Nationale des Centres de Lutte Contre le Cancer (FNCLCC) grading criteria of the biopsies and apparent diffusion coefficients (ADCs) of the biopsy sites were correlated. Concordance in grading between the specimen and at least one biopsy was achieved in 9 of 11 cases (81.8%). In 7 of 12 cases, fusion imaging was feasible without relevant contour deviation. Functional analysis revealed a tendency for high-grade regions (Grade 2/3 (G2/G3)) (median (range) ± standard deviation: 1.13 (0.78–1.70) ± 0.23 × 10⁻³ mm²/s) to have lower ADC values than low-grade regions (G1; 1.43 (0.64–2.03) ± 0.46 × 10⁻³ mm²/s). In addition, FNCLCC scoring of multiple tumor biopsies proved intratumoral heterogeneity as expected. The ADC appears to correlate with the FNCLCC grading criteria. Further studies are needed to determine whether functional imaging may supplement histopathological grading.

Retroperitoneal and Mesenteric Liposarcomas

Retroperitoneal liposarcomas are a rare entity and are comprised mostly of the well-differentiated and dedifferentiated subtypes. Eight-year survival ranges from 30% to 80% depending on histologic subtype and grade. Surgery is the cornerstone of treatment and compartment resection is the current standard. Mesenteric liposarcomas are extremely rare and comprise more high-grade lesions, with poorer prognosis of 50% 5-year overall survival. They are managed with a similar aggressive surgical approach. This review presents the current management of retroperitoneal and mesenteric liposarcomas.

Immunohistochemical expression and clinicopathological assessment of PD-1, PD-L1, NY-ESO-1, and MAGE-A4 expression in highly aggressive soft tissue sarcomas

Immunotherapy has altered the treatment paradigm for soft tissue sarcomas (STSs). Considering the limited information regarding the clinical significance of immunohistochemical markers in STS, the purpose of this study was to determine the clinical significance of programmed cell death-1 (PD-1), PD ligand-1(PD-L1), New York esophageal squamous cell carcinoma-1 (NY-ESO-1), and melanoma-associated antigen-A4 (MAGE-A4) expression in STSs. Twenty-two patients (median age, 72.5 years) with STSs treated at our hospital were included in this study. The specimens obtained at the time of biopsy were used to perform immunostaining for PD-1, PD-L1, NY-ESO, and MAGE-A4. The rates of PD-1-, PD-L1-, NY-ESO-, and MAGE-A4-positive cells and cases were calculated. The correlations among the positive cell rates of the immunohistochemical markers as well as their correlations with the histological grade, tumor size, or maximum standardized uptake (SUVmax) value were also determined. The average rates of PD-1-, PD-L1-, NY-ESO-, and MAGE-A4-positive cells were 4.39%, 28.0%, 18.2%, and 39.4%, respectively. PD-1-, PD-L1-, NY-ESO-1-, and MAGE-A4- positive cell rates showed weak to strong correlations with the SUVmax value. Thus, PD-1, PD-L1, NY-ESO, and MAGE-A4 expressions might be involved in the aggressive elements of STSs.

Voxel-wise supervised analysis of tumors with multimodal engineered features to highlight interpretable biological patterns

Background

Translation of predictive and prognostic image‐based learning models to clinical applications is challenging due in part to their lack of interpretability. Some deep‐learning‐based methods provide information about the regions driving the model output. Yet, due to the high‐level abstraction of deep features, these methods do not completely solve the interpretation challenge. In addition, low sample size cohorts can lead to instabilities and suboptimal convergence for models involving a large number of parameters such as convolutional neural networks.

Purpose

Here, we propose a method for designing radiomic models that combines the interpretability of handcrafted radiomics with a sub‐regional analysis.

Materials and methods

Our approach relies on voxel‐wise engineered radiomic features with average global aggregation and logistic regression. The method is illustrated using a small dataset of 51 soft tissue sarcoma (STS) patients where the task is to predict the risk of lung metastasis occurrence during the follow‐up period.

Results

Using positron emission tomography/computed tomography and two magnetic resonance imaging sequences separately to build two radiomic models, we show that our approach produces quantitative maps that highlight the signal that contributes to the decision within the tumor region of interest. In our STS example, the analysis of these maps identified two biological patterns that are consistent with STS grading systems and knowledge: necrosis development and glucose metabolism of the tumor.

Conclusions

We demonstrate how that method makes it possible to spatially and quantitatively interpret radiomic models amenable to sub‐regions identification and biological interpretation for patient stratification.

Spectrum of Flurodeoxyglucose Positron Emission Tomography/Computerized Tomography Findings in Tumors and Tumor-Like Conditions of the Musculoskeletal System

Bone and soft-tissue tumors display a wide range of metabolic activity on flurodeoxyglucose positron emission tomography/computerized tomography (FDG PET/CT) imaging due to their varying histopathological features. Several benign tumors show high FDG uptake similar to that seen in malignant lesions and their metabolic characteristics can overlap. Certain benign tumors can potentially undergo malignant transformation and FDG PET/CT can play an important role in detecting malignant change. The intensity of metabolic activity on FDG PET/CT correlates with histological grade of malignant tumors and also acts as a valuable prognostic factor. FDG PET/CT plays an important role in the staging work up of bone and soft-tissue malignancies. It has been found to be superior to conventional imaging techniques primarily for detecting distant metastatic disease. Because of its ability to detect metabolic changes, FDG PET/CT is a very useful in assessing response to treatment. Metabolic response seen on FDG PET is a powerful surrogate marker of histopathological response to chemotherapy. The purpose of this article is to study the variable patterns of FDG uptake in tumors of the musculoskeletal system, describe the clinical utility of FDG PET/CT in predicting malignant change in benign tumors and discuss its role in staging, response assessment, and prognostication of malignant lesions.

PET-CT for the diagnosis and treatment of primary musculoskeletal tumors in Chinese patients - experience from 255 patients in a single center

OBJECTIVE

The current study was carried out to assess the value of positron emission tomography (PET)/CT on the diagnosis and staging of primary musculoskeletal tumors.

METHODS

PET-CT test results and histopathological study reports of all the patients with primary musculoskeletal tumors in our department from January 2006 to July 2015 were retrospectively reviewed. Maximum standardized uptake value (SUVmax) in these PET-CT reports were recorded and analyzed respectively for each type of sarcoma.

RESULTS

A total of 255 patients were included in the final analysis. Sensitivity of SUVmax based diagnosis was 96.6% for primary malignant osseous sarcomas and 91.2% for soft tissue sarcomas. SUVmax of high-grade osseous sarcomas (average 8.4 ± 5.5) was significantly higher (p < 0.001) than low-grade osseous sarcomas (average 3.9 ± 1.8); based on current case series, SUVmax of high-grade soft tissue sarcomas (7.5 ± 5.1) was not significantly different (p = 0.229) from that of low-grade soft tissue sarcomas (5.3 ± 3.7). Significant decrease of SUVmax value after chemotherapy was associated with favorable prognosis in patients with osteosarcoma.

CONCLUSION

Results of the current study indicate that, the SUVmax based application of PET-CT can be a valuable supplementary method to histopathological tests regarding the diagnosis and staging of primary musculoskeletal sarcomas.

ADVANCES IN KNOWLEDGE

SUVmax based application of PET-CT is a highly sensitive method in diagnosis of primary osseous and soft tissue sarcomas in Chinese patients.

Chordoma: 18F-FDG PET/CT and MRI imaging features

OBJECTIVE

Examine the ¹⁸F-FDG PET/CT and MRI imaging characteristics of chordoma.

MATERIALS AND METHODS

Biopsy-proven chordoma with a pre-therapy ¹⁸F-FDG PET/CT from 2001 through 2019 in patients > 18 years old were retrospectively reviewed. Multiple PET/CT and MRI imaging parameters were assessed.

RESULTS

A total of 23 chordoma patients were included (16 M, 7 F; average age of 60.1 ± 13.0 years) with comparative MRI available in 22 cases. This included 13 sacrococcygeal, 9 mobile spine, and one clival lesions. On ¹⁸F-FDG PET/CT, chordomas demonstrated an average SUVmax of 5.8 ± 3.7, average metabolic tumor volume (MTV) of 160.2 ± 263.8 cm³, and average total lesion glycolysis (TLG) of 542.6 ± 1210 g. All demonstrated heterogeneous FDG activity. On MRI, chordomas were predominantly T2 hyperintense (22/22) and T1 isointense (18/22), contained small foci of T1 hyperintensity (17/22), and demonstrated heterogeneous enhancement (14/20). There were no statistically significant associations found between ¹⁸F-FDG PET/CT and MRI imaging features. There was no relationship of SUVmax (p = 0.53), MTV (p = 0.47), TLG (p = 0.48), maximal dimension (p = 0.92), or volume (p = 0.45) to the development of recurrent or metastatic disease which occurred in 6/22 patients over a mean follow-up duration of 4.1 ± 2.0 years.

CONCLUSION

On ¹⁸F-FDG PET/CT imaging, chordomas demonstrate moderate, heterogeneous FDG uptake. Predominant T2 hyperintensity and small foci of internal increased T1 signal are common on MRI. The inherent FDG avidity of chordomas suggests that ¹⁸F-FDG PET/CT may be a useful modality for staging, evaluating treatment response, and assessing for recurrent or metastatic disease.

Does the SUVmax of FDG-PET/CT Correlate with the ADC Values of DWI in Musculoskeletal Malignancies?

Purpose

To evaluate the correlation of maximum standardized uptake values (SUV_max) of ¹⁸F-Fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) with the apparent diffusion coefficient (ADC) of diffusion weighted imaging (DWI) in musculoskeletal malignancies.

Methods

Institutional ethics committee approved this retrospective study. Twenty-seven patients (mean age: 44.85 ± 24.07; 17 men and 10 women) with a total of 29 musculoskeletal tumors underwent both FDG-PET/CT and DWI between January 2017 and March 2020. Region-of-interest (ROI)-based maximal standardized uptake values (SUV_max) of the tumors were measured on FDG-PET/CT images. Two radiologists measured lesions' mean and minimum apparent diffusion coefficient (ADC_mean and ADC_min) using five distinct ROIs on DWI images. Pearson correlation analysis was used to assess the correlation between SUV_max and ADC values.

Results

There were 18 soft tissue tumors (62.1%) and 11 bone tumors (37.9%) with a mean maximum diameter of 9.4 ± 6.2 cm. The mean SUV_max, ADC_mean and ADC_min of the whole lesions were 12.93 ± 9.63, 0.85 ± 0.28 × 10^-3mm²/s and 0.61 ± 0.27 × 10^-3mm²/s, respectively. SUV_max had a weak correlation with tumor maximum diameter (r = 0.378, p = 0.043), whereas ADC_mean and ADC_min had none. There was strong inverse correlation between SUV_max and both ADC_mean (r = -0.616, p < 0.001) and ADC_min (r = -0.638, p < 0.001).

Conclusion

In musculoskeletal tumors, quantitative markers of FDG uptake and diffusion restriction strongly correlate.

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.

Mediastinal liposarcoma masquerading as penetrating aortic ulcer in the descending aorta: a case report

A 56-year-old woman with a history of hypertension and cerebral infarction was admitted to the hospital complaining of progressive and severe chest pain for 1 day. CT scan revealed a descending penetrating ulcer. Accordingly, she underwent an uneventful endovascular repair with a thoracic endograft. One month later the patient presented to our clinic with chest and back pain again. The contrast CT indicated that the periaortic mass grew larger, which interpreted as hematoma resulting from endoleak. But no endoleak was found by angiography. CT-guided needle biopsy was carried out, the histology of the mass revealed a pleomorphic liposarcoma. Liposarcomas are malignant fat-containing tumors derived from mesenchymal cells that typically occur in the extremities and retroperitoneum, mediastinal liposarcoma account for less than 1% in mediastinal malignancies; pleomorphic liposarcoma is the least common liposarcomas. Cases of liposarcoma invading vascular system are seldom, to our knowledge, it is the first case of mediastinal pleomorphic liposarcoma invaded the descending aorta. It is worth mentioning that in the modern endovascular era, the majority of aortic diseases are being repaired by endovascular techniques. When patients with growing periaortic mass post endovascular repair and endograft-related causes have been excluded, the rare possibility of mediastinal liposarcoma should arise as a differential diagnosis. Promptly CT-guided biopsy help establish an early diagnosis.

Longitudinal observation of solitary fibrous tumor translation into malignant pulmonary artery intimal sarcoma

BACKGROUND

Pulmonary artery intimal sarcoma (PAIS) is a rare malignant tumor that was usually misdiagnosed as chronic pulmonary thromboembolism.

CASE PRESENTATION

We previously reported a solitary fibrous tumor in the pulmonary artery presented with acute pulmonary embolism, which was identified by ^99mTc-Galacto-RGD₂ imaging. However, this patient had a recurrence in situ two-year after surgery, post-operative pathology revealed pulmonary artery intimal sarcoma. At one-year post-operation, ¹⁸F-FDG PET/CT was performed for exclusion of tumor metastasis, which showed FDG avid lesion in the T5, T10, and L5 vertebral bodies, as well as in bilateral ilium and right ischium.

CONCLUSIONS

This is the first longitudinal observation of a solitary fibrous tumor (SFT) development into a pulmonary artery intimal sarcoma (PAIS) and presented with multiple bone metastases.

Follicular dendritic cell sarcoma in the right chest wall: A case report

RATIONALE

Follicular dendritic cell sarcoma (FDCS) is a rare malignant tumor that originates from germinal center follicular dendritic cells, and can occur at both nodal and extranodal sites. There are very few described cases of FDCS arising in the chest wall.

PATIENT CONCERNS

A 44-year-old male patient presented with a history of right chest wall pain for 5 months.

DIAGNOSES

Positron emission tomography/computed tomography showed a significant increase in F-fluorodeoxyglucose uptake and multiple small axillary lymph nodes without hypermetabolic lesions. Immunohistochemistry results of a core-needle biopsy indicated FDCS, which was consistent with the postoperative pathological examination.

INTERVENTIONS

The patient underwent tumor resection with lymphadenectomy of level I axillary nodes. No metastasis in the lymph nodes was observed in the postoperative pathological examination. The patient did not accept chemotherapy or radiotherapy.

OUTCOMES

After 18 months, the patient remains in good condition with no evidence of disease recurrence.

LESSONS

This report highlights a rare case of a FDCS arising in the chest wall. Accurate clinical diagnosis and staging of this rare malignant sarcoma is essential for the developmnt of effective treatment strategies. Preoperative F-fluorodeoxyglucose positron emission tomography/computed tomography scanning combined with core-needle biopsy could provide differentiation between benign and malignant tumors, as well as lymph node involvement and metastatic status.

Roles of F-18-Fluoro-2-Deoxy-Glucose PET/Computed Tomography Scans in the Management of Post-Transplant Lymphoproliferative Disease in Pediatric Patient

Post-transplant lymphoproliferative disease is a well-known complication in transplant recipients. Evaluating the extent and stage of disease is important for management and follow-up. As a combination of anatomic and functional imaging, PET/CT is a sensitive and specific tool to stage and detect occult disease compared with conventional imaging. PET/CT also has a role in monitoring treatment response. Although PET/CT has been shown to be potentially useful in adults, evidence in children is insufficient. This review provides an overview of the use of PET/CT in post-transplant lymphoproliferative disease, especially in pediatric patients.

FDG PET Hybrid Imaging

Molecular imaging with positron emission tomography (PET) using tumour-seeking radiopharmaceuticals has gained wide acceptance in oncology with many clinical applications. The hybrid imaging modality PET/CT (computed tomography) allows assessing molecular as well as morphologic information at the same time. Therefore, PET/CT represents an efficient tool for whole-body staging and re-staging within one imaging modality. In oncology, the glucose analogue 18-F-fluorodeoxyglucose (FDG) is the most widely used PET/CT radiopharmaceutical in clinical routine. FDG PET and FDG PET/CT have been used for staging and re-staging of tumour patients in numerous studies. This chapter will discuss the use and the main indications of FDG PET/CT in oncology with special emphasis on lung cancer, lymphoma, head and neck cancer, melanoma and breast cancer (among other tumour entities). A review of the current literature is given with respect to primary diagnosis, staging and diagnosis of recurrent disease. Besides its integral role in diagnosis, staging and re-staging of disease in oncology, there is increasing evidence that FDG PET/CT can be used for therapy response assessment (possibly influencing therapeutic management and treatment planning) by evaluating tumour control, which will also be discussed in this chapter.

Comparison of 3T diffusion-weighted MRI and 18F-FDG PET/CT in musculoskeletal tumours: quantitative analysis of apparent diffusion coefficients and standardized uptake values

OBJECTIVE

To determine whether the apparent diffusion coefficient (ADC) on 3T MR imaging including diffusion-weighted MR imaging (DWI) correlate with the standardized uptake value (SUV) on 18F-FDG PET/CT in musculoskeletal tumours.

METHODS

This retrospective cohort study included 57 patients (36 males, 21 females, mean age 54 years, range 12-90 years) with pathologically confirmed soft tissue (n = 32) and bone (n = 25) tumours who underwent 3T MR imaging including DWI and whole-body 18F-FDG PET/CT before treatment. 14 patients had follow-up MR imaging and 18F-FDG PET/CT after treatment. The minimum (ADC_min) and mean (ADC_mean) ADCs of musculoskeletal tumour, ADC of normal skeletal muscle (ADC_mus), SUV_max and SUV_mean of musculoskeletal tumour were obtained. Correlation between ADCs and SUVs was assessed using Pearson correlation coefficients (r). ADC_min and SUV_max were compared between pretreatment and posttreatment by t-test.

RESULTS

There was inverse correlation between SUV_max and the ratio ADC_min/ADC_mus (r = - 0.505 to - 0.495, p ≤ 0.001) and between SUV_mean and the ratio ADC_mean/ADC_mus (r = - 0.501 to - 0.493, p = 0.001). After treatment ADC was significantly increased whereas SUV was significantly decreased (p = 0.001). There was significant correlation in percent change between the initial and follow-up values of ADC_min and SUV_max (r = 0.750 to 0.773, p ≤ 0.005). The ADC_min was increased by 163% and SUV_max was decreased by 61% in 11 patients with treatment response.

CONCLUSION

ADC at 3T MR DWI and SUV at 18F-FDG PET/CT have an inverse correlation in musculoskeletal tumours.

ADVANCES IN KNOWLEDGE

Our study showed that ADC at 3T DWI and SUV at 18F-FDG PET/CT had an inverse correlation in musculoskeletal tumours.

A case of primary pulmonary leiomyosarcoma

Primary pulmonary leiomyosarcoma (PPL) is a very rare malignant tumor which arises from bronchial smooth muscle and vessels. We report 48-year-old male who was diagnosed to have a small lung nodule in the right upper lung field by chest X ray film (XP). A disk shape small nodule was identified in the posterior segment of the right upper lobe by chest CT. Transbronchial lung biopsy (TBB) specimen showed a cluster of dense spindle cells with irregular shape nucleus and some necrosis. 18FluoroDeoxyGlucosePositoron Emission CT (PET-CT) showed that the tumor had high value of the maximal standard uptake value (SUVmax) with no metastasis to the lymph nodes nor other organs. The right upper lobectomy and lymph node dissection were performed and microscopic examination of the specimen showed that the tumor was grade 2 leiomyosarcoma and there was no pleural invasion, nor lymph node metastasis. Post-operative staging of the tumor including its grade was Stage IIA. Immunohistochemical analysis of the specimen showed a clear transition from normal bronchial smooth muscle bundle to leiomyosarcoma in the bronchial wall. The bronchial vessels were fairly preserved. These finding suggested that the leiomyosarcoma developed from bronchial smooth muscle.

A risk-based approach to identifying oligometastatic disease on imaging

Recognition of <3 metastases in <2 organs, particularly in cancers with a known predisposition to oligometastatic disease (OMD) (colorectal, prostate, renal, sarcoma and lung), offers the opportunity to focally treat the lesions identified and confers a survival advantage. The reliability with which OMD is identified depends on the sensitivity of the imaging technique used for detection and may be predicted from phenotypic and genetic factors of the primary tumour, which determine metastatic risk. Whole‐body or organ‐specific imaging to identify oligometastases requires optimization to achieve maximal sensitivity. Metastatic lesions at multiple locations may require a variety of imaging modalities for best visualisation because the optimal image contrast is determined by tumour biology. Newer imaging techniques used for this purpose require validation. Additionally, rationalisation of imaging strategies is needed, particularly with regard to timing of imaging and follow‐up studies. This article reviews the current evidence for the use of imaging for recognising OMD and proposes a risk‐based roadmap for identifying patients with true OMD, or at risk of metastatic disease likely to be OM.

Volume-based parameters on FDG PET may predict the proliferative potential of soft-tissue sarcomas

INTRODUCTION

Soft-tissue sarcomas (STS) are rare types of tumors that have variable levels of tumor differentiation. F-18 fluorodeoxyglucose positron emission tomography (FDG PET) has been established as an useful tool for STS patients, and the metabolic tumor volume (MTV) and total lesion glycolysis (TLG) are reported to be useful in various cancers. We compared the diagnostic value of four PET parameters (maximum standardized uptake value [SUVmax], SUVmean, MTV, and TLG) from two acquisition timings for predicting the expression of the pathological marker of cell proliferation Ki-67, based on pathological investigation.

MATERIALS AND METHODS

In this retrospective study, we investigated 20 patients (59 ± 19 years old, 18-87 years old) with pathologically confirmed STS who underwent FDG PET before surgical intervention. The patients fasted ≥ 6 h before the intravenous injection of FDG. The whole body was scanned twice; at an early phase (61.5 ± 2.6 min) and at a delayed phase (118.0 ± 2.1 min) post-injection. The SUVmax, SUVmean, MTV, and TLG of the primary lesion were measured with a tumor boundary determined by SUV ≥ 2.0. Ki-67 was measured using MIB-1 immunohistochemistry. We used Pearson's correlation coefficient to analyze the relationships between the PET parameters and Ki-67 expressions. The Kaplan-Meier analysis with the log-rank test was performed to compare overall survival between high-group and low-group at each of the four PET parameters and Ki-67 expression.

RESULTS

All four PET parameters at each phase showed significant correlations with Ki-67. Among them, the Pearson's correlation coefficient (r) was largest for TLG (r = 0.76 and 0.77 at the early and delayed phases, respectively), followed by MTV (0.70 and 0.72), SUVmax (r = 0.65 and 0.66), and SUVmean (r = 0.62 and r = 0.64). From early to delayed phases, the SUVmax and SUVmean both increased in all 20 patients, whereas the MTV and TLG increased in 13/20 (65%) and 16/20 (80%) patients, respectively. None of the %increases of the PET parameters were significantly correlated with Ki-67. The overall survival was shorter for high-SUVmax, high-SUVmean, high-TLG, and high-Ki-67 groups than the other groups, although the difference did not reach statistical significance.

CONCLUSION

The SUVmax, SUVmean, MTV, and TLG acquired at both 1 and 2 h after injection showed significant correlations with Ki-67. Among them, correlation coefficient with Ki-67 expression was highest for TLG, although the best parameter should be determined in a larger population. The delayed-phase FDG PET was equally useful as that of early-phase to predict tumor aggressiveness in STS.

Applications of PET/CT and PET/MR Imaging in Primary Bone Malignancies

Primary bone malignancies are characterized with anatomic imaging. However, in recent years, there has been an increased interest in PET/computed tomography scanning and PET/MRI with fludeoxyglucose F 18 for evaluating and staging musculoskeletal neoplasms. These hybrid imaging modalities have shown promise largely owing to their high sensitivity, ability to perform more thorough staging, and ability to monitor treatment response. This article reviews the current role of PET/computed tomography scanning and PET/MRI in primary malignancies of bone, with an emphasis on imaging characteristics, clinical usefulness, and current limitations.

Retrospective audit of 957 consecutive 18F-FDG PET-CT scans compared to CT and MRI in 493 patients with different histological subtypes of bone and soft tissue sarcoma

Background

The use of ¹⁸F-FDG PET–CT (PET–CT) is widespread in many cancer types compared to sarcoma. We report a large retrospective audit of PET–CT in bone and soft tissue sarcoma with varied grade in a single multi-disciplinary centre. We also sought to answer three questions. Firstly, the correlation between sarcoma sub-type and grade with ¹⁸FDG SUVmax, secondly, the practical uses of PET–CT in the clinical setting of staging (during initial diagnosis), restaging (new baseline prior to definitive intervention) and treatment response. Finally, we also attempted to evaluate the potential additional benefit of PET–CT over concurrent conventional CT and MRI.

Methods

A total of 957 consecutive PET–CT scans were performed in a single supra-regional centre in 493 sarcoma patients (excluding GIST) between 2007 and 2014. We compared, PET–CT SUVmax values in relation to histology and FNCCC grading. We compared PET–CT findings relative to concurrent conventional imaging (MRI and CT) in staging, restaging and treatment responses.

Results

High-grade (II/III) bone and soft tissue sarcoma correlated with high SUVmax, especially undifferentiated pleomorphic sarcoma, leiomyosarcoma, translocation induced sarcomas (Ewing, synovial, alveolar rhabdomyosarcoma), de-differentiated liposarcoma and osteosarcoma. Lower SUVmax values were observed in sarcomas of low histological grade (grade I), and in rare subtypes of intermediate grade soft tissue sarcoma (e.g. alveolar soft part sarcoma and solitary fibrous tumour). SUVmax variation was noted in malignant peripheral nerve sheath tumours, compared to the histologically benign plexiform neurofibroma, whereas PET–CT could clearly differentiate low from high-grade chondrosarcoma. We identified added utility of PET–CT in addition to MRI and CT in high-grade sarcoma of bone and soft tissues. An estimated 21% overall potential benefit was observed for PET–CT over CT/MRI, and in particular, in ‘upstaging’ of high-grade disease (from M0 to M1) where an additional 12% of cases were deemed M1 following PET–CT.

Conclusions

PET–CT in high-grade bone and soft tissue sarcoma can add significant benefit to routine CT/MRI staging. Further prospective and multi-centre evaluation of PET–CT is warranted to determine the actual predictive value and cost-effectiveness of PET–CT in directing clinical management of clinically complex and heterogeneous high-grade sarcomas.

Metabolic Tumor Volume by 18F-FDG PET/CT Can Predict the Clinical Outcome of Primary Malignant Spine/Spinal Tumors

BACKGROUND AND PURPOSE

Primary malignant spine/spinal tumors (PMSTs) are rare and life-threatening diseases. In this study, we demonstrated the advantage of volume-based 18F-FDG PET/CT metabolic parameter, metabolic tumor volume (MTV), for assessing the aggressiveness of PMSTs.

MATERIALS AND METHODS

We retrospectively reviewed 27 patients with PMSTs and calculated SUVmax, MTV, and total lesion glycolysis (TLG) to compare their accuracy in predicting progression-free survival (PFS) and overall survival (OS) by receiver operating characteristic (ROC) curve analysis. Univariate and multivariate analyses were used to compare the reliability of the metabolic parameters and various clinical factors.

RESULTS

MTV exhibited greater accuracy than SUVmax or TLG. The cut-off values for PFS and OS derived from the AUC data were MTV 45 ml and 83 ml and TLG 250 SUV⁎ml and 257 SUV⁎ml, respectively. MTV above cut-off value, but not TLG, was identified as significant prognostic factor for PFS by log-lank test (p = 0.04). In addition, MTV was the only significant predictive factors for PFS and OS in the multivariate analysis.

CONCLUSIONS

MTV was a more accurate predictor of PFS and OS in PMSTs compared to TLG or SUVmax and helped decision-making for guiding rational treatment options.

Quantitative assessment of simultaneous F-18 FDG PET/MRI in patients with various types of hepatic tumors: Correlation between glucose metabolism and apparent diffusion coefficient

PURPOSE

Metabolism and water diffusion may have a relationship or an effect on each other in the same tumor. Knowledge of their relationship could expand the understanding of tumor biology and serve the field of oncologic imaging. This study aimed to evaluate the relationship between metabolism and water diffusivity in hepatic tumors using a simultaneous positron emission tomography/magnetic resonance imaging (PET/MRI) system with F-18 fluorodeoxyglucose (FDG) and to reveal the metabolic and diffusional characteristics of each type of hepatic tumor.

METHODS

Forty-one patients (mean age 63 ± 13 years, 31 male) with hepatic tumors (18 hepatocellular carcinoma [HCC], six cholangiocarcinoma [CCC], 10 metastatic tumors, one neuroendocrine malignancy, and six benign lesions) underwent FDG PET/MRI before treatment. Maximum standard uptake (SUVmax) values from FDG PET and the apparent diffusion coefficient (ADC) from the diffusion-weighted images were obtained for the tumor and their relationships were examined. We also investigated the difference in SUVmax and ADC for each type of tumor.

RESULTS

SUVmax showed a negative correlation with ADC (r = -0.404, p = 0.009). The median of SUVmax was 3.22 in HCC, 6.99 in CCC, 6.30 in metastatic tumors, and 1.82 in benign lesions. The median of ADC was 1.039 × 10-3 mm/s2 in HCC, 1.148 × 10-3 mm/s2 in CCC, 0.876 × 10-3 mm/s2 in metastatic tumors, and 1.323 × 10-3 mm/s2 in benign lesions. SUVmax was higher in metastatic tumors than in benign lesions (p = 0.023). Metastatic tumors had a lower ADC than CCC (p = 0.039) and benign lesions (p = 0.004). HCC had a lower ADC than benign lesions, with a suggestive trend (p = 0.06).

CONCLUSION

Our results indicate that SUVmax is negatively correlated with ADC in hepatic tumors, and each group of tumors has different metabolic and water diffusivity characteristics. Evaluation of hepatic tumors by PET/MRI could be helpful in understanding tumor characteristics.

Pictorial review of 18F-FDG PET/CT findings in musculoskeletal lesions

We herein reviewed ¹⁸F-fluoro-2-deoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography (CT) findings in a number of musculoskeletal lesions including malignant tumors, benign tumors, and tumor-like lesions with correlations to other radiographic imaging modalities, and described the diversity of the ¹⁸F-FDG PET/CT findings of this entity. Malignant primary musculoskeletal tumors are typically ¹⁸F-FDG avid, whereas low-grade malignant tumors show mild uptake. Benign musculoskeletal tumors generally show a faint uptake of ¹⁸F-FDG, and tumor-like conditions also display various uptake patterns of ¹⁸F-FDG. Although musculoskeletal tumors show various uptakes of ¹⁸F-FDG on PET/CT, its addition to morphological imaging modalities such as CT and MRI is useful for the characterization and differentiation of musculoskeletal lesions.

Recurrent Follicular Dendritic Cell Sarcoma of the Parotid Gland Imaged with 18F-FDG PET/CT

Follicular dendritic cell sarcoma (FDCS) is an extremely rare tumor with only 67 cases of head and neck FDCS reported in the literature. A 65-year-old female had a 6-cm follicular dendritic cell sarcoma resected from the left parotid gland with close margins. It recurred 1 year later as a 5-cm mass that was intensely [18F] fluoro-2-deoxy-D-glucose (18F-FDG) avid on positron emission tomography/computed tomography (PET/CT) and was re-excised. A follow-up PET/CT did not show any metastatic disease. The use of 18F-FDG PET/CT in the management of FDCS warrants further research. We present the 18F-FDG PET/CT imaging findings of this rare tumor.

Preoperative evaluation of renal cell carcinoma by using 18F-FDG PET/CT

PURPOSE

This study aimed to characterize the FDG uptake of renal cell carcinoma (RCC) by the pathological subtype and nuclear grade.

PATIENTS AND METHODS

We retrospectively identified patients who underwent F-FDG PET and subsequent partial or radical nephrectomy for renal tumors. The relationships of the SUV of renal tumor with subtypes, nuclear grade, and clinicopathological variables were investigated.

RESULTS

Ninety-two tumors were analyzed, including 52 low-grade (G1 and G2) and 18 high-grade (G3 and G4) clear cell RCC; 7 chromophobe, 5 papillary, and 1 unclassified RCC; and 9 benign tumors (7 angiomyolipoma and 2 oncocytoma). The SUVs of high-grade clear cell RCC (mean ± SD, 6.8 ± 5.1) and papillary RCC (6.6 ± 3.7) were significantly higher than that of the controls (2.2 ± 0.3). The SUV of high-grade clear cell RCC was higher than that of low-grade tumors (median, 4.0 vs. 2.2; P < 0.001). The optimal SUV cutoff value of 3.0 helped to differentiate high-grade from low-grade clear cell RCC, with 89% sensitivity and 87% specificity. On multiple regression analysis, a high grade was the most significant predictor of SUV for clear cell RCC.

CONCLUSIONS

FDG uptake higher than that observed in normal kidney tissues suggests a high-grade clear cell RCC or papillary RCC subtype. FDG-PET using SUV may have a role in prediction of pathological grade of renal tumor.

The value of 18F-FDG PET in pediatric patients with post-transplant lymphoproliferative disorder at initial diagnosis

PTLD is a serious complication of both solid organ and BMT. This study assessed whether (18) F-FDG PET, when added to CT scan, had additional value in the initial evaluation of PTLD in pediatric patients and whether PET/CT at baseline can reliably guide biopsy. This retrospective study evaluated 34 consecutive pediatric patients (14 female), aged 3.5-17.0 yr (mean age: 9.9 yr, s.d.: 4.9 yr), who had undergone (18) F-FDG PET/CT from May 2007 to December 2014 at initial diagnosis of PTLD following heart (n = 13), lung (n = 8), kidney (n = 4), liver (n = 3), liver and bowel (n = 3), and bone marrow (n = 3) transplantation. PTLD was diagnosed histopathologically in 33 patients and was based on clinical findings, elevated EBV, and imaging and follow-up results in one patient. On lesion-based analysis, (18) F-FDG PET showed more lesions than conventional CT scan (168 vs. 134), but CT revealed 22 lesions negative on PET. On per patient analysis, PET detected more lesions in 13 patients, CT identified more abnormalities in seven, and both showed the same number of lesions in 14. Adding (18) F-FDG PET to CT scans upstaged the disease in seven patients (20.5%). A combination of (18) F-FDG PET and CT was also useful in guiding biopsy, being positive in 36 of 39 samples (92.3%). These findings indicated that (18) F-FDG PET and CT are complementary at initial staging of pediatric PTLD and that (18) F-FDG PET/CT scanning can guide biopsies.

Simultaneous [18F]FDG-PET/MRI: Correlation of Apparent Diffusion Coefficient (ADC) and Standardized Uptake Value (SUV) in Primary and Recurrent Cervical Cancer

Objectives

Previous non–simultaneous PET/MR studies have shown heterogeneous results about the correlation between standardized uptake values (SUVs) and apparent diffusion coefficients (ADCs). The aim of this study was to investigate correlations in patients with primary and recurrent tumors using a simultaneous PET/MRI system which could lead to a better understanding of tumor biology and might play a role in early response assessment.

Methods

We included 31 patients with histologically confirmed primary (n = 14) or recurrent cervical cancer (n = 17) who underwent simultaneous whole-body ¹⁸F-FDG-PET/MRI comprising DWI. Image analysis was performed by a radiologist and a nuclear physician who identified tumor margins and quantified ADC and SUV. Pearson correlations were calculated to investigate the association between ADC and SUV.

Results

92 lesions were detected. We found a significant inverse correlation between SUV_max and ADC_min (r = -0.532, p = 0.05) in primary tumors as well as in primary metastases (r = -0.362, p = 0.05) and between SUV_mean and ADC_min (r = -0.403, p = 0.03). In recurrent local tumors we found correlations for SUV_max and ADC_min (r = -0.747, p = 0.002) and SUV_mean and ADC_min (r = -0.773, p = 0.001). Associations for recurrent metastases were not significant (p>0.05).

Conclusions

Our study demonstrates the feasibility of fast and reliable measurement of SUV and ADC with simultaneous PET/MRI. In patients with cervical cancer we found significant inverse correlations for SUV and ADC which could play a major role for further tumor characterization and therapy decisions.

Positron Emission Tomography for the Response Evaluation following Treatment with Chemotherapy in Patients Affected by Colorectal Liver Metastases: A Selected Review

The aim of the present paper is to review the scientific literature concerning the usefulness of (18)F-FDG PET/CT in the evaluation of response to chemotherapy in patients affected by liver metastases from colorectal cancer. Material and Methods. Studies were identified by searching PubMed electronic databases. Both prospective and retrospective studies were included. Information regarding the figure of merit of PET for the evaluation of therapy response was extracted and analyzed. Results. Existing data suggests that (18)F-FDG PET/CT may have an outstanding role in evaluating the response. The sensitivity of PET in detecting therapy response seems to be greater than conventional imaging (CT and MRI). PET/CT response is strictly related to better overall survival and progression-free survival. Conclusions. PET/CT is more than a promising technique to assess the response to chemotherapy in colorectal and liver metastases. However, to be fully validated, this examination needs further studies by recruiting more patients.

Value of FDG PET/CT in Patient Management and Outcome of Skeletal and Soft Tissue Sarcomas

Fluorodeoxyglucose (FDG)-PET/computed tomography (CT) has been increasingly used in bone and soft tissue sarcomas and provides advantages in the initial tumor staging, tumor grading, therapy assessment, and recurrence detection. FDG-PET/CT metabolic parameters are reliable predictors of survival in sarcomas and could be implemented in risk stratification models along with other prognostic factors in these patients.

PET response criteria in solid tumors predicts progression-free survival and time to local or distant progression after chemotherapy with regional hyperthermia for soft-tissue sarcoma

We evaluated the prognostic accuracy of established PET and CT response criteria in patients with soft-tissue sarcoma (STS) after combined chemotherapy plus regional hyperthermia (RHT).

METHODS

Seventy-three patients underwent (18)F-FDG PET/CT before and after 2-4 cycles of neoadjuvant chemotherapy with RHT for STS. Progression-free survival (PFS) and time to local and distant progression were among other factors correlated with response according to PET Response Criteria in Solid Tumors (PERCIST 1.0) and Response Evaluation Criteria in Solid Tumors (RECIST 1.1).

RESULTS

Metabolic response by PERCIST (n = 44/73) was an independent predictor for PFS (P = 0.002; hazard ratio [HR], 0.35; 95% confidence interval [CI], 0.18-0.68) and time to local or distant progression. Other independent predictors for PFS by multivariate analysis were adjuvant radiotherapy (P = 0.010; HR, 0.39; 95% CI, 0.20-0.80) and a baseline tumor size less than 5.7 cm (P = 0.012; HR, 0.43; 95% CI, 0.22-0.83). Response by RECIST 1.1 was seen in a small group of patients (n = 22/73) and allowed prediction of PFS for patients with sarcoma outside the abdomen (P = 0.048; HR, 0.13; 95% CI, 0.02-0.98).

CONCLUSION

Metabolic response by (18)F-FDG PET predicts PFS and time to local and distant progression after 2-4 cycles of neoadjuvant chemotherapy plus RHT for STS.

Evaluation of several FDG PET parameters for prediction of soft tissue tumour grade at primary diagnosis and recurrence

OBJECTIVES

This study evaluates the diagnostic accuracy of SUV-based parameters derived from [(18) F]-2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) in order to optimize non-invasive prediction of soft tissue tumour (STT) grade.

METHODS

One hundred and twenty-nine lesions from 123 patients who underwent FDG-PET for primary staging (n = 79) or assessment of recurrence (n = 44) of STT were analyzed retrospectively. Histopathology was the reference standard for tumour grading. Absolute values and tumour-to-liver ratios of several standardized uptake value (SUV) parameters were correlated with tumour grading.

RESULTS

At primary diagnosis SUVmax, SUVpeak, SUVmax/SUVliver and SUVpeak/SUVliver showed good correlation with tumour grade. SUVpeak (area under the receiver-operating-characteristic, AUC-ROC: 0.82) and SUVpeak/SUVliver (AUC-ROC: 0.82) separated best between low grade (WHO intermediate, grade 1 sarcoma, and low risk gastrointestinal stromal tumours, GISTs) and high grade (grade 2/3 sarcoma and intermediate/high risk GISTs) lesions: optimal threshold for SUVpeak/SUVliver was 2.4, which resulted in a sensitivity of 79 % and a specificity of 81 %. At disease recurrence, the AUC-ROC was <0.75 for each parameter.

CONCLUSIONS

A tumour SUVpeak of at least 2.4 fold mean liver uptake predicts high grade histopathology with good diagnostic accuracy at primary staging. At disease recurrence, FDG-PET does not reliably separate high and low grade lesions.

KEY POINTS

• Several SUV parameters accurately predict soft tissue sarcoma grade at primary diagnosis. • Tumour-to-liver ratios are of comparable value to absolute SUV parameters. • SUV peak /SUV liver >2.4 had 79 % sensitivity and 81 % specificity for high grade lesions. • At recurrence, FDG PET does not reliably indicate high grade sarcomas.

Evaluation of imaging utilization prior to referral of musculoskeletal tumors: a prospective study

BACKGROUND

Imaging studies are essential when evaluating a patient with a musculoskeletal neoplasm, and they represent a potential waste of resources when used inappropriately. The objective of this study was to prospectively evaluate a consecutive series of patients for inappropriate utilization of imaging prior to referral to a tertiary care facility. Our hypothesis was that advanced imaging is overutilized prior to referral of musculoskeletal neoplasms to a tertiary care center.

METHODS

All new patients referred for evaluation of a musculoskeletal neoplasm were prospectively analyzed over a three-month time period. All pre-referral imaging studies were recorded, including radiographs, computed tomographic scans, magnetic resonance imaging scans, bone scans, and 18-fluorodeoxyglucose positron emission tomography scans. Studies were reviewed by two musculoskeletal radiologists and two orthopaedic oncologists and were defined with use of specific preselected criteria as inappropriate if they were not indicated for diagnosis or treatment, if they required repeating because of excessive time since the study was obtained, or if they had poor image quality or technique.

RESULTS

We evaluated 298 consecutive patients (550 imaging studies). The inappropriate utilization rate was 1.5% (three of 204) for radiographs, 36.5% (twenty-three of sixty-three) for computed tomographic scans, 26.7% (fifty-six of 210) for magnetic resonance imaging scans, 45.1% (twenty-three of fifty-one) bone scans, and 45.5% (ten of twenty-two) for positron emission tomography scans. The overall inappropriate use of advanced imaging (magnetic resonance imaging, computed tomography, bone scan, positron emission tomography) was 32.4% (112 of 346 images). With regard to inappropriate use of magnetic resonance imaging, there was no difference between orthopaedic surgeons (28.2%) and primary care physicians (26.5%).

CONCLUSIONS

Our data indicate a high prevalence (32.4%) of inappropriate advanced imaging of musculoskeletal tumors prior to referral. This represents a substantial cost to the patient and health-care system, a potential delay of referral, an increase in radiation exposure, and identification of other incidental findings.

Diffusion-weighted imaging of the liver: techniques and applications

Diffusion-weighted imaging (DWI) is a technique that assesses the cellularity, tortuosity of the extracellular/extravascular space, and cell membrane density based on differences in water proton mobility in tissues. The strength of the diffusion weighting is reflected by the b value. DWI using several b values enables the quantification of the apparent diffusion coefficient. DWI is increasingly used in liver imaging for multiple reasons: it can add useful qualitative and quantitative information to conventional imaging sequences; it is acquired relatively quickly; it is easily incorporated into existing clinical protocols; and it is a noncontrast technique.

Correlation between standardized uptake value and apparent diffusion coefficient of neoplastic lesions evaluated with whole-body simultaneous hybrid PET/MRI

OBJECTIVE

The purpose of this study was to assess the correlation between standardized uptake value (SUV) and apparent diffusion coefficient (ADC) of neoplastic lesions in the use of a simultaneous PET/MRI hybrid system.

SUBJECTS AND METHODS

Twenty-four patients with known primary malignancies underwent FDG PET/CT. They then underwent whole-body PET/MRI. Diffusion-weighted imaging was performed with free breathing and a single-shot spin-echo echo-planar imaging sequence with b values of 0, 350, and 750 s/mm(2). Regions of interest were manually drawn along the contours of neoplastic lesions larger than 1 cm, which were clearly identified on PET and diffusion-weighted images. Maximum SUV (SUVmax) on PET/MRI and PET/CT images, mean SUV (SUVmean), minimum ADC (ADCmin), and mean ADC (ADCmean) were recorded on PET/MR images for each FDG-avid neoplastic soft-tissue lesion with a maximum of three lesions per patient. Pearson correlation coefficient was used to asses the following relations: SUVmax versus ADCmin on PET/MR and PET/CT images, SUVmean versus ADCmean, and ratio of SUVmax to mean liver SUV (SUV ratio) versus ADCmin. A subanalysis of patients with progressive disease versus partial treatment response was performed with the ratio of SUVmax to ADCmin for the most metabolically active lesion.

RESULTS

Sixty-nine neoplastic lesions (52 nonosseous lesions, 17 bone metastatic lesions) were evaluated. The mean SUVmax from PET/MRI was 7.0 ± 6.0; SUVmean, 5.6 ± 4.6; mean ADCmin, 1.10 ± 0.58; and mean ADCmean, 1.48 ± 0.72. A significant inverse Pearson correlation coefficient was found between PET/MRI SUVmax and ADCmin (r = -0.21, p = 0.04), between SUVmean and ADCmean (r = -0.18, p = 0.07), and between SUV ratio and ADCmin (r = -0.27, p = 0.01). A similar inverse Pearson correlation coefficient was found between the PET/CT SUVmax and ADCmin. Twenty of 24 patients had previously undergone PET/CT; five patients had a partial treatment response, and six had progressive disease according to Response Evaluation Criteria in Solid Tumors 1.1. The ratio between SUVmax and ADCmin was higher among patients with progressive disease than those with a partial treatment response.

CONCLUSION

Simultaneous PET/MRI is a promising technology for the detection of neoplastic disease. There are inverse correlations between SUVmax and ADCmin and between SUV ratio and ADCmin. Correlation coefficients between SUVmax and ADCmin from PET/MRI were similar to values obtained with SUVmax from the same-day PET/CT. Given that both SUV and ADC are related to malignancy and that the correlation between the two biomarkers is relatively weak, SUV and ADC values may offer complementary information to aid in determination of prognosis and treatment response. The combined tumoral biomarker, ratio between SUVmax and ADCmin, may be useful for assessing progressive disease versus partial treatment response.