Comparison of whole-body STIR-MRI and 99mTc-methylene-diphosphonate scintigraphy in children with suspected multifocal bone lesions

Whole-body MRI: detecting bone metastases from prostate cancer

Whole-body magnetic resonance imaging (WB-MRI) is currently used worldwide for detecting bone metastases from prostate cancer. The 5-year survival rate for prostate cancer is > 95%. However, an increase in survival time may increase the incidence of bone metastasis. Therefore, detecting bone metastases is of great clinical interest. Bone metastases are commonly located in the spine, pelvis, shoulder, and distal femur. Bone metastases from prostate cancer are well-known representatives of osteoblastic metastases. However, other types of bone metastases, such as mixed or inter-trabecular type, have also been detected using MRI. MRI does not involve radiation exposure and has good sensitivity and specificity for detecting bone metastases. WB-MRI has undergone gradual developments since the last century, and in 2004, Takahara et al., developed diffusion-weighted Imaging (DWI) with background body signal suppression (DWIBS). Since then, WB-MRI, including DWI, has continued to play an important role in detecting bone metastases and monitoring therapeutic effects. An imaging protocol that allows complete examination within approximately 30 min has been established. This review focuses on WB-MRI standardization and the automatic calculation of tumor total diffusion volume (tDV) and mean apparent diffusion coefficient (ADC) value. In the future, artificial intelligence (AI) will enable shorter imaging times and easier automatic segmentation.

Magnetic resonance imaging of diffusion characteristics following collagenase clostridium histolyticum injection in Dupuytren's contracture

PurposeWe aimed to evaluate the extent of collagenase clostridium histolyticum (CCH) diffusion in Dupuytren's contracture (DC) for tissues outside of the contracture cord using Magnetic Resonance Imaging (MRI) immediately after CCH injection. Methods: 10 male patients aged 57-79 with DC of the metacarpophalangeal (MCP) joints were examined. Extension deficits were 10-60°(mean, 34.3) and 0-60°(mean, 26.6) in the MCP and proximal interphalangeal (PIP) joints, respectively. CCH injection was performed according to the standard method. MRI was performed within 15 min of CCH injection. Results: In all 10 cases, the extended area of high-intensity signal change outside of the cord was observed on short-T1 inversion recovery images (STIRs). Continuity from the insertion site was observed in the area of signal change involving the flexor tendon and neurovascular bundle. The signal change area spanned distally and proximally beyond the injection level. The signal change area expanded along the tendon sheath but no signal changes were observed inside the flexor tendon, suggesting the tendon sheath serves as a protective barrier from the CCH solution. After 1 week of injection, the mean decrease in contracture was 32.5°(94.7%) for the MCP joint and 19.8°(74.4%) for the PIP joint. In nine out of 10 cases, the extension deficit was within five degrees of full extension in the affected finger. There was no neurovascular injury or tendon rupture at 3 months of observation. Conclusions: MRI indicated the possible leakage of the drug outside of the cord during the early phase after administration, suggesting that CCH could persistently affect healthy tissues until CCH inactivates its enzyme process.

Whole-body magnetic resonance imaging in children - how and why? A systematic review

Whole-body magnetic resonance imaging (MRI) is increasingly being used for a number of indications. Our aim was to review and describe indications and scan protocols for diagnostic value of whole-body MRI for multifocal disease in children and adolescents, we conducted a systematic search in Medline, Embase and Cochrane for all published papers until November 2018. Relevant subject headings and free text words were used for the following concepts: 1) whole-body, 2) magnetic resonance imaging and 3) child and/or adolescent. Included were papers in English with a relevant study design that reported on the use and/or findings from whole-body MRI examinations in children and adolescents. This review includes 54 of 1,609 papers identified from literature searches. Chronic nonbacterial osteomyelitis, lymphoma and metastasis were the most frequent indications for performing a whole-body MRI. The typical protocol included a coronal STIR (short tau inversion recovery) sequence with or without a coronal T1-weighted sequence. Numerous studies lacked sufficient data for calculating images resolution and only a few studies reported the acquired voxel volume, making it impossible for others to reproduce the protocol/images. Only a minority of the included papers assessed reliability tests and none of the studies documented whether the use of whole-body MRI affected mortality and/or morbidity. Our systematic review confirms significant variability of technique and the lack of proven validity of MRI findings. The information could potentially be used to boost attempts towards standardization of technique, reporting and guidelines development.

Whole-body magnetic resonance imaging in pediatric oncology - recommendations by the Oncology Task Force of the ESPR

The purpose of this recommendation of the Oncology Task Force of the European Society of Paediatric Radiology (ESPR) is to indicate reasonable applications of whole-body MRI in children with cancer and to address useful protocols to optimize workflow and diagnostic performance. Whole-body MRI as a radiation-free modality has been increasingly performed over the last two decades, and newer applications, as in screening of children with germ-line mutation cancer-related gene defects, are now widely accepted. We aim to provide a comprehensive outline of the diagnostic value for use in daily practice. Based on the results of our task force session in 2018 and the revision in 2019 during the ESPR meeting, we summarized our group's experiences in whole-body MRI. The lack of large evidence by clinical studies is challenging when focusing on a balanced view regarding the impact of whole-body MRI in pediatric oncology. Therefore, the final version of this recommendation was supported by the members of Oncology Task Force.

MR Imaging of Pediatric Musculoskeletal Tumors:: Recent Advances and Clinical Applications

Pediatric musculoskeletal tumors comprise approximately 10% of childhood neoplasms, and MR imaging has been used as the imaging evaluation standard for these tumors. The role of MR imaging in these cases includes identification of tumor origin, tissue characterization, and definition of tumor extent and relationship to adjacent structures as well as therapeutic response in posttreatment surveillance. Technical advances have enabled quantitative evaluation of biochemical changes in tumors. This article reviews recent updates to MR imaging of pediatric musculoskeletal tumors, focusing on advanced MR imaging techniques and providing information on the relevant physics of these techniques, clinical applications, and pitfalls.

18F-FDG PET-CT versus MRI for detection of skeletal metastasis in Ewing sarcoma

OBJECTIVE

To determine the level of discrepancy between magnetic resonance imaging (MRI) and ¹⁸F-FDG PET-CT in detecting osseous metastases in patients with Ewing sarcoma.

METHODS

Twenty patients with histopathologically confirmed Ewing sarcoma between 2000 and 2017 who underwent ¹⁸F-FDG PET-CT and MRI within a 4-week range were included. Each imaging modality was evaluated by a separate observer. Reference diagnosis of each lesion was based on histopathology or consensus of an expert panel using all available data, including at least 6 months' follow-up. Sensitivity, specificity, and predictive values were determined. Osseous lesions were analyzed on a patient and a lesion basis. Factors possibly related to false-negative findings were evaluated using Pearson's Chi-squared or Fisher's exact test.

RESULTS

A total of 112 osseous lesions were diagnosed in 13 patients, 107 malignant and 5 benign. Seven patients showed no metastases on either ¹⁸F-FDG PET-CT or MRI. Forty-one skeletal metastases (39%) detected with MRI did not show increased ¹⁸F-FDG uptake on ¹⁸F-FDG PET-CT (false-negative). Lesion-based sensitivities and specificities were 62% (95%CI 52-71%) and 100% (48-100%) for ¹⁸F-FDG PET-CT; and 99% (97-100%) and 100% (48-100%) for MRI respectively. Bone lesions were more likely to be false-negative on ¹⁸F-FDG PET-CT if hematopoietic bone marrow extension was widespread and active (p = 0.001), during or after (neo)-adjuvant treatment (p = 0.001) or when the lesion was smaller than 10 mm (p < 0.001).

CONCLUSION

Although no definite conclusions can be drawn from this small retrospective study, it shows that caution is needed when using ¹⁸F-FDG PET-CT for diagnosing skeletal metastases in Ewing sarcoma. Poor contrast between metastases and active hematopoietic bone marrow, chemotherapeutic treatment, and/or small size significantly decrease the diagnostic yield of ¹⁸F-FDG PET-CT, but not of MRI.

ACR Appropriateness Criteria® Acutely Limping Child Up To Age 5

Imaging plays in important role in the evaluation of the acutely limping child. The decision-making process about initial imaging must consider the level of suspicion for infection and whether symptoms can be localized. The appropriateness of specific imaging examinations in the acutely limping child to age 5 years is discussed with attention in each clinical scenario to the role of radiography, ultrasound, nuclear medicine, computed tomography, and magnetic resonance imaging. Common causes of limping such as toddler's fracture, septic arthritis, transient synovitis, and osteomyelitis are discussed. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Whole-body magnetic resonance imaging for detection of skeletal metastases in children and young people with primary solid tumors - systematic review

BACKGROUND

Many solid neoplasms have a propensity for osteomedullary metastases of which detection is important for staging and subsequent treatment. Whole-body magnetic resonance imaging (WB-MRI) has been shown to accurately detect osteomedullary metastases in adults, but these findings cannot be unconditionally extrapolated to staging of children with malignant solid tumors.

OBJECTIVE

To conduct a literature review on the sensitivity of WB-MRI for detecting skeletal metastases in children with solid tumors.

MATERIALS AND METHODS

Searches in MEDLINE and EMBASE databases up to 15 May 2017 were performed to identify studies on the diagnostic value of WB-MRI. Inclusion criteria were children and adolescents (age <21 years) with a primary solid tumor who were evaluated for skeletal metastases by WB-MRI and compared to any type of reference standard. The number of included patients had to be at least five and data on true positives, true negatives, false-positives and false-negatives had to be extractable.

RESULTS

Five studies including 132 patients (96 patients with solid tumors) were eligible. Patient groups and used reference tests were heterogeneous, producing unclear or high risk of bias. Sensitivity of WB-MRI ranged between 82% and 100%. The positive predictive value of WB-MRI was variable among the studies and influenced by the used reference standard.

CONCLUSION

Although WB-MRI may seem a promising radiation-free technique for the detection of skeletal metastases in children with solid tumors, published studies are small and too heterogeneous to provide conclusive evidence that WB-MRI can be an alternative to currently used imaging techniques.

Multifocal bone and bone marrow lesions in children - MRI findings

Polyostotic bone and bone marrow lesions in children may be due to various disorders. Radiographically, lytic lesions may become apparent after loss of more than 50% of the bone mineral content. Scintigraphy requires osteoblastic activity and is not specific. MRI may significantly contribute to the correct diagnosis and management. Accurate interpretation of MRI examinations requires understanding of the normal conversion pattern of bone marrow in childhood and of the appearances of red marrow rests and hyperplasia. Differential diagnosis is wide: Malignancies include metastases, multifocal primary sarcomas and hematological diseases. Benign entities include benign tumors and tumor-like lesions, histiocytosis, infectious and inflammatory diseases, multiple stress fractures/reactions and bone infarcts/ischemia.

Advances in the management of osteosarcoma

Osteosarcoma, a bone cancer most commonly seen in adolescents and young adults, is usually a high-grade malignancy characterized by a very high risk for the development of pulmonary metastases. High-grade osteosarcomas are usually treated by preoperative and postoperative chemotherapy and surgery, with a very limited number of active agents available. Rarer lower-grade variants such as parosteal and periosteal osteosarcoma or low-grade central osteosarcoma are treated by surgery only. Imaging to search for possible metastases focuses on the lung. Computed tomography is the most sensitive method but cannot reliably distinguish small metastases from benign lesions. Advances of local imaging and surgical reconstruction now allow the use of limb-salvage in an ever-increasing proportion of patients. While still troubled by complications, non-invasive endoprosthesis-lengthening mechanisms have led to an increased uptake of limb-salvage, even for young, skeletally immature patients. Radiotherapy is employed when osteosarcomas cannot be removed with clear margins, but very high doses are required, and both proton and carbon-ion radiotherapy are under investigation. Unfortunately, the past 30 years have witnessed few, if any, survival improvements. Novel agents have not led to universally accepted changes of treatment standards. In patients with operable high-grade osteosarcomas, the extent of histological response to preoperative chemotherapy is a significant predictive factor for both local and systemic control. Attempts to improve prognosis by adapting postoperative treatment to response, recently tested in a randomized, prospective setting by the European and American Osteosarcoma Study Group, have not been proven to be beneficial. Many agree that only increased knowledge about osteosarcoma biology will lead to novel, effective treatment approaches and will be able to move the field forward.

MRI findings of new uptake in the femoral head detected on follow-up bone scans

OBJECTIVE. The purpose of this article is to suggest clinical indications for MRI in patients with breast cancer who have new uptake lesions in the femoral head on follow-up bone scans, by evaluating the incidence and causes of new uptake lesions. MATERIALS AND METHODS. Between January 2002 and July 2013, a total of 145 patients with breast cancer who showed new uptake in the femoral head on follow-up bone scans were included in our study. They were classified into two groups: group 1 consisted of 125 patients without known bone metastases, and group 2 consisted of 20 patients who already had bone metastases other than that in the femoral head. The Fisher exact test was performed for the statistical analysis. Thereafter, we reviewed MR images for characterization of the new abnormal uptake in the femoral head. RESULTS. New uptake lesions in the femoral head were metastatic in only 4.8% (6/125) of group 1 patients but in 75% (15/20) of group 2 patients (p < 0.0001). In both groups, no patient with a single uptake lesion in the femoral head had bone metastasis, whereas all patients with more than five new uptake lesions, including those of the femoral head, showed bone metastasis. Most MRI diagnoses for new uptake in the femoral head were fibrocystic change (15/30, 50%) and subchondral fracture (11/30, 36.7%). CONCLUSION. Most of the new uptake lesions in the femoral head detected on the follow-up bone scans in patients with breast cancer were benign. However, MRI could be considered in patients with known bone metastasis or with multiple new uptake lesions on bone scans.

(18)F-FDG PET as a single imaging modality in pediatric neuroblastoma: comparison with abdomen CT and bone scintigraphy

OBJECTIVE

The purpose of this study was to evaluate the diagnostic performance of (18)F-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) as a single imaging agent in neuroblastoma in comparison with other imaging modalities.

METHODS

A total of 30 patients with pathologically proven neuroblastoma who underwent FDG PET for staging were enrolled. Diagnostic performance of FDG PET and abdomen CT was compared in detecting soft tissue lesions. FDG PET and bone scintigraphy (BS) were compared in bone metastases. Maximal standardized uptake value (SUVmax) of primary or recurrent lesions was calculated for quantitative analysis.

RESULTS

Tumor FDG uptake was detected in 29 of 30 patients with primary neuroblastoma. On initial FDG PET, SUVmax of primary lesions were lower in early stage (I-II) than in late stage (III-IV) (3.03 vs. 5.45, respectively, p = 0.019). FDG PET was superior to CT scan in detecting distant lymph nodes (23 vs. 18 from 23 lymph nodes). FDG PET showed higher accuracy to identify bone metastases than BS both on patient-based analyses (100 vs. 94.4 % in sensitivity, 100 vs. 77.8 % in specificity), and on lesion-based analyses (FDG PET: 203 lesions, BS: 86 lesions). Sensitivity and specificity of FDG PET to detect recurrence were 87.5 % and 93.8, respectively.

CONCLUSION

FDG PET was superior to CT in detecting distant LN metastasis and to BS in detecting skeletal metastasis in neuroblastoma. BS might be eliminated in the evaluation of neuroblastoma when FDG PET is performed.

Nuclear medicine and multimodality imaging of pediatric neuroblastoma

Neuroblastoma is an embryonic tumor of the peripheral sympathetic nervous system and is metastatic or high risk for relapse in nearly 50% of cases. Therefore, exact staging with radiological and nuclear medicine imaging methods is crucial for defining the adequate therapeutic choice. Tumor cells express the norepinephrine transporter, which makes metaiodobenzylguanidine (MIBG), an analogue of norepinephrine, an ideal tumor specific agent for imaging. MIBG imaging has several disadvantages, such as limited spatial resolution, limited sensitivity in small lesions and the need for two or even more acquisition sessions. Most of these limitations can be overcome with positron emission tomography (PET) using [F-18]2-fluoro-2-deoxyglucose [FDG]. Furthermore, new tracers, such as fluorodopa or somatostatin receptor agonists, have been tested for imaging neuroblastoma recently. However, MIBG scintigraphy and PET alone are not sufficient for operative or biopsy planning. In this regard, a combination with morphological imaging is indispensable. This article will discuss strategies for primary and follow-up diagnosis in neuroblastoma using different nuclear medicine and radiological imaging methods as well as multimodality imaging.

Whole-body MR imaging for staging of malignant tumors in pediatric patients: results of the American College of Radiology Imaging Network 6660 Trial

PURPOSE

To compare whole-body magnetic resonance (MR) imaging with conventional imaging for detection of distant metastases in pediatric patients with common malignant tumors.

MATERIALS AND METHODS

This institutional review board-approved, HIPAA-compliant, multicenter prospective cohort study included 188 patients (109 male, 79 female; mean age, 10.2 years; range, < 1 to 21 years) with newly diagnosed lymphoma, neuroblastoma, or soft-tissue sarcoma. Informed consent was obtained and all patients underwent noncontrast material-enhanced whole-body MR imaging and standard-practice conventional imaging. All images were reviewed centrally by 10 pairs of readers. An independent panel verified the presence or absence of distant metastases. Detection of metastasis with whole-body MR and conventional imaging was quantified by using the area under the receiver operating characteristic curve (AUC). The effects of tumor subtype, patient age, and distant skeletal and pulmonary disease on diagnostic accuracy were also analyzed.

RESULTS

Of the 134 eligible patients, 66 (33 positive and 33 negative for metastasis) were selected for image review and analysis. Whole-body MR imaging did not meet the noninferiority criterion for accuracy when compared with conventional imaging for detection of metastasis (difference between average AUCs was -0.03 [95% confidence interval: -0.10, 0.04]); however, the average AUC for solid tumors was significantly higher than that for lymphomas (P = .006). More skeletal metastases were detected by using whole-body MR imaging than by using conventional imaging (P = .03), but fewer lung metastases were detected (P < .001). Patient age did not affect accuracy.

CONCLUSION

The noninferior accuracy for diagnosis of distant metastasis in patients with common pediatric tumors was not established for the use of whole-body MR imaging compared with conventional methods. However, improved accuracy was seen with whole-body MR imaging in patients with nonlymphomatous tumors.

The diagnostic value of 18F-FDG PET and MRI in paediatric histiocytosis

PURPOSE

To analyse the diagnostic value of (18)F-FDG PET and MRI for the evaluation of active lesions in paediatric Langerhans cell histiocytosis.

METHODS

We compared 21 (18)F-FDG PET scans with 21 MRI scans (mean time interval 17 days) in 15 patients (11 male, 4 female, age range 4 months to 19 years) with biopsy-proven histiocytosis. Primary criteria for the lesion-based analysis were signs of vital histiocyte infiltrates (bone marrow oedema and contrast enhancement for MRI; SUV greater than the mean SUV of the right liver lobe for PET). PET and MR images were analysed separately and side-by-side. The results were validated by biopsy or follow-up scans after more than 6 months.

RESULTS

Of 53 lesions evaluated, 13 were confirmed by histology and 40 on follow-up investigations. The sensitivity and specificity of PET were 67 % and 76 % and of MRI were 81 % and 47 %, respectively. MRI showed seven false-positive bone lesions after successful chemotherapy. PET showed five false-negative small bone lesions, one false-negative lesion of the skull and three false-negative findings for intracerebral involvement. PET showed one false-positive lesion in the lymphoid tissue of the head and neck region and two false-positive bone lesions after treatment. Combined PET/MR analysis decreased the number of false-negative findings on primary staging, whereas no advantage over PET alone was seen in terms of false-positive or false-negative results on follow-up.

CONCLUSION

Our retrospective analysis suggests a pivotal role of (18)F-FDG PET in lesion follow-up due to a lower number of false-positive findings after chemotherapy. MRI showed a higher sensitivity and is indispensable for primary staging, evaluation of brain involvement and biopsy planning. Combined MRI/PET analysis improved sensitivity by decreasing the false-negative rate during primary staging indicating a future role of simultaneous whole-body PET/MRI for primary investigation of paediatric histiocytosis.

Whole-body diffusion-weighted MRI: tips, tricks, and pitfalls

OBJECTIVE

We examine the clinical impetus for whole-body diffusion-weighted MRI and discuss how to implement the technique with clinical MRI systems. We include practical tips and tricks to optimize image quality and reduce artifacts. The interpretative pitfalls are enumerated, and potential challenges are highlighted.

CONCLUSION

Whole-body diffusion-weighted MRI can be used for tumor staging and assessment of treatment response. Meticulous technique and knowledge of potential interpretive pitfalls will help to avoid mistakes and establish this modality in radiologic practice.

Imaging pediatric bone sarcomas

Primary malignant bone tumors are rare and account for about 6% of all new pediatric cancer cases per year in the United States. Identification of the lesion not uncommonly occurs as a result of imaging performed for trauma. Clinical and standard imaging characteristics of the various tumor types are evolving in concert with treatment advancements and clinical trial regimens. This article reviews the 3 most common pediatric bone sarcomas-osteosarcoma, Ewing sarcoma, and chondrosarcoma-and their imaging as applicable to contemporary disease staging and monitoring, and explores the roles of evolving imaging techniques.

Discomfort in children undergoing unsedated MRI

Magnetic resonance imaging (MRI) scans for research purposes usually do not directly benefit the children scanned, so that review boards need to assess whether the risk of harm or discomfort is minimal. This study aimed at providing empirical data on discomfort related to unsedated MRI in children aged 5-12 years. Secondary objectives were to determine whether lower age is associated with higher levels of discomfort and to investigate which other characteristics of subjects and/or procedures may be associated with higher levels of discomfort. Self-report scores, observation scores, heart rate standard deviation scores, and incremental salivary cortisol levels were obtained from 54 children aged 5-12 years with non-acute conditions undergoing diagnostic MRI. Of the 54 children, 10 scored relatively high values on the self-report score and on one or two of the other measures, and another 15 scored relatively high on the self-report score alone. Rather than an age effect, associations were found between parents' trait anxiety and observation score values and between use of contrast fluid (requiring the insertion of a venous cannula) and high incremental salivary cortisol levels. In conclusion, MRI-related discomfort may be regarded as minimal for more than half of children aged 5-12.

Diagnostic accuracy of whole-body MRI/DWI image fusion for detection of malignant tumours: a comparison with PET/CT

OBJECTIVE

To prospectively evaluate the diagnostic accuracy of whole-body T2-weighted (wbT2), whole-body diffusion-weighted imaging (wbDWI) and wbT2/wbDWI image fusion for malignant tumour detection compared with PET/CT.

METHODS

Sixty-eight patients (44 men; 60 ± 14 years) underwent PET/CT for staging of malignancy and were consecutively examined by 1.5-Tesla MRI including wbT2 and wbDWI. Two radiologists independently assessed wbDWI, wbT2, wbT2 + wbDWI (side-by-side) and wbT2 + wbDWI + wbT2/wbDWI image fusion for the presence of malignancy. PET/CT served as a reference standard.

RESULTS

PET/CT revealed 374 malignant lesions in 48/64 (75%) patients. Detection rates and positive predictive value (PPV) of wbT2 and wbDWI alone were 64% and 84%, and 57% and 93%, respectively. Detection rates and PPV of wbT2 and wbDWI for side-by-side analysis without and with fused images were 72% and 89%, and 74% and 91%, respectively. The detection rate was significantly higher with side-by-side analysis and fused image analysis compared with wbT2 and wbDWI alone (p = .0159; p < .0001). There was no significant difference between fused image interpretation and side-by-side analysis.

CONCLUSIONS

WbDWI allows detection of malignant lesions with a similar detection rate to wbT2. Side-by-side analysis of wbT2 and wbDWI significantly improves the overall detection rate and fused image data provides no added value.

[Whole-body MRI and FDG-PET/CT imaging diagnostics in oncology]

The advent of whole-body MRI (WB-MRI) has introduced a systemic approach to oncologic imaging compared to established sequential, multi-modal diagnostic algorithms. Hardware innovations, such as whole-body scanners at 1.5 Tesla and also recently 3 Tesla, combined with acquisition acceleration techniques, have made WB-MRI clinically feasible. With this method dedicated assessment of individual organs with various soft tissue contrast, high spatial resolution and contrast media dynamics can be combined with whole-body anatomic coverage.PET/CT has established itself as a powerful modality in the staging of patients suffering from malignant tumors. In addition to the morphologic information provided by the CT component of this hybrid modality, the PET component contributes invaluable metabolic information, which greatly enhances accuracy in the assessment of lymphatic spread and viability of tumor tissue. Whole-body MR diffusion imaging is a novel and promising technique which may contribute to superior sensitivity in the detection of tumor manifestations. In the assessment of distant metastatic spread WB-MRI is highly sensitive and has advantages over PET/CT, especially in those tumors frequently spreading to the liver, bone or brain. WB-MRI is also very attractive as a radiation-free alternative for imaging of pediatric tumor patients in whom multiple follow-up examinations may be required.WB-MRI allows for precise assessment of the bone marrow and has been proven to be highly accurate for the staging of hematologic diseases, such as multiple myeloma. In this article recent developments and applications of WB-MRI in oncologic imaging are addressed and compared to the results of PET/CT.

Whole-body MR imaging with the use of parallel imaging for detection of skeletal metastases in pediatric patients with small-cell neoplasms: comparison with skeletal scintigraphy and FDG PET/CT

BACKGROUND

In pediatric patients with small-cell tumors, there is an increasing demand for accurate and early detection of skeletal, especially bone marrow, metastases as new treatment protocols are introduced. Whole-body MR imaging (WB-MR) and (18)F-fluorodeoxyglucose PET/CT (FDG PET/CT) are new promising imaging methods that can detect metastases before osteoblastic host response occurs, which is the basis for detection of metastases by skeletal scintigraphy (SSC).

OBJECTIVE

To assess the ability of WB-MR to detect marrow metastases in children with small-cell neoplasms and compare its performance with that of FDG PET/CT and SSC.

MATERIALS AND METHODS

During a 16-month period, 26 children and adolescents with histopathologically proven small-cell neoplasms underwent WB-MR, FDG PET/CT and Tc-phosphonate-based SSC in a random order within a 25-day period. Metastases were localized in relation to eight regions of the body.

RESULTS

WB-MR revealed metastases in 39 out of a total of 208 regions in 26 patients (sensitivity 97.5%, specificity 99.4%, positive predictive value 97.5%, negative predictive value 99.4%), SSC in 12 regions (sensitivity 30%, specificity 99.4%, PPV 92.3%, NPV 85.6%) and FDG PET/CT in 36 regions (sensitivity 90.0%, specificity 100%, PPV 100%, NPV 97.7%). Both WB-MR and FDG PET/CT showed excellent agreement (kappa) with the final diagnosis (96.9% and 93.6% respectively), whereas SSC showed only moderate agreement (39.6%).

CONCLUSION

Our results suggest that WB-MR and FDG PET/CT studies are robust imaging modalities for screening for skeletal metastases, and are far more accurate than SSC. The lack of radiation is an additional advantage of WB-MR, especially in the pediatric population.

Image quality improvement of composed whole-spine MR images by applying a modified homomorphic filter--first results in cases of multiple myeloma

To establish a modified homomorphic filter (BiFiC) for post-processing of composed MR images in clinical routine and to evaluate it in special regards to image quality and diagnostic safety. Twenty-three whole-spine examinations were post-processed with the filter. Qualitative image evaluation included documentation of lesions and their visualization at original and post-processed images. Variations of signal intensities were calculated pixel by pixel and visualized by color-coded maps. Quantitative data evaluation was conducted by region-by-region analysis with standardized regions of interests. The BiFiC filter could be implemented successfully on the scanner's software platform and used within clinical routine. Color-coded maps could demonstrate that the BiFiC filter improves the signal uniformity in all cases, including images with metallic artifacts caused by implants. The subjective image quality of the post-processed images was improved in 22 out of the 23 MR examinations; in one case it was rated as equal. All pathologies were visualized on post-processed images without the need of additional contrast adjustments. The implemented BiFiC filter significantly improves image signal homogeneity. The algorithm can consequently be integrated into clinical routine as an automatic image post-processing step.

Pre vivo, ex vivo and in vivo evaluations of [68Ga]-EDTMP

INTRODUCTION

The objectives of this study were to develop a simple preparation method for [68Ga]-EDTMP and to evaluate the applicability of [68Ga]-EDTMP as a potential positron emission tomography (PET) bone imaging agent using pre vivo, ex vivo and in vivo models.

METHODS

[68Ga]-EDTMP was prepared using 68Ga]-gallium chloride eluted from the 68Ge/68Ga generator and commercially available Multibone kits. Binding affinity to bone compartments was evaluated using a recently established pre vivo model. In vivo (microPET) and ex vivo experiments were performed in mice, and the results of which were compared with those obtained with [18F]-fluoride.

RESULTS

[68Ga]-EDTMP was accessible via simple kit preparation and predominantly accumulated in bone tissue in vivo, ex vivo and pre vivo. Binding to mineral bone was irreversible, and low binding was observed in organic bone. In vivo microPET evaluation revealed predominant uptake in bone with renal excretion. Compared with [18F]-fluoride, the uptake was lower and the PET image quality was reduced.

CONCLUSIONS

From the present evaluation, apart from the autonomy for PET centers without an onsite cyclotron, the advantage of [68Ga]-EDTMP over [18F]-fluoride is not apparent and the future clinical prospect of [68Ga]-EDTMP remains speculative.

DEVELOPMENT OF A WHOLE BODY MAGNETIC RESONANCE IMAGING PROTOCOL IN NORMAL DOGS AND CANINE CANCER PATIENTS

Whole body magnetic resonance imaging (whole body MR imaging) could potentially provide accurate cancer staging as a single imaging modality. This study was done to develop a whole body MR imaging protocol for a 1.5T MR instrument using four normal Beagle dogs (Phase 1) and then to assess the protocol's feasibility in cancer-bearing dogs (Phase II). In Phase I, anesthetized dogs were placed in dorsal recumbency with limbs flexed along the torso. T1, T2, and short tau inversion recovery sequences were acquired by spin echo or fast spin echo, and also using the more rapid single shot fast spin echo and gradient echo pulse sequences. Three large overlapping fields of view (FOV) were used to visualize the entire body and the sagittal and dorsal imaging planes were compared. Relative examination time, image quality, organ visibility and signal intensity were evaluated. Phase I results were used to establish a protocol that balanced image quality with examination time. In Phase II, whole body MR imaging was done on 10 dogs with cancer. Examination times were 60-75 min. Image quality was sufficient for all known lesions to be visualized, including mass lesions, pulmonary infiltrate, and lymphadenomegaly. Skeletal detail was sufficient to visualize known neoplastic lesions of the appendicular skeleton, yet it was suboptimal because of the large FOV and use of the body coil. Additional modifications of a whole body MR imaging protocol and continued technological improvements in MR imaging will further increase its potential for veterinary cancer staging.

Whole-body diffusion-weighted imaging: Technical improvement and preliminary results

PURPOSE

To optimize the free-breathing whole-body diffusion-weighted imaging (WB-DWI) protocol by using the short TI inversion-recovery diffusion-weighted echo-planar imaging (STIR-DWEPI) sequence and the built-in body coil. Additionally, to evaluate the feasibility of tumor screening using high-resolution three-dimensional (3D) maximum intensity projection (MIP) images.

MATERIALS AND METHODS

The prescan procedure of STIR-DWEPI was modified using the data from 30 volunteers. During each exam, an optimized center frequency (CF) was used to minimize the slice offsets in consecutive scan stations. Prescan time was reduced from 50 seconds to 20 seconds with improved station profile. Total scan time was 30 minutes for five stations and 1.2 m coverage. A total of 30 patients with histologically-proven malignant disease were scanned under the final protocol using a built-in body coil. The image quality and the degree of background body signal suppression were assessed.

RESULTS

Free-breathing WB-DWI was 100% successfully performed in all patients, without slice misregistration, fat contamination, significant distortion, or nonuniformity. The reconstructed 3D-MIP images were adequate to depict malignant lesions in all 30 patients. The results of WB-DWI were found to be comparable to those of single-photon emission computed tomography (SPECT) and positron emission tomography (PET).

CONCLUSION

Stable and high-resolution WB-DWI is feasible using the technical improvements described in this study. WB-DWI might have important clinical value for the detection of primary and metastatic malignancies within the whole body. The potential for diagnosis and therapeutic assessment of tumors should be further assessed in a larger patient cohort.

Impact of whole-body MRI and FDG-PET on staging and assessment of therapy response in a patient with Ewing sarcoma

In patients with Ewing sarcoma, precise staging is not only crucial for the therapeutic regimen but also for a reliable evaluation of response to therapy. We report on a 15-year-old girl with metastatic spread of a Ewing sarcoma who, apart from conventional staging by bone scan, chest X-ray and CT, was subsidiary examined by FDG-PET and whole-body MRI before and after chemotherapy. Both modalities detected more bone lesions than the bone scan, which led to an altered strategy for radiotherapy. Both examinations might be a great asset to stage-adjusted therapy regimens, ultimately influencing patient outcome.

Total-body MR-imaging in oncology

Although MRI is an effective modality in oncology, state-of-the-art total-body MRI (TB-MRI) in the past was infeasible in the diagnostic work-up, due to the need for repeated examinations with repositioning and separate surface coils to cover all body parts. To overcome this limitation, either a moving table platform in combination with the body-coil or a special designed rolling table platform with one body phased-array coil have been implemented with promising results for both tumor staging and metastases screening. Since 2004, state-of-the-art TB-MR imaging with high spatial resolution has become feasible using a newly developed 1.5 Tesla TB-MRI system with multiple receiver channels. This review gives an overview based on the recent literature as well as our own experience concerning the possibilities, challenges, and limitations of TB-MRI in oncology, emphasizing both oncological staging and early tumor detection in asymptomatic subjects.

Whole-body MRI and PET-CT in the management of cancer patients

Mortality rate, prognosis, and treatment outcome of cancer patients depend strongly on the detection of malignancy at an early stage and efficient monitoring of the disease. Multimodality diagnostic approaches are now widely applied for tumor detection, staging, and follow-up. However, the introduction of whole-body imaging modalities into clinical practice has substantially expanded diagnostic options. PET-CT has increased diagnostic accuracy by providing "anatometabolic" information by fusing tumor glucose-uptake measures from the PET examination and accurate delineation of anatomical structures given by spiral CT. Since PET-CT is associated with high doses of ionizing radiation, it is used in mainly tumor staging and screening within the scope of tertiary prevention. Here promising results have been reported for various tumor entities. MRI provides excellent tissue contrast, detailed morphological information and lack of ionizing radiation. MRI has been employed for the assessment of focal pathologies in specific anatomical regions. Whole-body MRI scanners using multiple receiver channels with parallel acquisition techniques now allow tumor screening from head to toe within substantially shorter examination times and without compromises in image resolution. We report our experience with these two novel techniques and discuss their benefits and drawbacks in terms of systemic tumor screening.

Whole-body MRI in the detection of bone marrow infiltration in patients with plasma cell neoplasms in comparison to the radiological skeletal survey

To compare the diagnostic value of whole-body MRI versus radiological skeletal survey (RSS) in staging patients with plasma cell neoplasms (PCN) and to evaluate the possible therapeutic impact of the replacement of RSS by whole-body MRI. Fifty-four patients with PCN [multiple myeloma (MM), n=47; monoclonal gammopathy of unknown significance (MGUS), n=7] were studied by whole-body MRI and RSS in a monocenter prospective analysis from August 2002 to May 2004. The MRIs were performed using a rolling table platform "AngioSURF" for unlimited field of view with a 1.5-T system (Magnetom Sonata/Maestro Class, Siemens Medical Solutions, Erlangen, Germany). A coronal STIR sequence (TR5500-4230/TE102-94/TI160) was used for imaging of the different body regions, including the head, neck, thorax, abdomen, pelvis and upper and lower extremities. The RSS consisted of eight different projections of the axial and appendicular skeleton. In 41/54 (74%) patients, the results of the whole-body MRI and RSS were concordant. In 11/54 (20%) patients, both imaging techniques were negative. Bone involvement was observed in 30/54 (55%) patients; however, whole-body MRI revealed this more extensively than the RSS in 27/30 (90%) patients with concordant positive imaging findings. In 3/30 (10%) patients, both imaging techniques demonstrated a similar extent of bone marrow infiltration. In 10/54 (19%) patients, the whole-body MRI was superior to RSS in detecting bone marrow infiltration, whereas the RSS was negative. In 3/54 (6%) patients, the RSS was proven to be false positive by the clinical course, whereas the whole-body MRI was truly negative. Whole-body MRI is a fast and highly effective method for staging PCN patients by the use of a rolling table platform. Moreover, it is more sensitive and specific than RSS and reveals bone marrow infiltration and extensive disease more reliably. Therefore, whole-body MRI should be performed as an additional method of exactly staging PCN patients and - with more data in the field - may even prove to be an alternate and more sensitive staging procedure than RSS in PCN patients.

Binding studies of [18F]-fluoride and polyphosphonates radiolabelled with [99mTc], [111In], [153Sm] and [188Re] on bone compartments: verification of the pre vivo model?

INTRODUCTION

Although the first polyphosphonates (PP) were introduced to nuclear medicine as bone imagers in the early 70s, mechanisms involved in uptake still remain speculative. Controversies range from adsorption onto the mineral phase with disputed binding to the organic phase, over incorporation into the mineralisation process to a combination of both mechanisms. Other factors such as solubility of the complex, concentration of ligand or effects of the radionuclide have also been discussed as possible parameters influencing bone uptake. Therefore, the present work aimed to verify the recently presented pre vivo model which was developed to rate the influence of various factors on the binding of differently radiolabelled PP and [18F]-fluoride on synthetic bone matrix.

METHODS

Radiolabelled polyphosphonates and [18F]-fluoride were added to a vial containing lyophilised and milled spongiosa (Sp) or cortical bone (Co) in Hank's Balanced Salt Solution. After incubation, the radioactivity was measured in the gamma-counter before and after filtration. The percentage of irreversibly bound radioactivity was calculated. Same experiments were performed after decalcification of Sp and Co with hydrochloric acid.

RESULTS

Descriptively, [111In] increases the uptake of EDTMP in each case compared to similarly prepared [(99m)Tc]-analogues: [111In]-EDTMP > [(99m)Tc]-EDTMP, [111In]-/In-EDTMP > [(99m)Tc]-/In-EDTMP and [111In]-/Re-EDTMP > [(99m)Tc]-/Re-EDTMP. [188Re]-EDTMP shows higher binding than the carrier-added analogue, contradicting recent in vivo findings of [(188)Re]-PP. However, our findings on human matrix are consistent with those of a previous study using artificial bone material. Binding on decalcified tissue was very low (PP) to moderate ([18F]-fluoride) and reversible. Remarkable is also the unrivalled high uptake of [18F]-fluoride, showing no reduced uptake on Co and Sp as compared to hydroxyapatite (HA) and amorphous calcium phosphate (ACP).

CONCLUSION

The binding of the evaluated bone seekers on these human bone matrices follows a comparable pattern as on artificial bone. The present study substantiates the fact that binding predominantly occurs on the inorganic compartment of bone. The best correlation was found between HA and Co. Therefore, HA can serve as a matrix for representative binding studies.

Whole-body MRI of paediatric malignant tumours: comparison with conventional oncological imaging methods

PURPOSE

To evaluate the usefulness of whole-body (WB) MRI for detecting metastases from paediatric malignant tumours in comparison with conventional oncological imaging methods.

MATERIALS AND METHODS

Using a 1.5-T system, a coronal short tau inversion recovery (STIR) sequence was obtained in all patients. In addition, sagittal fat-suppressed T2-weighted, sagittal STIR, or coronal fat-suppressed pre-contrast and post-contrast T1-weighted sequences were performed. Patients who underwent WB MRI and conventional oncological imaging within 15 days were enrolled in the study. In total, 58 bone scintigraphies, 26 iodine-123 (123I) meta-iodo-benzylguanidine (MIBG) scintigraphies, and 48 CT scans were available for comparison in 36 patients (median age 3.5 years; 21 boys, 15 girls) who underwent 82 WB MRI examinations. Skeletal and extraskeletal metastases were evaluated for a variety of tumour types.

RESULTS

Concordance rate of WB MRI between two readers was 74%. In detecting metastases, WB MRI had higher sensitivity (99%) and PPV (94%) than bone scintigraphy (26 and 76%, respectively). In detecting skeletal metastases, WB MRI revealed higher sensitivity (100%) than 123I-MIBG scintigraphy (25%) and CT (10%). In contrast, WB MRI showed lower PPV in detecting skeletal and extraskeletal metastases (8 and 57%, respectively) than 123I-MIBG scintigraphy (100%), and lower sensitivity (60%) in detecting extraskeletal metastases than CT (100%). In 2 of 11 untreated patients, tumour staging was upgraded from stage 3 to 4 according to WB MRI findings. In 3 patients, WB MRI revealed early treatment responses (<1 year) of skeletal metastases.

CONCLUSIONS

WB MRI can substitute for bone scintigraphy in detecting skeletal metastases of paediatric malignant tumours, and it is useful in evaluating initial tumour staging and early treatment responses. However, it still has only a complementary role in detecting extraskeletal metastases.

Fast STIR whole-body MR imaging in children

Fast spin-echo short inversion time inversion-recovery (STIR) whole-body magnetic resonance (MR) imaging is an evolving technique that allows imaging of the entire body in a reasonable time. Its wide availability and lack of radiation exposure makes this method appealing for the evaluation of children. Since 2001, the authors conducted 140 pediatric whole-body MR imaging studies and correlated the findings with those from conventional imaging examinations. Bone marrow lesions, including marrow infiltration from lymphoma, metastases, and tumor-related edema, appeared with high signal intensity and were more easily detected on STIR images than with scintigraphy. Focal parenchymal lesions could be distinguished by their slightly different signal intensity, but pathologic lymph nodes could not be differentiated from normal nodes on the basis of signal intensity. The STIR technique is highly sensitive for detection of pathologic lesions, but it is not specific for malignancy; thus, the method cannot be used to differentiate benign conditions from malignant neoplastic lesions. Although fast STIR whole-body MR imaging permits evaluation of the entire skeleton and all viscera with a single examination, more experience and data are needed to determine its efficacy for staging neoplasms and assessing other multifocal disease in children.

Is there a need for contrast-enhanced T1-weighted MRI of the spine after inconspicuous short τ inversion recovery imaging?

To assess the use of contrast-enhanced T1-weighted images in comparison with short tau inversion recovery (STIR) images for the detection of vertebral bone marrow abnormalities. A total of 201 vertebral magnetic resonance (MR) examinations were included in a prospective trial. Examinations were performed on a 0.5-T MR scanner. The examination protocol included STIR, T2-weighted turbo spin-echo and T1-weighted spin-echo images before and after administration of gadopentetate dimeglumine. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of STIR images were calculated. In the case of abnormal STIR images the additional information from contrast-enhanced images was evaluated using Fisher's exact test. The value of the combined evaluation of STIR and contrast-enhanced T1-weighted images was compared with that of the combined assessment of T2-weighted and contrast-enhanced T1-weighted images. The PPV and the NPV of STIR images for detection of vertebral bone marrow abnormalities were 99.3 and 95.9%. In the case of normal STIR images no relevant additional information was found with contrast-enhanced T1-weighted images, while in the case of abnormal STIR images significant supplementary information was obtained. There was no difference in the diagnostic value when comparing combined assessment of STIR and contrast-enhanced T1-weighted images with combined evaluation of T2-weighted and contrast-enhanced T1-weighted images. Normal STIR images allow contrast-enhanced T1-weighted images for detection of bone marrow abnormalities to be omitted, whereas further imaging is needed in case of abnormal STIR images.

Metastatic disease of the spine

Metastases of the spine occur in the spinal cord, dura extramedullary, epidural space, and vertebral bodies. Imaging modalities can be used to evaluate patient symptoms, screen and detect lesions, assess localization and the compartments involved (extradural, epidural, subdural, and paraspinal), and suggest therapeutic strategies. The suggested flow chart for metastases is (1) in asymptomatic patients suspected for metastases and (2) in the patient with neurological symptoms. Imaging modalities are indispensable in differential diagnosis because some nontumoral lesions can mimic metastases.