High signal in bone marrow at diffusion-weighted imaging with body background suppression (DWIBS) in healthy children

Impact of fat content on lumbar spine DWI performance: A sex-based comparative study

Purpose

Sex-based differences in lumbar spine's fat content in adults are minimal, but significant variations exist in diffusion-weighted imaging (DWI) signal characteristics. This study aimed to investigate fat content's impact on DWI performance in lumbar spine and potential sex differences.

Methods

A retrospective analysis was conducted on upper abdominal MRI examinations in asymptomatic adult. The lumbar 1 vertebral apparent diffusion coefficient (ADC) values and fat fraction were measured. Using DWI images (b = 800 s/mm2), the lumbar 1 vertebral signal was categorized into high and iso-low signal groups. A univariate and multivariate analysis was conducted to investigate the influence of fat fraction on DWI performance. Finally, the participants were divided into three groups to analyze sex differences in the effect of fat content on DWI performance.

Results

202 subjects, 99 men were included. Fat content significantly influenced lumbar spine DWI signal in both sexes (p < 0.05). The effect on ADC values was significant only in women (p < 0.001). Women demonstrated a significantly higher proportion of high DWI signal than men in the low (p = 0.002) and middle (p = 0.012) fat content groups. Additionally, women had higher ADC values in the low fat group (p = 0.004) but lower values in the high fat group (p = 0.004).

Conclusion

Fat content significantly impacts the DWI signal of lumbar spine, with a slight sex difference observed. These sex differences suggest that DWI signals may provide valuable information about the bone marrow beyond fat content.

Pediatric Pelvis

The development of the pelvis follows a predictable pattern of ossification that involves the maturation of bone, synchondroses, and apophyses. These growth centers appear and close at distinct times during skeletal maturity and give rise to structural changes in the pelvis that can be distinctively appreciated on various imaging modalities. Accurate interpretation of radiologic images requires knowledge of skeletal development because the varying appearance of the maturing pediatric pelvis may be mistaken for pathology. In addition, many normal features within the pelvis can be erroneously perceived as injury. This article incorporates a multimodality review of normal pelvic maturation, a discussion of developmental variants, and a description of common injuries unique to the pediatric pelvis.

Detection of bone marrow metastases in children and young adults with solid cancers with diffusion-weighted MRI

OBJECTIVE

To compare the diagnostic accuracy of diffusion-weighted (DW)-MRI with b-values of 50 s/mm2 and 800 s/mm2 for the detection of bone marrow metastases in children and young adults with solid malignancies.

METHODS

In an institutional review board-approved prospective study, we performed 51 whole-body DW-MRI scans in 19 children and young adults (14 males, 5 females; age range: 1-25 years) with metastasized cancers before (n = 19 scans) and after (n = 32 scans) chemotherapy. Two readers determined the presence of focal bone marrow lesions in 10 anatomical areas. A third reader measured ADC and SNR of focal lesions and normal marrow. Simultaneously acquired 18F-FDG-PET scans served as the standard of reference. Data of b = 50 s/mm2 and 800 s/mm2 images were compared with the Wilcoxon signed-rank test. Inter-reader agreement was evaluated with weighted kappa statistics.

RESULTS

The SNR of bone marrow metastases was significantly higher compared to normal bone marrow on b = 50 s/mm2 (mean ± SD: 978.436 ± 1239.436 vs. 108.881 ± 109.813, p < 0.001) and b = 800 s/mm2 DW-MRI (499.638 ± 612.721 vs. 86.280 ± 89.120; p < 0.001). On 30 out of 32 post-treatment DW-MRI scans, reconverted marrow demonstrated low signal with low ADC values (0.385 × 10-3 ± 0.168 × 10-3mm2/s). The same number of metastases (556/588; 94.6%; p > 0.99) was detected on b = 50 s/mm2 and 800 s/mm2 images. However, both normal marrow and metastases exhibited low signals on ADC maps, limiting the ability to delineate metastases. The inter-reader agreement was substantial, with a weighted kappa of 0.783 and 0.778, respectively.

CONCLUSION

Bone marrow metastases in children and young adults can be equally well detected on b = 50 s/mm2 and 800 s/mm2 images, but ADC values can be misleading.

Improved Detection of Bone Metastases in Children and Young Adults with Ferumoxytol-enhanced MRI

Purpose To evaluate if ferumoxytol can improve the detection of bone marrow metastases at diffusion-weighted (DW) MRI in pediatric and young adult patients with cancer. Materials and Methods In this secondary analysis of a prospective institutional review board-approved study (ClinicalTrials.gov identifier NCT01542879), 26 children and young adults (age range: 2-25 years; 18 males) underwent unenhanced or ferumoxytol-enhanced whole-body DW MRI between 2015 and 2020. Two reviewers determined the presence of bone marrow metastases using a Likert scale. One additional reviewer measured signal-to-noise ratios (SNRs) and tumor-to-bone marrow contrast. Fluorine 18 (18F) fluorodeoxyglucose (FDG) PET and follow-up chest CT, abdominal and pelvic CT, and standard (non-ferumoxytol enhanced) MRI served as the reference standard. Results of different experimental groups were compared using generalized estimation equations, Wilcoxon rank sum test, and Wilcoxon signed rank test. Results The SNR of normal bone marrow was significantly lower at ferumoxytol-enhanced MRI compared with unenhanced MRI at baseline (21.380 ± 19.878 vs 102.621 ± 94.346, respectively; P = .03) and after chemotherapy (20.026 ± 7.664 vs 54.110 ± 48.022, respectively; P = .006). This led to an increased tumor-to-marrow contrast on ferumoxytol-enhanced MRI scans compared with unenhanced MRI scans at baseline (1397.474 ± 938.576 vs 665.364 ± 440.576, respectively; P = .07) and after chemotherapy (1099.205 ± 864.604 vs 500.758 ± 439.975, respectively; P = .007). Accordingly, the sensitivity and diagnostic accuracy for detecting bone marrow metastases were 96% (94 of 98) and 99% (293 of 297), respectively, with the use of ferumoxytol-enhanced MRI compared with 83% (106 of 127) and 95% (369 of 390) with the use of unenhanced MRI. Conclusion Use of ferumoxytol helped improve the detection of bone marrow metastases in children and young adults with cancer. Keywords: Pediatrics, Molecular Imaging-Cancer, Molecular Imaging-Nanoparticles, MR-Diffusion Weighted Imaging, MR Imaging, Skeletal-Appendicular, Skeletal-Axial, Bone Marrow, Comparative Studies, Cancer Imaging, Ferumoxytol, USPIO © RSNA, 2023 ClinicalTrials.gov registration no. NCT01542879 See also the commentary by Holter-Chakrabarty and Glover in this issue.

Whole-body MRI in children: state of the art

Whole-body magnetic resonance imaging (WBMRI) is an increasingly popular technique in paediatric imaging. It provides high-resolution anatomical information, with the potential for further exciting developments in acquisition of functional data with advanced MR sequences and hybrid imaging with radionuclide tracers. WBMRI demonstrates the extent of disease in a range of multisystem conditions and, in some cases, disease burden prior to the onset of clinical features. The current applications of WBMRI in children are hereby reviewed, along with suggested anatomical stations and sequence protocols for acquisition.

Whole body magnetic resonance imaging in healthy children and adolescents. Bone marrow appearances of the axial skeleton

OBJECTIVE

To describe the findings of focal high signal on T2 weighted (T2W) images of the bone marrow in the axial skeleton as assessed by whole-body MRI in healthy and asymptomatic children and adolescents.

MATERIAL AND METHODS

We assessed the bone marrow of the mandible, shoulder girdle, thorax, spine, and pelvis on water-only Dixon T2W sequences as part of a whole-body MRI protocol in 196 healthy and asymptomatic children aged 5-19 years. Intensity (0-2 scale) and extension (1-4 scale) of focal high signal areas in the bone marrow were scored and divided into minor or major findings, based on intensity and extension to identify the potentially conspicuous lesions in a clinical setting.

RESULTS

We registered 415 areas of increased signal in the axial skeleton whereof 75 (38.3%) were major findings. Fifty-eight (29.6%) individuals had at least one major finding, mainly located in the pelvis (54, 72%). We found no differences according to gender. The number of minor findings increased with age (p = 0.020), but there were no significant differences in the number of major findings. The most conspicuous findings were in the pelvis, spine and sternum.

CONCLUSION

Non-specific bone marrow T2W hyperintensities in the axial skeleton are frequently detected on whole-body MRI in healthy, asymptomatic children. Awareness of this is important as some findings may resemble clinically silent lesions in children with suspected multifocal skeletal disease.

Stereotactic body radiotherapy for spinal oligometastases: a review on patient selection and the optimal methodology

Stereotactic body radiotherapy (SBRT) has excellent local control and low toxicity for spinal metastases and is widely performed for spinal oligometastases. However, its additional survival benefit to standard of care, including systemic therapy, is unknown because the results of large-scale randomized controlled trials regarding SBRT for oligometastases have not been reported. Consequently, the optimal patient population among those with spinal oligometastases and the optimal methodology for spine SBRT remain unclear. The present review article discusses two topics: evidence-based optimal patient selection and methodology. The following have been reported to be good prognostic factors: young age, good performance status, slow-growing disease with a long disease-free interval, minimal disease burden, and mild fluorodeoxyglucose accumulation in positron emission tomography. In addition, we proposed four measures as the optimal SBRT method for achieving excellent local control: (i) required target delineation; (ii) recommended dose fraction schedule (20 or 24 Gy in a single fraction for spinal oligometastases and 35 Gy in five fractions for lesions located near the spinal cord); (iii) optimizing dose distribution for the target; (iv) dose constraint options for the spinal cord.

Whole-body magnetic resonance imaging for the diagnosis of metastasis in children and adolescents: a systematic review and meta-analysis

Whole-body magnetic resonance imaging (WB-MRI) is a noninvasive imaging method that can be used to diagnose and stage tumors, as well as to assess therapeutic responses in oncology. The objective of this meta-analysis was to evaluate the accuracy of WB-MRI for the diagnosis of metastases in pediatric patients. The following electronic databases were searched: Medline, Embase, Cochrane Central Register of Controlled Trials, Scientific Electronic Library Online, Latin-American and Caribbean Health Sciences Literature, Cumulative Index to Nursing and Allied Health Literature, Web of Science, and ClinicalTrials.gov. All of the selected studies included children and adolescents with histopathological confirmation of a primary tumor. Collectively, the studies included 118 patients ranging in age from 7 months to 19 years. The pooled sensitivity and specificity of WB-MRI were, respectively, 0.964 (95% CI: 0.944-0.978; I² = 0%) and 0.902 (95% CI: 0.882-0.919; I² = 98.4%), with an area under the curve (AUC) of 0.991. We found that WB-MRI had good accuracy for the diagnosis of metastases in pediatric patients and could therefore provide an alternative to complete the staging of tumors in such patients, being a safer option because it does not involve the use of ionizing radiation.

The signal intensity characteristics of normal bone marrow in diffusion weighted imaging at various menstrual status women

PURPOSE

Diffuse hyperintensities of the bone marrow in whole-body diffusion-weighted (DW) imaging (DWI) have been encountered more frequently in females aged 21-50 compared to elder females or men. Therefore, we aimed to visually evaluate DWI among pre-, peri- and postmenopausal women and to verify whether it correlates also quantitatively with hormonal status.

METHOD

The prospective study was approved by our institutional review board and informed consent was obtained in a total of 70 healthy premenopausal, perimenopausal, and postmenopausal women aged 40-58 years from February 2017 to October 2017. The bone marrow DW imaging signal characteristics were visually evaluated in comparison to the erector spinae muscle. Imaging data were acquired using a 1.5 T MRI yielding signal intensity values from a DWI-pulse sequence (b-value of 800 s/mm²; apparent diffusion coefficient (ADC) maps from b-values of 0-800 s/mm²), and a T2 mapping sequence covering the L2-L4 lumbar vertebrae. Serous estradiol (E2), follicle stimulating hormone (FSH), and luteinizing hormone (LH) were measured through venous blood assay. The relationship of the mean DW signal intensity (SI_DWI) with T2 values, female hormone level, and mean ADC were analyzed using Spearman's rho test.

RESULTS

The proportion of diffuse DWI hyperintensities of the bone marrow was significantly higher in premenopausal (91% (21/23)) women compared to peri- (75% (18/24)) and postmenopausal (8% (2/23)) women. A positive correlation was observed for the mean SI_DWI (median [interquartile range], 47.33 [30.14]) and mean T2 (mean ± SD, 121.01 ± 13.54) (r = 0.438, p < 0.001) as well as for the mean SI_DWI and E2 (median [interquartile range], 52.45 [92.78]) (r = 0.407, p < 0.001). A negative correlation was observed for the mean SI_DWI and serous FSH (median [interquartile range], 15.55 [42.08]) as well as for the mean SI_DWI and serous LH (median [interquartile range], 6.96 [31.06]) (r = -0.557, p < 0.001; r = -0.535, p < 0.001; respectively), but no significant correlation was found for mean SI_DWI and mean ADC (mean ± SD, 599.36 ± 82.70) (r = 0.099, p = 0.415). A negative correlation was also encountered for the mean T2 values and serous FSH (r = -0.339, p = 0.004) as well as for the mean T2 values and serous LH (r = -0.281, p = 0.018).

CONCLUSIONS

The mean SI_DWI correlates positively with mean T2 and serous E2 values, while there's no significant correlation with mean ADC, indicating that T2 shine-through effects might interfere with bone marrow signaling on DW images. Knowledge of the bone marrow signal characteristics changing in DW images in close relationship with menstrual status is essential to correctly interpret DWI in clinical practice.

Assessment of disease activity using a whole-body MRI derived radiological activity index in chronic nonbacterial osteomyelitis

BACKGROUND

Based on the recently developed ChRonic nonbacterial Osteomyelitis MRI Scoring tool (CROMRIS), we developed a radiological activity index (RAI-CROMRIS) to obtain a quantification of the overall bone involvement in individual patients.

METHODS

Whole Body Magnetic Resonance Imaging (WB-MRI) images were scored according to parameters included in the RAI-CROMRIS: bone marrow hyperintensity, signal extension, soft tissue/periosteal hyperintensity, bony expansion, vertebral collapse. These parameters were evaluated for each bone unit yielding a score from 0 to 7 and summed up as RAI-CROMRIS including all bone units. We assessed clinical disease activity using a physician global assessment (PGA) and radiological findings in 76 treatment-naïve patients; 46 of 76 were evaluated at 6 and 12 months after initial WB-MRI. Quantitative variables were compared using the Mann-Whitney U test for unmatched groups and the Wilcoxon signed-rank test for paired groups. Correlation was evaluated using Spearman's rank coefficient (r_s).

RESULTS

There was a significant correlation between RAI-CROMRIS and PGA (r_s = 0.32; p = 0.0055), between RAI-CROMRIS and presence of elevated erythrocyte sedimentation rate (p = 0.013) and C-reactive protein (p = 0.0001) at baseline. The RAI-CROMRIS decreased from a median of 17 at baseline to 12 at 6 months (p = 0.004) and remained stable (median 11) at 12 months. A correlation between the RAI-CROMRIS and the PGA was observed at baseline (r_s = 0.41; p = 0.004) and during follow up at 6 months (r_s = 0.33; p = 0.025) and 12 months (r_s = 0.38; p = 0.010). The baseline RAI-CROMRIS (median 20) was significantly higher in patients who subsequently received bisphosphonates than in patients who received other treatments (median 12) and decreased significantly after bisphosphonates (p = 0.008).

CONCLUSIONS

The RAI-CROMRIS was correlated with clinical and laboratory measures of disease activity showing significant short-term changes following treatment with bisphosphonates. This tool could be used in clinical practice and clinical trials after validation.

Whole-body [18F]-FDG-PET/MRI for staging of pediatric non-Hodgkin lymphoma: first results from a single-center evaluation

Aim

In 2015, the revised International Pediatric Non-Hodgkin Lymphoma Staging System was published. It mentions [¹⁸F]-FDG-PET/MRI as the latest method to perform whole-body imaging. However, supporting data are pending. Our aim was to investigate the performance of whole-body [¹⁸F]-FDG-PET/MRI in pediatric non-Hodgkin lymphoma patients by using a limited number of MRI sequences.

Materials and methods

Ten pediatric patients with histologically proven non-Hodgkin lymphoma underwent whole-body [¹⁸F]-FDG-PET/MRI at staging. The retrospective analysis included three steps: First, [¹⁸F]-FDG-PET and MR scans were evaluated separately by a nuclear medicine physician and a pediatric radiologist. Nineteen nodal and two extranodal regions as well as six organs were checked for involvement. Second, discrepant findings were reviewed together in order to reach consensus. Third, [¹⁸F]-FDG-PET/MRI findings were correlated with the results of other clinical investigations.

Results

Of the 190 lymph node regions evaluated, four were rated controversial. Consensus was reached by considering metabolic, functional and morphologic information combined. Concordantly, [¹⁸F]-FDG-PET and MRI detected Waldeyer’s ring involvement in two patients whose Waldeyer’s ring was negative on clinical assessment. In four patients MRI showed pleural effusion. However, in only two of them an increased glucose metabolism as a reliable sign of pleural involvement was detectable. In six patients [¹⁸F]-FDG-PET and MRI detected skeletal lesions although bone marrow biopsy was positive in only one of them.

Conclusion

Despite the small number of cases evaluated, whole-body [¹⁸F]-FDG-PET turned out to be a valuable tool for staging of pediatric non-Hodgkin lymphoma.

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.

Chronic nonbacterial osteomyelitis - clinical and magnetic resonance imaging features

BACKGROUND

Chronic nonbacterial osteomyelitis (CNO) is a rare autoinflammatory bone disorder. Little information exists on the use of imaging techniques in CNO.

MATERIALS AND METHODS

We retrospectively reviewed clinical and MRI findings in children diagnosed with CNO between 2012 and 2018. Criteria for CNO included unifocal or multifocal inflammatory bone lesions, symptom duration >6 weeks and exclusion of infections and malignancy. All children had an MRI (1.5 tesla) performed at the time of diagnosis; 68 of these examinations were whole-body MRIs including coronal short tau inversion recovery sequences, with additional sequences in equivocal cases.

RESULTS

We included 75 children (26 boys, or 34.7%), with mean age 10.5 years (range 0-17 years) at diagnosis. Median time from disease onset to diagnosis was 4 months (range 1.5-72.0 months). Fifty-nine of the 75 (78.7%) children presented with pain, with or without swelling or fever, and 17 (22.7%) presented with back pain alone. Inflammatory markers were raised in 46/75 (61.3%) children. Fifty-four of 75 (72%) had a bone biopsy. Whole-body MRI revealed a median number of 6 involved sites (range 1-27). Five children (6.7%) had unifocal disease. The most commonly affected bones were femur in 46 (61.3%) children, tibia in 48 (64.0%), pelvis in 29 (38.7%) and spine in 20 (26.7%). Except for involvement of the fibula and spine, no statistically significant differences were seen according to gender.

CONCLUSION

Nearly one-fourth of the children presented with isolated back pain, particularly girls. The most common sites of disease were the femur, tibia and pelvic bones. Increased inflammatory markers seem to predict the number of MRI sites involved.

Artificial intelligence for interpretation of segments of whole body MRI in CNO: pilot study comparing radiologists versus machine learning algorithm

BACKGROUND

To initiate the development of a machine learning algorithm capable of comparing segments of pre and post pamidronate whole body MRI scans to assess treatment response and to compare the results of this algorithm with the analysis of a panel of paediatric radiologists.

METHODS

Whole body MRI of patients under the age of 16 diagnosed with CNO and treated with pamidronate at a tertiary referral paediatric hospital in United Kingdom between 2005 and 2017 were reviewed. Pre and post pamidronate images of the commonest sites of involvement (distal femur and proximal tibia) were manually selected (n = 45). A machine learning algorithm was developed and tested to assess treatment effectiveness by comparing pre and post pamidronate scans. The results of this algorithm were compared with the results of a panel of radiologists (ground truth).

RESULTS

When tested initially the machine algorithm predicted 4/7 (57.1%) examples correctly in the multi class model, and 5/7 (71.4%) correctly in the binary group. However when compared to the ground truth, the machine model was able to classify only 33.3% of the samples correctly but had a sensitivity of 100% in detecting improvement or worsening of disease.

CONCLUSION

The machine learning could detect new lesions or resolution of a lesion with good sensitivity but failed to classify stable disease accurately. However, further validation on larger datasets are required to improve the specificity and accuracy of the machine model.

Whole-Body Diffusion-Weighted MRI Compared to 18 FFDG PET/CT in Initial Staging and Therapy Response Assessment of Hodgkin Lymphoma in Pediatric Patients

PURPOSE

The aim of our study was to compare whole-body diffusion-weighted MRI (WB-DWI-MRI) to fluoro-2-deoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in the assessment of initial staging and treatment response in pediatric patients with Hodgkin lymphoma.

MATERIALS AND METHODS

This prospective study comprised 11 children with Hodgkin lymphoma. Whole-body DWI-MRI and FDG-PET/CT were obtained at baseline and after 2 cycles of chemotherapy. Two radiologists measured the apparent diffusion coefficient (ADC) values of the sites of involvement agreed upon in consensus and 1 nuclear medicine physician assessed the PET/CT. Reliability of radiologists' ratings was assessed by intraclass correlation coefficients (ICC_2,1). The sensitivity and positive predictive value (PPV) of DW-MRI relative to PET/CT were calculated for nodal and extranodal sites. The patients were staged according to both modalities. Association of treatment responses was assessed through the Pearson correlation between the ADC ratios and the change standardized uptake value (SUV) between baseline and follow-up.

RESULTS

There was good agreement between the raters for nodal and extranodal ADC measurements. The sensitivity and PPV of DW-MRI relative to PET/CT of nodal disease was 0.651 and 1.0, respectively, at baseline, and 0.697 and 0.885 at follow-up. The sensitivity and PPV of extranodal disease were 0.545 and 0.6 at baseline, and 0.167 and 0.333 at follow-up. Diffusion-weighted MRI determined correct tumor stage in 8 of 11 examinations. There was poor correlation between the ADC ratios and the absolute change in SUV between baseline and follow-up (0.348).

CONCLUSION

Our experience showed that WB-DWI-MRI is inferior to PET/CT for initial staging and assessment of treatment response of Hodgkin lymphoma in pediatric patients.

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.

Is MRI imaging in pediatric age totally safe? A critical reprisal

Current radiological literature is strongly focussed on radiation imaging risks. Indeed, given there is a small but actual augment in cancer risk from exposure to ionizing radiation in children, it is important to understand what the risk of alternative techniques could be. We retrospectively review literature data concerning possible MR imaging risks, focussing on the biological effects of MR, sedation and gadolinium compound risks when dealing with infant patients. The main concerns can be summarized in: (1) Biological effects of non-ionizing electromagnetic fields (EMF) employed-whose mechanisms of interaction with human tissues are polarization, induced current, and thermal heating, respectively. (2) Risks associated with noises produced during MRI examinations. (3) Hazards from ferromagnetic external and/or implanted devices-whose risk of being unintentionally brought inside MR room is higher in children than in adults. (4) Risks associated with sedation or general anaesthesia, essential problem in performing MR in very young patients, due to the exam long-lasting. (5) Risks related to gadolinium-based contrast agents, especially considering the newly reported brain deposition.

Diagnostic performance of 18F-FDG PET/CT and whole-body diffusion-weighted imaging with background body suppression (DWIBS) in detection of lymph node and bone metastases from pediatric neuroblastoma

OBJECTIVE

Recent many studies have shown that whole body "diffusion-weighted imaging with background body signal suppression" (DWIBS) seems a beneficial tool having higher tumor detection sensitivity without ionizing radiation exposure for pediatric tumors. In this study, we evaluated the diagnostic performance of whole body DWIBS and ¹⁸F-FDG PET/CT for detecting lymph node and bone metastases in pediatric patients with neuroblastoma.

METHODS

Subjects in this retrospective study comprised 13 consecutive pediatric patients with neuroblastoma (7 males, 6 females; mean age, 2.9 ± 2.0 years old) who underwent both ¹⁸F-FDG PET/CT and whole-body DWIBS. All patients were diagnosed as neuroblastoma on the basis of pathological findings. Eight regions of lymph nodes and 17 segments of skeletons in all patients were evaluated. The images of ¹²³I-MIBG scintigraphy/SPECT-CT, bone scintigraphy/SPECT, and CT were used to confirm the presence of lymph node and bone metastases. Two radiologists trained in nuclear medicine evaluated independently the uptake of lesions in ¹⁸F-FDG PET/CT and the signal-intensity of lesions in whole-body DWIBS visually. Interobserver difference was overcome through discussion to reach a consensus. The sensitivities, specificities, and overall accuracies of ¹⁸F-FDG PET/CT and whole-body DWIBS were compared using McNemer's test. Positive predictive values (PPVs) and negative predictive values (NPVs) of both modalities were compared using Fisher's exact test.

RESULTS

The total numbers of lymph node regions and bone segments which were confirmed to have metastasis in the total 13 patients were 19 and 75, respectively. The sensitivity, specificity, overall accuracy, PPV, and NPV of ¹⁸F-FDG PET/CT for detecting lymph node metastasis from pediatric neuroblastoma were 100, 98.7, 98.9, 95.0, and 100%, respectively, and those for detecting bone metastasis were 90.7, 73.1, 80.3, 70.1, and 91.9%, respectively. In contrast, the sensitivity, specificity, overall accuracy, PPV, and NPV of whole-body DWIBS for detecting bone metastasis from pediatric neuroblastoma were 94.7, 24.0, 53.0, 46.4 and 86.7%, respectively, whereas those for detecting lymph node metastasis were 94.7, 85.3, 87.2, 62.1, and 98.5%, respectively. The low specificity, overall accuracy, and PPV of whole-body DWIBS for detecting bone metastasis were due to a high incidence of false-positive findings (82/108, 75.9%). The specificity, overall accuracy, and PPV of whole-body DWIBS for detecting lymph node metastasis were also significantly lower than those of ¹⁸F-FDG PET/CT for detecting lymph node metastasis, although the difference between these 2 modalities was less than that for detecting bone metastasis.

CONCLUSION

The specificity, overall accuracy, and PPV of whole-body DWIBS are significantly lower than those of ¹⁸F-FDG PET/CT because of a high incidence of false-positive findings particularly for detecting bone metastasis, whereas whole-body DWIBS shows a similar level of sensitivities for detecting lymph node and bone metastases to those of ¹⁸F-FDG PET/CT. DWIBS should be carefully used for cancer staging in children because of its high incidence of false-positive findings in skeletons.

High Signal in Bone Marrow on Diffusion-Weighted Imaging of Female Pelvis: Correlation With Anemia and Fibroid-Associated Symptoms

BACKGROUND

The diffusion-weighted imaging (DWI) signals of the female pelvic bone marrow show great variability and are usually high in female patients with fibroid-associated symptoms and anemia.

PURPOSE

To ascertain clinical factors contributing to high signal intensity in the bone marrow of the female pelvis on DWI.

STUDY TYPE

Retrospective case-control study.

SUBJECTS

A single-institution review of 221 female patients underwent a pelvic magnetic resonance study from December 2012 to July 2014.

FIELD STRENGTH/SEQUENCE

1.5T/DWI (b = 0 and 1000) and apparent diffusion coefficient (ADC).

ASSESSMENT

The ADC of pelvic bone marrow and the muscle-normalized signal intensity (SI) on DWI (mnDWI) were measured. A brightness grading scale ranging from 0 to 4 was used for pelvic bone assessment. Clinical factors, namely, age, the lowest hemoglobin level in the last 6 months, the presence of large uterine fibroids, and/or adenomyosis and fibroid-associated symptoms were recorded.

STATISTICAL TESTS

The relationships between the brightness grade and clinical factors were evaluated through multinomial logistic regression, and correlations of mnDWI and the ADC with the clinical factors were analyzed through the Kruskal-Wallis test, Jonckheere's trend test, and the Mann-Whitney U-test with Bonferroni correction.

RESULTS

Age and the hemoglobin level were inversely associated with the bone marrow brightness grade on DWI (both P < 0.05), whereas the presence of fibroid-associated symptoms showed a positive association (P = 0.028). The ADC and mnDWI in women younger than 50 years were significantly higher than those in older women (both P < 0.0001). The ADC had no significant correlation with anemia (P = 0.511), whereas mnDWI increased as the severity of anemia increased (P = 0.00154).

DATA CONCLUSION

Our study showed an association of high DWI SI of pelvic bone marrow with anemia in premenopausal women.

LEVEL OF EVIDENCE

4 Technical Efficacy Stage 3 J. Magn. Reson. Imaging 2018;48:1024-1033.

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.

How PET/MR Can Add Value For Children With Cancer

PURPOSE

To review how PET/MR technology could add value for pediatric cancer patients.

RECENT FINDINGS

Since many primary tumors in children are evaluated with MRI and metastases are detected with PET/CT, integrated PET/MR can be a time-efficient and convenient solution for pediatric cancer staging. 18F-FDG PET/MR can assess primary tumors and the whole body in one imaging session, avoid repetitive anesthesia and reduce radiation exposure compared to 18F-FDG PET/CT. This article lists 10 action points, which might improve the clinical value of PET/MR for children with cancer. However, even if PET/MR proves valuable, it cannot enter mainstream applications if it is not accessible to the majority of pediatric cancer patients. Therefore, innovations are needed to make PET/MR scanners affordable and increase patient throughput.

SUMMARY

PET/MR offers opportunities for more efficient, accurate and safe diagnoses of pediatric cancer patients. The impact on patient management and outcomes has to be substantiated by large-scale prospective clinical trials.

Whole-body MRI in pediatric patients with cancer

Cancer is the leading cause of natural death in the pediatric populations of developed countries, yet cure rates are greater than 70% when a cancer is diagnosed in its early stages. Recent advances in magnetic resonance imaging methods have markedly improved diagnostic and therapeutic approaches, while avoiding the risks of ionizing radiation that are associated with most conventional radiological methods, such as computed tomography and positron emission tomography/computed tomography. The advent of whole-body magnetic resonance imaging in association with the development of metabolic- and function-based techniques has led to the use of whole-body magnetic resonance imaging for the screening, diagnosis, staging, response assessment, and post-therapeutic follow-up of children with solid sporadic tumours or those with related genetic syndromes. Here, the advantages, techniques, indications, and limitations of whole-body magnetic resonance imaging in the management of pediatric oncology patients are presented.

Whole-body MRI in children: Would a 3D STIR sequence alone be sufficient for investigating common paediatric conditions? A comparative study

OBJECTIVES

To test the performance of a single 3D IR T2-Weighted sequence compared to a Whole-body MRI protocol including DWI, T1-Weighted and STIR 3D IR (3S) in a pediatric population.

METHODS

Two radiologists (15 and 30 years of experience),reviewed WBMRIs: first the STIR alone and 2 weeks later the 3S protocol. The indications were variable. Only positive findings were explicitly reported. A third reader compared the results to gold standard (GS) exams specific for the pathology. Agreement between the two readers, sensitivity and positive predictive value of STIR were calculated.

RESULTS

fifty-four WBMRIs were included (16 suspected child abuse, 8 chronic recurrent multifocal osteomyelitis (CRMO), 11 lymphomas, 4 osteosarcomas, 9 neuroblastomas, 6 histiocytosis). The mean age was 6 years 10 months, range: 1 month to 15 years. Agreement between readers was of 0.87 [0.82-0.91] for 3D STIR, and 0.89 [0.83-0.93] for the 3S protocol. For reader 1 sensitivity of 3D STIR was 81.6% and of 3S 81.0%. For reader 2 it was 74.1% for 3D STIR and 74.7% for 3S. For both readers and for both protocols, the positive predictive value (PPV) depended on the type of disease (for example 100% histocytosis and osteosarcomas, >90% for child abuse, >85% CRMO but <70% for lymphoma and neuroblastoma).

CONCLUSIONS

Sensitivities were not different between the 2 protocols, for each reader and were different between the 2 readers for each protocol.

Diffusion-weighted Imaging Using Readout-segmented EPI Reveals Bony Metastases from Neuroblastoma

Identifying neuroblastoma (NBL) metastases is crucial to treatment and prognosis. Metaiodobenzylguanidine and Tc99M bone scans are standard for identifying bony metastases but can underestimate disease. Diffusion-weighted imaging (DWI) of the spine has shown promise in evaluating bony metastases but has been limited by artifacts. Readout-segmented echo planar imaging is a technique for DWI that minimizes artifacts allowing for improved identification of spinal disease. This report illustrates the utility of DWI of the spine using readout-segmented echo planar imaging in the detection of bony NBL metastases in a child, lending support that DWI should be included in magnetic resonance imaging scans for NBL.

Signal characteristics of normal adult bone marrow in whole-body diffusion-weighted imaging

BACKGROUND

Knowledge of the signal characteristics of normal adult bone marrow in whole-body diffusion-weighted (DW) images (WB-DWI) is essential for correctly interpreting DW images in clinical practice; however, these factors have not yet been clearly determined.

PURPOSE

To evaluate the signal characteristics of normal adult bone marrow in WB-DWI, to correlate these characteristics with age and gender, and to determine the causes of these phenomena.

MATERIAL AND METHODS

Ninety-eight healthy volunteers underwent WB-DWI (b = 0 and 800 s/mm(2)). Two radiologists visually evaluated the signal characteristics of bone marrow in DW images separately. One radiologist measured the apparent diffusion coefficient (ADC) of the thoracic and lumbar vertebrae, bilateral femur (including head, neck, and proximal and distal femoral shaft), bilateral humeral head, ilium, and scapula. The signal characteristics of normal bone marrow were analyzed.

RESULTS

The visual evaluation results of DW images indicated that hyperintensity of bone marrow was more frequently seen in women aged 21-50 years (68.4%) than in men aged 21-50 years (3.3%) (P < 0.001), men aged 51-81 years (5.9%) (P < 0.001), and women aged 51-81 years (15.4%) (P = 0.001). However, no statistically significant difference was found between men and women aged 51-81 years (P = 0.565). The ADC of bone marrow was significantly higher in women than in men aged 21-50 years. Bone marrow ADC showed significant negative correlation with age in women but not in men.

CONCLUSION

The signal intensity of bone marrow varies with age and gender in DW images. ADC and the T2 shine-through effect contributed to the bone marrow signal intensity in DW images, and the latter effect may predominate.

Features and perspectives of MR enterography for pediatric Crohn disease assessment

The aim of this paper is to provide indications for performing magnetic resonance enterography (MRE) in Crohn's disease (CD), the essential technical elements of MRE techniques and typical findings in patients with CD. Patients suffering from CD frequently require cross-sectional imaging. By performing MRE, it is possible to obtain results comparable to those obtained with endoscopy in terms of identifying and assessing disease activity and better than other cross-sectional imaging techniques, such as CT, in the evaluation of the fibrosis and complications of disease. The MR imaging of diffusion MR is a technique which enables medical staff to add important additional information and which may replace the use of intravenous contrast agents in the near future. Magnetic resonance enterography is an accurate tool for assessing bowel disease and the various complications associated with CD. The lack of exposure to non-ionizing radiation is an important advantage of this imaging technique, especially in the case of pediatric patients. Familiarity with common and pathognomonic imaging features of CD is essential for every clinician involved in the treatment of inflammatory bowel disease and the care of patients.

Whole-body MRI in paediatric oncology

Imaging plays a crucial role in the diagnosis and follow-up of paediatric malignancies. Until recently, computed tomography (CT) has been the imaging technique of choice in children with cancer, but nowadays there is an increasing interest in the use of functional imaging techniques like positron emission tomography and single-photon emission tomography. These later techniques are often combined with CT allowing for simultaneous acquisition of image data on the biological behaviour of tumour, as well as the anatomical localisation and extent of tumour spread. Because of the small but not negligible risk of radiation induced secondary cancers and the significantly improved overall survival rates of children with cancer, there is an increasing interest in the use of alternative imaging techniques that do not use ionising radiation. Magnetic resonance imaging (MRI) is a radiation-free imaging tool that allows for acquiring images with a high spatial resolution and excellent soft tissue contrast throughout the body. Moreover, recent technological advances have resulted in fast diagnostic sequences for whole-body MR imaging (WB-MRI), including functional techniques such as diffusion weighted imaging. In this review, the current status of the technique and major clinical applications of WB-MRI in children with cancer will be discussed.

Whole-Body MRI in Children: Current Imaging Techniques and Clinical Applications

Whole-body magnetic resonance imaging (MRI) is increasingly used in children to evaluate the extent and distribution of various neoplastic and non-neoplastic diseases. Not using ionizing radiation is a major advantage of pediatric whole-body MRI. Coronal and sagittal short tau inversion recovery imaging is most commonly used as the fundamental whole-body MRI protocol. Diffusion-weighted imaging and Dixon-based imaging, which has been recently incorporated into whole-body MRI, are promising pulse sequences, particularly for pediatric oncology. Other pulse sequences may be added to increase diagnostic capability of whole-body MRI. Of importance, the overall whole-body MRI examination time should be less than 30-60 minutes in children, regardless of the imaging protocol. Established and potentially useful clinical applications of pediatric whole-body MRI are described.

Diffusion-weighted imaging in pediatric body MR imaging: principles, technique, and emerging applications

Diffusion-weighted (DW) imaging is an emerging technique in body imaging that provides indirect information about the microenvironment of tissues and lesions and helps detect, characterize, and follow up abnormalities. Two main challenges in the application of DW imaging to body imaging are the decreased signal-to-noise ratio of body tissues compared with neuronal tissues due to their shorter T2 relaxation time, and image degradation related to physiologic motion (eg, respiratory motion). Use of smaller b values and newer motion compensation techniques allow the evaluation of anatomic structures with DW imaging. DW imaging can be performed as a breath-hold sequence or a free-breathing sequence with or without respiratory triggering. Depending on the mobility of water molecules in their microenvironment, different normal tissues have different signals at DW imaging. Some normal tissues (eg, lymph nodes, spleen, ovarian and testicular parenchyma) are diffusion restricted, whereas others (eg, gallbladder, corpora cavernosa, endometrium, cartilage) show T2 shine-through. Epiphyses that contain fatty marrow and bone cortex appear dark on both DW images and apparent diffusion coefficient maps. Current and emerging applications of DW imaging in pediatric body imaging include tumor detection and characterization, assessment of therapy response and monitoring of tumors, noninvasive detection and grading of liver fibrosis and cirrhosis, detection of abscesses, and evaluation of inflammatory bowel disease.

The role of whole-body MRI in pediatric oncology

Pediatric whole-body (WB) magnetic resonance imaging (MRI) is an established technique that, with improved accessibility and advances in technology, is being used with increasing frequency for a wide variety of applications. The advantages of WB MRI (over other imaging modalities), particularly its lack of ionizing radiation (of particular concern in pediatric imaging due to children's increased sensitivity to ionizing radiation) and the ability of MRI to image the bone marrow, solid organs, and soft tissues with superior soft-tissue contrast resolution to other techniques, promise that WB MRI has great potential in conditions that are diffuse or multifocal. There is particular interest in its role in the field of pediatric oncology (eg, lymphoma, neuroblastoma, sarcoma, and Langerhans cell histiocytosis). The main disadvantages of WB MRI are its relatively long scanning times, artifacts from motion (requiring patient cooperation or general anesthesia), and limited specificity. However, advances in hardware and imaging techniques, including additional sequences (out-of-phase imaging, diffusion-weighted imaging, and contrast enhancement) are reducing the impact of some of these challenges.

Diffusion-weighted magnetic resonance imaging in management of bladder cancer, particularly with multimodal bladder-sparing strategy

Bladder-sparing strategy for muscle-invasive bladder cancer (MIBC) is increasingly demanded instead of radical cystectomy plus urinary diversion. Multimodal therapeutic approaches consisting of transurethral resection, chemotherapy, radiotherapy and/or partial cystectomy improve patients’ quality of life by preserving their native bladder and sexual function without compromising oncological outcomes. Because a favorable response to chemoradiotherapy (CRT) is a prerequisite for successful bladder preservation, predicting and monitoring therapeutic response is an essential part of this approach. Diffusion-weighted magnetic resonance imaging (DW-MRI) is a functional imaging technique increasingly applied to various types of cancers. Contrast in this imaging technique derives from differences in the motion of water molecules among tissues and this information is useful in assessing the biological behavior of cancers. Promising results in predicting and monitoring the response to CRT have been reported in several types of cancers. Recently, growing evidence has emerged showing that DW-MRI can serve as an imaging biomarker in the management of bladder cancer. The qualitative analysis of DW-MRI can be applied to detecting cancerous lesion and monitoring the response to CRT. Furthermore, the potential role of quantitative analysis by evaluating apparent diffusion coefficient values has been shown in characterizing bladder cancer for biological aggressiveness and sensitivity to CRT. DW-MRI is a potentially useful tool for the management of bladder cancer, particularly in multimodal bladder-sparing approaches for MIBC.

Bone abnormal signal incidentally found in pre-biopsy diffusion-weighted MRI for suspected prostate cancer: what does it reflect?

OBJECTIVE

To clarify the clinical significance of incidentally found diffusion-weighted MRI (DW-MRI)-positive findings on pre-biopsy MRI in patients with suspected prostate cancer.

PATIENTS AND METHODS

754 consecutive patients with suspected prostate cancer underwent pelvic MRI including DW-MRI. 43 DW-MRI-positive bone lesions were found in 27 patients. Imaging findings of these lesions were compared with the clinical diagnosis.

RESULTS

Of the 43 DW-MRI-positive bone lesions, 21 (48.8%) were diagnosed as metastatic prostate cancer. The remaining 22 (51.2%) were diagnosed as red bone marrow in 17, enchondroma in 1, ganglion in 1, osteoma in 1, fibrous dysplasia in 1 and bone infarction in 1. Enchondroma, ganglion, osteoma and fibrous dysplasia all showed T1-weighted imaging (T1WI) low and T2-weighted imaging (T2WI) high signals, while others, including prostate cancer metastases, showed T1WI and T2WI low signals. Of the 40 lesions with T1WI and T2WI low signals, metastatic prostate cancer had higher apparent diffusion coefficient values (median 0.42 × 10(-3) mm(2)/s) than other lesions (0.26 × 10(-3) mm(2)/s; p < 0.0001).

CONCLUSIONS

DW-MRI-positive bone lesions represent various coexisting types of bone lesions, including metastatic cancer in patients with suspected prostate cancer. T2WI findings and apparent diffusion coefficient values can be helpful in diagnosing metastatic cancer.

Paediatric acquired pathological vertebral collapse

Vertebral collapse is a significant event in the paediatric patient with a real potential for associated deformity and morbidity. While in adults the causes tend towards the malignant, particularly metastatic and metabolic disease, the paediatric population demonstrates a different range of diagnoses. This article reviews the typical imaging findings of the more common underlying acquired pathological causes of vertebral collapse in children, including Langerhans cell histiocytosis, chronic recurrent multifocal osteomyelitis, osteogenesis imperfecta. Other causes include pyogenic osteomyelitis and tuberculosis and neoplastic lesions, either primary, metastatic or of haematological origin.

Ionising radiation-free whole-body MRI versus (18)F-fluorodeoxyglucose PET/CT scans for children and young adults with cancer: a prospective, non-randomised, single-centre study

BACKGROUND

Imaging tests are essential for staging of children with cancer. However, CT and radiotracer-based imaging procedures are associated with substantial exposure to ionising radiation and risk of secondary cancer development later in life. Our aim was to create a highly effective, clinically feasible, ionising radiation-free staging method based on whole-body diffusion-weighted MRI and the iron supplement ferumoxytol, used off-label as a contrast agent.

METHODS

We compared whole-body diffusion-weighted MRI with standard clinical (18)F-fluorodeoxyglucose ((18)F-FDG) PET/CT scans in children and young adults with malignant lymphomas and sarcomas. Whole-body diffusion-weighted magnetic resonance images were generated by coregistration of colour-encoded ferumoxytol-enhanced whole-body diffusion-weighted MRI scans for tumour detection with ferumoxytol-enhanced T1-weighted MRI scans for anatomical orientation, similar to the concept of integrated (18)F-FDG PET/CT scans. Tumour staging results were compared using Cohen's κ statistics. Histopathology and follow-up imaging served as the standard of reference. Data was assessed in the per-protocol population. This study is registered with ClinicalTrials.gov, number NCT01542879.

FINDINGS

22 of 23 recruited patients were analysed because one patient discontinued before completion of the whole-body scan. Mean exposure to ionising radiation was 12·5 mSv (SD 4·1) for (18)F-FDG PET/CT compared with zero for whole-body diffusion-weighted MRI. (18)F-FDG PET/CT detected 163 of 174 malignant lesions at 1325 anatomical regions and whole-body diffusion-weighted MRI detected 158. Comparing (18)F-FDG PET/CT to whole-body diffusion-weighted MRI, sensitivities were 93·7% (95% CI 89·0-96·8) versus 90·8% (85·5-94·7); specificities 97·7% (95% CI 96·7-98·5) versus 99·5% (98·9-99·8); and diagnostic accuracies 97·2% (93·6-99·4) versus 98·3% (97·4-99·2). Tumour staging results showed very good agreement between both imaging modalities with a κ of 0·93 (0·81-1·00). No adverse events after administration of ferumoxytol were recorded.

INTERPRETATION

Ferumoxytol-enhanced whole-body diffusion-weighted MRI could be an alternative to (18)F-FDG PET/CT for staging of children and young adults with cancer that is free of ionising radiation. This new imaging test might help to prevent long-term side-effects from radiographic staging procedures.

FUNDING

Thrasher Research Fund and Clinical Health Research Institute at Stanford University.

Whole-body MRI for initial staging of paediatric lymphoma: prospective comparison to an FDG-PET/CT-based reference standard

OBJECTIVE

To compare whole-body MRI, including diffusion-weighted imaging (whole-body MRI-DWI), with FDG-PET/CT for staging newly diagnosed paediatric lymphoma.

METHODS

A total of 36 children with newly diagnosed lymphoma prospectively underwent both whole-body MRI-DWI and FDG-PET/CT. Whole-body MRI-DWI was successfully performed in 33 patients (mean age 13.9 years). Whole-body MRI-DWI was independently evaluated by two blinded observers. After consensus reading, an unblinded expert panel evaluated the discrepant findings between whole-body MRI-DWI and FDG-PET/CT and used bone marrow biopsy, other imaging data and clinical information to derive an FDG-PET/CT-based reference standard.

RESULTS

Interobserver agreement of whole-body MRI-DWI was good [all nodal sites together (κ = 0.79); all extranodal sites together (κ = 0.69)]. There was very good agreement between the consensus whole-body MRI-DWI- and FDG-PET/CT-based reference standard for nodal (κ = 0.91) and extranodal (κ = 0.94) staging. The sensitivity and specificity of consensus whole-body MRI-DWI were 93 % and 98 % for nodal staging and 89 % and 100 % for extranodal staging, respectively. Following removal of MRI reader errors, the disease stage according to whole-body MRI-DWI agreed with the reference standard in 28 of 33 patients.

CONCLUSIONS

Our results indicate that whole-body MRI-DWI is feasible for staging paediatric lymphoma and could potentially serve as a good radiation-free alternative to FDG-PET/CT.

KEYPOINTS

• Accurate staging is important for treatment planning and assessing prognosis • Whole-body MRI-DWI could be a good radiation-free alternative to FDG-PET/CT • Interobserver agreement of whole-body MRI-DWI is good • Agreement between whole-body MRI and the FDG-PET/CT reference standard is good • Most discrepancies were caused by suboptimal accuracy of size measurements on MRI.

Magnetic resonance imaging of the immature skeleton

Magnetic resonance (MR) is unique in its ability to allow assessment of bone marrow, epiphyseal, physeal, and articular cartilage as well as tendons and ligaments. An understanding of skeletal maturation and the accompanying changes on MR is of utmost importance in pediatric radiology. In particular, it is important to recognize the normal spectrum related to ossification and marrow transformation. This review will include a brief description of main indications and common pitfalls in musculoskeletal MR in children. Also, we will focus on the MR appearance of the growing pediatric skeleton on the most commonly used sequences.

Advances in pediatric oncology MRI

Refined stratification of disease is thought to result in better survival from childhood malignant disease while minimizing the adverse effects of anticancer therapies. There is a potential for magnetic resonance imaging (MRI) to contribute to such stratification by improved tissue characterization, anatomical depiction, staging, and assessment of early treatment response. Recent advances in pediatric MRI outside the central nervous system (CNS) are reviewed in this context. The focus is on new applications for conventional MRI and on clinical implementation of tissue-specific and quantitative techniques. This area is largely unexplored, and potential directions for research are indicated.

Comparison of PET-CT and magnetic resonance diffusion weighted imaging with body suppression (DWIBS) for initial staging of malignant lymphomas

OBJECTIVE

To evaluate the clinical impact of diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) in staging of malignant lymphoma.

METHODS

Twenty-three patients with proven malignant lymphomas were prospectively enrolled. DWIBS (b=0, 1000 s/mm(2)) examinations and PET-CT were performed respectively on an Intera 1.5 T unit and a Gyroscan PET-CT scan (Philips Medical system, Best, the Netherland). The criteria for positive node involvement were a size over 10 mm or an apparent diffusion coefficient (ADC) value under 0.7510(-3) mm(2)/s for nodes under 10mm. For extranodal analysis, a high or heterogeneous signal on DWIBS was considered as positive. In cases of discordance, the reference standard for each region or organ was established at 6 months after the diagnosis according to all available clinical, biological information, as well as histological evidence or follow-up to prove or disprove the presence of disease.

RESULTS

DWIBS and PET-CT results were congruent in 333 node regions on the 345 areas analyzed, with excellent agreement (κ=0.97, P<0.0001). From 433 organs analyzed (one patient had splenectomy) extranodal disease was detected in 22 organs on DWIBS. The two imaging techniques agreed on 430 organs (κ=0.99, P<0.0001). Finally, Ann Arbor stages based on DWIBS and those of PET/CT were in agreement for 23 patients.

CONCLUSIONS

For malignant lymphoma in a pre-therapeutic context, agreement between diffusion-weighted whole-body imaging and PET/CT is high for Ann Arbor staging.

Role of diffusion-weighted imaging in differentiating benign and malignant pediatric abdominal tumors

BACKGROUND

Solid malignant tumors are more highly cellular than benign lesions and hence have a restricted diffusion of water molecules.

OBJECTIVE

To evaluate whether diffusion-weighted MR imaging (DWI) can differentiate between benign and malignant pediatric abdominal tumors.

MATERIALS AND METHODS

We retrospectively analyzed DWI scans of 68 consecutive children with 39 benign and 34 malignant abdominal masses. To calculate the apparent diffusion coefficient (ADC) maps and ADC values, we used 1.5-T sequences at TR/TE/b-value of 5,250-7,500/54-64/b = 0, 500 and 3-T sequences at 3,500-4,000/66-73/b = 0, 500, 800. ADC values were compared between benign and malignant and between data derived at 1.5 tesla (T) and at 3 tesla magnetic field strength, using the Mann-Whitney-Wilcoxon test, ANOVA and a receiver operating curve (ROC) analysis.

RESULTS

There was no significant difference in ADC values obtained at 1.5 T and 3 T (P = 0.962). Mean ADC values (× 10(-3) mm(2)/s) were 1.07 for solid malignant tumors, 1.6 for solid benign tumors, 2.9 for necrotic portions of malignant tumors and 3.1 for cystic benign lesions. The differences between malignant and benign solid tumors were statistically significant (P = 0.000025). ROC analysis revealed an optimal cut-off ADC value for differentiating malignant and benign solid tumors as 1.29 with excellent inter-observer reliability (alpha score 0.88).

CONCLUSION

DWI scans and ADC values can contribute to distinguishing between benign and malignant pediatric abdominal tumors.

Sickle cell-related bone marrow complications: the utility of diffusion-weighted magnetic resonance imaging

In sickle cell disease diffusion-weighted imaging (DWI) are helpful, costeffective, and promising techniques for differentiating bone marrow involvements. So we suggest to consider a MR diffusion panoramic study (whole-body diffusion MR) when multiple follow-up imaging is required in young patients who are at high risk for chronic radiation damage, so that alternatives to PET study may be taken into consideration.

TP53 p.R337H is a conditional cancer-predisposing mutation: further evidence from a homozygous patient

BACKGROUND

Adrenocortical carcinomas (ACCs) are among the most common childhood cancers occurring in infants affected with the Li-Fraumeni and Li- Fraumeni-like (LFS/LFL) syndromes, which are caused by dominant germline mutations in the TP53 gene. In Brazil, a particular mutation, occurring in the tetramerisation domain of the gene, p.R337H, is exceedingly common due to a founder effect and is strongly associated with ACC. In this report, we describe the phenotype and long-term clinical follow-up of a female child diagnosed with ACC and homozygous for the TP53 p.R337H founder mutation.

CASE PRESENTATION

At age 11 months, the patient was diagnosed with a virilising anaplastic adrenal cortical tumour, which was completely excised without disturbing the adrenal capsule. Family history was consistent with an LFL tumour pattern, and genotyping identified the TP53 p.R337H mutation in both alleles in genomic DNA from lymphocytes and fibroblasts. Haplotype analysis confirmed the occurrence of the mutation in the same founder haplotype previously described in other Brazilian patients. No other germline or somatic TP53 mutations or rearrangements were identified. At age 9 years, the child was asymptomatic and had no evidence of endocrine derangements. Full body and brain magnetic resonance imaging (MRI) failed to detect any suspicious proliferative lesions, and cardiopulmonary exercise testing results were within the normal reference for the child's age, ruling out a major exercise capacity deficiency.

CONCLUSION

This is the first clinical and aerobic functional capacity documentation of a patient who carries two mutant TP53 alleles and no wild-type allele. Our results support the hypothesis that TP53 p.R337H, the most common TP53 mutation ever described in any population, is a conditional mutant. Furthermore, our observations over a long period of clinical follow-up suggest that TP53 p.R337H homozygotes do not have a more severe disease phenotype than do heterozygote carriers of the same mutation. Patients with the homozygous TP53 p.R337H genotype will require careful surveillance for lifetime cancer risk and for effects on metabolic capacity later in life.

Chronic recurrent multifocal osteomyelitis (CRMO): a longitudinal case series review

BACKGROUND

Chronic recurrent multifocal osteomyelitis (CRMO) is an autoinflammatory disorder that is currently diagnosed based on clinical, radiologic, pathological and longitudinal findings.

OBJECTIVE

To provide detailed descriptions of CRMO lesion patterns seen on radiographs and MRI and to suggest clinical use of whole-body MRI and propose noninvasive diagnostic strategy.

MATERIALS AND METHODS

Retrospective longitudinal study (1989-2010) of 31 children (22 girls, 9 boys) diagnosed with CRMO. Imaging data were evaluated by two pediatric radiologists.

RESULTS

Mean age at diagnosis was 11 years (3-17). A total of 108 lesions were investigated. The most common sites were the long bone metaphyses (56 lesions in 24 children) especially femoral and tibial (20/24); pelvis (10/31); spine (9/31); clavicle (6/31) and mandible (3/31). In long bones, the radiologic appearance was normal (22/56), mixed lytic and sclerotic (20/56), sclerotic (8/56) or lytic (6/56) often juxtaphyseal (36/56), with hyperostosis or periosteal thickening (10/56). Vertebral involvement was often multifocal (6/9). Medullary edema was seen on MRI (42) with epiphyseal (23/42) or soft-tissue (22/42) inflammation and juxtaphyseal nodule-like appearance (7/42). Whole-body MRI (15/31) was key in detecting subclinical lesions.

CONCLUSION

CRMO is a polymorphous disorder in which whole-body MRI is extremely useful for showing subclinical edema. Vertebral collapse requires long-term monitoring.

Marrow: red, yellow and bad

Bone marrow is one of the largest and most dynamic tissues in the body, and it is well-depicted on conventional MRI sequences. However, often only perfunctory attention is paid to the bone marrow on musculoskeletal imaging studies, raising the risk of delayed or missed diagnoses. To guide appropriate recognition of normal variants and pathological processes involving the marrow compartment, this article describes and depicts the physiological spatiotemporal pattern of conversion of hematopoietic red marrow to fatty yellow marrow during childhood and adolescence, and the characteristic imaging findings of disorders involving marrow hyperplasia/reconversion, marrow infiltration/deposition and marrow depletion/failure.