Whole-body magnetic resonance imaging in children: state of the art

Magnetic resonance imaging of the musculoskeletal system in the diagnosis of rheumatic diseases in the pediatric population

Magnetic resonance imaging (MRI) of the musculoskeletal system is an examination increasingly performed for suspected juvenile idiopathic arthritis, chronic nonbacterial osteomyelitis and juvenile idiopathic inflammatory myopathies, as well as other rheumatic diseases of developmental age. T1-, T2- and PD-weighted with or without fat suppression or short tau inversion recovery/turbo inversion recovery magnitude (STIR/TIRM) sequences and post-contrast sequences are evaluated to diagnose pathological changes in the synovial membrane, subchondral bone marrow and surrounding soft tissues. Magnetic resonance imaging allows detection of synovitis, tenosynovitis, bursitis, and enthesitis as well as bone marrow edema and soft tissue edema. Several pediatric-specific MRI scoring systems have been developed and validated to standardize and facilitate the assessment of the extent of the inflammatory process and disease activity in MRI. Early detection of inflammatory changes allows the inclusion of comprehensive pharmacotherapy giving the possibility of permanent remission and objective measurement of the effectiveness of treatment.

Whole-body MRI in children and adolescents: Can T2-weighted Dixon fat-only images replace standard T1-weighted images in the assessment of bone marrow?

OBJECTIVE

When performing whole-body MRI for bone marrow assessment in children, optimizing scan time is crucial. The aim was to compare T2 Dixon fat-only and TSE T1-weighted sequences in the assessment of bone marrow high signal areas seen on T2 Dixon water-only in healthy children and adolescents.

MATERIALS AND METHODS

Whole-body MRIs from 196 healthy children and adolescents aged 6 to 19 years (mean 12.0) were obtained including T2 TSE Dixon and T1 TSE-weighted images. Areas with increased signal on T2 Dixon water-only images were scored using a novel, validated scoring system and classified into "minor" or "major" findings according to size and intensity, where "major" referred to changes easily being misdiagnosed as pathology in a clinical setting. Areas were assessed for low signal on T2 Dixon fat-only images and, after at least three weeks to avoid recall bias, on the T1-weighted sequence by two experienced pediatric radiologists.

RESULTS

1250 high signal areas were evaluated on T2 Dixon water-only images. In 1159/1250 (92.7%) low signal was seen on both T2 Dixon fat-only and T1-weighted sequences while in 24 (1.9%) it was not present on either sequence, with an absolute agreement of 94.6%. Discordant findings were found in 67 areas, of which in 18 (1.5%) low signal was visible on T1-weighted images alone and in 49 (3.9%) on T2 Dixon fat-only alone. The overall kappa value between the two sequences was 0.39. The agreement was higher for major as compared to minor findings (kappa values of 0.69 and 0.29, respectively) and higher for the older age groups.

CONCLUSION

T2 Dixon fat-only can replace T1-weighted sequence on whole-body MRI for bone marrow assessment in children over the age of nine, thus reducing scan time.

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.

Infantile myofibromatosis: review of imaging findings and emphasis on correlation between MRI and histopathological findings

BACKGROUND

Infantile myofibromatosis (IM) is the most common fibrous tumor of infancy. MRI is considered the gold standard in IM evaluation. Very little has been published about IM with histopathology correlation in the pediatric age.

PURPOSE

Describe imaging findings in IM and correlate MRI findings with histopathology.

MATERIAL AND METHODS

Imaging findings of 17 patients with IM were retrospectively analyzed including CT, US and MRI. Signal characteristics on T1-, T2-weighted and STIR imaging, extent of T2-hyperintensity, degree & pattern of enhancement, diffusion restriction, location & margins, & involvement of adjacent structures were tabulated. Histopathology findings included cellularity, collagenization, myxoid changes, atypia, mitosis & microscopic invasion. Established grading scores were utilized.

RESULTS

Relative to normal skeletal muscle, on T1-weighted imaging, 9 lesions had similar signal while the remaining had a mixture of iso & hypo intensity; whereas on T2-weighted and STIR imaging, all 12 lesions demonstrated a mixture of iso, hypo & hyperintensity. T2-hyperintensity was grade 2 in one, grade 3 in 8 & grade 4 in 3 lesions. Intensity of enhancement was grade 2 in one, grade 3 in 8 & grade 4 in 3 lesions. Enhancement was predominantly peripheral in all 12 lesions. Extent of T2-hyperintensity & degree of enhancement corresponded to variable grades on histopathology. CT and US showed nonspecific findings.

CONCLUSION

On MRI, IM has a mixture of signal intensity with predominant hyperintense signal on T2W images. However various signal & enhancement features correlated poorly with specific histopathologic grades.

Whole-body magnetic resonance imaging: techniques and non-oncologic indications

Whole-body MRI is increasingly utilized for assessing oncologic and non-oncologic diseases in infants, children and adolescents. Focusing on the non-oncologic indications, this review covers technical elements required to perform whole-body MRI, the advantages and limitations of the technique, and protocol modifications tailored to specific indications. Rheumatologic diseases account for the majority of non-oncologic whole-body MRI performed in pediatric patients at the author's institution. Whole-body MRI helps in establishing the diagnosis, documenting disease extent and severity, and monitoring treatment response in enthesitis-related arthritis (ERA) and chronic recurrent multifocal osteomyelitis (CRMO). Other non-oncologic indications for whole-body MRI include osteomyelitis (usually pyogenic), pyrexia of unknown origin, neuromuscular disorders, inherited and inflammatory myopathies such as juvenile dermatomyositis and polymyositis, avascular necrosis, and fat/storage disorders. Use of whole-body MRI in postmortem imaging is rising, while whole-body MRI in non-accidental injury is considered to be of limited value. Imaging findings for a range of these indications are reviewed with whole-body MRI examples.

Imaging of cancer predisposition syndromes

Pediatric cancer predisposition syndromes comprise a group of diseases characterized by specific tumors or a concomitance of tumors in infants, children and adolescents, suggesting a genetic cancer susceptibility condition. Most but not all have germline pathogenic variants on genetic testing. For some children with cancer predisposition syndromes, this diagnosis is based on their own or a family history of related neoplasms, or associated clinical manifestations. These tumors have variable incidence and age of onset. Imaging encompasses investigation in symptomatic children for diagnosis, staging and monitoring for treatment response and metastatic disease, as well as surveillance for primary tumors in asymptomatic children. In this review the author focuses on the role of surveillance imaging in childhood cancer predisposition syndromes, whole-body magnetic resonance imaging (whole-body MRI) in particular. Diagnosis and staging of specific tumors are addressed elsewhere in this series. The benefits of surveillance imaging include early detection and improved outcomes and are still being established for a number of cancer predisposition syndromes. The benefits must be weighed against risks including potential technique-related issues relating to sedation or contrast agents, false-positive imaging findings, and cost - both financial and psychosocial. The author discusses general principles for whole-body MRI interpretation along with findings in specific syndromes where whole-body MRI screening is recommended, such as Li-Fraumeni syndrome.

Whole-Body Magnetic Resonance Imaging in the Oncology Setting: An Overview and Update on Recent Advances

Whole-body magnetic resonance imaging is becoming an important tool in oncology as a nonirradiating imaging technique since recent technological advances allowed the incorporation of high-quality imaging in an adequate time. Moreover, the noninjection of radioisotope/intravenous contrast, low cost compared with traditional nuclear medicine techniques, and fast acquisition times are another distinct feature. Thus, the purpose of this article is to review the whole-body magnetic resonance imaging protocol and its main applications in the oncology setting.

Pulmonary atelectasis in newborns with clinically treatable diseases who are on mechanical ventilation: clinical and radiological aspects

Objective

To analyze the radiological aspects of pulmonary atelectasis in newborns on mechanical ventilation and treated in an intensive care unit, associating the characteristics of atelectasis with the positioning of the head and endotracheal tube seen on the chest X-ray, as well as with the clinical variables.

Materials and Methods

This was a retrospective cross-sectional study of 60 newborns treated between 1985 and 2015. Data were collected from medical records and radiology reports. To identify associations between variables, we used Fisher's exact test. The level of significance was set at p < 0.05.

Results

The clinical characteristics associated with improper positioning of the endotracheal tube were prematurity and a birth weight of less than 1000 g. Among the newborns evaluated, the most common comorbidity was hyaline membrane disease. Atelectasis was seen most frequently in the right upper lobe, although cases of total atelectasis were more common in the left lung. Malpositioning of the head showed a trend toward an association with atelectasis in the left upper lobe.

Conclusion

Pulmonary atelectasis is a common complication in newborns on mechanical ventilation. Radiological evaluation of the endotracheal tube placement provides relevant information for the early correction of this condition.

Chronic recurrent multifocal osteomyelitis exhibiting predominance of periosteal reaction

Chronic recurrent multifocal osteomyelitis is an idiopathic nonpyogenic autoinflammatory bone disorder involving multiple sites, with clinical progression persisting for more than 6 months and which may have episodes of remission and exacerbation in the long term. It represents up to 2-5% of the cases of osteomyelitis, with an approximate incidence of up to 4/1,000,000 individuals, and average age of disease onset estimated between 8-11 years, predominantly in females. The legs are the most affected, with a predilection for metaphyseal regions along the growth plate. We describe the case of a female patient, aged 2 years and 5 months, with involvement of the left ulna, right jaw and left tibia, showing a predominance of periosteal reaction as main finding.

Evaluation of the indications for performing magnetic resonance imaging of the female pelvis at a referral center for cancer, according to the American College of Radiology criteria

Objective

To evaluate the indications for performing magnetic resonance imaging of the female pelvis at a referral center for cancer.

Materials and Methods

This was a retrospective, single-center study, conducted by reviewing medical records and imaging reports. We included 1060 female patients who underwent magnetic resonance imaging of the pelvis at a cancer center between January 2013 and June 2014. The indications for performing the examination were classified according to the American College of Radiology (ACR) criteria.

Results

The mean age of the patients was 52.6 ± 14.8 years, and 49.8% were perimenopausal or postmenopausal. The majority (63.9%) had a history of cancer, which was gynecologic in 29.5% and nongynecologic in 34.4%. Of the patients evaluated, 44.0% had clinical complaints, the most common being pelvic pain (in 11.5%) and bleeding (in 9.8%), and 34.7% of patients had previously had abnormal findings on ultrasound. Most (76.7%) of the patients met the criteria for undergoing magnetic resonance imaging, according to the ACR guidelines. The main indications were evaluation of tumor recurrence after surgical resection (in 25.9%); detection and staging of gynecologic neoplasms (in 23.3%); and evaluation of pelvic pain or of a mass (in 17.1%).

Conclusion

In the majority of the cases evaluated, magnetic resonance imaging was clearly indicated according to the ACR criteria. The main indication was local recurrence after surgical treatment of pelvic malignancies, which is consistent with the routine protocols at cancer centers.

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.

Whole-body magnetic resonance imaging in the diagnosis and follow-up of multicentric infantile myofibromatosis: A case report

Myofibromatosis is an uncommon disorder of infancy, characterized by proliferation of myofibroblasts in solitary or multiple nodules. The clinical characteristics depend on the involved sites: Myofibromatosis may develop as a musculoskeletal form, with non-painful swellings and eventual mass effect symptoms, or as a generalized form with visceral involvement and organ failure. Prognosis and therapy vary between the abovementioned patterns. When there is no visceral involvement, the tumors may regress spontaneously; however, the visceral form may represent a lifethreatening condition with poor outcome and it requires aggressive management. Imaging assessment of disease spread is mandatory to determine diagnosis, prognosis and therapy. Due to the young age of the patients, a radiation-free evaluation is recommended. We herein describe a case of musculoskeletal myofibromatosis diagnosed in a 3-month-old male infant, investigated by serial wholebody magnetic resonance imaging (MRI) examination. The histological analysis and MRI characteristics enabled a correct diagnosis and organ involvement assessment with no radiation exposure. Moreover, whole-body MRI sequences provided a detailed evaluation of the disease within a short time frame, reducing the time of sedation, which is required to perform MRI in very young patients. Therefore, whole-body MRI was found to be accurate and safe in the diagnosis and follow-up of multicentric infantile myofibromatosis.

The value of anterior displacement of the abdominal aorta in diagnosing neuroblastoma in children

Objective

To determine the value of anterior displacement of the abdominal aorta, when present at any level or only at the level of the adrenal gland, contralateral to the mass, in diagnosing neuroblastoma on computed tomography or magnetic resonance imaging in children up to 7 years of age.

Materials and Methods

Imaging examinations of 66 patients were classified by consensus as for the presence of anterior aorta displacement and were compared with the pathology report.

Results

We found anterior abdominal aorta displacement in 26 (39.39%) of the 66 patients evaluated. Among those 26 patients, we identified neuroblastoma in 22 (84.62%), nephroblastoma in 3 (11.54%), and Burkitt lymphoma in 1 (3.85%). The positive predictive value was 84.62%, and the specificity was 88.24%. The displacement of the aorta was at the adrenal level, contralateral to the mass, in 14 cases, all of which were attributed to neuroblastoma.

Conclusion

When the abdominal aorta is displaced at the level of the adrenal gland, contralateral to the mass, it can be said that the diagnosis is neuroblastoma, whereas abdominal aorta displacement occurring at other abdominal levels has a positive predictive value for neuroblastoma of approximately 85%.

Speeding up PET/MR for cancer staging of children and young adults

OBJECTIVE

Combining ¹⁸F-FDG PET with whole-body MR for paediatric cancer staging is practically feasible if imaging protocols can be streamlined. We compared ¹⁸F-FDG PET/STIR with accelerated ¹⁸F-FDG PET/FSPGR for whole-body tumour imaging in children and young adults.

METHODS

Thirty-three children and young adults (17.5 ± 5.5 years, range 10-30) with malignant lymphoma or sarcoma underwent a ¹⁸F-FDG PET staging examination, followed by ferumoxytol-enhanced STIR and FSPGR whole-body MR. ¹⁸F-FDG PET scans were fused with MR data and the number and location of tumours on each integrated examination were determined. Histopathology and follow-up imaging served as standard of reference. The agreement of each MR sequence with the reference and whole-body imaging times were compared using Cohen's kappa coefficient and Student's t-test, respectively.

RESULTS

Comparing ¹⁸F-FDG PET/FSPGR to ¹⁸F-FDG PET/STIR, sensitivities were 99.3 % for both, specificities were statistically equivalent, 99.8 versus 99.9 %, and the agreement with the reference based on Cohen's kappa coefficient was also statistically equivalent, 0.989 versus 0.992. However, the total scan-time for accelerated FSPGR of 19.8 ± 5.3 minutes was significantly shorter compared to 29.0 ± 7.6 minutes for STIR (p = 0.001).

CONCLUSION

F-FDG PET/FSPGR demonstrated equivalent sensitivities and specificities for cancer staging compared to ¹⁸F-FDG PET/STIR, but could be acquired with shorter acquisition time.

KEY POINTS

• Breath-hold FSPGR sequences shorten the data acquisition time for whole-body MR and PET/MR. • Ferumoxytol provides long-lasting vascular contrast for whole-body MR and PET/MR. • ¹⁸ F-FDG PET/FSPGR data provided equal sensitivity and specificity for cancer staging compared to ¹⁸ F-FDG PET/STIR.

Whole-body MRI: non-oncological applications in paediatrics

Whole-body magnetic resonance imaging (WBMRI) is a fast and accurate method for detecting and monitoring of diseases throughout the entire body without exposure to ionizing radiation. Among emerging non-oncological potential applications of WBMRI, rheumatological diseases play an important role. Rheumatological WBMRI applications include the evaluation of chronic multifocal recurrent osteomyelitis, dermatomyositis, fever of unknown origin, arthritis, and connective tissue diseases. Aim of this review is to give an overview of the use of WBMRI in rheumatological field.