Use of super resolution reconstruction MRI for surgical planning in Placenta accreta spectrum disorder: Case series

INTRODUCTION

Comprehensive imaging using ultrasound and MRI of placenta accreta spectrum (PAS) aims to prevent catastrophic haemorrhage and maternal death. Standard MRI of the placenta is limited by between-slice motion which can be mitigated by super-resolution reconstruction (SRR) MRI. We applied SRR in suspected PAS cases to determine its ability to enhance anatomical placental assessment and predict adverse maternal outcome.

METHODS

Suspected PAS patients (n = 22) underwent MRI at a gestational age (weeks + days) of (32+3±3+2, range (27+1-38+6)). SRR of the placental-myometrial-bladder interface involving rigid motion correction of acquired MRI slices combined with robust outlier detection to reconstruct an isotropic high-resolution volume, was achieved in twelve. 2D MRI or SRR images alone, and paired data were assessed by four radiologists in three review rounds. All radiologists were blinded to results of the ultrasound, original MR image reports, case outcomes, and PAS diagnosis. A Random Forest Classification model was used to highlight the most predictive pathological MRI markers for major obstetric haemorrhage (MOH), bladder adherence (BA), and placental attachment depth (PAD).

RESULTS

At delivery, four patients had placenta praevia with no abnormal attachment, two were clinically diagnosed with PAS, and six had histopathological PAS confirmation. Pathological MRI markers (T2-dark intraplacental bands, and loss of retroplacental T2-hypointense line) predicting MOH were more visible using SRR imaging (accuracy 0.73), in comparison to 2D MRI or paired imaging. Bladder wall interruption, predicting BA, was only easily detected by paired imaging (accuracy 0.72). Better detection of certain pathological markers predicting PAD was found using 2D MRI (placental bulge and myometrial thinning (accuracy 0.81)), and SRR (loss of retroplacental T2-hypointense line (accuracy 0.82)).

DISCUSSION

The addition of SRR to 2D MRI potentially improved anatomical assessment of certain pathological MRI markers of abnormal placentation that predict maternal morbidity which may benefit surgical planning.

A National Referral Service for Paediatric Brachytherapy: An Evolving Practice and Outcomes Over 13 Years

AIMS

Most children requiring radiotherapy receive external beam treatment and few have tumours suitable for brachytherapy. No paediatric radiotherapy centre will treat enough patients from its own normal catchment population for expertise in brachytherapy to be developed and sustained. Following discussion and agreement in the national paediatric radiotherapy group, a service for paediatric brachytherapy in the UK has been developed. We report the process that has evolved over more than 10 years, with survival and functional outcome results.

MATERIALS AND METHODS

Since 2009, potential patients have been referred to the central paediatric oncology multidisciplinary team meeting, where imaging, pathology and treatment options are discussed. Since 2013, the National Soft Tissue Sarcoma Advisory Panel has also reviewed most patients, with the principal aim of advising on the most suitable primary tumour management for complex patients. Clinical assessment and examination under anaesthetic with biopsies may be undertaken to confirm the appropriateness of brachytherapy, either alone or following conservative surgery. Fractionated high dose rate brachytherapy was delivered to a computed tomography planned volume after implantation of catheters under ultrasound imaging guidance. Since 2019, follow-up has been in a dedicated multidisciplinary clinic.

RESULTS

From 2009 to 2021 inclusive, 35 patients (16 female, 19 male, aged 8 months to 17 years 6 months) have been treated. Histology was soft-tissue sarcoma in 33 patients and carcinoma in two. The treated site was pelvic in 31 patients and head and neck in four. With a median follow-up of 5 years, the local control and overall survival rates are 100%. Complications have been few, and functional outcome is good.

CONCLUSION

Brachytherapy is effective for selected paediatric patients, resulting in excellent tumour control and good functional results. It is feasible to deliver paediatric brachytherapy at a single centre within a national referral service.

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.

Abdominal US in Pediatric Inflammatory Multisystem Syndrome Associated with SARS-CoV-2 (PIMS-TS)

Background Children with pediatric inflammatory syndrome temporally associated with SARS-CoV-2 (PIMS-TS), also known as multisystem inflammatory syndrome in children, present with abdominal pain among other nonspecific symptoms. Although initial imaging features of PIMS-TS have been reported, the duration of sonographic features remains unknown. Purpose To describe the abdominal US features of PIMS-TS at initial presentation and follow-up. Materials and Methods A retrospective review of children and young adults presenting with clinical features suspicious for PIMS-TS between April 2020 and June 2021 was carried out. US features were documented and reviewed at initial presentation and follow-up. Descriptive statistics were used and interobserver variability was calculated. Results Of 140 children and young adults presenting with suspected PIMS-TS, 120 had confirmed PIMS-TS (median age, 9 years; interquartile range, 7-12 years; 65 male patients) and 102 underwent abdominal US at presentation. PIMS-TS was present as a single abnormality in 109 of the 120 patients (91%) and abdominal symptoms were present in 104 of the 109 (95%). US examinations were abnormal in 86 of 102 patients (84%), with ascites being the most common abnormality in 65 (64%; 95% CI: 54, 73). Bowel wall thickening was present at US in 14 of the 102 patients (14%; 95% CI: 7, 20) and mesenteric inflammation was present in 16 (16%; 95% CI: 9, 23); all of these patients presented with abdominal symptoms. Among the patients with bowel wall thickening, the distal and terminal ileum were most involved (eight of 14 patients, 57%). Abdominal symptoms decreased to seven of 56 patients (13%) in those followed up at 6 months. Thirty-eight patients underwent follow-up US, and the presence of bowel inflammation had decreased to three of 27 patients (11%; 95% CI: -1, 23) in those followed up for less than 2 months and 0 of 17 (0%) in those followed up for more than 2 months. Conclusion Of 102 patients with pediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2 who underwent US at presentation, 14 (14%) had abdominal US findings of bowel inflammation and 16 (16%) had mesenteric edema. All US abnormalities resolved after 2 months. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by van Rijn and Pajkrt in this issue.

Super-resolution Reconstruction MRI Application in Fetal Neck Masses and Congenital High Airway Obstruction Syndrome

Objective

Reliable airway patency diagnosis in fetal tracheolaryngeal obstruction is crucial to select and plan ex utero intrapartum treatment (EXIT) surgery. We compared the clinical utility of magnetic resonance imaging (MRI) super-resolution reconstruction (SRR) of the trachea, which can mitigate unpredictable fetal motion effects, with standard 2-dimensional (2D) MRI for airway patency diagnosis and assessment of fetal neck mass anatomy.

Study Design

A single-center case series of 7 consecutive singleton pregnancies with complex upper airway obstruction (2013-2019).

Setting

A tertiary fetal medicine unit performing EXIT surgery.

Methods

MRI SRR of the trachea was performed involving rigid motion correction of acquired 2D MRI slices combined with robust outlier detection to reconstruct an isotropic high-resolution volume. SRR, 2D MRI, and paired data were blindly assessed by 3 radiologists in 3 experimental rounds.

Results

Airway patency was correctly diagnosed in 4 of 7 cases (57%) with 2D MRI as compared with 2 of 7 cases (29%) with SRR alone or paired 2D MRI and SRR. Radiologists were more confident (P = .026) in airway patency diagnosis when using 2D MRI than SRR. Anatomic clarity was higher with SRR (P = .027) or paired data (P = .041) in comparison with 2D MRI alone. Radiologists detected further anatomic details by using paired images versus 2D MRI alone (P < .001). Cognitive load, as assessed by the NASA Task Load Index, was increased with paired or SRR data in comparison with 2D MRI.

Conclusion

The addition of SRR to 2D MRI does not increase fetal airway patency diagnostic accuracy but does provide improved anatomic information, which may benefit surgical planning of EXIT procedures.

European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB): An Update on the Pediatric CEUS Registry on Behalf of the "EFSUMB Pediatric CEUS Registry Working Group"

The European Federation of Ultrasound in Medicine and Biology (EFSUMB) created the "EFSUMB Pediatric Registry" (EFSUMB EPR) with the purpose of collecting data regarding the intravenous application of pediatric contrast-enhanced ultrasound (CEUS). The primary aim was to document the current clinical practice and usefulness of the technique and secondarily to assess CEUS safety in children. We issue the preliminary results of this database and examine the overall practice of CEUS in children in Europe.

18F-FDG PET/MRI for Staging and Interim Response Assessment in Pediatric and Adolescent Hodgkin Lymphoma: A Prospective Study with 18F-FDG PET/CT as the Reference Standard

Treatment regimens for pediatric Hodgkin lymphoma (HL) depend on accurate staging and treatment response assessment, based on accurate disease distribution and metabolic activity depiction. With the aim of radiation dose reduction, we compared the diagnostic performance of ¹⁸F-FDG PET/MRI with a ¹⁸F-FDG PET/CT reference standard for staging and response assessment. Methods: Twenty-four patients (mean age, 15.4 y; range, 8-19.5 y) with histologically proven HL were prospectively and consecutively recruited in 2015 and 2016, undergoing both ¹⁸F-FDG PET/CT and ¹⁸F-FDG PET/MRI at initial staging (n = 24) and at response assessment (n = 21). The diagnostic accuracy of ¹⁸F-FDG PET/MRI for both nodal and extranodal disease was compared with that of ¹⁸F-FDG PET/CT, which was considered the reference standard. Discrepancies were retrospectively classified as perceptual or technical errors, and ¹⁸F-FDG PET/MRI and ¹⁸F-FDG PET/CT were corrected by removing perceptual error. Agreement with Ann Arbor staging and Deauville grading was also assessed. Results: For nodal and extranodal sites combined, corrected staging ¹⁸F-FDG PET/MRI sensitivity was 100% (95% CI, 96.7%-100%) and specificity was 99.5% (95% CI, 98.3%-99.9%). Corrected response-assessment ¹⁸F-FDG PET/MRI sensitivity was 83.3% (95% CI, 36.5%-99.1%) and specificity was 100% (95% CI, 99.2%-100%). Modified Ann Arbor staging agreement between ¹⁸F-FDG PET/CT and ¹⁸F-FDG PET/MRI was perfect (κ = 1.0, P = 0.000). Deauville grading agreement between ¹⁸F-FDG PET/MRI and ¹⁸F-FDG PET/CT was excellent (κ = 0.835, P = 0.000). Conclusion: ¹⁸F-FDG PET/MRI is a promising alternative to ¹⁸F-FDG PET/CT for staging and response assessment in children with HL.

Contrast-enhanced ultrasound of the small organs in children

In pediatric and adult populations, intravenous contrast-enhanced ultrasound (CEUS) remains off-label for imaging of organs other than the liver and heart. This limited scope inhibits potential benefits of the new modality from a more widespread utilization. Yet, CEUS is potentially useful for imaging small organs such as the thyroid gland, lymph nodes, testes, ovaries and uterus, with all having locations and vasculature favorable for this type of examination. In the adult population, the utility of CEUS has been demonstrated in a growing number of studies for the evaluation of these small organs. The aim of this article is to present a review of pediatric CEUS of the thyroid gland, lymph nodes, testes, ovaries and uterus as well as to draw from the adult literature indications for possible applications in children.

Contrast-enhanced ultrasound of the pediatric bowel

Contrast-enhanced ultrasound (CEUS) has emerged as a valuable modality for bowel imaging in adults and children. CEUS enables visualization of the perfusion of the bowel wall and of the associated mesentery in healthy and disease states. In addition, CEUS images can be used to make quantitative measurements of contrast kinetics, allowing for objective assessment of bowel wall enhancement. Bowel CEUS is commonly applied to evaluate inflammatory bowel disease and to monitor treatment response. It has also been applied to evaluate necrotizing enterocolitis, intussusception, appendicitis and epiploic appendagitis, although experience with these applications is more limited. In this review article, we present the current experience using CEUS to evaluate the pediatric bowel with emphasis on inflammatory bowel disease, extrapolating the established experience from adult studies. We also discuss emerging applications of CEUS as an adjunct or problem-solving tool for evaluating bowel perfusion.

How to use abdominal X-rays in preterm infants suspected of developing necrotising enterocolitis

Necrotising enterocolitis (NEC) in preterm babies is a serious gastrointestinal emergency with potentially devastating consequences. Prompt and accurate diagnosis continues to be a challenge for health professionals. Early identification of clinical warning signs is extremely important, but the diagnosis relies heavily on the interpretation of abdominal radiographs. Postgraduate training of paediatricians and neonatologists in neonatal abdominal radiography is scarce, and there is variability of radiological input to neonatal services. Lack of a standardised approach and descriptive terminology for interpretation may result in inadequate communication between clinical and surgical teams, inaccurate diagnosis, inappropriate treatment, and unnecessary cessation of feeds and transfers to surgical units. This paper offers a guide designed for the doctor who on a busy night shift needs to interpret an abdominal radiograph and decide on a differential diagnosis of NEC in a preterm baby. It helps to provide structure and standardisation to interpretation of radiological signs using a comprehensive but simple method to support the clinical diagnosis. Our aim is to enhance the correct diagnosis of NEC.

Whole-body magnetic resonance imaging in paediatric Hodgkin lymphoma - evaluation of quantitative magnetic resonance metrics for nodal staging

BACKGROUND

Whole-body MRI is used for staging paediatric Hodgkin lymphoma, commonly using size thresholds, which fail to detect disease in normal-size lymph nodes.

OBJECTIVE

To investigate quantitative whole-body MRI metrics for nodal characterisation.

MATERIALS AND METHODS

Thirty-seven children with Hodgkin lymphoma underwent 1.5-tesla (T) whole-body MRI using short tau inversion recovery (STIR) half-Fourier-acquisition single-shot turbo-spin-echo and diffusion-weighted imaging (DWI). 18Flourine-2-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET)/CT was acquired as the reference standard. Two independent readers assessed 11 nodal sites. The readers measured short-axis-diameter, apparent diffusion coefficient, (ADC) and normalised T2-signal intensity of the largest lymph node at each site. We used receiver operating characteristics (ROC)/area-under-the-curve (AUC) analysis for each MRI metric and derived sensitivity and specificity for nodes with short-axis diameter ≥10 mm. Sub-analysis of sensitivity and specificity was performed with application of ADC cut-off values (<0.77, <1.15 and <1.79×10-3 mm2 s-1) to 5- to 9-mm nodes.

RESULTS

ROC/AUC values for reader 1/reader 2 were 0.80/0.80 and 0.81/0.81 for short-axis-diameter measured using DWI and STIR half-Fourier-acquisition single-shot turbo spin echo, respectively; 0.67/0.72 for normalised T2 signal intensity and 0.74/0.67 for ADC. Sensitivity and specificity for a short-axis diameter ≥10 mm were 84.2% and 66.7% for Reader 1 and 82.9% and 68.9% for Reader 2. Applying a short-axis-diameter ≥10-mm threshold followed by ADC cut-offs to normal-size 5- to 9-mm nodes resulted in sensitivity and specificity for Reader 1 of 88.8% and 60%, 92.1% and 56.7%, and 100% and 16.7%; and for Reader 2, 86.1% and 67.2%, 95.3% and 65.6%, and 100% and 19.7%; and ADC thresholds of <0.77, <1.15, and <1.79×10-3 mm2 s-1, respectively.

CONCLUSION

Nodal size measurement provides the best single classifier for nodal disease status in paediatric Hodgkin lymphoma. Combined short-axis diameter and ADC thresholds marginally improve sensitivity and drop specificity compared with size classification alone.

Imaging features of extranodal involvement in paediatric Hodgkin lymphoma

Detecting extranodal disease in paediatric Hodgkin lymphoma is of great importance for both treatment and prognosis. Different imaging techniques can be used to identify these extranodal sites. This pictorial essay provides an overview of imaging features of extranodal disease manifestation in paediatric Hodgkin lymphoma.

Whole-body MRI for staging and interim response monitoring in paediatric and adolescent Hodgkin's lymphoma: a comparison with multi-modality reference standard including 18F-FDG-PET-CT

OBJECTIVES

To prospectively investigate concordance between whole-body MRI (WB-MRI) and a composite reference standard for initial staging and interim response evaluation in paediatric and adolescent Hodgkin's lymphoma.

METHODS

Fifty patients (32 male, age range 6-19 years) underwent WB-MRI and standard investigations, including 18F-FDG-PET-CT at diagnosis and following 2-3 chemotherapy cycles. Two radiologists in consensus interpreted WB-MRI using prespecified definitions of disease positivity. A third radiologist reviewed a subset of staging WB-MRIs (n = 38) separately to test for interobserver agreement. A multidisciplinary team derived a primary reference standard using all available imaging/clinical investigations. Subsequently, a second multidisciplinary panel rereviewed all imaging with long-term follow-up data to derive an enhanced reference standard. Interobserver agreement for WB-MRI reads was tested using kappa statistics. Concordance for correct classification of all disease sites, true positive rate (TPR), false positive rate (FPR) and kappa for staging/response agreement were calculated for WB-MRI.

RESULTS

There was discordance for full stage in 74% (95% CI 61.9-83.9%) and 44% (32.0-56.6%) of patients against the primary and enhanced reference standards, respectively. Against the enhanced reference standard, the WB-MRI TPR, FPR and kappa were 91%, 1% and 0.93 (0.90-0.96) for nodal disease and 79%, < 1% and 0.86 (0.77-0.95) for extra-nodal disease. WB-MRI response classification was correct in 25/38 evaluable patients (66%), underestimating response in 26% (kappa 0.30, 95% CI 0.04-0.57). There was a good agreement for nodal (kappa 0.78, 95% CI 0.73-0.84) and extra-nodal staging (kappa 0.60, 95% CI 0.41-0.78) between WB-MRI reads CONCLUSIONS: WB-MRI has reasonable accuracy for nodal and extra-nodal staging but is discordant with standard imaging in a substantial minority of patients, and tends to underestimate disease response.

KEY POINTS

• This prospective single-centre study showed discordance for full patient staging of 44% between WB-MRI and a multi-modality reference standard in paediatric and adolescent Hodgkin's lymphoma. • WB-MRI underestimates interim disease response in paediatric and adolescent Hodgkin's lymphoma. • WB-MRI shows promise in paediatric and adolescent Hodgkin's lymphoma but currently cannot replace conventional staging pathways including 18F-FDG-PET-CT.

Juvenile idiopathic arthritis: what is the utility of ultrasound?

Juvenile idiopathic arthritis (JIA) is a heterogeneous condition and an important cause of acquired disability in children. Evidence supports early treatment to prevent future complications. This relies on prompt diagnosis, achieved by a high index of clinical suspicion and supportive evidence, including the detection of joint and or tendon inflammation. Ultrasound is a readily accessible, well-tolerated, safe and accurate modality for assessing joints and the surrounding soft tissues. It can also be used to guide therapy into those joints and tendon sheaths resistant to systemic treatments. Ultrasound imaging is highly operator dependent, and the developing skeleton poses unique challenges in interpretation with sonographic findings that can mimic pathology and vice versa. Ultrasound technology has been rapidly improving and is more accessible than ever before. In this article, we review the normal appearances, highlight potential pitfalls and present the key pathological findings commonly seen in JIA.

Intra- and interobserver variability of whole-tumour apparent diffusion coefficient measurements in nephroblastoma: a pilot study

BACKGROUND

The apparent diffusion coefficient (ADC) is potentially useful for assessing treatment response in nephroblastoma (Wilms tumour). However the precision of ADC measurements in these heterogeneous lesions is unknown.

OBJECTIVE

To assess intra- and interobserver variability of whole-tumour ADC measurements in viable parts of nephroblastomas at diagnosis and after preoperative chemotherapy.

MATERIALS AND METHODS

We included children with histopathologically proven nephroblastoma who had undergone MRI with diffusion-weighted imaging before and after preoperative chemotherapy. Three independent observers performed whole-tumour ADC measurements of all lesions, excluding non-enhancing areas. One observer evaluated all lesions on two occasions. We performed analyses using Bland-Altman plots and concordance correlation coefficient (CCC) calculations with 95% limits of agreement for median ADC, difference between pre- and post-chemotherapy median ADC (ADC shift) and percentage of pixels with ADC values <1.0 × 10(-3) mm(2)/s.

RESULTS

In 22 lesions (13 pretreatment and 9 post-treatment) in 10 children the interobserver variability in median ADC and ADC shift were within the interval of approximately ±0.1 × 10(-3) mm(2)/s (limits of agreement for median ADC ranged -0.08-0.11 × 10(-3) mm(2)/s and for ADC-shift -0.11-0.09 × 10(-3) mm(2)/s). The interobserver variability for percentage of low-ADC pixels was larger and also biased. The calculated CCC confirmed good intra- and interobserver agreement (ρ-c ranging from 0.968 to 0.996).

CONCLUSION

Measurements of whole-tumour ADC values excluding necrotic areas seem to be sufficiently precise for detection of chemotherapy-related change.

Dynamic contrast-enhanced MRI improves accuracy for detecting focal splenic involvement in children and adolescents with Hodgkin disease

BACKGROUND

Accurate assessment of splenic disease is important for staging Hodgkin lymphoma.

OBJECTIVE

The purpose of this study was to assess T2-weighted imaging with and without dynamic contrast-enhanced (DCE) MRI for evaluation of splenic Hodgkin disease.

MATERIALS AND METHODS

Thirty-one children with Hodgkin lymphoma underwent whole-body T2-weighted MRI with supplementary DCE splenic imaging, and whole-body PET-CT before and following chemotherapy. Two experienced nuclear medicine physicians derived a PET-CT reference standard for splenic disease, augmented by follow-up imaging. Unaware of the PET-CT, two experienced radiologists independently evaluated MRI exercising a locked sequential read paradigm (T2-weighted then DCE review) and recorded the presence/absence of splenic disease at each stage. Performance of each radiologist was determined prior to and following review of DCE-MRI. Incorrect MRI findings were ascribed to reader (lesion present on MRI but missed by reader) or technical (lesion not present on MRI) error.

RESULTS

Seven children had splenic disease. Sensitivity/specificity of both radiologists for the detection of splenic involvement using T2-weighted images alone was 57%/100% and increased to 100%/100% with DCE-MRI. There were three instances of technical error on T2-weighted imaging; all lesions were visible on DCE-MRI.

CONCLUSIONS

T2-weighted imaging when complemented by DCE-MRI imaging may improve evaluation of Hodgkin disease splenic involvement.

Utility of diffusion-weighted imaging in the presurgical diagnosis of an infected urachal cyst

Urachal cysts are one of a spectrum of urachal abnormalities that occur following failure of regression of the allantois and presumptive bladder between 4 weeks and 6 weeks of gestation. Infection is the most common complication of this rare congenital anomaly. The nonspecific presentation may mimic other pathological processes, underlining their clinical and radiological significance. Imaging investigations typically include US and CT, both of which are limited in their ability to characterize lesions. We report the case of a 5-year-old presenting with macroscopic haematuria in whom diffusion-weighted MRI (DWI) suggested the diagnosis of an infected urachal cyst, which was confirmed surgically. We discuss the radiological findings in multiple imaging modalities and present the application of DWI in this context as a means of improving the radiological diagnostic yield.

Imaging 'the lost tribe': a review of adolescent cancer imaging. Part 2: imaging of complications of cancer treatment

Adolescent cancers are treated with a host of chemotherapy agents, radiotherapy and stem cell transplantation. The complications of these treatments may contribute significantly to the morbidity and mortality in this age group, with imaging playing a role in identifying some of these complications. This second article reviews the imaging of acute and early complications relating to adolescent cancer treatment, many of which may also be seen in the treatment of paediatric patients. Late effects involving endocrine and reproductive systems or psychosocial considerations are not discussed in this paper, although these are clearly important issues in long-term survivors.

Imaging 'the lost tribe': a review of adolescent cancer imaging. Part 1

Although a small proportion of all cancer registrations, malignancy in adolescence and young adulthood remains the most common natural cause of death in this age group. Advances in the management and outcomes of childhood cancer have not been matched within the adolescent population, with increasing incidence and poorer survival seen amongst teenagers with cancer compared with other populations. There have been increasing moves towards specific adolescent oncology centres, with the aim of centralising expertise, however, ‘adolescent imaging’ does not exist as a speciality in the same way that paediatric imaging does, with responsibility for imaging adolescent patients sometimes falling to paediatric radiologists and sometimes to ‘adult’ radiologists, usually with a specific interest in a tumour type or body system. In this article, imaging of the more common malignancies, encountered in adolescent patients is reviewed. Complications of treatment are reviewed in another article to give an overview of adolescent oncology imaging practice.

Tumors in pediatric patients at diffusion-weighted MR imaging: apparent diffusion coefficient and tumor cellularity

PURPOSE

To prospectively assess whether there is a relationship between the apparent diffusion coefficient (ADC) and the histopathologic cell count and whether the ADC can enable differentiation of benign and malignant extracranial mass lesions in children.

MATERIALS AND METHODS

Institutional ethics approval and parent or guardian consent were obtained. Eleven malignant and eight benign lesions in 19 children (11 girls, eight boys; median age, 3.9 years; age range, 11 days to 15.5 years) who underwent magnetic resonance (MR) imaging of extracranial mass lesions-including a diffusion-weighted sequence (with b values 0, 500, and 1000 sec/mm(2))-and histopathologic analysis to prove findings were studied. The median ADC within each mass lesion was compared with the median cell count for 10 high-power microscopic fields in the specimen. The inverse regression between cell count and ADC was calculated. The difference in ADC between benign and malignant lesions was assessed by using the Mann-Whitney U test.

RESULTS

There was an inverse relationship between ADC and cell count, expressed as ADC (in x10(-3) mm(2)/sec) = 0.56 + (66.2/cell count), with a relatively good fit to the observed data (analysis of variance R(2) = 0.541, F = 20.0, P < .001). The ADCs of benign lesions ranged from (0.84-2.83) x 10(-3) mm(2)/sec (median, 1.35 x 10(-3) mm(2)/sec; standard deviation, 0.68). The ADCs of malignant lesions ranged from (0.73-1.53) x 10(-3) mm(2)/sec (median, 1.00 x 10(-3) mm(2)/sec; standard deviation, 0.29). There was no significant difference in ADC between benign and malignant lesions (Mann-Whitney U = 22, P = .069). All highly cellular (>150 cells per high-power field) lesions had an ADC lower than 1.5 x 10(-3) mm(2)/sec.

CONCLUSION

Although there is a significant relationship between cellularity and ADC, cell count probably is not the sole determinant of the ADC. Use of the ADC cannot enable accurate differentiation of malignant and benign lesions.

Atypical abdominal paediatric lymphangiomatosis: diagnosis aided by diffusion-weighted MRI

We report a 4-year-old child with a mesenteric mass, which on ultrasound, CT and conventional MRI appeared solid, raising lymphoma as a possible diagnosis. Diffusion weighted MRI (DW-MRI), however, suggested a low-cellularity lesion, making lymphoma less likely. Biopsy confirmed lymphangioma. DW-MRI may be a useful adjunct to conventional imaging, even in the abdomen.