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

Pediatric primary renal lymphoma presenting with multiple masses: A challenging case report and narrative review

RATIONALE

Only 20 cases of pediatric primary renal non-Hodgkin's lymphoma have been reported since 1995, rare cases and a variety of imaging manifestations have led to difficulties in its diagnosis and treatment.

PATIENT CONCERNS

Herein, we share in detail a case of primary renal lymphoma (PRL) in a child and summarize the common clinical manifestations, imaging features, and prognostic factors of pediatric PRL by retrospectively analyzing cases reported in the literature. A 2-year-old boy presented to the clinic with a large mass on the right side of his abdomen along with loss of appetite.

DIAGNOSES

Imaging revealed a large right renal mass, nearly replacing the entire renal tissue, along with numerous small nodules in the left kidney. Given no local adenopathy and metastases, the diagnosis was unclear. A percutaneous renal puncture was performed, which proved the diagnosis of Burkitt's lymphoma. Since no bone marrow involvement, this child was diagnosed with pediatric PRL.

INTERVENTIONS

This PRL boy was treated with the NHL-BFM95 protocol and supportive care.

OUTCOMES

Unfortunately, this boy died of multiple organ failure in the fifth month of treatment.

LESSONS

As per literature review, the presentation of pediatric PRL is fatigue, loss of appetite, weight loss, abdominal swelling, or other nonspecific symptoms. Although in 81% of cases it often infiltrates the bilateral kidneys, urine abnormalities caused by pediatric PRL are uncommon. 76.2% of pediatric PRL were boys and 2/3 of all cases presented as diffuse renal enlargement. Those PRL presented as masses could easily be misdiagnosed as WT or other malignancies. Absent of local enlarged lymph node, no necrosis or calcification suggest atypical presentation of renal masses and a percutaneous biopsy is needed in timely establishing the accurate diagnosis for appropriate treatment. Based on our experience, percutaneous renal puncture core biopsy is a safe procedure.

Ferumoxytol-Enhanced MRI in Children and Young Adults: State of the Art

Ferumoxytol is an ultrasmall iron oxide nanoparticle that was originally approved by the FDA in 2009 for IV treatment of iron deficiency in adults with chronic kidney disease. Subsequently, its off-label use as an MRI contrast agent increased in clinical practice, particularly in pediatric patients in North America. Unlike conventional MRI contrast agents that are based on the rare earth metal gadolinium (gadolinium-based contrast agents), ferumoxytol is biodegradable and carries no potential risk of nephrogenic systemic fibrosis. At FDA-approved doses, ferumoxytol shows no long-term tissue retention in patients with intact iron metabolism. Ferumoxytol provides unique MRI properties, including long-lasting vascular retention (facilitating high-quality vascular imaging) and retention in reticuloendothelial system tissues, thereby supporting a variety of applications beyond those possible with gadolinium-based contrast agents (GBCAs). This Clinical Perspective describes clinical and early translational applications of ferumoxytol-enhanced MRI in children and young adults through off-label use in a variety of settings, including vascular, cardiac, and cancer imaging, drawing on the institutional experience of the authors. In addition, we describe current advances in pre-clinical and clinical research using ferumoxytol in cellular and molecular imaging as well as the use of ferumoxytol as a novel potential cancer therapeutic agent.

Hemorrhage and necrosis of the liver caused by hepatic arteriovenous malformations in a fetus: A case report

RATIONALE

Hepatic arteriovenous malformations (HAVMs) are a rare disorder reported in association with hereditary hemorrhagic telangiectasia (HHT), known as Rendu-Osler-Weber syndrome. HAVMs are usually detected in adulthood.

PATIENT CONCERNS

A 29-year-old pregnant woman underwent a routine prenatal examination at 37 weeks of pregnancy.

DIAGNOSIS AND INTERVENTIONS

There were fetal liver anomalies detected by prenatal ultrasonography and were managed. Furthermore, a hepatic mass was detected and was subsequently analyzed by fetal magnetic resonance imaging. There were no typical imaging findings in this case which was once misdiagnosed as a hepatoblastoma.

OUTCOMES

Considering the massive hepatic lesion, labor induction was performed on a pregnant woman to avoid adverse maternal and fetal outcomes. Histopathological examination confirmed the diagnosis of HAVMs. Lesions detected by imaging were determined to be hemorrhagic and necrotic.

LESSONS

Prenatal hepatic hemorrhage and necrosis due to an arteriovenous malformation are rare. The authors describe their observations and results.

Role of Diffusion Weighted MRI (DW-MR) in Detection of Satellite Lesions Not Detected with Multiphase CT Scans in Hepatoblastoma and Its Implications for Management

OBJECTIVE

To evaluate the role of diffusion-weighted magnetic resonance imaging (DW-MR) in hepatoblastoma as compared to multiphase contrast enhanced computed tomography (CECT) scans for detection of satellite lesions.

METHODS

In this prospective study on new cases of hepatoblastoma, multiphase CECT scans and DW-MR were performed before initiation of chemotherapy. Results of interpretation were compared for detection of satellite lesions. PRETEXT grouping and risk categorization was done according to SIOPEL based on CECT scan.

RESULTS

Nine boys and 1 girl with hepatoblastoma, with median age of 11.5 mo were included. All patients were stratified as high-risk group with 2 (20%) in PRETEXT II and 8 (80%) in PRETEXT III. In 2 of 10 (20%) patients, additional satellite lesions were detected on DW-MR, which upgraded their stage. One of the two patients had one satellite lesion identified on CECT, while additional seven satellite lesions were identified on DW-MR imaging. For the other patient, CECT showed no satellite lesion while DW-MR detected six satellite lesions.

CONCLUSION

MRI has become the gold standard investigation for evaluation of hepatoblastoma. DW-MR, which is a contrast free technique, is a better tool for assessment of satellite lesions which are usually missed on CECT. This would help in proper staging, planning of management and prognostication.

Neonatal vascular anomalies manifesting as soft-tissue masses

The broad and heterogeneous spectrum of vascular anomalies ranges from an innocuous localized cutaneous discoloration to complex, extensive and life-threatening diagnoses. While many of these lesions are present at birth, smaller and deeper lesions might be clinically occult for months or years. Certain vascular anomalies commonly manifest in the prenatal or neonatal period and often have suggestive clinical and imaging features that can aid the radiologist in making a correct diagnosis. The characteristics of such lesions presenting very early in life, particularly those manifesting as soft-tissue masses, are the focus of this review.

One-stop local and whole-body staging of children with cancer

Accurate staging and re-staging of cancer in children is crucial for patient management. Currently, children with a newly diagnosed cancer must undergo a series of imaging tests, which are stressful, time-consuming, partially redundant, expensive, and can require repetitive anesthesia. New approaches for pediatric cancer staging can evaluate the primary tumor and metastases in a single session. However, traditional one-stop imaging tests, such as CT and positron emission tomography (PET)/CT, are associated with considerable radiation exposure. This is particularly concerning for children because they are more sensitive to ionizing radiation than adults and they live long enough to experience secondary cancers later in life. In this review article we discuss child-tailored imaging tests for tumor detection and therapy response assessment - tests that can be obtained with substantially reduced radiation exposure compared to traditional CT and PET/CT scans. This includes diffusion-weighted imaging (DWI)/MRI and integrated [F-18]2-fluoro-2-deoxyglucose (18F-FDG) PET/MRI scans. While several investigators have compared the value of DWI/MRI and 18F-FDG PET/MRI for staging pediatric cancer, the value of these novel imaging technologies for cancer therapy monitoring has received surprisingly little attention. In this article, we share our experiences and review existing literature on this subject.

DWI and ADC value versus ADC ratio in the characterization of solid renal masses: radiologic-pathologic correlation

Background

Renal masses are becoming an increasingly common finding on cross-sectional images. Characterization of the nature of the lesion either neoplastic or not, benign or malignant as well as further subtype characterization is becoming an important factor in determining management plan. The purpose of our study with to assess the sensitivity and specificity of both ADC mean value and ADC ratio in such characterization along with the calculation of different cutoff values to differentiate between different varieties, using pathological data as the main gold standard for diagnosis.

Results

Our study included 50 patients with a total of 72 masses. A final diagnosis was reached in 69 masses by pathological examination and three masses had clinical and laboratory signs of infection. We had a total of 49 malignant lesions (68%) and 23 benign lesions (32%). The ADC value of ccRCC (1.4 × 10−3 mm2/s) was significantly higher than all other renal masses. A cutoff ADC value of > 1.1 and a cutoff ADC ratio of > 0.56 can be used to differentiate between clear cell renal cell carcinoma and other lesions and an ADC value of < 0.8 and an ADC ratio of ≤ 0.56 to differentiate papillary renal cell carcinoma from other masses. There was no statistically significant ADC value to differentiate between benign and malignant lesions but a statistically significant ADC ratio (> 0.52) was reached.

Conclusion

ADC value and ADC ratio can be used as an adjunct tool in the characterization of different renal masses, with ADC ratio having a higher sensitivity, which can affect the prognosis and management of the patient.

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.

Confounding factors in breast magnetic resonance fingerprinting: B 1 + , slice profile, and diffusion effects

PURPOSE

Magnetic resonance fingerprinting (MRF) offers rapid quantitative imaging but may be subject to confounding effects (CE) if these are not included in the model-based reconstruction. This study characterizes the influence of in-plane B 1 + , slice profile and diffusion effects on T₁ and T₂ estimation in the female breast at 1.5T.

METHODS

Simulations were used to predict the influence of each CE on the accuracy of MRF and to investigate the influence of electronic noise and spiral aliasing artefacts. The experimentally observed bias in regions of fibroglandular tissue (FGT) and fatty tissue (FT) was analyzed for undersampled spiral breast MRF data of 6 healthy volunteers by performing MRF reconstruction with and without a CE.

RESULTS

Theoretic analysis predicts T₁ under-/T₂ overestimation if the nominal flip angles are underestimated and inversely, T₁ under-/T₂ overestimation if omitting slice profile correction, and T₁ under-/T₂ underestimation if omitting diffusion in the signal model. Averaged over repeated signal simulations, including spiral aliasing artefacts affected precision more than accuracy. Strong in-plane B 1 + effects occurred in vivo, causing T₂ left-right inhomogeneity between both breasts. Their correction decreased the T₂ difference from 29 to 5 ms in FGT and from 29 to 9 ms in FT. Slice profile correction affected FGT T₂ most strongly, resulting in -22% smaller values. For the employed spoiler gradient strengths, diffusion did not affect the parameter maps, corresponding well with theoretic predictions.

CONCLUSION

Understanding CEs and their relative significance for an MRF sequence is important when defining an MRF signal model for accurate parameter mapping.

Comparison of models of diffusion in Wilms' tumours and normal contralateral renal tissue

Objective

ADC (Apparent Diffusion Coefficient) derived from Diffusion-Weighted Imaging (DWI) has shown promise as a non-invasive quantitative imaging biomarker in Wilms’ tumours. However, many non-Gaussian models could be applied to DWI. This study aimed to compare the suitability of four diffusion models (mono exponential, IVIM [Intravoxel Incoherent Motion], stretched exponential, and kurtosis) in Wilms’ tumours and the unaffected contralateral kidneys.

Materials and methods

DWI data were retrospectively reviewed (110 Wilms’ tumours and 75 normal kidney datasets). The goodness of fit for each model was measured voxel-wise using Akaike Information Criteria (AIC). Mean AIC was calculated for each tumour volume (or contralateral normal kidney tissue). One-way ANOVAs with Greenhouse–Geisser correction and post hoc tests using the Bonferroni correction evaluated significant differences between AIC values; the lowest AIC indicating the optimum model.

Results

IVIM and stretched exponential provided the best fits to the Wilms’ tumour DWI data. IVIM provided the best fit for the normal kidney data. Mono exponential was the least appropriate fitting method for both Wilms’ tumour and normal kidney data.

Discussion

The diffusion weighted signal in Wilms’ tumours and normal kidney tissue does not exhibit a mono-exponential decay and is better described by non-Gaussian models of diffusion.

Radiological response and histological findings in nephroblastoma: Is the any correlation?

INTRODUCTION

The Sociétè Internationale d'Oncologie Pédiatrique advocates for neoadjuvant chemotherapy in the management of nephroblastoma. Postoperatively, histological findings are used to assign risk classification to resected tumours. The aim of this study is to compare the response demonstrated by pre-operative imaging to the amount of necrosis seen on histology postoperatively.

PATIENTS AND METHODS

About 33 patients with nephroblastoma over a 10 year period had adequate imaging and histology records for this study. Three methods were used to assess tumour change following neoadjuvant therapy and were compared with histological records. 1. An estimation of necrosis, 2. Surface areas of apparent necrosis within the tumour measured on static imaging, 3. The change in volume of the mass. Pearson coefficient was calculated to measure the correlation between histologically observed necrosis and radiological changes. Results were considered significant if P< 0.05.

RESULTS

There was no correlation between radiological changes on pre-operative imaging and the percentage of necrosis seen on histology. Change in tumour size on radiological studies showed a moderate correlation to percentage tumour necrosis on histology but was unable to predict tumour risk classification.

CONCLUSIONS

In nephroblastoma, there is a moderate correlation between the decrease in size of a mass noted on imaging following chemotherapy and the degree of necrosis found postoperatively on histology. Change in tumour size cannot be used to predict histological risk classification. It is not possible to predict the histological risk classification of a nephroblastoma based on the changes demonstrated on non-contrasted magnetic resonance imaging or computed tomography preoperatively.

Differentiation of benign and malignant lymph nodes in pediatric patients on ferumoxytol-enhanced PET/MRI

The composition of lymph nodes in pediatric patients is different from that in adults. Most notably, normal lymph nodes in children contain less macrophages. Therefore, previously described biodistributions of iron oxide nanoparticles in benign and malignant lymph nodes of adult patients may not apply to children. The purpose of our study was to evaluate if the iron supplement ferumoxytol improves the differentiation of benign and malignant lymph nodes in pediatric cancer patients on ¹⁸F-FDG PET/MRI. Methods: We conducted a prospective clinical trial from May 2015 to December 2018 to investigate the value of ferumoxytol nanoparticles for staging of children with cancer with ¹⁸F-FDG PET/MRI. Ferumoxytol is an FDA-approved iron supplement for the treatment of anemia and has been used "off-label" as an MRI contrast agent in this study. Forty-two children (7-18 years, 29 male, 13 female) received a ¹⁸F-FDG PET/MRI at 2 (n=20) or 24 hours (h) (n=22) after intravenous injection of ferumoxytol (dose 5 mg Fe/kg). The morphology of benign and malignant lymph nodes on ferumoxytol-enhanced T2-FSE sequences at 2 and 24 h were compared using a linear regression analysis. In addition, ADCmean-values, SUV-ratio (SUV_max lesion/SUV_mean liver) and R2*-relaxation rate of benign and malignant lymph nodes were compared with a Mann-Whitney-U test. The accuracy of different criteria was assessed with a receiver operating characteristics (ROC) curve. Follow-up imaging for at least 6 months served as the standard of reference. Results: We examined a total of 613 lymph nodes, of which 464 (75.7%) were benign and 149 (24.3%) were malignant. On ferumoxytol-enhanced T2-FSE images, benign lymph nodes showed a hypointense hilum and hyperintense parenchyma, while malignant lymph nodes showed no discernible hilum. This pattern was not significantly different at 2 h and 24 h postcontrast (p=0.82). Benign and malignant lymph nodes showed significantly different ferumoxytol enhancement patterns, ADCmean values of 1578 and 852 x10^-6 mm²/s, mean SUV-ratios of 0.5 and 2.8, and mean R2*-relaxation rate of 127.8 and 84.4 Hertz (Hz), respectively (all p<0.001). The accuracy of ADCmean, SUV-ratio and pattern (area under the curve (AUC): 0.99; 0.98; 0.97, respectively) was not significantly different (p=0.07). Compared to these three parameters, the accuracy of R2* was significantly lower (AUC: 0.93; p=0.001). Conclusion: Lymph nodes in children show different ferumoxytol-enhancement patterns on MRI than previously reported for adult patients. We found high accuracy (>90%) of ADCmean, SUV-ratio, pattern, and R2* measurements for the characterization of benign and malignant lymph nodes in children. Ferumoxytol nanoparticle accumulation at the hilum can be used to diagnose a benign lymph node. In the future, the delivery of clinically applicable nanoparticles to the hilum of benign lymph nodes could be harnessed to deliver theranostic drugs for immune cell priming.

The role of imaging in the initial investigation of paediatric renal tumours

Imaging has a key role in the assessment of paediatric renal tumours, especially when the initial treatment approach is to proceed to standard chemotherapy without histological confirmation. In Europe, according to the International Society of Paediatric Oncology guidelines, core needle biopsy is not routinely done unless the child is older than 10 years. Between age 6 months and 9 years, the child is treated with a standard regimen of preoperative chemotherapy unless there are concerns about non-Wilms' tumour pathology. Atypical imaging findings could therefore stratify a child into a different treatment protocol, and can prompt the need for pretreatment histology. This review details the latest protocols and techniques used in the assessment of paediatric renal tumours. Important imaging findings are discussed, especially the features that might prompt the need for a pretreatment biopsy. Local radiology practices vary, but both MRI and CT are widely used as routine imaging tests for the assessment of paediatric renal tumours in Europe. Advances in imaging technology and MRI sequences are facilitating the development of new techniques, which might increase the utility of imaging in terms of predicting tumour histology and clinical behaviour. Several of these new imaging techniques are outlined here.

Usefulness of Diffusion-Weighted Magnetic Resonance Imaging Using Apparent Diffusion Coefficient Values for Diagnosis of Infantile Hemangioma

OBJECTIVE

The objective of this study was to determine whether apparent diffusion coefficient (ADC) values obtained from diffusion-weighted imaging allow differentiation between infantile hemangiomas (IHs) and malignant soft tissue tumors.

METHODS

A retrospective review was performed on magnetic resonance images of pediatric patients with IHs and malignant soft tissue tumors from January 2014 to December 2016, which comprised 7 patients with 8 IHs and 6 patients with 6 malignant soft tissue tumors. We calculated and compared the ADC values of each lesion. Receiver operating characteristic curve analysis was performed to determine a cutoff value for the ADC.

RESULTS

There was a statistically significant difference between the ADC values of IHs and those of malignant soft tissue tumors (1.32 [1.27-1.72] × 10 mm/s vs 0.67 [0.57-0.79] × 10 mm/s; P < 0.001), with no overlap between the 2 groups.

CONCLUSIONS

The ADC values obtained from diffusion-weighted imaging were useful in differentiating IHs from malignant soft tissue tumors in pediatric patients.

Diffusion-weighted MRI for differentiating Wilms tumor from neuroblastoma

PURPOSE

Wilms tumor (WT) and neuroblastoma (NB) are the most common pediatric abdominal malignant neoplasms of the kidney and adrenal gland. Differentiating them from each other is essential since their treatments are different. Here, we aimed to show the diffusion characteristics of WT and NB for differentiation.

METHODS

Diffusion-weighted imaging (DWI) of 17 histopathologically diagnosed lesions (10 NB and 7 WT in 8 female and 9 male patients) was evaluated retrospectively. The apparent diffusion coefficient (ADC) value for each tumor was calculated using region-of-interest (ROI) measurements by two observers. The mean ADC values were compared, and receiver operating characteristics (ROC) curve analysis was performed. Intraclass correlation was evaluated for the reliability of ADC measurement.

RESULTS

The mean ADC values measured by two observers were 0.787±0.09 ×10-3 mm2/s and 0.768±0.08 ×10-3 mm2/s for WT, and 0.524±0.16 ×10-3 mm2/s and 0.529±0.16 ×10-3 mm2/s for NB, respectively (P = 0.006 and P = 0.011). Intraclass correlation coefficient was 0.955. Utilizing ROC curve analysis, a cutoff ADC value of ≤0.645 ×10-3 mm2/s was obtained to differentiate NB from WT.

CONCLUSION

ADC values of NBs were significantly lower than WT with a perfect interobserver agreement. We suggest that DWI may have a role in differentiating the two tumors.

Can diffusion-weighted imaging distinguish between benign and malignant pediatric liver tumors?

BACKGROUND

There are limited data on utility of diffusion-weighted imaging (DWI) in the evaluation of pediatric liver lesions.

OBJECTIVE

To determine whether qualitative and quantitative DWI can be used to differentiate benign and malignant pediatric liver lesions.

MATERIALS AND METHODS

We retrospectively reviewed MRIs in children with focal liver lesions to qualitatively evaluate lesions noting diffusion restriction, T2 shine-through, increased diffusion, hypointensity on DWI and apparent diffusion coefficient (ADC) maps, and intermediate signal on both, and to measure ADC values. Pathology confirmation or a combination of clinical, laboratory and imaging features, and follow-up was used to determine final diagnosis.

RESULTS

We included 112 focal hepatic lesions in 89 children (median age 11.5 years, 51 female), of which 92 lesions were benign and 20 malignant. Interobserver agreement was almost perfect for both qualitative (kappa 0.8735) and quantitative (intraclass correlation coefficient [ICC] 0.96) diffusion assessment. All malignant lesions showed diffusion restriction. Most benign lesions other than abscesses were not restricted. There was significant association of qualitative restriction with malignancy and non-restriction with benignancy (Fisher exact test P<0.0001). Mean normalized ADC values of malignant lesions (1.23x10^-3 mm²/s) were lower than benign lesions (1.62x10^-3 mm²/s; Student's t-test, P<0.015). However, there was significant overlap of ADC between benign and malignant lesions, with wide range for each diagnosis. Receiver operating characteristic (ROC) analysis revealed an area under the curve (AUC) of 0.63 for predicting malignancy using an ADC cut-off value of ≤1.20x10^-3 mm²/s, yielding a sensitivity of 78% and a specificity of 54% for differentiating malignant from benign lesions.

CONCLUSION

Qualitative diffusion restriction in pediatric liver lesions is a good predictor of malignancy and can help to differentiate between benign and malignant lesions, in conjunction with conventional MR sequences. Even though malignant lesions demonstrated significantly lower ADC values than benign lesions, the use of quantitative diffusion remains limited in its utility for distinguishing them because of the significant overlap and wide ranges of ADC values.

Diffusion-weighted MRI and intravoxel incoherent motion model for diagnosis of pediatric solid abdominal tumors

Background

Pediatric retroperitoneal tumors in the renal bed are often large and heterogeneous, and their diagnosis based on conventional imaging alone is not possible. More advanced imaging methods, such as diffusion‐weighted (DW) MRI and the use of intravoxel incoherent motion (IVIM), have the potential to provide additional biomarkers that could facilitate their noninvasive diagnosis.

Purpose

To assess the use of an IVIM model for diagnosis of childhood malignant abdominal tumors and discrimination of benign from malignant lesions.

Study Type

Retrospective.

Population

Forty‐two pediatric patients with abdominal lesions (n = 32 malignant, n = 10 benign), verified by histopathology.

Field Strength/Sequence

1.5T MRI system and a DW‐MRI sequence with six b‐values (0, 50, 100, 150, 600, 1000 s/mm²).

Assessment

Parameter maps of apparent diffusion coefficient (ADC), and IVIM maps of slow diffusion coefficient (D), fast diffusion coefficient (D*), and perfusion fraction (f) were computed using a segmented fitting model. Histograms were constructed for whole‐tumor regions of each parameter.

Statistical Tests

Comparison of histogram parameters of and their diagnostic performance was determined using Kruskal–Wallis, Mann–Whitney U, and receiver‐operating characteristic (ROC) analysis.

Results

IVIM parameters D* and f were significantly higher in neuroblastoma compared to Wilms' tumors (P < 0.05). The ROC analysis showed that the best diagnostic performance was achieved with D* 90^th percentile (area under the curve [AUC] = 0.935; P = 0.002; cutoff value = 32,376 × 10⁻⁶ mm²/s) and f mean values (AUC = 1.00; P < 0.001; cutoff value = 14.7) in discriminating between neuroblastoma (n = 11) and Wilms' tumors (n = 8). Discrimination between tumor types was not possible with IVIM D or ADC parameters. Malignant tumors revealed significantly lower ADC, D, and higher D* values than in benign lesions (all P < 0.05).

Data Conclusion

IVIM perfusion parameters could distinguish between malignant childhood tumor types, providing potential imaging biomarkers for their diagnosis.

Level of Evidence: 4

Technical Efficacy: Stage 2

J. Magn. Reson. Imaging 2018;47:1475–1486.

Role of diffusion-weighted imaging in distinguishing thoracoabdominal neuroblastic tumours of various histological types and differentiation grades

INTRODUCTION

Diffusion-weighted MR imaging (DWI) has demonstrated a great potential to help distinguish benign from malignant tumours in paediatric body. Our purpose is to evaluate whether DWI allow discrimination of thoracoabdominal neuroblastic tumours of various histological types and differentiation grades.

METHODS

We retrospectively analysed DWI scans of the thoracoabdominal neuroblastic tumours in 25 children (11 girls, 14 boys). DWI was performed with two b-values of 0 and 800 s/mm² on a 3.0T MR scanner. The apparent diffusion coefficient (ADC) values of different classifications of tumours were compared with Independent-Samples T Test.

RESULTS

In the 25 cases, ganglioneuroma (GN) was in 3 cases, ganglioneuroblastoma (GNB) in 7 (GNB-Intermixed in 4, GNB-Nodular in 3) and neuroblastoma (NB) in 15. In three cases of GNB-Nodular, two cases had poorly differentiated nodules and another had differentiated nodules. In 15 cases of NB, poorly differentiated, differentiated and undifferentiated tumours were, respectively, in eight, five and two cases. The ADC value of the NB was significantly lower than that of GN/GNB (P < 0.001). The ADC of GNB-Nodular/NB was significantly less than that of GN/GNB-Intermixed (P < 0.0001). In GNB-Nodular/NB detection, there was a cut-off value of 1.165 × 10^-3  mm² /s. In GNB-Nodular/NB, the tumours with poorly differentiated and undifferentiated lesions (n = 12) had significantly smaller ADC than those with differentiated composition (n = 6) (P = 0.0012).

CONCLUSION

ADC of DWI is highly valuable for discriminating thoracoabdominal neuroblastic tumours of different histological types and differentiation grades.

Contrast-enhanced CT features of hepatoblastoma: Can we predict histopathology?

BACKGROUND

Hepatoblastoma is the most common hepatic malignancy occurring in the pediatric population. Intratumoral cellular behavior varies, and the small-cell undifferentiated histopathology carries a poorer prognosis than other tissue subtypes. Neoadjuvant chemotherapy is recommended for this tumor subtype prior to surgical resection in most cases. Early identification of tumors with poor prognosis could have a significant clinical impact. Objective The aim of this work was to identify imaging features of small-cell undifferentiated subtype hepatoblastoma that can help distinguish this subtype from more favorable tumors and potentially guide the clinical management. We also sought to characterize contrast-enhanced CT (CECT) features of hepatoblastoma that correlate with metastatic disease and patient outcome.

MATERIALS AND METHODS

Our study included 34 patients (24 males, 10 females) with a mean age of 16months (range: 0-46months) with surgically confirmed hepatoblastoma and available baseline abdominal imaging by CECT. Clinical data and CT abdominal images were retrospectively analyzed.

RESULTS

Five tumors with small-cell undifferentiated components were identified. All of these tumors demonstrated irregular margins on CT imaging. Advanced PRETEXT stage, vascular invasion and irregular margins were associated with metastatic disease and decreased survival. Capsular retraction was also significantly associated with decreased survival. Irregular tumor margins demonstrated statistically significant association with the presence of small-cell undifferentiated components. No other imaging feature showed statistically significant association.

CONCLUSION

Tumor margin irregularity, vascular invasion, capsular retraction, and PRETEXT stage correlate with worse patient outcomes. Irregular tumor margin was the only imaging feature significantly associated with more aggressive tumor subtype.

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.

Magnetic resonance imaging based functional imaging in paediatric oncology

Imaging is central to management of solid tumours in children. Conventional magnetic resonance imaging (MRI) is the standard imaging modality for tumours of the central nervous system (CNS) and limbs and is increasingly used in the abdomen. It provides excellent structural detail, but imparts limited information about tumour type, aggressiveness, metastatic potential or early treatment response. MRI based functional imaging techniques, such as magnetic resonance spectroscopy, diffusion and perfusion weighted imaging, probe tissue properties to provide clinically important information about metabolites, structure and blood flow. This review describes the role of and evidence behind these functional imaging techniques in paediatric oncology and implications for integrating them into routine clinical practice.

Diffusion-weighted imaging in pediatric body magnetic resonance imaging

Diffusion-weighted MRI is being increasingly used in pediatric body imaging. Its role is still emerging. It is used for detection of tumors and abscesses, differentiation of benign and malignant tumors, and detection of inflamed bowel segments in inflammatory bowel disease in children. It holds great promise in the assessment of therapy response in body tumors, with apparent diffusion coefficient (ADC) value as a potential biomarker. Significant overlap of ADC values of benign and malignant processes and less reproducibility of ADC measurements are hampering its widespread use in clinical practice. With standardization of the technique, diffusion-weighted imaging (DWI) is likely to be used more frequently in clinical practice. We discuss the principles and technique of DWI, selection of b value, qualitative and quantitative assessment, and current status of DWI in evaluation of disease processes in the pediatric body.

Diffusion-weighted MR imaging of mediastinal lymphadenopathy in children

PURPOSE

To assess mediastinal lymphadenopathy in children with diffusion-weighted MR imaging.

MATERIALS AND METHODS

Retrospective analysis of 29 consecutive children (18 boys and 11 girls aged 2-15 years) with mediastinal lymphadenopathy. They underwent single-shot echo planar diffusion-weighted MR imaging of the mediastinum with b factors of 0, 300, and 600 s/mm(2). The ADC value of the mediastinal lymph nodes was calculated and correlated with biopsy results; statistical analysis was also performed.

RESULTS

The mean ADC value for malignant mediastinal lymphadenopathy (n = 20) (0.99 ± 0.18 × 10(-3) mm(2)/s) was significantly lower (P = 0.001) than that for benign lymphadenopathy (n = 9) (1.35 ± 0.26 × 10(-3) mm(2)/s). There was significant difference between ADC values for non-Hodgkin lymphoma and metastatic nodes (P = 0.04). For differentiating malignant from benign mediastinal lymphadenopathy, the best result was obtained when an ADC value of 1.22 × 10(-3) mm(2)/s was used as a threshold value; area under the curve was 0.861, accuracy 93.1 %, sensitivity 100 %, specificity of 77.8 %, positive predictive value 90.9 %, and negative predictive value of 100 %.

CONCLUSION

Diffusion-weighted MR imaging is a promising non-invasive imaging modality that can be used for differentiation of malignant from benign mediastinal lymphadenopathy in children.

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.

Diffusion-weighted perinatal postmortem magnetic resonance imaging as a marker of postmortem interval

Objective

To evaluate perinatal body organ apparent diffusion coefficient (ADC) values at postmortem magnetic resonance imaging (PMMR) in order to evaluate postmortem changes.

Methods

Postmortem diffusion-weighted imaging (DWI) of the thorax and abdomen were performed with diffusion gradient values b = 0, 500, and 1000 s/mm² on 15 foetal and childhood cases (mean 33.3 ± 7.8 weeks gestation) compared to 44 live infants (mean age 75.5 ± 53.4 days). Mean ADC values were calculated from regions of interest (ROIs) for the lungs, liver, spleen and renal cortex, compared to normative live infantile body ADC values of similar gestational age.

Results

Mean ADC values were significantly lower in postmortem cases than in normal controls for liver (0.88 10^-3 mm²/s ± SD 0.39 vs. 1.13 ± 0.13; p < 0.05) and renal cortex (0.85 ± 0.26 vs. 1.19 ± 0.13; p < 0.05) but not spleen or muscle. Mean lung ADC values were significantly higher than normal controls (1.06 ± 0.18 vs. 0 ± 0; p < 0.001), and there was a significant correlation between postmortem interval and lung ADC (R² = 0.55).

Conclusion

Lung PMMR ADC values are related to postmortem interval, making them a potential marker of time since death. Further research is needed to understand the organ-specific changes which occur in the postmortem period.

Key Points

• Liver and spleen PM ADC values were lower than controls.

• Lung ADC changes correlate with PM interval.

• These findings may be useful in medicolegal cases.

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.

Pediatric oncology surveillance imaging: two recommendations. Abandon CT scanning, and randomize to imaging or solely clinical follow-up

Radiologic assessments in children with cancer provide information crucial to patient management at diagnosis and during follow-up. Many studies have now been published, however, questioning the usefulness of off-therapy surveillance imaging. There is growing concern regarding the hazards from diagnostic irradiation to young patients, most notably from CT scanning. In this paper we advocate abandoning repeated CT surveillance in young patients with a previously treated solid malignancy not arising in the central nervous system. In addition, randomized studies of imaging surveillance versus no imaging surveillance strategies are needed to determine whether earlier detection of recurrence results in improved survival.