Gadolinium-enhanced imaging of pediatric thoracic lymphoma: is intravenous contrast really necessary?

Gadolinium-based contrast media does not improve the staging of neuroblastoma image-defined risk factors at diagnosis

BACKGROUND

Neuroblastoma risk stratification relies on prognostic risk factors and image-defined risk factors (IDRFs). Evaluating neuroblastoma typically involves magnetic resonance imaging (MRI) with gadolinium-based contrast media (GBCM, "contrast"). However, there are concerns regarding adverse effects and cost of GBCM. We aimed to assess the impact of intravenous GBCM on interobserver agreement for neuroblastoma staging on baseline MRI.

PROCEDURE

We reviewed baseline MRI scans of 50 children with abdominopelvic neuroblastomas confirmed by histopathology. Duplicate sets of images were created, with post-contrast T1-weighted sequences removed from one set. Four pediatric radiologists independently analyzed the scans in a randomized manner. They recorded primary tumor size, presence of IDRFs, and metastatic lesions. Agreement among the reviewers was measured using kappa and Fleiss kappa statistics.

RESULTS

Mean age of included children was 3.3 years (range: 0.01-14.9 years), and 20 [40%] were females. Mean tumor size was 5.7 cm in greatest axial diameter. Pre-contrast versus post-contrast MRI showed excellent agreement for tumor measurement. Overlapping confidence intervals (CIs) were seen in nearly all categories of interobserver agreement on the presence or absence of individual IDRFs, with agreement ranging from poor to substantial, regardless of the presence of contrast. The overall interobserver agreement on the presence of at least one IDRF was substantial with contrast (kappa = .63; 95% CI: .52-.75) and moderate without contrast (kappa = .5; 95% CI: .39-.61); although the overlapping CIs suggest a lack of meaningful difference. Similarly, interobserver agreement on the presence or absence of individual sites of metastatic disease ranged from poor to substantial. The interobserver agreement on the overall determination of presence of metastatic disease was fair with contrast (kappa = .49; 95% CI: .38-.61) and moderate without contrast (kappa = .71; 95% CI: .59-.826).

CONCLUSIONS

Contrast does not improve tumor size measurement or radiologist agreement on the presence or absence of IDRFs or metastatic disease in children with newly diagnosed neuroblastoma.

[18F]FDG PET/MRI in children suffering from lymphoma: does MRI contrast media make a difference?

OBJECTIVES

Evaluate the influence of an MRI contrast agent application on primary and follow-up staging in pediatric patients with newly diagnosed lymphoma using [18F]FDG PET/MRI to avoid adverse effects and save time and costs during examination.

METHODS

A total of 105 [18F]FDG PET/MRI datasets were included for data evaluation. Two different reading protocols were analyzed by two experienced readers in consensus, including for PET/MRI-1 reading protocol unenhanced T2w and/or T1w imaging, diffusion-weighted imaging (DWI), and [18F]FDG PET imaging and for PET/MRI-2 reading protocol an additional T1w post contrast imaging. Patient-based and region-based evaluation according to the revised International Pediatric Non-Hodgkin's Lymphoma (NHL) Staging System (IPNHLSS) was performed, and a modified standard of reference was applied comprising histopathology and previous and follow-up cross-sectional imaging. Differences in staging accuracy were assessed using the Wilcoxon and McNemar tests.

RESULTS

In patient-based analysis, PET/MRI-1 and PET/MRI-2 both determined a correct IPNHLSS tumor stage in 90/105 (86%) exams. Region-based analysis correctly identified 119/127 (94%) lymphoma-affected regions. Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy for PET/MRI-1 and PET/MRI-2 were 94%, 97%, 90%, 99%, 97%, respectively. There were no significant differences between PET/MRI-1 and PET/MRI-2.

CONCLUSIONS

The use of MRI contrast agents in [18F]FDG PET/MRI examinations has no beneficial effect in primary and follow-up staging of pediatric lymphoma patients. Therefore, switching to a contrast agent-free [18F]FDG PET/MRI protocol should be considered in all pediatric lymphoma patients.

CLINICAL RELEVANCE STATEMENT

This study gives a scientific baseline switching to a contrast agent-free [18F]FDG PET/MRI staging in pediatric lymphoma patients. This could avoid side effects of contrast agents and saves time and costs by a faster staging protocol for pediatric patients.

KEY POINTS

• No additional diagnostic benefit of MRI contrast agents at [18F]FDG PET/MRI examinations of pediatric lymphoma primary and follow-up staging • Highly accurate primary and follow-up staging of pediatric lymphoma patients at MRI contrast-free [18F]FDG PET/MRI.

Optimized Whole-Body PET MRI Sequence Workflow in Pediatric Hodgkin Lymphoma Patients

¹⁸F-FDG PET/MRI might be the diagnostic method of choice for Hodgkin lymphoma patients, as it combines significant metabolic information from PET with excellent soft-tissue contrast from MRI and avoids radiation exposure from CT. However, a major issue is longer examination times than for PET/CT, especially for younger children needing anesthesia. Thus, a targeted selection of suitable whole-body MRI sequences is important to optimize the PET/MRI workflow. Methods: The initial PET/MRI scans of 84 EuroNet-PHL-C2 study patients from 13 international PET centers were evaluated. In each available MRI sequence, 5 PET-positive lymph nodes were assessed. If extranodal involvement occurred, 2 splenic lesions, 2 skeletal lesions, and 2 lung lesions were also assessed. A detection rate was calculated dividing the number of visible, anatomically assignable, and measurable lesions in the respective MRI sequence by the total number of lesions. Results: Relaxation time-weighted (T2w) transverse sequences with fat saturation (fs) yielded the best result, with detection rates of 95% for nodal lesions, 62% for splenic lesions, 94% for skeletal lesions, and 83% for lung lesions, followed by T2w transverse sequences without fs (86%, 49%, 16%, and 59%, respectively) and longitudinal relaxation time-weighted contrast-enhanced transverse sequences with fs (74%, 35%, 57%, and 55%, respectively). Conclusion: T2w transverse sequences with fs yielded the highest detection rates and are well suited for accurate whole-body PET/MRI in lymphoma patients. There is no evidence to recommend the use of contrast agents.

The contrast-enhanced MRI can be substituted by unenhanced MRI in identifying and automatically segmenting primary nasopharyngeal carcinoma with the aid of deep learning models: An exploratory study in large-scale population of endemic area

BACKGROUND AND OBJECTIVES

Administration of contrast is not desirable for all cases in clinical setting, and no consensus in sequence selection for deep learning model development has been achieved, thus we aim to explore whether contrast-enhanced magnetic resonance imaging (ceMRI) can be substituted in the identification and segmentation of nasopharyngeal carcinoma (NPC) with the aid of deep learning models in a large-scale cohort.

METHODS

A total of 4478 eligible individuals were randomly split into training, validation and test sets, and self-constrained 3D DenseNet and V-Net models were developed using axial T1-weighted imaging (T1WI), T2WI or enhanced T1WI (T1WIC) images separately. The differential diagnostic performance between NPC and benign hyperplasia were compared among models using chi-square test. Segmentation evaluation metrics, including dice similarity coefficient (DSC) and average surface distance (ASD), were compared using paired student's t-test between T1WIC and T1WI or T2WI models or M_T1/T2, a merged output of malignant region derived from T1WI and T2WI models.

RESULTS

All models exhibited similar satisfactory diagnostic performance in discriminating NPC from benign hyperplasia, all attaining overall accuracy over 99.00% in all T stages of NPC. And T1WIC model exhibited similar average DSC and ASD with those of M_T1/T2 (DSC, 0.768±0.070 vs 0.764±0.070; ASD, 1.573±10.954 mm vs 1.626±10.975 mm 1.626±0.975 mm vs 1.573±0.954 mm, all p > 0.0167) in primary NPC using DenseNet, but yielded a significantly higher DSC and lower ASD than either T1WI model or T2WI model (DSC, 0.759±0.065 or 0.755±0.071; ASD, 1.661±0.898 mm or 1.722±1.133 mm, respectively, all p < 0.01) in the entire test set of NPC cohort. Moreover, the average DSCs and ASDs were not statistically significant between T1WIC model and M_T1/T2 in both.

Magnetic resonance imaging of the pediatric mediastinum: updates, tips and tricks

Magnetic resonance imaging (MRI) of the pediatric mediastinum is challenging for the practicing radiologist. Many confounding factors add to the complexity of pediatric mediastinal MRI including small patient size, broad spectrum of mediastinal pathologies, motion artifacts and the need for sedation in a significant portion of children. However, with special attention to motion-reduction techniques and knowledge of pediatric-specific considerations, pediatric radiologists can help to provide accurate and timely diagnosis and also prevent multimodality imaging where MRI might be all that is needed. The purpose of this paper was present a practical review of pediatric mediastinal MRI with particular emphasis on diseases where MRI is the primary imaging modality of choice. Additionally, the author addresses those mediastinal processes for which MRI serves as a secondary problem-solving imaging tool.

[Lymphoma in children and adolescents]

CLINICAL/METHODOLOGICAL ISSUE

Lymphoma is the third most common neoplasm in children. Detection, accurate staging, and restaging are important for all radiologists involved in the diagnosis of children.

STANDARD RADIOLOGICAL METHODS

Magnetic resonance imaging (MRI), positron emission tomography/computed tomography (PET/CT), CT, ultrasound, X‑ray.

METHODOLOGICAL INNOVATIONS

Whole-body imaging (MRI and PET-MRI or PET-CT) play a key role in diagnostics and for therapy selection in Hodgkin lymphoma.

PERFORMANCE

In particular, hybrid imaging using ¹⁸F‑FDG PET is proving to be a powerful method for staging and restaging.

ACHIEVEMENTS

Standardization of imaging and inclusion in therapy studies (e.g. within the framework of the EuroNet-PHL-C2 study) improves diagnostics and simultaneously reduces therapy-related side effects.

PRACTICAL RECOMMENDATIONS

In Hodgkin lymphoma, deviations from the prescribed diagnostic procedure should be avoided. In clinically very heterogeneous non-Hodgkin lymphoma (NHL), on the other hand, the diagnostic procedure should be adapted to the actual clinical condition of the child. The role of interim PET in NHL is currently still the subject of clinical discussion.

MRI and PET/MRI in hematologic malignancies

The role of MRI differs considerably between the three main groups of hematological malignancies: lymphoma, leukemia, and myeloma. In myeloma, whole‐body MRI (WB‐MRI) is recognized as a highly sensitive test for the assessment of myeloma, and is also endorsed by clinical guidelines, especially for detection and staging. In lymphoma, WB‐MRI is presently not recommended, and merely serves as an alternative technique to the current standard imaging test, [¹⁸F]FDG‐PET/CT, especially in pediatric patients. Even for lymphomas with variable FDG avidity, such as extranodal mucosa‐associated lymphoid tissue lymphoma (MALT), contrast‐enhanced computed tomography (CT), but not WB‐MRI, is presently recommended, despite the high sensitivity of diffusion‐weighted MRI and its ability to capture treatment response that has been reported in the literature. In leukemia, neither MRI nor any other cross‐sectional imaging test (including positron emission tomography [PET]) is currently recommended outside of clinical trials. This review article discusses current clinical applications as well as the main research topics for MRI, as well as PET/MRI, in the field of hematological malignancies, with a focus on functional MRI techniques such as diffusion‐weighted imaging and dynamic contrast‐enhanced MRI, on the one hand, and novel, non‐FDG PET imaging probes such as the CXCR4 radiotracer [⁶⁸Ga]Ga‐Pentixafor and the amino acid radiotracer [¹¹C]methionine, on the other hand.

Level of Evidence: 5

Technical Efficacy Stage: 3

J. Magn. Reson. Imaging 2020;51:1325–1335.