Diagnostic performance of FDG-PET/MRI and WB-DW-MRI in the evaluation of lymphoma: a prospective comparison to standard FDG-PET/CT

A Radiation-Free Approach Based on the Whole-Body MRI Has Shown a High Level of Accuracy in the Follow-Up of Lymphoma Patients-A Single Center Retrospective Study

Background: Recurrence, even after years from the last treatment, characterizes lymphoproliferative disorders. Therefore, patients in complete remission from the disease should be followed up with periodic clinical checks. There is not a consensus on the role of imaging for this aim, because the radiological techniques used at the time of diagnosis expose patients to a risk of ionizing radiation damage. Whole-body magnetic resonance imaging with diffusion-weighted imaging (WB-MRI-DWI) has given similar results to gold standard techniques in detecting lymphoma in the involved sites without ionizing radiation. In this retrospective real-life study, we aimed to assess the accuracy of WB-MRI-DWI during follow-ups of lymphoma patients in terms of sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Methods: Lymphoma patients who were subject to at least one WB-MRI-DWI during follow-up between February 2010 and February 2022 were enrolled. Results: Based on our investigation, the calculated sensitivity of WB-MRI-DWI was 100% (95% CI: 99.4-100.0), the specificity was 98.6% (95% CI: 97.4-99.3), PPV was 79% (95% CI: 75.9-81.9), and NPV was 100% (95% CI: 99.4-100.0). Conclusions: Despite the possibility of poor patient compliance and the identification of false positives, WB-MRI-DWI examination demonstrated an excellent sensitivity in ruling out the disease relapse.

[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.

FDG PET/CT versus Bone Marrow Biopsy for Diagnosis of Bone Marrow Involvement in Non-Hodgkin Lymphoma: A Systematic Review

The management of non-Hodgkin lymphoma (NHL) patients requires the identification of bone marrow involvement (BMI) using a bone marrow biopsy (BMB), as recommended by international guidelines. Multiple studies have shown that [18F]FDG positron emission tomography, combined with computed tomography (PET/CT), may provide important information and may detect BMI, but there is still an ongoing debate as to whether it is sensitive enough for NHL patients in order to replace or be used as a complimentary method to BMB. The objective of this article is to systematically review published studies on the performance of [18F]FDG PET/CT in detecting BMI compared to the BMB for NHL patients. A population, intervention, comparison, and outcome (PICO) search in PubMed and Scopus databases (until 1 November 2021) was performed. A total of 41 studies, comprising 6147 NHL patients, were found to be eligible and were included in the analysis conducted in this systematic review. The sensitivity and specificity for identifying BMI in NHL patients were 73% and 90% for [18F]FDG PET/CT and 56% and 100% for BMB. For aggressive NHL, the sensitivity and specificity to assess the BMI for the [18F]FDG PET/CT was 77% and 94%, while for the BMB it was 58% and 100%. However, sensitivity and specificity to assess the BMI for indolent NHL for the [18F]FDG PET/CT was 59% and 85%, while for the BMB it was superior, and equal to 94% and 100%. With regard to NHL, a [18F]FDG PET/CT scan can only replace BMB if it is found to be positive and if patients can be categorized as having advanced staged NHL with high certainty. [18F]FDG PET/CT might recover tumors missed by BMB, and is recommended for use as a complimentary method, even in indolent histologic subtypes of NHL.

Whole-body MRI versus an [18F]FDG-PET/CT-based reference standard for early response assessment and restaging of paediatric Hodgkin's lymphoma: a prospective multicentre study

OBJECTIVES

To compare WB-MRI with an [18F]FDG-PET/CT-based reference for early response assessment and restaging in children with Hodgkin's lymphoma (HL).

METHODS

Fifty-one children (ages 10-17) with HL were included in this prospective, multicentre study. All participants underwent WB-MRI and [18F]FDG-PET/CT at early response assessment. Thirteen of the 51 patients also underwent both WB-MRI and [18F]FDG-PET/CT at restaging. Two radiologists independently evaluated all WB-MR images in two separate readings: without and with DWI. The [18F]FDG-PET/CT examinations were evaluated by a nuclear medicine physician. An expert panel assessed all discrepancies between WB-MRI and [18F]FDG-PET/CT to derive the [18F]FDG-PET/CT-based reference standard. Inter-observer agreement for WB-MRI was calculated using kappa statistics. Concordance, PPV, NPV, sensitivity and specificity for a correct assessment of the response between WB-MRI and the reference standard were calculated for both nodal and extra-nodal disease presence and total response evaluation.

RESULTS

Inter-observer agreement of WB-MRI including DWI between both readers was moderate (κ 0.46-0.60). For early response assessment, WB-MRI DWI agreed with the reference standard in 33/51 patients (65%, 95% CI 51-77%) versus 15/51 (29%, 95% CI 19-43%) for WB-MRI without DWI. For restaging, WB-MRI including DWI agreed with the reference standard in 9/13 patients (69%, 95% CI 42-87%) versus 5/13 patients (38%, 95% CI 18-64%) for WB-MRI without DWI.

CONCLUSIONS

The addition of DWI to the WB-MRI protocol in early response assessment and restaging of paediatric HL improved agreement with the [18F]FDG-PET/CT-based reference standard. However, WB-MRI remained discordant in 30% of the patients compared to standard imaging for assessing residual disease presence.

KEY POINTS

• Inter-observer agreement of WB-MRI including DWI between both readers was moderate for (early) response assessment of paediatric Hodgkin's lymphoma. • The addition of DWI to the WB-MRI protocol in early response assessment and restaging of paediatric Hodgkin's lymphoma improved agreement with the [18F]FDG-PET/CT-based reference standard. • WB-MRI including DWI agreed with the reference standard in respectively 65% and 69% of the patients for early response assessment and restaging.

Whole-body diffusion-weighted MRI in lymphoma-comparison of global apparent diffusion coefficient histogram parameters for differentiation of diseased nodes of lymphoma patients from normal lymph nodes of healthy individuals

Background

Morphologic features yield low diagnostic accuracy to distinguish between diseased and normal lymph nodes. The purpose of this study was to compare diseased lymphomatous and normal lymph nodes using global apparent diffusion coefficient (gADC) histogram parameters derived from whole-body diffusion-weighted MRI (WB-DWI).

Methods

1.5 Tesla WB-DWI of 23 lymphoma patients and 20 healthy volunteers performed between 09/2010 and 07/2015 were retrospectively reviewed. All diseased nodal groups in the lymphoma cohort and all nodes visible on b900 images in healthy volunteers were segmented from neck to groin to generate a total diffusion volume (tDV). A connected component-labelling algorithm separated spatially distinct nodes. Mean, median, skewness, kurtosis, minimum, maximum, interquartile range (IQR), standard deviation (SD), 10^th and 90^th centile of the gADC distribution were derived from the tDV of each patient/volunteer and from spatially distinct nodes. gADC and regional nodal ADC parameters were compared between malignant and normal nodes using t-tests and ROC curve analyses. A P value ≤0.05 was deemed statistically significant.

Results

Mean, median, IQR, 10th and 90th centiles of gADC and regional nodal ADC values were significantly lower in diseased compared with normal lymph nodes. Skewness, kurtosis and tDV were significantly higher in lymphoma. The SD, min and max gADC showed no significant difference between the two groups (P>0.128). The diagnostic accuracies of gADC parameters by AUC from highest to lowest were: 10th centile, mean, median, 90th centile, skewness, kurtosis and IQR. A 10th centile gADC threshold of 0.68×10^-3 mm²/s identified diseased lymphomatous nodes with 91% sensitivity and 95% specificity.

Conclusions

WB-DWI derived gADC histogram parameters can distinguish between malignant lymph nodes of lymphoma patients and normal lymph nodes of healthy individuals.

[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.

Abdominal and pelvic 18F-FDG PET/MR: a review of current and emerging oncologic applications

Positron emission tomography (PET) using fluorodeoxyglucose (¹⁸F-FDG) combined with magnetic resonance imaging (MR) is an emerging hybrid modality that has shown utility in evaluating abdominal and pelvic disease entities. Together, the high soft tissue contrast and metabolic/functional imaging capabilities make this modality ideal for oncologic imaging in many organ systems. Its clinical utility continues to evolve and future research will help solidify its role in oncologic imaging. In this manuscript, we aim to (1) provide an overview of the various PET/MR systems, describing the strengths and weaknesses of each system, and (2) review the oncologic applications for ¹⁸F-FDG PET/MR in the abdomen and pelvis.

[Hybrid imaging in lymphoma]

Hybrid imaging using the tracer [18F]FDG (2‑deoxy-2-fluoro-D-glucose) is regarded as the backbone of the diagnostic workup of lymphomas. All international guidelines, and especially the Lugano and RECIL (Response Evaluation Criteria in Lymphoma) guidelines, currently recommend [18F]FDG-PET/CT (positron emission tomography/computed tomography) for staging and treatment response assessment. With the exception of pediatric lymphomas, neither PET/MRI (magnetic resonance imaging) nor whole-body MRI are currently endorsed by international guidelines, despite the fact that both techniques have clear advantages over [18F]FDG-PET/CT in the assessment of lymphomas with variable FDG avidity. Of the new, more specific PET tracers that are being evaluated for the use in lymphomas, the CXCR4 (CXC motif chemokine receptor 4) tracer [68Ga]Pentixafor is of particular interest, as initial studies have shown that it may be used to visualize frequently non-FDG-avid lymphomas such as small-cell lymphocytic lymphoma, mucosa-associated lymphoid tissue (MALT) lymphoma and lymphomplasmacytic lymphoma.

Diffusion-weighted MRI for initial staging in Hodgkin`s lymphoma: comparison with FDG PET

PURPOSE

To evaluate the use of diffusion-weighted MRI (DWI) for initial staging of Hodgkin`s lymphoma and compare it to FDG PET.

METHODS

Forty-one patients with Hodgkin`s lymphoma (14 f, 27 m, median age 39 y) were included in this retrospective study. All patients underwent FDG PET/MR for initial staging, including DWI. The Lugano classification was used to describe disease extent. A combination of follow-up imaging and histopathology served as the reference standard. Method agreement was assessed using weighted kappa (κ). The accuracy of the imaging methods was evaluated using ROC curve analysis.

RESULTS

Regarding the Lugano stage, DWI and FDG PET had identical results in 34/41 cases (κ = 0.77). Sensitivity and specificity for nodal involvement was 89.9% and 93.8% for DWI, and 93.8% and 86.9% for FDG PET, respectively. In regard to extranodal involvement, sensitivity and specificity were 88.5% and 99.3% for DWI and 92.3% and 92.7% for FDG PET. The accuracy of both methods for nodal (p = 0.06) and extranodal involvement (p = 0.66) did not differ significantly.

CONCLUSION

Despite high sensitivity and specificity, DWI in free breathing cannot be currently recommended as an alternative to FDG PET in initial staging of Hodgkin`s lymphoma due to substantial differences in regard to therapy-determining Lugano Stage.

Role of intravoxel incoherent motion parameters in gastroesophageal cancer: relationship with 18F-FDG-positron emission tomography, computed tomography perfusion and magnetic resonance perfusion imaging parameters

BACKGROUND

Identification of pretherapeutic predictive markers in gastro-esophageal cancer is essential for individual-oriented treatment. This study evaluated the relationship of multimodality parameters derived from intravoxel incoherent motion method (IVIM), 18F-FDG-positron emission tomography (PET), computed tomography (CT) perfusion and dynamic contrast enhanced magnetic resonance imaging (MRI) in patients with gastro-esophageal cancer and investigated their histopathological correlation.

METHODS

Thirty-one consecutive patients (28 males; median age 63.9 years; range 37-84 years) with gastro-esophageal adenocarcinoma (N.=22) and esophageal squamous cell carcinoma (N.=9) were analyzed. IVIM parameters: pseudodiffusion (D*), perfusion fraction (fp), true diffusion (D) and the threshold b-value (bval); PET-parameters: SUV<inf>max</inf>, metabolic tumor volume (MTV) and total lesion glycolysis (TLG); CT perfusion parameters: blood flow (BF), blood volume (BV) and mean transit time (MTT); and MR perfusion parameters: time to enhance, positive enhancement integral, time-to-peak (TTP), maximum-slope-of-increase, and maximum-slope-of-decrease were determined, and correlated to each other and to histopathology.

RESULTS

IVIM and PET parameters showed significant negative correlations: MTV and bval (r<inf>s</inf> =-0.643, P=0.002), TLG and bval (r<inf>s</inf>=-0.699, P<0.01) and TLG and fp (r<inf>s</inf>=-0.577, P=0.006). Positive correlation was found for TLG and D (r<inf>s</inf>=0.705, P=0.000). Negative correlation was found for bval and staging (r<inf>s</inf>=0.590, P=0.005). Positive correlation was found for positive enhancement interval and BV (r<inf>s</inf>=0.547, P=0.007), BF and regression index (r<inf>s</inf>=0.753, P=0.005) and for time-to-peak and staging (r<inf>s</inf>=0.557, P=0.005).

CONCLUSIONS

IVIM parameters (bval, fp, D) provide quantitative information and correlate with PET parameters (MTV, TLG) and staging. IVIM might be a useful tool for additional characterization of gastro-esophageal cancer.

[Extranodal abdominal lymphomas]

BACKGROUND

Extranodal manifestations occur in up to 40% of non-Hodgkin lymphomas. The prevalence of extranodal involvement has increased.

OBJECTIVES

A comprehensive overview on lymphoma involvement in the parenchymatous abdominal organs, the gastrointestinal tract, and the peritoneal cavity under due consideration of clinical implications is given.

MATERIALS AND METHODS

A selective literature search with analysis of dedicated original research articles and reviews was carried out. Clinical guidelines are discussed.

RESULTS

Extranodal abdominal lymphoma involvement usually occurs secondarily in advanced disease. Sites involved most frequently are the liver and the gastrointestinal tract. Extranodal abdominal lymphoma involvement is more common in the immunocompromised patient.

CONCLUSION

Imaging findings of extranodal abdominal lymphoma are variable. Lymphoma is an important differential diagnosis to be considered in unclear tumor diseases.

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.

Can diffusion-weighted whole-body MRI replace contrast-enhanced CT for initial staging of Hodgkin lymphoma in children and adolescents?

BACKGROUND

Although positron emission tomography with 18F-fluoro-2-deoxyglucose (FDG-PET/CT) has been recommended as the method of choice for lymphoma staging, it has limited availability in several countries, therefore, studies comparing whole-body magnetic resonance imaging (MRI) to conventional staging methods or to FDG-PET/CT are an important tool to establish whole-body MRI as an alternative to these methods.

OBJECTIVE

To compare whole-body MRI versus conventional imaging methods for staging of Hodgkin lymphoma in children and adolescents.

MATERIALS AND METHODS

The study included 22 patients ages 5 to 21 years. Staging was performed using conventional imaging methods and whole-body MRI. Conventional imaging methods were defined as computed tomography (CT) of the neck, chest, abdomen and pelvis and ultrasonography of the neck and/or abdomen. We calculated the sensitivity of these methods for Hodgkin lymphoma staging and their sensitivity and specificity for detecting sites of nodal and extranodal involvement.

RESULTS

The sensitivity of whole-body MRI for Hodgkin lymphoma staging was superior to that of conventional imaging methods (95.5% vs. 86.4%, respectively), but both methods had similar sensitivity and specificity for detecting involvement of nodal sites (99.1% and 100% vs. 97.3% and 100%, respectively) and extranodal sites (90.5% and 98.7% vs. 90.5% and 99.4%, respectively).

CONCLUSION

Whole-body MRI has excellent sensitivity for staging of Hodgkin lymphoma in children and adolescents. It can thus be considered an alternative for this purpose, particularly because it does not expose patients to ionizing radiation.

Positron emission tomography/magnetic resonance imaging (PET/MRI): An update and initial experience at HC-FMUSP

The new technology of PET/MRI is a prototype of hybrid imaging, allowing for the combination of molecular data from PET scanning and morphofunctional information derived from MRI scanning. Recent advances regarding the technical aspects of this device, especially after the development of MRI-compatible silicon photomultipliers of PET, permitted an increase in the diagnostic performance of PET/MRI translated into dose reduction and higher imaging quality. Among several clinical applications, PET/MRI gains ground initially in oncology, where MRI per se plays an essential role in the assessment of primary tumors (which is limited in the case of PET/CT), including prostate, rectal and gynecological tumors. On the other hand, the evaluation of the lungs remains an enigma although new MRI sequences are being designed to overcome this. More clinical indications of PET/MRI are seen in the fields of neurology, cardiology and inflammatory processes, and the use of PET/MRI also opens perspectives for pediatric populations as it involves very low radiation exposure. Our review aimed to highlight the current indications of PET/MRI and discuss the challenges and perspectives of PET/MRI at HC-FMUSP.

18F-FDG PET/MR imaging of lymphoma nodal target lesions: Comparison of PET standardized uptake value (SUV) with MR apparent diffusion coefficient (ADC)

To compare positron emission tomography (PET) standardized uptake value (SUV) with magnetic resonance (MR) apparent diffusion coefficient (ADC) of nodal target lesions in patients with F-fluoro-2-deoxyglucose (FDG)-avid lymphomas by simultaneous PET/MR.Patients with histologically proven Hodgkin and non-Hodgkin lymphoma underwent PET/MR limited field of view of FDG-avid target nodal lesions. For PET images, a region of interest (ROI) was drawn around the target nodal lesion and the SUVmax and SUVmean was measured. For MR ADC measurements a ROI was placed over the target nodal lesion on diffusion-weighted imaging (DWI) and ADCmin and ADCmean (mean ADC) values within the ROI were recorded.Thirty-nine patients (19 women, 20 men; 13 patients with Hodgkin lymphoma and 26 with non-Hodgkin lymphoma) were included in the analysis. Sixty-six nodal lesions detected by PET/CT (19 PET-negative and 47 PET-positive) were analyzed by PET/MR. PET/MR quantitative assessments showed that ADCmin and ADCmean were accurate for discriminating positive from negative nodal lymphoma, with an AUC of 0.927 and 0.947, respectively. The ROC curve analysis of ADCmean versus SUVmax and SUVmean was not statistically significant (difference=0.044, P = .08 and difference = 0.045, P = .07; respectively). A substantial inverse association was observed between ADCmean with SUVmean and SUVmax (rho = -0.611; -0.607; P < .0001, respectively). A moderate inverse association was found between ADCmin with SUVmean and SUVmax (rho = -0.529, -0.520; P < .0001, respectively). Interobserver variability of quantitative assessment showed very good agreement for all variables (ICC>0.87).A significant correlation between ADCs and SUVs is found in FDG avid lymphomas. ADCmean is not inferior to PET SUV in discriminating positive and negative nodal lymphomas. Further larger studies are warranted to validate quantitative PET/MR for lymphoma patient management.

Diagnostic accuracy of diffusion-weighted imaging- magnetic resonance imaging compared to positron emission tomography/computed tomography in evaluating and assessing pathological response to treatment in adult patients with lymphoma: A systematic review

The use of Positron emission tomography/computerised tomography (PET/CT) is well established in the staging and assessment of treatment response of lymphoma. Recent studies have suggested that whole body diffusion-weighted imaging -magnetic resonance imaging (WB-DW-MRI) may be an alternative to PET/CT in both staging and assessment of treatment response. A systematic review was performed to assess the ability of DW-MRI in the assessment of treatment response in lymphoma. Pubmed, Medline, Web of Science and Embase databases were queried for studies examining whole body DW-MRI compared to PET/CT in adult patients using a protocol of search terms. We carried out an extensive assessment of titles, abstracts and full texts of relevant paper as well as quality assessment with the Quality Assessment of Diagnostic Accuracy (QUADAS-2) tool. Eight studies were found to meet the criteria and were included in our review and analysis. Overall, the quality of studies was found to be moderate, with good inter-rater agreement (K = 0.74). Data analysis showed that lesion-based assessment in 5 studies with pooled results had a sensitivity and specificity of 94.7% and 99.3%. Assessment with Cohen's Kappa coefficient showed agreement to be excellent (K = 0.88). Three studies were included for qualitative analysis, two of which showed good equivalence between PET/CT and DW-MRI. WB-DWI-MRI can be considered a sensitive and specific method for assessing treatment response in Lymphoma without the use of ionising radiation or administration of F-18 Flurodeoxyglucose. Further studies are needed to evaluate the optimum b-values in assessing treatment response.

Combined PET/MRI: Global Warming-Summary Report of the 6th International Workshop on PET/MRI, March 27-29, 2017, Tübingen, Germany

The 6th annual meeting to address key issues in positron emission tomography (PET)/magnetic resonance imaging (MRI) was held again in Tübingen, Germany, from March 27 to 29, 2017. Over three days of invited plenary lectures, round table discussions and dialogue board deliberations, participants critically assessed the current state of PET/MRI, both clinically and as a research tool, and attempted to chart future directions. The meeting addressed the use of PET/MRI and workflows in oncology, neurosciences, infection, inflammation and chronic pain syndromes, as well as deeper discussions about how best to characterise the tumour microenvironment, optimise the complementary information available from PET and MRI, and how advanced data mining and bioinformatics, as well as information from liquid biomarkers (circulating tumour cells and nucleic acids) and pathology, can be integrated to give a more complete characterisation of disease phenotype. Some issues that have dominated previous meetings, such as the accuracy of MR-based attenuation correction (AC) of the PET scan, were finally put to rest as having been adequately addressed for the majority of clinical situations. Likewise, the ability to standardise PET systems for use in multicentre trials was confirmed, thus removing a perceived barrier to larger clinical imaging trials. The meeting openly questioned whether PET/MRI should, in all cases, be used as a whole-body imaging modality or whether in many circumstances it would best be employed to give an in-depth study of previously identified disease in a single organ or region. The meeting concluded that there is still much work to be done in the integration of data from different fields and in developing a common language for all stakeholders involved. In addition, the participants advocated joint training and education for individuals who engage in routine PET/MRI. It was agreed that PET/MRI can enhance our understanding of normal and disrupted biology, and we are in a position to describe the in vivo nature of disease processes, metabolism, evolution of cancer and the monitoring of response to pharmacological interventions and therapies. As such, PET/MRI is a key to advancing medicine and patient care.

Imaging children suffering from lymphoma: an evaluation of different 18F-FDG PET/MRI protocols compared to whole-body DW-MRI

OBJECTIVES

The objectives of this study were to evaluate and compare the diagnostic potential of different PET/MRI reading protocols, entailing non-enhanced / contrast-enhanced and diffusion-weighted ¹⁸F-FDG PET/MR imaging and whole-body diffusion-weighted MRI for lesion detection and determination of the tumor stage in pediatric lymphoma patients.

METHODS

A total of 28 ¹⁸F-FDG PET/MRI datasets were included for analysis of four different reading protocols: (1) PET/MRI utilizing sole unenhanced T2w and T1w imaging, (2) PET/MRI utilizing additional contrast enhanced sequences, (3) PET/MR imaging utilizing unenhanced, contrast enhanced and DW imaging or (4) WB-DW-MRI. Statistical analyses were performed on a per-patient and a per-lesion basis. Follow-up and prior examinations as well as histopathology served as reference standards.

RESULTS

PET/MRI correctly identified all 17 examinations with active lymphoma disease, while WB-DW-MRI correctly identified 15/17 examinations. Sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy were 96%, 96.5%, 97%, 95%, and 96% for PET/MRI₁; 97%, 96.5%, 97%, 96.5%, and 97% for PET/MRI₂; 97%, 96.5%, 97%, 96.5%, and 97% for PET/MRI₃ and 77%, 96%, 96%, 78.5% and 86% for MRI-DWI.

CONCLUSION

¹⁸F-FDG PET/MRI is superior to WB-DW-MRI in staging pediatric lymphoma patients. Neither application of contrast media nor DWI leads to a noticeable improvement of the diagnostic accuracy of PET/MRI. Thus, unenhanced PET/MRI may play a crucial role for the diagnostic work-up of pediatric lymphoma patients in the future.

18F-FDG-PET/MRI in lymphoma patients

The introduction of hybrid PET/MRI imaging using integrated systems into clinical practice has opened up the possibility of reducing the radiation dose from hybrid imaging by eliminating the contribution from computed tomography. Studies comparing the possibilities of PET/CT and PET/MRI imaging demonstrated it is possible to use the advantages of the high contrast resolution of magnetic resonance for soft tissue and bone marrow along with PET records in a quality comparable to PET/CT imaging. The significant feature for PET imaging in Hodgkińs lymphoma is that it is a tissue with high levels of radiopharmaceutical accumulation, which decreases proportionally after successful therapeutic effect, the effect of therapy is assessed using Deauville score system on interim examinations. While the efficacy of prognosis determined using the Deauville scale in HL is widely accepted, it turns out that in DLBCL, the prognostic value of PET imaging is bound to the evaluation of subtypes. PET/MRI scanning can be used to evaluate a relapse if follicular lymphoma has already been treated, or to confirm transformation into more aggressive forms. In children and adults with Burkitt's lymphoma, negative findings after induction therapy have a high negative predictive value for relapse prognosis.

Diffuse Large B-Cell Lymphoma in the Era of Precision Oncology: How Imaging Is Helpful

Diffuse large B cell lymphoma (DLBCL) is the most common histological subtype of Non-Hodgkin's lymphoma. As treatments continues to evolve, so do imaging strategies, and positron emission tomography (PET) has emerged as the most important imaging tool to guide oncologists in the diagnosis, staging, response assessment, relapse/recurrence detection,and therapeutic decision making of DLBCL. Other imaging modalities including magnetic resonance imaging (MRI), computed tomography (CT), ultrasound, and conventional radiography are also used in the evaluation of lymphoma. MRI is useful for nervous system and musculoskeletal system involvement and is emerging as a radiation free alternative to PET/CT. This article provides a comprehensive review of both the functional and morphological imaging modalities, available in the management of DLBCL.

18F-FDG PET/CT Imaging of Hodgkin Lymphoma in a Child with Common Variable Immunodeficiency

Common variable immunodeficiency is characterized by low levels of serum immunoglobulins and antibodies, recurrent infections, and a predisposition to malignancy. Here, we present the ¹⁸F-FDG PET/CT findings of a 7-y-old boy with common variable immunodeficiency and Hodgkin lymphoma.

Imaging of primary pediatric lymphoma of bone

BACKGROUND

Primary pediatric bone lymphoma is a rare form of non-Hodgkin lymphoma. Unlike nodal forms of lymphoma, imaging abnormalities in lymphoma of bone do not resolve rapidly in conjunction with treatment and radiologic findings can remain abnormal for years, making it difficult to evaluate treatment response.

OBJECTIVE

To evaluate the utility of imaging in assessment of patients with primary pediatric bone lymphoma.

MATERIALS AND METHODS

At our institution between 2004 and 2013, six cases of pathology-proven primary pediatric bone lymphoma were diagnosed. Retrospective chart review was performed to assess imaging utilization. Our data were qualitatively compared with existing literature to construct an algorithm for imaging patients with primary lymphoma of bone.

RESULTS

Imaging evaluation of patients with primary pediatric bone lymphoma was highly variable at our institution. Conventional imaging was routinely used to evaluate response to treatment, despite lack of appreciable osseous change. Imaging in the absence of symptoms did not alter clinical management. Only positron emission tomography CT (PET/CT) proved capable of demonstrating imaging changes from the pretreatment to the post-treatment scans that were consistent with the clinical response to treatment.

CONCLUSION

Surveillance imaging is likely unnecessary in patients with a known diagnosis of pediatric lymphoma of bone. Pretreatment and post-treatment PET/CT is likely sufficient to assess response. There is little data to support the use of interim and surveillance PET/CT.