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Di Giuliano F, Picchi E, Pucci N, Minosse S, Ferrazzoli V, Pizzicannella G, Angeloni C, Nasso D, Chiaravalloti A, Garaci F, Floris R. Comparison between diffusion-weighted magnetic resonance and positron-emission tomography in the evaluation of treated lymphomas with mediastinal involvement. THE EGYPTIAN JOURNAL OF RADIOLOGY AND NUCLEAR MEDICINE 2022. [DOI: 10.1186/s43055-022-00825-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Abstract
Background
The persistence of residual tissue after treatment is frequent in patients with mediastinal lymphomas and it is often characterized by 18F-Flurodeoxyglucose Positron Emission Tomography (18F-FDG PET) uptake. This study aims to investigate the usefulness of diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) sequence in residual tissues of treated mediastinal lymphomas and to compare it with 18F-FDG PET-CT.
Results
We included 21 patients with mediastinal Hodgkin and non-Hodgkin lymphomas who showed residual masses on PET-CT imaging at end of treatment and underwent DWIBS-Magnetic Resonance Imaging (MRI). SUVmax and Apparent Diffusion Coefficient (ADC) values of residual masses were assessed quantitatively, including measurement of mean ADC. 15 patients showed radiotracer uptake at 18F-FDG PET-CT, among them only 3 had positive DWIBS-MRI with low ADC values (median value: 0.90 mm2/s). The mediastinal biopsy in these 3 “double positive” patients confirmed pathological residual tissue. All the patients with positive 18F-FDG PET-CT but negative DWIBS-MRI (n = 18) with high ADC values (median value: 2.05 mm2/s) were confirmed negative by biopsy.
Conclusions
DWIBS-MRI examination combined with ADC measurement allowed to discriminate pathological and non-pathological residual tissue in patients with treated mediastinal lymphoma. These preliminary results seem to pave the way for a leading role of the MRI which could be a useful alternative to the 18F-FDG PET/CT.
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Spijkers S, Littooij AS, Kwee TC, Tolboom N, Beishuizen A, Bruin MCA, Enríquez G, Sábado C, Miller E, Granata C, de Lange C, Verzegnassi F, de Keizer B, Nievelstein RAJ. 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. Eur Radiol 2021; 31:8925-8936. [PMID: 34021390 PMCID: PMC8589741 DOI: 10.1007/s00330-021-08026-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 03/21/2021] [Accepted: 04/28/2021] [Indexed: 02/06/2023]
Abstract
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.
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Affiliation(s)
- Suzanne Spijkers
- Department of Radiology and Nuclear Medicine, University Medical Centre Utrecht/Wilhelmina Children's Hospital, Utrecht University, Heidelberglaan 100, 3584, CX, Utrecht, The Netherlands.
| | - Annemieke S Littooij
- Department of Radiology and Nuclear Medicine, University Medical Centre Utrecht/Wilhelmina Children's Hospital, Utrecht University, Heidelberglaan 100, 3584, CX, Utrecht, The Netherlands
- Princess Máxima Centre for Paediatric Oncology, Utrecht, The Netherlands
| | - Thomas C Kwee
- Department of Radiology, Medical Imaging Centre, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands
| | - Nelleke Tolboom
- Department of Radiology and Nuclear Medicine, University Medical Centre Utrecht/Wilhelmina Children's Hospital, Utrecht University, Heidelberglaan 100, 3584, CX, Utrecht, The Netherlands
- Princess Máxima Centre for Paediatric Oncology, Utrecht, The Netherlands
| | - Auke Beishuizen
- Princess Máxima Centre for Paediatric Oncology, Utrecht, The Netherlands
- Department of Paediatric Oncology/Haematology, Erasmus Medical Centre-Sophia Children's Hospital, Rotterdam, The Netherlands
| | - Marrie C A Bruin
- Princess Máxima Centre for Paediatric Oncology, Utrecht, The Netherlands
| | - Goya Enríquez
- Department of Pediatric Radiology, University Hospital Vall d'Hebron, Institut de Recerca Vall d'Hebron, Barcelona, Spain
| | - Constantino Sábado
- Department of Paediatric Oncology and Haematology, University Hospital Vall d'Hebron, Barcelona, Spain
| | - Elka Miller
- Department of Medical Imaging, CHEO, University of Ottawa, Ottawa, Canada
| | - Claudio Granata
- Department of Radiology, Institute for Maternal and Child Health IRCCS Burlo Garofolo, Trieste, Italy
| | - Charlotte de Lange
- Department of Diagnostic Imaging and Intervention, Oslo University Hospital, Rikshospitalet, Oslo, Norway
| | - Federico Verzegnassi
- Oncohematology Unit, Institute for Maternal and Child Health IRCCS Burlo Garofolo, Trieste, Italy
| | - Bart de Keizer
- Department of Radiology and Nuclear Medicine, University Medical Centre Utrecht/Wilhelmina Children's Hospital, Utrecht University, Heidelberglaan 100, 3584, CX, Utrecht, The Netherlands
- Princess Máxima Centre for Paediatric Oncology, Utrecht, The Netherlands
| | - Rutger A J Nievelstein
- Department of Radiology and Nuclear Medicine, University Medical Centre Utrecht/Wilhelmina Children's Hospital, Utrecht University, Heidelberglaan 100, 3584, CX, Utrecht, The Netherlands
- Princess Máxima Centre for Paediatric Oncology, Utrecht, The Netherlands
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Donners R, Yiin RSZ, Blackledge M, Koh DM. Whole-body diffusion-weighted MRI of normal lymph nodes: prospective apparent diffusion coefficient histogram and nodal distribution analysis in a healthy cohort. Cancer Imaging 2021; 21:64. [PMID: 34838136 PMCID: PMC8627090 DOI: 10.1186/s40644-021-00432-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 11/12/2021] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Whole body DWI (WB-DWI) enables the identification of lymph nodes for disease evaluation. However, quantitative data of benign lymph nodes across the body are lacking to allow meaningful comparison of diseased states. We evaluated apparent diffusion coefficient (ADC) histogram parameters of all visible lymph nodes in healthy volunteers on WB-DWI and compared differences in nodal ADC values between anatomical regions. METHODS WB-DWI was performed on a 1.5 T MR system in 20 healthy volunteers (7 female, 13 male, mean age 35 years). The b900 images were evaluated by two radiologists and all visible nodes from the neck to groin areas were segmented and individual nodal median ADC recorded. All segmented nodes in a patient were summated to generate the total nodal volume. Descriptors of the global ADC histogram, derived from individual node median ADCs, including mean, median, skewness and kurtosis were obtained for the global volume and each nodal region per patient. ADC values between nodal regions were compared using one-way ANOVA with Bonferroni post hoc tests and a p-value ≤0.05 was deemed statistically significant. RESULTS One thousand sixty-seven lymph nodes were analyzed. The global mean and median ADC of all lymph nodes were 1.12 ± 0.27 (10- 3 mm2/s) and 1.09 (10- 3 mm2/s). The average median ADC skewness was 0.25 ± 0.02 and average median ADC kurtosis was 0.34 ± 0.04. The ADC values of intrathoracic, portal and retroperitoneal nodes were significantly higher (1.53 × 10- 3, 1.75 × 10- 3 and 1.58 × 10- 3 mm2/s respectively) than in other regions. Intrathoracic, portal and mesenteric nodes were relatively uncommon, accounting for only 3% of the total nodes segmented. CONCLUSIONS The global mean and median ADC of all lymph nodes were 1.12 ± 0.27 (10- 3 mm2/s) and 1.09 (10- 3 mm2/s). Intrathoracic, portal and retroperitoneal nodes display significantly higher ADCs. Normal intrathoracic, portal and mesenteric nodes are infrequently visualized on WB-DWI of healthy individuals. TRIAL REGISTRATION Royal Marsden Hospital committee for clinical research registration number 09/H0801/86, 19.10.2009.
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Affiliation(s)
- Ricardo Donners
- Department of Diagnostic Radiolog, The Royal Marsden NHS Foundation Trust, Downs Road, Sutton, London, Surrey, SM2 5PT, UK.
| | - Raphael Shih Zhu Yiin
- Department of Diagnostic Radiology, Changi General Hospital, 2 Simei St 3, Singapore, 529889, Singapore
| | - Matthew Blackledge
- Institute of Cancer Research, 15 Cotswold Road, Sutton, London, SM2 5NG, UK
| | - Dow-Mu Koh
- Department of Diagnostic Radiology, Institute of Cancer Research and The Royal Marsden NHS, Foundation Trust, Downs Road, Sutton, London, Surrey, SM2 5PT, UK
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Donners R, Yiin RSZ, Koh DM, De Paepe K, Chau I, Chua S, Blackledge MD. 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. Quant Imaging Med Surg 2021; 11:3549-3561. [PMID: 34341730 DOI: 10.21037/qims-21-50] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 03/26/2021] [Indexed: 01/03/2023]
Abstract
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), 10th and 90th 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.
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Affiliation(s)
- Ricardo Donners
- Department of Radiology, University Hospital Basel, Petersgraben 4, 4031 Basel, Switzerland.,Department of Radiology, Royal Marsden Hospital, Sutton SM2 5PT, UK
| | | | - Dow-Mu Koh
- Department of Radiology, Royal Marsden Hospital, Sutton SM2 5PT, UK.,Cancer Research UK Cancer Imaging Centre, The Institute of Cancer Research, Sutton SM2 5NG, UK
| | - Katja De Paepe
- Department of Radiology, University Hospitals Leuven, Herestaat 49, Belgium
| | - Ian Chau
- Gastrointestinal and Lymphoma Unit, The Royal Marsden Hospital, Surrey SM2 5PT, UK
| | - Sue Chua
- Department of Nuclear Medicine and PET, Royal Marsden Hospital, Sutton SM2 5PT, UK
| | - Matthew D Blackledge
- Cancer Research UK Cancer Imaging Centre, The Institute of Cancer Research, Sutton SM2 5NG, UK
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Brancato V, Aiello M, Della Pepa R, Basso L, Garbino N, Nicolai E, Picardi M, Salvatore M, Cavaliere C. Automatic Prediction and Assessment of Treatment Response in Patients with Hodgkin's Lymphoma Using a Whole-Body DW-MRI Based Approach. Diagnostics (Basel) 2020; 10:diagnostics10090702. [PMID: 32948043 PMCID: PMC7555579 DOI: 10.3390/diagnostics10090702] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 09/11/2020] [Accepted: 09/15/2020] [Indexed: 12/25/2022] Open
Abstract
The lack of validation and standardization represents the main drawback for a clear role of whole-body diffusion weighted imaging (WB-DWI) for prediction and assessment of treatment response in Hodgkin’s lymphoma (HL). We explored the reliability of an automatic approach based on the WB-DWI technique for prediction and assessment of response to treatment in patients with HL. The study included 20 HL patients, who had whole-body positron emission tomography (PET)/ magnetic resonance Imaging (MRI) performed before, during and after chemotherapy. Using the syngo.via MR Total Tumor Load tool, we automatically extracted values of diffusion volume (DV) and its associated histogram features by WB-DWI images, and evaluated their utility in predicting and assessing interim and end-of-treatment (EOT) response. The Mann–Whitney test followed by receiver operator characteristic (ROC) analysis was performed between features and their inter-time point percentage differences for patients having a complete or partial treatment response, revealing that several WB-DWI associated features allowed for prediction of interim response and both prediction and assessment of EOT response. Our proposed method offers huge advantages in terms of saving time and work, enabling clinicians to draw conclusions relating to HL treatment response in a fully automatic way, and encloses, also, all DWI advantages compared to PET/ computed tomography (CT).
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Affiliation(s)
- Valentina Brancato
- IRCCS SDN (Istituto di Ricovero e Cura a Carattere Scientifico, SYNLAB istituto di Diagnostica Nucleare), 80143 Napoli, Italy; (V.B.); (L.B.); (N.G.); (E.N.); (M.S.); (C.C.)
| | - Marco Aiello
- IRCCS SDN (Istituto di Ricovero e Cura a Carattere Scientifico, SYNLAB istituto di Diagnostica Nucleare), 80143 Napoli, Italy; (V.B.); (L.B.); (N.G.); (E.N.); (M.S.); (C.C.)
- Correspondence:
| | - Roberta Della Pepa
- Department of Clinical Medicine and Surgery, Hematology Section, Federico II University of Naples, 80131 Naples, Italy; (R.D.P.); (M.P.)
| | - Luca Basso
- IRCCS SDN (Istituto di Ricovero e Cura a Carattere Scientifico, SYNLAB istituto di Diagnostica Nucleare), 80143 Napoli, Italy; (V.B.); (L.B.); (N.G.); (E.N.); (M.S.); (C.C.)
| | - Nunzia Garbino
- IRCCS SDN (Istituto di Ricovero e Cura a Carattere Scientifico, SYNLAB istituto di Diagnostica Nucleare), 80143 Napoli, Italy; (V.B.); (L.B.); (N.G.); (E.N.); (M.S.); (C.C.)
| | - Emanuele Nicolai
- IRCCS SDN (Istituto di Ricovero e Cura a Carattere Scientifico, SYNLAB istituto di Diagnostica Nucleare), 80143 Napoli, Italy; (V.B.); (L.B.); (N.G.); (E.N.); (M.S.); (C.C.)
| | - Marco Picardi
- Department of Clinical Medicine and Surgery, Hematology Section, Federico II University of Naples, 80131 Naples, Italy; (R.D.P.); (M.P.)
| | - Marco Salvatore
- IRCCS SDN (Istituto di Ricovero e Cura a Carattere Scientifico, SYNLAB istituto di Diagnostica Nucleare), 80143 Napoli, Italy; (V.B.); (L.B.); (N.G.); (E.N.); (M.S.); (C.C.)
| | - Carlo Cavaliere
- IRCCS SDN (Istituto di Ricovero e Cura a Carattere Scientifico, SYNLAB istituto di Diagnostica Nucleare), 80143 Napoli, Italy; (V.B.); (L.B.); (N.G.); (E.N.); (M.S.); (C.C.)
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Diffusion-Weighted Imaging in Oncology: An Update. Cancers (Basel) 2020; 12:cancers12061493. [PMID: 32521645 PMCID: PMC7352852 DOI: 10.3390/cancers12061493] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 05/28/2020] [Accepted: 06/01/2020] [Indexed: 02/06/2023] Open
Abstract
To date, diffusion weighted imaging (DWI) is included in routine magnetic resonance imaging (MRI) protocols for several cancers. The real additive role of DWI lies in the "functional" information obtained by probing the free diffusivity of water molecules into intra and inter-cellular spaces that in tumors mainly depend on cellularity. Although DWI has not gained much space in some oncologic scenarios, this non-invasive tool is routinely used in clinical practice and still remains a hot research topic: it has been tested in almost all cancers to differentiate malignant from benign lesions, to distinguish different malignant histotypes or tumor grades, to predict and/or assess treatment responses, and to identify residual or recurrent tumors in follow-up examinations. In this review, we provide an up-to-date overview on the application of DWI in oncology.
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Shapira-Zaltsberg G, Wilson N, Trejo Perez E, Abbott L, Dinning S, Kapoor C, Davila J, Smith B, Miller E. Whole-Body Diffusion-Weighted MRI Compared to 18 FFDG PET/CT in Initial Staging and Therapy Response Assessment of Hodgkin Lymphoma in Pediatric Patients. Can Assoc Radiol J 2020; 71:217-225. [PMID: 32062992 DOI: 10.1177/0846537119888380] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
PURPOSE The aim of our study was to compare whole-body diffusion-weighted MRI (WB-DWI-MRI) to fluoro-2-deoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in the assessment of initial staging and treatment response in pediatric patients with Hodgkin lymphoma. MATERIALS AND METHODS This prospective study comprised 11 children with Hodgkin lymphoma. Whole-body DWI-MRI and FDG-PET/CT were obtained at baseline and after 2 cycles of chemotherapy. Two radiologists measured the apparent diffusion coefficient (ADC) values of the sites of involvement agreed upon in consensus and 1 nuclear medicine physician assessed the PET/CT. Reliability of radiologists' ratings was assessed by intraclass correlation coefficients (ICC2,1). The sensitivity and positive predictive value (PPV) of DW-MRI relative to PET/CT were calculated for nodal and extranodal sites. The patients were staged according to both modalities. Association of treatment responses was assessed through the Pearson correlation between the ADC ratios and the change standardized uptake value (SUV) between baseline and follow-up. RESULTS There was good agreement between the raters for nodal and extranodal ADC measurements. The sensitivity and PPV of DW-MRI relative to PET/CT of nodal disease was 0.651 and 1.0, respectively, at baseline, and 0.697 and 0.885 at follow-up. The sensitivity and PPV of extranodal disease were 0.545 and 0.6 at baseline, and 0.167 and 0.333 at follow-up. Diffusion-weighted MRI determined correct tumor stage in 8 of 11 examinations. There was poor correlation between the ADC ratios and the absolute change in SUV between baseline and follow-up (0.348). CONCLUSION Our experience showed that WB-DWI-MRI is inferior to PET/CT for initial staging and assessment of treatment response of Hodgkin lymphoma in pediatric patients.
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Affiliation(s)
- Gali Shapira-Zaltsberg
- Department of Medical Imaging, Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada.,University of Ottawa, Ontario, Canada
| | - Nagwa Wilson
- Department of Medical Imaging, Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada.,University of Ottawa, Ontario, Canada
| | - Esther Trejo Perez
- University of Ottawa, Ontario, Canada.,Research Institute, Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada
| | - Lesleigh Abbott
- University of Ottawa, Ontario, Canada.,Department of Hematology/Oncology, Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada
| | - Stephen Dinning
- University of Ottawa, Ontario, Canada.,Division of Nuclear Medicine, Department of Medicine, Ottawa Hospital, Ontario, Canada
| | - Cassandra Kapoor
- Department of Medical Imaging, Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada
| | - Jorge Davila
- Department of Medical Imaging, Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada.,University of Ottawa, Ontario, Canada
| | - Barry Smith
- Department of Medical Imaging, Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada
| | - Elka Miller
- Department of Medical Imaging, Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada.,University of Ottawa, Ontario, Canada
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