BACKGROUND:Technetium-99 m-dimercaptosuccinic acid (DMSA) renal cortical scintigraphy is commonly used in the evaluation of children with urinary tract infections. Pyelonephritis and post-pyelonephritic scarring manifest as renal cortical defects on DMSA renal scintigraphy, including DMSA Single Photon Emission Computed Tomography (SPECT) imaging. SPECT image quality can be degraded by blurring related to respiratory motion. Thus we hypothesize that image quality will be improved with estimation and correction of respiratory motion. PURPOSE:The purpose of this study is to develop and evaluate a data-driven methodology that estimates surrogate respiratory signals and then employs these surrogate signals in correction of respiratory-motion in pediatric DMSA renal SPECT imaging. METHODS:The XCAT digital anthropomorphic phantom was used with SPECT Monte Carlo simulation to form a population of 100 ms projections of DMSA renal SPECT imaging acquired with clinically relevant count-levels. These 100 ms projections emulated the framing of list-mode acquisitions at Boston Children's Hospital (BCH). The axial (superior/inferior) center-of-count-mass (aCOM) approach was utilized to estimate a surrogate respiratory signal for combining the 100 ms projections into seven respiratory-motion states with each having different extents of motion. The motion-states were then reconstructed and rigid-body respiratory-motion of the kidneys between the three motion-states on either side of the center state versus the center state was estimated by rigid-body registration. This estimated motion was then used to correct respiratory motion as part of a second pass through reconstruction of the projections of the motion states. To evaluate the surrogate signal, Pearson's correlation coefficient was calculated between the true respiratory signals used in creating the XCAT projection data and the surrogate respiratory signals. The respiratory motion corrected reconstructions and the images reconstructed without respiratory motion compensation were quantitatively compared to the ground truth images (where no respiratory motion was simulated) using the Normalized Root Mean Square Error (NRMSE) as a measure of fidelity. RESULTS:The average over our entire population of XCAT phantoms of Pearson's correlation coefficient (r) between the aCOM estimated surrogate respiratory and the actual average motion simulated for each of the 100 ms time intervals was 0.76. The average standard error of the estimate (SEE) for this r-value was 3.06 mm. For the group of XCAT phantoms with a simulated average amplitude of motion between 6-10 mm, there were no significant differences in the NRMSE versus ground truth reconstructions for the reconstructions with either the estimated or true motion correction methods compared against reconstructions without motion correction. For the groups with simulated average amplitudes of motion between 10-14 mm, 14-18 mm, and >18 mm, there were significant differences in the NRMSE for the reconstructions with motion with either the estimated and true motion correction applied in comparison to reconstructions without motion correction. CONCLUSION:Respiratory motion correction in pediatric renal SPECT imaging using a data-driven approach can improve image quality, with potential for improved diagnostic accuracy for studies with a moderate amount of motion.

BACKGROUND:Respiratory motion is known to cause blurring in Single-Photon Emission Computed Tomography (SPECT) images which can mask or mimic disease. Pediatric imaging with 99mTc-labeled dimercaptosuccinic acid (DMSA) is used to assess cortical defects in kidneys and may be especially susceptible to artifacts introduced by respiratory motion due to the thin kidney cortices and small kidney volumes seen in many pediatric patients. PURPOSE:The purpose of this study was to assess a data-driven method to estimate respiratory motion signals in pediatric 99mTc-DMSA renal SPECT and to evaluate the impact of respiratory motion correction on image quality. METHODS:Listmode 99mTc-DMSA SPECT data were acquired for 77 pediatric patients aged from 6 weeks to 20 years. The data were binned into 100 ms temporal frames and forward-projected kidney masks were used in determining the axial center-of-mass (aCOM) of counts in each temporal frame as a surrogate renal respiratory motion signal for each patient. Amplitudes of respiratory motion in the lateral, anterior-posterior and axial (superior-inferior) axes were determined using a rigid-body six-degree-of-freedom intensity-based registration method and evaluated as a function of patient weight. Welch t-tests were performed to compare the respiratory motion amplitudes of male and female patients. Subsequently, a rigid-body 6-degree-of-freedom respiratory motion correction was applied during reconstruction and the images were quantitatively assessed for improvement in contrast and sharpness. RESULTS:Renal respiratory motion surrogate signals were estimated for 69 patients, after eight were removed due to gross body motion. Axial, lateral and anterior-posterior translational renal respiratory motion amplitudes were all found to positively correlate with patient weight, with lateral motion showing the strongest correlation. Respiratory motion was largest in the axial direction where it ranged from (2.19  ±  0.48) mm for the patients under 7 kg to (6.96  ±  3.07) mm for patients over 60 kg. No significant differences were found in axial or anterior-posterior renal respiratory motion between male and female patients, but lateral motion was slightly lower for females. Quantitative assessment of reconstructed images showed that respiratory motion correction improved contrast and sharpness as a function of estimated amplitude of axial respiratory motion, suggesting a threshold where motion correction becomes beneficial. CONCLUSIONS:A data-driven respiratory motion estimation method found significant positive correlation in renal motion amplitudes and weight for pediatric DMSA SPECT studies. The derived respiratory signals were used to perform rigid-body respiratory motion correction during reconstruction. The renal respiratory motion correction reduced cortical blurring and improved contrast in some patients, generally those with the largest estimated motion, highlighting potential for this method to improve diagnostic accuracy.

The North American consensus guidelines recommend a weight-based administered activity for renal cortical scintigraphy with 99mTc-dimercaptosuccinic acid (DMSA; 1.85 MBq/kg or 0.05 mCi/kg). Patients weighing less than 10 kg are recommended to receive a minimum administered activity of 18.5 MBq (0.5 mCi), irrespective of their weight. This approach is presumably to provide sufficient counts for adequate image quality, but it has not been rigorously evaluated. To compare the adequacy of image quality of infant DMSA renal SPECT examinations obtained using the minimum administered activity recommended by the consensus guidelines with simulated data utilizing a strict weight-based dosage. Phase 1: Datasets of 55 infants (29 females, 26 males, median age 3.0 months and weight 5.6 kg) undergoing DMSA SPECT from 2016 to 2021 were identified with 7 used for training and 48 used for study analysis. Data from patients receiving the administered activity recommended by the consensus guidelines (“full dosage”, group A) were processed using binomial resampling to add Poisson noise to mimic a strict weight-based scheme (“simulated reduced dosage”, group A′). Three experienced nuclear medicine physicians, who were blinded to group membership and clinical information, independently evaluated adequacy of image quality for clinical interpretation on a 4-point scale. Student’s paired t-test was utilized for group comparisons and inter-rater agreements were calculated using kappa statistics. Phase 2: Group A′ simulated data were compared to a second cohort of 99mTc-DMSA SPECT cases where the administered activity followed a strict weight-based regime (“true reduced dosage”, group B). Subjects weighing between 4-7 kg were selected (group A′, 10 patients, 4 females, 6 males, median age 3.00 months and weight 5.35 kg) to compare with similar-weight group B subjects (10 patients, 5 females, 5 males, median age 2.50 months and weight 6.05 kg). The same observers and 4-point scale from phase 1 were used. The Wilcoxon rank sum test was utilized for analysis. Observers’ ratings were combined for analysis resulting in n=144 case-pairs (3 observers × 48 case-pairs) in phase 1. In phase 1, the ratings of groups A and A′ were identical for 73.6

The 2024 update of the North American consensus guidelines for pediatric administered radiopharmaceutical activities (NAGL) is presented. Under the auspices of the Image Gently Alliance, a working group of 19 pediatric nuclear medicine experts, including clinicians, technologists, and physicists, worked for 2 y to update the 2016 NAGL, its most recent version. Building on previous success, the current recommendations regarding pediatric diagnostic nuclear medicine were reviewed systematically regarding their continued pertinence, the need for modification, and whether any recent protocols should be added. The working group reviewed and approved the 2024 update of the NAGL, and the update was subsequently approved by the Image Gently Alliance in the spring of 2024. None of the 23 protocols listed in the 2016 NAGL were removed; however, 9 were modified, and 6 new protocols (13N-NH3 and 83Rb for cardiac imaging; 18F-DOPA, 68Ga-DOTATATE, 68Ga-DOTATOC, and Na123I for thyroid cancer imaging) were added. Five of 6 new protocols involve PET imaging, reflecting an increase in the routine use of PET in children in the past decade. This 2024 update addresses the impact of advances in imaging equipment, reconstruction, image processing, and clinical practice and the introduction of new radiopharmaceutical agents into the practice of pediatric nuclear medicine.

The practice of radiology unequivocally has transformed human medicine for the better, enabling procedures and diagnoses that otherwise would be impossible, incredibly expensive, or would require open surgery. However, the cost associated with this benefit is the burden of stochastic radiation effects. Risk-benefit analysis in radiology has always centered on the question of dose, but the conversations historically have taken place among only radiology professionals, with patients being left out of the discussion.

99mTc-labeled dimercaptosuccinic acid (99mTc-DMSA) imaging is a well-established and highly sensitive method for the diagnosis of several renal cortical disorders affecting children and adults. Beginning in 2014, 99mTc-DMSA availability was severely impaired when it was added to the Drug Shortages List of the U.S. Food and Drug Administration and was commercially unavailable thereafter. The agent shortage negatively impacted practitioners' ability to evaluate renal cortical defects in children and adults and changed renal imaging practice. A survey among pediatric nuclear medicine clinicians confirmed the clinical need for 99mTc-DMSA. Finally, in early 2023 the Food and Drug Administration again approved 99mTc-DMSA in the United States. During the 99mTc-DMSA shortage, established practitioners may not have had the opportunity of using 99mTc-DMSA as they were accustomed in their experience. Also, newer imaging specialists and referring physicians and technologists may not have benefited from having 99mTc-DMSA in their training. Therefore, it is time to bring back 99mTc-DMSA into the armamentarium of imaging methods available to evaluate regional cortical renal function.

BACKGROUND:Pediatric molecular imaging requires a balance between administering an activity that will yield sufficient diagnostic image quality while maintaining patient radiation exposure at acceptable levels. In current clinical practice, this balance is arrived at by the current North American Consensus Guidelines in which patient weight is used to recommend the administered activity (AA). PURPOSE:We have previously demonstrated that girth (waist circumference at the level of the kidneys) is better at equalizing image quality than patient weight for pediatric Tc-99m DMSA renal function imaging. However, the correlation between image quality (IQ), AA, and patient girth has not been rigorously and systematically developed. In this work, we generate a series of curves showing the tradeoff between AA and IQ as a function of patient girth, providing the data for standards bodies to develop the next generation of dosing guideline for pediatric DMSA SPECT. METHODS:An anthropomorphic phantom series that included variations in age (5, 10, and 15 years), gender (M, F), local body morphometry (5, 10, 50, 90, and 95th girth percentiles), and kidney size (±15% standard size), was used to generate realistic SPECT projections. A fixed and clinically challenging defect-to-organ volume percentage (0.49% of renal cortex value) was used to model a focal defect with zero uptake (i.e., full local loss of renal function). Task-based IQ assessment methods were used to rigorously measure IQ in terms of renal perfusion defect detectability. This assessment was performed at multiple count levels (corresponding to various AAs) for groups of patients that had similar girths and defect sizes. Receiver-operating characteristics (ROC) analysis was applied; the area under the ROC curve (AUC) was used as a figure-of-merit for task performance. Curves showing the tradeoff between AUC and AA were generated for these groups of phantoms. RESULTS:Overall, the girth-based dosing method suggested different amounts of AA compared to weight-based dosing for the phantoms that had a relatively large body weight but a small girth or phantoms with relatively small bodyweight but large girth. Reductions of AA to 62.9% compared to weight-based dosing guidelines can potentially be realized while maintaining a baseline (AUC = 0.80) IQ for certain 15-year-olds who have a relatively small girth and large defect size. Note that the task-based IQ results are heavily dependent on the simulated defect size for the defect detection task and the appropriate AUC value must be decided by the physicians for this diagnostic task. These results are based purely on simulation and are subject to future clinical validation. CONCLUSIONS:The study provides simulation-based IQ-AA data for a girth-based dosing method for pediatric renal SPECT, suggesting that patient waist circumference at the level of kidneys should be considered in selecting the AA needed to achieve an acceptable IQ. This data may be useful for standards bodies to develop girth-based dosing guidelines.

When pregnancy is discovered during or after a diagnostic examina-tion, the physician or the patient may request an estimate of the radia-tion dose received by the fetus as per guidelines and standard operating procedures. This study provided the imaging community with dose estimates to the fetus from PET/CT with protocols that are adapted to University of Michigan low-dose protocols for patients known to be pregnant. Methods: There were 9 patients analyzed with data for the first, second, and third trimesters, the availability of which is quite rare. These images were used to calculate the size-specific dose estimate (SSDE) from the CT scan portion and the SUV and 18F-FDG uptake dose from the PET scan portion using the MIRD formula-tion. The fetal dose estimates were tested for correlation with each of the following independent measures: gestational age, fetal volume, average water-equivalent diameter of the patient along the length of the fetus, SSDE, SUV, and percentage of dose from 18F-FDG. Step-wise multiple linear regression analysis was performed to assess the partial correlation of each variable. To our knowledge, this was the first study to determine fetal doses from CT and PET images. Results: Fetal self-doses from 18F for the first, second, and third trimesters were 2.18 mGy (single data point), 0.74-1.82 mGy, and 0.017-0.0017 mGy, respectively. The combined SSDE and fetal self-dose ranged from 1.2 to 8.2 mGy. These types of images from pregnant patients are rare. Conclusion: Our data indicate that the fetal radiation expo -sure from 18F-FDG PET and CT performed, when medically neces-sary, on pregnant women with cancer is low. All efforts should be made to minimize fetal radiation exposure by modifying the protocol.

Both the development of kidney function in healthy children and autoregulation ability of kidney function in patients with asymmetric kidneys are important in clinical diagnosis and treatment of kidney-related diseases, but there are however only limited studies. This study aimed to investigate development of kidney function in normal children with healthy symmetric kidneys and autoregulation of the healthy kidney compensating the functional loss of a diseased one in children with asymmetric kidneys. Two hundred thirty-seven children (156 male, 81 female) from 0 to 20y (average 4.6y ± 5.1) undergoing 99mTc-MAG3 renography were included, comprising 134 with healthy symmetrically functioning kidneys and 103 with asymmetric kidneys. Clearance was calculated from kidney uptakes at 1–2 min. A developmental model between MAG3 clearance (CL) and patient age in normal group was identified (CL = 84.39Age0.395 ml/min, r = 0.957, p < 0.001). The clearance autoregulation rate in abnormal group with asymmetric kidneys was defined as the ratio of the measured MAG3 clearance and the normal value predicted from the renal developmental model of normal group. No significant difference of MAG3 clearance (p = 0.723) was found between independent abnormal group and normal group. The autoregulation rate of kidney clearance in abnormal group was 94.2% on average, and no significant differences were found between two age groups (p = 0.49), male and female (p = 0.39), and left kidney and right kidney (p = 0.92) but two different grades of asymmetric kidneys (p = 0.02). The healthy kidney of two asymmetric kidneys can automatically regulate total kidney function up to 94% of two symmetric kidneys in normal children.

Single photon emission computed tomography (SPECT) using 99mTc-labelled dimercaptosuccinic acid (DMSA) is an important clinical tool for renal imaging in children. It is important to minimize the imaging dose administrated in pediatric renal DMSA SPECT, because the potential radiation risk is much elevated in younger children compared to adults. In this study, we investigate the feasibility of applying a deep learning (DL) denoising network for post-processing the reconstructed images when the imaging dose is significantly reduced (by as much as four times). We demonstrated this approach in the experiments with quarter-dose data obtained from a set of standard clinical acquisitions on 1,000 subjects, wherein a 3D convolutional autoencoder (CAE) network was trained on the image data of 800 subjects and evaluated on that of 200 subjects. The quantitative results demonstrate that the DL network could significantly suppress the increased noise level in the quarter-dose data, yielding 22.6% reduction in mean-squared-error (rMSE) (p-value <10 -6 ) from the standard dose reference; it also increased the image similarity to the standard dose reference as quantified by the structural similarity index measure (SSIM) (p-value <10 -6 ).

Positron emission tomography (PET) has been widely used in paediatric oncology. 2-Deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) is the most commonly used radiopharmaceutical for PET imaging. For oncological brain imaging, different amino acid PET radiopharmaceuticals have been introduced in the last years. The purpose of this document is to provide imaging specialists and clinicians guidelines for indication, acquisition, and interpretation of [18F]FDG and radiolabelled amino acid PET in paediatric patients affected by brain gliomas. There is no high level of evidence for all recommendations suggested in this paper. These recommendations represent instead the consensus opinion of experienced leaders in the field. Further studies are needed to reach evidence-based recommendations for the applications of [18F]FDG and radiolabelled amino acid PET in paediatric neuro-oncology. These recommendations are not intended to be a substitute for national and international legal or regulatory provisions and should be considered in the context of good practice in nuclear medicine. The present guidelines/standards were developed collaboratively by the EANM and SNMMI with the European Society for Paediatric Oncology (SIOPE) Brain Tumour Group and the Response Assessment in Paediatric Neuro-Oncology (RAPNO) working group. They summarize also the views of the Neuroimaging and Oncology and Theranostics Committees of the EANM and reflect recommendations for which the EANM and other societies cannot be held responsible.

Arnoldo Piccardo (1), Nathalie L. Albert (2), Lise Borgwardt (3), Frederic H Fahey (4), Darren Hargrave (5),Norbert Galldiks (6,7), Lars Kurch (8), Nina Jehanno (9), Ian Law (3), Ruth Lim (10), Egesta Lopci (11), Lisbeth Marner (12), Giovanni Morana (13), Tina Young Poussaint (4), Victor J Seghers (14,15), Barry L. Shulkin (16), Katherine E. Warren (17), Tatjana Traub-Weidinger (18), Pietro Zucchetta (19).

PEDIATRICS have increased tissue radio-sensitivity and longer potential lifespan when compared to adults. Therefore, their risk of developing health problems such as cancer per unit administered activity (AA) is significantly higher than adults [1] , emphasizing the need to the reduce activity administered. Tc-99m dimercaptosuccinic acid (DMSA) SPECT imaging is performed to evaluate children with pyelonephritis and scarring to the kidneys resulting from infection [2] . CT scans are not acquired during the DMSA imaging protocol to reduce radiation exposure to pediatric patients. Instead, typically attenuation maps are formed by filling segmentations from the emission data with uniform attenuation coefficients. This process is inaccurate and can lead to reduced image quantitation and quality, which motivates our work to develop a deep learning (DL) method to estimate these attenuation maps from emission data [3] .