The evidence-based role of catecholaminergic PET tracers in Neuroblastoma. A systematic review and a head-to-head comparison with mIBG scintigraphy.

BACKGROUND: Molecular imaging is pivotal in staging and response assessment of children with neuroblastoma (NB). [123I]-metaiodobenzylguanidine (mIBG) is the standard imaging method; however, it is characterised by low spatial resolution, time-consuming acquisition procedures and difficult interpretation. Many PET catecholaminergic radiotracers have been proposed as a replacement for [123I]-mIBG, however they have not yet made it into clinical practice. We aimed to review the available literature comparing head-to-head [123I]-mIBG with the most common PET catecholaminergic radiopharmaceuticals. METHODS: We searched the PubMed database for studies performing a head-to-head comparison between [123I]-mIBG and PET radiopharmaceuticals including meta-hydroxyephedrine ([11C]C-HED), 18F-18F-3,4-dihydroxyphenylalanine ([18F]DOPA) [124I]mIBG and Meta-[18F]fluorobenzylguanidine ([18F]mFBG). Review articles, preclinical studies, small case series (< 5 subjects), case reports, and articles not in English were excluded. From each study, the following characteristics were extracted: bibliographic information, technical parameters, and the sensitivity of the procedure according to a patient-based analysis (PBA) and a lesion-based analysis (LBA). RESULTS: Ten studies were selected: two regarding [11C]C-HED, four [18F]DOPA, one [124I]mIBG, and three [18F]mFBG. These studies included 181 patients (range 5-46). For the PBA, the superiority of the PET method was reported in two out of ten studies (both using [18F]DOPA). For LBA, PET detected significantly more lesions than scintigraphy in seven out of ten studies. CONCLUSIONS: PET/CT using catecholaminergic tracers shows superior diagnostic performance than mIBG scintigraphy. However, it is still unknown if such superiority can influence clinical decision-making. Nonetheless, the PET examination appears promising for clinical practice as it offers faster image acquisition, less need for sedation, and a single-day examination.

Small Bowel Transit Scintigraphy in Children With Pediatric Intestinal Pseudo-Obstruction.

INTRODUCTION: Objective evidence of small intestinal dysmotility is a key criterion for the diagnosis of pediatric intestinal pseudo-obstruction (PIPO). Small bowel scintigraphy (SBS) allows for objective measurement of small bowel transit (SBT), but limited data are available in children. We aimed to evaluate the utility of SBS in children suspected of gastrointestinal dysmotility. METHODS: Patients undergoing gastric emptying studies for suspected foregut dysmotility, including PIPO, from 2016 to 2022 at 2 tertiary children's hospitals were recruited to an extended protocol of gastric emptying studies to allow for assessment of SBT. PIPO was classified based on antroduodenal manometry (ADM). SBT was compared between PIPO and non-PIPO patients. Scintigraphic parameters were assessed and correlated against ADM scores. RESULTS: Fifty-nine patients (16 PIPO and 43 non-PIPO diagnoses) were included. SBS was performed with liquid and solid meals in 40 and 26 patients, respectively. As compared to the non-PIPO group, PIPO patients had a significantly lower median percentage of colonic filling at 6 hours, with both liquid (48% vs 83%) and solid tests (5% vs 65%). SBT in PIPO patients with myopathic involvement was significantly slower than in patients with neuropathic PIPO, both for liquid and solid meal. A significant correlation was found between solid SBT and ADM scores (r = -0.638, P = 0.036). DISCUSSION: SBS provides a practically feasible assessment of small intestinal motility. It shows a potential utility to help diagnose and characterize PIPO. SBS seems most discriminative in PIPO patients with myopathic involvement. Studies in a larger pediatric population and across different ages are required.

Radiological and surgical correlation of pelviureteric junction obstruction in positional anomalies of the kidney in children.

Pelviureteric junction obstruction, also known as ureteropelvic junction obstruction, is a congenital narrowing of the urinary excretory tract at the junction between the renal pelvis and the ureter and is a common cause of congenital pelvicalyceal dilatation. The outcome is variable, from spontaneous resolution to renal parenchymal function loss in cases of untreated high-grade obstruction. Abnormalities in renal ascent, rotation and vascularity can be associated with pelviureteric junction obstruction and easily overlooked radiologically. In this pictorial review, we explore the anatomical, radiological and surgical correlations of pelviureteric junction obstruction in the context of a normal kidney and a spectrum of renal abnormalities, including hyper-rotation (also known as renal malrotation), failed renal ascent, fusion anomalies and accessory crossing renal vessels. For each scenario, we provide technical tips on how to identify the altered anatomy at the first ultrasound assessment and correlation with scintigraphic, cross-sectional and postoperative imaging where appropriate. A detailed ultrasound protocol specifically to assess and characterise pelviureteric junction obstruction in paediatric patients is also offered.

Naturally occurring stable calcium isotope ratios are a novel biomarker of bone calcium balance in chronic kidney disease.

Dysregulated calcium homeostasis is common in chronic kidney disease and causally associated with disorders of bone mineralization. However, radiological measures and biomarkers do not allow accurate evaluation of bone calcium balance. Non-radioactive calcium isotopes, 42Ca and 44Ca, are present in our diet and sequestered into body compartments following principles of kinetic isotope fractionation. Isotopically light 42Ca is preferentially incorporated into bone, while heavier 44Ca is excreted. The ratio (44/42Caserum) increases when bone formation exceeds resorption and vice versa, reflecting bone calcium balance. We measured these calcium isotopes by inductively coupled plasma mass-spectrometry in blood, urine and feces of 42 children with chronic kidney disease and 92 receiving dialysis therapy. We compared the isotope ratios with bone biomarkers and determined total bone mineral content by dual-energy x-ray absorptiometry and peripheral quantitative CT expressed as age-adjusted z-scores. The 44/42Caserum ratio positively correlated with serum calcium, 25-hydroxyvitamin D and alkaline phosphatases and inversely with serum parathyroid hormone and other bone resorption markers. The 44/42Caserum ratio positively correlated with age-adjusted z-scores of tibial trabecular bone mineral density and total bone mineral content measured by peripheral quantitative CT, and hip bone mineral density measured by dual-energy X-ray absorptiometry. Significant and independent predictors of total bone mineral content, measured by, were the 44/42Caserum ratio and parathyroid hormone. The 44/42Caserum ratio, repeated after four weeks, highly correlated with baseline values. When adjusted for calcium-containing medications and kidney impairment, the 44/42Caserum ratio in patients receiving dialysis was 157% lower than that of age-matched children and 29% lower than levels in elderly women with osteoporosis, implying significantly lower bone mineral content. Thus, calcium isotope ratios may provide a novel, sensitive and non-invasive method of assessing bone calcium balance in chronic kidney disease.

Clinical impact of primary tumour 123ImIBG response to induction chemotherapy in children with high-risk neuroblastoma.

BACKGROUND: More than 50% children with high-risk neuroblastoma (HR-NBL) experience disease progression, which we hypothesise is due to non-response of primary tumour to treatment. Current imaging techniques are unable to characterise response in primary tumour (necrotic versus viable tissue) at diagnosis or follow-up. OBJECTIVES: Compare clinico-histological characteristics between primary 123ImIBG-avid tumours that became entirely 123ImIBG-non-avid (responders) after induction chemotherapy (IC) versus primary 123ImIBG-avid tumour that remained 123ImIBG-avid (non-responders). METHODS: Retrospective review of clinico-radiological data of children diagnosed with 123ImIBG-avid HR-NBL at our centre (2005-2016). Patients received Rapid COJEC IC and two additional courses of TVD if metastatic response was inadequate. Primary tumour 123ImIBG response was assessed qualitatively as positive, negative or intermediate at diagnosis and after IC. Post-surgical histopathology slices were marked considering percentage of viable tissue. RESULTS: Sixteen of 61 patients showed complete primary tumour 123ImIBG response, 20 partial response, while 25 no response. There was no statistically significant difference between clinical demographics of complete responders and group of non- or partial responders. Mean percentage of viable tumour cells was higher in non-responders than in complete responders (44.6% vs 20.6%; p = 0.05). Five-year EFS was significantly higher in complete responders than non-responders (43 ± 15% vs 7 ± 6%; p < 0.005). CONCLUSIONS: 123ImIBG response in primary HR-NBL correlates with amount of necrotic tissue, skeletal metastatic 123ImIBG response and outcome. An entirely 123ImIBG non-avid tumour can still harbour viable tumour cells. Therefore, our findings do not support utility of primary tumour 123ImIBG response in decision making regarding residual tumour surgery. Combining both, primary and metastatic 123ImIBG response will improve interpretability of clinical trial results.

Comparison Between Diffusion-Weighted MRI and 123 I-mIBG Uptake in Primary High-Risk Neuroblastoma.

BACKGROUND: High-risk neuroblastoma (HR-NB) has a variable response to preoperative chemotherapy. It is not possible to differentiate viable vs. nonviable residual tumor before surgery. PURPOSE: To explore the association between apparent diffusion coefficient (ADC) values from diffusion-weighted magnetic resonance imaging (DW-MRI), 123 I-meta-iodobenzyl-guanidine (123 I-mIBG) uptake, and histology before and after chemotherapy. STUDY TYPE: Retrospective. SUBJECTS: Forty patients with HR-NB. FIELD STRENGTH/SEQUENCE: 1.5T axial DW-MRI (b = 0,1000 s/mm2 ) and T2 -weighted sequences. 123 I-mIBG scintigraphy planar imaging (all patients), with additional 123 I-mIBG single-photon emission computed tomography / computerized tomography (SPECT/CT) imaging (15 patients). ASSESSMENT: ADC maps and 123 I-mIBG SPECT/CT images were coregistered to the T2 -weighted images. 123 I-mIBG uptake was normalized with a tumor-to-liver count ratio (TLCR). Regions of interest (ROIs) for primary tumor volume and different intratumor subregions were drawn. The lower quartile ADC value (ADC25prc ) was used over the entire tumor volume and the overall level of 123 I-mIBG uptake was graded into avidity groups. STATISTICAL TESTS: Analysis of variance (ANOVA) and linear regression were used to compare ADC and MIBG values before and after treatment. Threshold values to classify tumors as viable/necrotic were obtained using ROC analysis of ADC and TLCR values. RESULTS: No significant difference in whole-tumor ADC25prc values were found between different 123 I-mIBG avidity groups pre- (P = 0.31) or postchemotherapy (P = 0.35). In the "intratumor" analysis, 5/15 patients (prechemotherapy) and 0/14 patients (postchemotherapy) showed a significant correlation between ADC and TLCR values (P < 0.05). Increased tumor shrinkage was associated with lower pretreatment tumor ADC25prc values (P < 0.001); no association was found with pretreatment 123 I-mIBG avidity (P = 0.17). Completely nonviable tumors had significantly lower postchemotherapy ADC25prc values than tumors with >10% viable tumor (P < 0.05). Both pre- and posttreatment TLCR values were significantly higher in patients with >50% viable tumor than those with 10-50% viable tumor (P < 0.05). DATA CONCLUSION: 123 I-mIBG avidity and ADC values are complementary noninvasive biomarkers of therapeutic response in HR-NB. LEVEL OF EVIDENCE: 4. TECHNICAL EFFICACY STAGE: 3.

Routine serum biomarkers, but not dual-energy X-ray absorptiometry, correlate with cortical bone mineral density in children and young adults with chronic kidney disease.

BACKGROUND: Biomarkers and dual-energy X-ray absorptiometry (DXA) are thought to be poor predictors of bone mineral density (BMD). The Kidney Disease: Improving Global Outcomes guidelines suggest using DXA if the results will affect patient management, but this has not been studied in children or young adults in whom bone mineral accretion continues to 30 years of age. We studied the clinical utility of DXA and serum biomarkers against tibial cortical BMD (CortBMD) measured by peripheral quantitative computed tomography, expressed as Z-score CortBMD, which predicts fracture risk. METHODS: This was a cross-sectional multicentre study in 26 patients with CKD4 and 5 and 77 on dialysis. RESULTS: Significant bone pain that hindered activities of daily living was present in 58%, and 10% had at least one low-trauma fracture. CortBMD and cortical mineral content Z-scores were lower in dialysis compared with CKD patients (P = 0.004 and P = 0.02). DXA BMD hip and lumbar spine Z-scores did not correlate with CortBMD or biomarkers. CortBMD was negatively associated with parathyroid hormone (PTH; r = -0.44, P < 0.0001) and alkaline phosphatase (ALP; r = -0.22, P = 0.03) and positively with calcium (Ca; r = 0.33, P = 0.001). At PTH <3 times upper limit of normal, none of the patients had a CortBMD below -2 SD (odds ratio 95% confidence interval 7.331 to infinity). On multivariable linear regression PTH (ß = -0.43 , P < 0.0001), ALP (ß = -0.36, P < 0.0001) and Ca (ß = 0.21, P = 0.005) together predicted 57% of variability in CortBMD. DXA measures did not improve this model. CONCLUSIONS: Taken together, routinely used biomarkers, PTH, ALP and Ca, but not DXA, are moderate predictors of cortical BMD. DXA is not clinically useful and should not be routinely performed in children and young adults with CKD 4-5D.

Importance of Magnetic Resonance Imaging With Diffusion-weighted Imaging in Guiding Biopsy of Nodular Ganglioneuroblastoma: A Case Report.

BACKGROUND: Nodular ganglioneuroblastoma is a rare peripheral neuroblastic tumor of variable prognosis. Accurate diagnosis, staging, and risk categorization can be particularly challenging in patients with nodular ganglioneuroblastoma due to the inherent heterogeneity of these lesions. CASE PRESENTATION: We illustrate the use of diffusion-weighted magnetic resonance imaging to identify tumor nodules and guide tumor biopsy in an almost 5-year-old boy with a large abdominal tumor. CONCLUSIONS: Diffusion-weighted magnetic resonance imaging was successful in detecting and guiding biopsy of a poorly differentiated neuroblastoma nodule within the context of a well-differentiated ganglioneuroma, allowing the diagnosis and characterization of a ganglioneuroblastoma nodular, thus influencing the child's prognosis and treatment.

DNAJC6 Mutations Disrupt Dopamine Homeostasis in Juvenile Parkinsonism-Dystonia.

BACKGROUND: Juvenile forms of parkinsonism are rare conditions with onset of bradykinesia, tremor and rigidity before the age of 21 years. These atypical presentations commonly have a genetic aetiology, highlighting important insights into underlying pathophysiology. Genetic defects may affect key proteins of the endocytic pathway and clathrin-mediated endocytosis (CME), as in DNAJC6-related juvenile parkinsonism. OBJECTIVE: To report on a new patient cohort with juvenile-onset DNAJC6 parkinsonism-dystonia and determine the functional consequences on auxilin and dopamine homeostasis. METHODS: Twenty-five children with juvenile parkinsonism were identified from a research cohort of patients with undiagnosed pediatric movement disorders. Molecular genetic investigations included autozygosity mapping studies and whole-exome sequencing. Patient fibroblasts and CSF were analyzed for auxilin, cyclin G-associated kinase and synaptic proteins. RESULTS: We identified 6 patients harboring previously unreported, homozygous nonsense DNAJC6 mutations. All presented with neurodevelopmental delay in infancy, progressive parkinsonism, and neurological regression in childhood. 123 I-FP-CIT SPECT (DaTScan) was performed in 3 patients and demonstrated reduced or absent tracer uptake in the basal ganglia. CSF neurotransmitter analysis revealed an isolated reduction of homovanillic acid. Auxilin levels were significantly reduced in both patient fibroblasts and CSF. Cyclin G-associated kinase levels in CSF were significantly increased, whereas a number of presynaptic dopaminergic proteins were reduced. CONCLUSIONS: DNAJC6 is an emerging cause of recessive juvenile parkinsonism-dystonia. DNAJC6 encodes the cochaperone protein auxilin, involved in CME of synaptic vesicles. The observed dopamine dyshomeostasis in patients is likely to be multifactorial, secondary to auxilin deficiency and/or neurodegeneration. Increased patient CSF cyclin G-associated kinase, in tandem with reduced auxilin levels, suggests a possible compensatory role of cyclin G-associated kinase, as observed in the auxilin knockout mouse. DNAJC6 parkinsonism-dystonia should be considered as a differential diagnosis for pediatric neurotransmitter disorders associated with low homovanillic acid levels. Future research in elucidating disease pathogenesis will aid the development of better treatments for this pharmacoresistant disorder. © 2020 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Guidelines on nuclear medicine imaging in neuroblastoma.

Nuclear medicine has a central role in the diagnosis, staging, response assessment and long-term follow-up of neuroblastoma, the most common solid extracranial tumour in children. These EANM guidelines include updated information on 123I-mIBG, the most common study in nuclear medicine for the evaluation of neuroblastoma, and on PET/CT imaging with 18F-FDG, 18F-DOPA and 68Ga-DOTA peptides. These PET/CT studies are increasingly employed in clinical practice. Indications, advantages and limitations are presented along with recommendations on study protocols, interpretation of findings and reporting results.

Validation of the mIBG skeletal SIOPEN scoring method in two independent high-risk neuroblastoma populations: the SIOPEN/HR-NBL1 and COG-A3973 trials.

BACKGROUND: Validation of the prognostic value of the SIOPEN mIBG skeletal scoring system in two independent stage 4, mIBG avid, high-risk neuroblastoma populations. RESULTS: The semi-quantitative SIOPEN score evaluates skeletal meta-iodobenzylguanidine (mIBG) uptake on a 0-6 scale in 12 anatomical regions. Evaluable mIBG scans from 216 COG-A3973 and 341 SIOPEN/HR-NBL1 trial patients were reviewed pre- and post-induction chemotherapy. The prognostic value of skeletal scores for 5-year event free survival (5 yr.-EFS) was tested in the source and validation cohorts. At diagnosis, both cohorts showed a gradual non-linear increase in risk with cumulative scores. Several approaches were explored to test the relationship between score and EFS. Ultimately, a cutoff score of ≤3 was the most useful predictor across trials. A SIOPEN score ≤ 3 pre-induction was found in 15% SIOPEN patients and in 22% of COG patients and increased post-induction to 60% in SIOPEN patients and to 73% in COG patients. Baseline 5 yr.-EFS rates in the SIOPEN/HR-NBL1 cohort for scores ≤3 were 47% ± 7% versus 26% ± 3% for higher scores at diagnosis (p < 0.007) and 36% ± 4% versus 14% ± 4% (p < 0.001) for scores obtained post-induction. The COG-A3973 showed 5 yr.-EFS rates for scores ≤3 of 51% ± 7% versus 34% ± 4% for higher scores (p < 0.001) at diagnosis and 43% ± 5% versus 16% ± 6% (p = 0.004) for post-induction scores. Hazard ratios (HR) significantly favoured patients with scores ≤3 after adjustment for age and MYCN-amplification. Optimal outcomes were recorded in patients who achieved complete skeletal response. CONCLUSIONS: Validation in two independent cohorts confirms the prognostic value of the SIOPEN skeletal score. In particular, patients with an absolute SIOPEN score > 3 after induction have very poor outcomes and should be considered for alternative therapeutic strategies.

Paediatric nuclear medicine imaging.

Background: Nuclear medicine imaging explores tissue viability and function by using radiotracers that are taken up at cellular level with different mechanism. This imaging technique can also be used to assess blood flow and transit through tubular organs. Nuclear medicine imaging has been used in paediatrics for decades and this field is continuously evolving. Sources of data: The data presented comes from clinical experience and some milestone papers on the subject. Areas of agreement: Nuclear medicine imaging is well-established in paediatric nephro-urology in the context of urinary tract infection, ante-natally diagnosed hydronephrosis and other congenital renal anomalies. Also, in paediatric oncology, I-123-meta-iodobenzyl-guanidine has a key role in the management of children with neuroblastic tumours. Bone scintigraphy is still highly valuable to localize the source of symptoms in children and adolescents with bone pain when other imaging techniques have failed. Thyroid scintigraphy in neonates with congenital hypothyroidism is the most accurate imaging technique to confirm the presence of ectopic functioning thyroid tissue. Areas of controversy: Radionuclide transit studies of the gastro-intestinal tract are potentially useful in suspected gastroparesis or small bowel or colonic dysmotility. However, until now a standardized protocol and a validated normal range have not been agreed, and more work is necessary. Research is ongoing on whether magnetic resonance imaging (MRI), with its great advantage of great anatomical detail and no ionizing radiations, can replace nuclear medicine imaging in some clinical context. On the other hand, access to MRI is often difficult in many district general hospitals and general anaesthesia is frequently required, thus adding to the complexity of the examination. Growing points: Patients with bone pain and no cause for it demonstrated on MRI can benefit from bone scintigraphy with single photon emission tomography and low-dose computed tomography. This technique can identify areas of mechanical stress at cortical bone level, difficult to demonstrate on MRI, which can act as pain generators. Positron emission tomography (PET) is being tested in the staging, response assessment and at the end of treatment of several paediatric malignancies. PET is becoming more widely utilized in neurology in the pre-surgical assessment of some children with drug resistant epilepsy. Areas timely for developing research: The use of PET/MRI scanners is very attractive as it combines benefits of MR imaging with the assessment of cellular viability and metabolism with PET in one examination. This imaging technique will allow important research on tumour in-vivo metabolism (possible applications include lymphomas, neuroblastomas, malignant germ cell tumours andbrain tumours), with the aim of offering a personalized biological profile of the tumour in a particular patient. Ground-breaking research is also envisaged in neurosciences, especially in epilepsy, using PET tracers that would enable a better identification of the epileptogenic focus, and in psychiatry, with the use of radiolabeled neurotransmitters. In paediatric nephro-urology, the identification of the asymptomatic child with ante-natally diagnosed hydronephrosis at risk of losing renal parenchymal function if left untreated is another area of active research involving radionuclide renography.

Laparoscopic strategies in complex upper urinary tract obstruction.

OBJECTIVES: We enumerate the various laparoscopic strategies to resolve upper urinary tract (UUT) obstruction in the context of variations in anatomy and report their outcomes. PATIENTS AND METHODS: Retrospective review of primary laparoscopic UUT reconstructions performed between May 2012 and May 2021. Anomalies included: malrotated kidney (MRK), horseshoe kidney (HSK), duplex kidney (DK), pure intrarenal pelvis (IRP) and mid-ureteric stenosis (MUS). Success was defined by postoperative resolution of symptoms, improvement of anterior-posterior renal pelvic diameter (APD) on US and drainage on Mag3. Complications were categorised by Clavien-Dindo grading. Outcomes compared using the student's t-test with P < 0.05 considered statistically significant. RESULTS: Of the 214 laparoscopic primary UUT reconstructions, 37 (17.2 %) were: 13-MRK, 12-HSK, 4-DK, 4-IRP and 4-MUS. Median age at surgery was 5-years (range 0.3-15). Dismembered pyeloplasty: 8; pyeloplasty with renal sinus dissection: 8; neo-PUJ anastomosis: 8; primary ureterocalycostomy: 7; pyeloureterostomy: 2; and uretero-ureterostomy: 4. Median follow-up was 43-months (range 8-108) with a success rate of 94.5 % (35/37). Complete resolution of symptoms in 20/21 patients; improvement of hydronephrosis on US in 35/37 patients (median pre-operative APD 27 mm vs. median postoperative APD 8 mm) [P < 0.001]; improvement of drainage on diuretic renogram in 32/34 kidneys and stable/improved DRF in 34/35 kidneys (median preoperative DRF - 45 % vs. median postoperative DRF - 47 %) [P > 0.05]. Postoperative complications managed medically (II Clavien) included urinary tract infections - 2 patients (5 %), stent-related symptoms in 2 (5 %) and umbilical port site collection in 1 patient (3 %). Recurrent pelvi-ureteric junction obstruction PUJO occurred in one patient (3 %) requiring redo surgery (IIIb Clavien), renal stones in 1 (3 %) which resolved with ESWL (IIIb Clavien); in 1 (3 %) patient with a HSK there was complete loss of ipsilateral kidney function but this was managed conservatively up to date (I Clavien). CONCLUSION: Laparoscopic transperitoneal approach allows the prompt recognition of in-situ anatomical variants. UUT obstruction in such settings calls for a variety of strategies with excellent outcomes.

Bone scintigraphy with SPECT/CT in paediatric patients with neck and back pain in comparison with other imaging modalities: the experience of a tertiary paediatric referral centre.

OBJECTIVE: Retrospective review of the additional clinical value provided by single photon emission computed tomography-computed tomography (SPECT/CT) in children and adolescents with back pain. METHODS: A total of 207 consecutive paediatric patients (94 males, 113 females, age range 5-17 years, median age 14 years) were reviewed after referral to the spinal surgery clinic of a paediatric teaching hospital between November 2009 and February 2021. All patients had either only whole spine X-rays or whole spine x-rays and MRI, along with bone scan with planar whole-body images and SPECT/CT (with spot views of painful area). RESULTS: X-ray identified the pain generator in 23 of 177 (13.0%) cases. MRI identified the pain generator in 49 of 165 (29.7%) cases. SPECT/CT reported relevant positive findings which identified the pain generator in 107 of 185 (57.8%) cases. SPECT/CT changed patients' management in 72 of 185 (38.9%) cases. SPECT/CT was most effective at identifying the pain generator in cases of facet arthropathy, previous vertebral fracture and patients with previous deformity correction, where the pain generator was identified in 76.5% (13 of 17), 71.4% (5 of 7) and 63.4% (26 of 41) of cases, respectively. CT settings were adjusted to minimise the radiation burden (50 mAs/80kVp under 8 years, 24 mAs/110 kVp over 8 years). CONCLUSION: The role of SPECT/CT in diagnosing back pain is justified in selected paediatric patients, particularly with diagnostic uncertainty using conventional imaging. The CT component of the SPECT/CT study produced a lower radiation dose than conventional CT imaging, whilst producing bone images of diagnostic quality.

Airway deposition of nebulized gene delivery nanocomplexes monitored by radioimaging agents.

Receptor-targeted nanocomplexes are nonviral vectors developed for gene delivery to the airway epithelium for the treatment of pulmonary disease associated with cystic fibrosis. The present study aimed to optimize the delivery of the nanocomplex by nebulization, and to monitor the in vivo deposition of radiolabeled vector in the airways of a large animal model by γ-camera scintigraphy. Large White weaner pigs were nebulized with nanocomplexes mixed with technetium-99m radiopharmaceuticals. The aerosol deposition scans suggested that the nebulized radiovectors were deposited mainly in the trachea-main bronchi and in the midregion of the lungs. The plasmid biodistribution, assessed by real-time PCR, correlated with the scintigraphy images. The highest plasmid copy numbers were found in the bronchial areas and in the tissues proximal to the main bronchi bifurcation. Immunohistochemistry detected transgene expression in the tracheal and bronchial ciliated epithelium. Histological analysis of lung tissue showed no evidence of inflammation, and no increase in inflammatory cytokines or inflammatory cells was detected in the bronchoalveolar lavage. The deposition of nebulized nanocomplexes coassociated with technetium-99m can be monitored by nuclear medicine techniques. The use of a noninvasive strategy to follow the delivery of the vector could improve the clinical management of patients undergoing cystic fibrosis gene therapy.

Loss-of-Function Variants in DRD1 in Infantile Parkinsonism-Dystonia.

The human dopaminergic system is vital for a broad range of neurological processes, including the control of voluntary movement. Here we report a proband presenting with clinical features of dopamine deficiency: severe infantile parkinsonism-dystonia, characterised by frequent oculogyric crises, dysautonomia and global neurodevelopmental impairment. CSF neurotransmitter analysis was unexpectedly normal. Triome whole-genome sequencing revealed a homozygous variant (c.110C>A, (p.T37K)) in DRD1, encoding the most abundant dopamine receptor (D1) in the central nervous system, most highly expressed in the striatum. This variant was absent from gnomAD, with a CADD score of 27.5. Using an in vitro heterologous expression system, we determined that DRD1-T37K results in loss of protein function. Structure-function modelling studies predicted reduced substrate binding, which was confirmed in vitro. Exposure of mutant protein to the selective D1 agonist Chloro APB resulted in significantly reduced cyclic AMP levels. Numerous D1 agonists failed to rescue the cellular defect, reflected clinically in the patient, who had no benefit from dopaminergic therapy. Our study identifies DRD1 as a new disease-associated gene, suggesting a crucial role for the D1 receptor in motor control.

Bone Mineral Density and Vascular Calcification in Children and Young Adults With CKD 4 to 5 or on Dialysis.

Introduction: Older adults with chronic kidney disease (CKD) can have low bone mineral density (BMD) with concurrent vascular calcification. Mineral accrual by the growing skeleton may protect young people with CKD from extraosseous calcification. Our hypothesis was that children and young adults with increasing BMD do not develop vascular calcification. Methods: This was a multicenter longitudinal study in children and young people (5-30 years) with CKD stages 4 to 5 or on dialysis. BMD was assessed by tibial peripheral quantitative computed tomography (pQCT) and lumbar spine dual-energy X-ray absorptiometry (DXA). The following cardiovascular imaging tests were undertaken: cardiac computed tomography for coronary artery calcification (CAC), ultrasound for carotid intima media thickness z-score (cIMTz), pulse wave velocity z-score (PWVz), and carotid distensibility for arterial stiffness. All measures are presented as age-adjusted and sex-adjusted z-scores. Results: One hundred participants (median age 13.82 years) were assessed at baseline and 57 followed up after a median of 1.45 years. Trabecular BMD z-score (TrabBMDz) decreased (P = 0.01), and there was a nonsignificant decrease in cortical BMD z-score (CortBMDz) (P = 0.09). Median cIMTz and PWVz showed nonsignificant increase (P = 0.23 and P = 0.19, respectively). The annualized increase in TrabBMDz (ΔTrabBMDz) was an independent predictor of cIMTz increase (R 2 = 0.48, ß = 0.40, P = 0.03). Young people who demonstrated statural growth (n = 33) had lower ΔTrabBMDz and also attenuated vascular changes compared with those with static growth (n = 24). Conclusion: This hypothesis-generating study suggests that children and young adults with CKD or on dialysis may develop vascular calcification even as their BMD increases. A presumed buffering capacity of the growing skeleton may offer some protection against extraosseous calcification.

Shortwave Infrared Imaging Enables High-Contrast Fluorescence-Guided Surgery in Neuroblastoma.

Fluorescence-guided surgery is set to play a pivotal role in the intraoperative management of pediatric tumors. Shortwave infrared imaging (SWIR) has advantages over conventional near-infrared I (NIR-I) imaging with reduced tissue scattering and autofluorescence. Here, two NIR-I dyes (IRDye800CW and IR12), with long tails emitting in the SWIR range, were conjugated with a clinical-grade anti-GD2 monoclonal antibody (dinutuximab-beta) to compare NIR-I and SWIR imaging for neuroblastoma surgery. A first-of-its-kind multispectral NIR-I/SWIR fluorescence imaging device was constructed to allow an objective comparison between the two imaging windows. Conjugates were first characterized in vitro. Tissue-mimicking phantoms, imaging specimens of known geometric and material composition, were used to assess the sensitivity and depth penetration of the NIR-I/SWIR device, showing a minimum detectable volume of ∼0.9 mm3 and depth penetration up to 3 mm. In vivo, fluorescence imaging using the NIR-I/SWIR device showed a high tumor-to-background ratio (TBR) for both dyes, with anti-GD2-IR800 being significantly brighter than anti-GD2-IR12. Crucially, the system enabled higher TBR at SWIR wavelengths than at NIR-I wavelengths, verifying SWIR imaging enables high-contrast delineation of tumor margins. This work demonstrates that by combining the high specificity of anti-GD2 antibodies with the availability and translatability of existing NIR-I dyes, along with the advantages of SWIR in terms of depth and tumor signal-to-background ratio, GD2-targeted NIR-I/SWIR-guided surgery could improve the treatment of patients with neuroblastoma, warranting investigation in future clinical trials. SIGNIFICANCE: Multispectral near-infrared I/shortwave infrared fluorescence imaging is a versatile system enabling high tumor-to-background signal for safer and more complete resection of pediatric tumors during surgery.

Transpyloric propagation and liquid gastric emptying in children with foregut dysmotility.

BACKGROUND/OBJECTIVES: Gastric emptying (GE) requires precise antropyloroduodenal coordination for effective transpyloric flow, the mechanisms of which are still unclear. We aimed to correlate gastric antral function assessed by antroduodenal manometry (ADM) with GE scintigraphy (GES) for liquid feeds in children with suspected gastrointestinal dysmotility. METHODS: Children who underwent both ADM and GES over a five-year period were reviewed. ADM tracings were re-analyzed to assess antral frequency, amplitude, and motility index (MI) pre-prandially and postprandially. Transpyloric propagation (TPP) was defined as antegrade propagated antral activity preceding duodenal phase III of the migrating motor complex (MMC). TPP was defined as "poor" if occurring in <50% of all presented duodenal phases III. For GES, regions of interest over the whole stomach, fundus, and antrum were drawn to calculate GE half-time (GE-T1/2 ) and retention rate (RR) in each region at 1 and 2 h. RESULTS: Forty-seven children (median age: 7.0 years) were included. Twenty-two had PIPO, 14 functional GI disorders, and 11 gastroparesis. Children with poor TPP had longer GE-T1/2 (113.0 vs 66.5 min, p = 0.028), higher RR of the whole stomach and fundus at 1 h (79.5% vs 63.5%, p = 0.038; 60.0% vs 41.0%, p = 0.022, respectively) and 2 h (51.0% vs 10.5%, p = 0.005; 36.0% vs 6.5%, p = 0.004, respectively). The pre-prandial antral amplitude of contractions inversely correlated with GE-T1/2 , RR of the whole stomach, and fundus at 2 h. CONCLUSIONS: TPP during phase III of the MMC correlated with gastric emptying of liquid and its assessment on ADM might predict abnormalities in postprandial gastric function.