18 F-FDG PET/CT in Pediatric ALK-Positive Histiocytosis With Isolated CNS Involvement.

ABSTRACT: An 11-year-old girl presented with focal impaired awareness seizures. MRI brain demonstrated a T2 hyperintense cortical lesion in the left temporal lobe with surrounding vasogenic edema. 18 F-FDG PET/CT was arranged to assess metabolic activity of the cerebral lesion, to screen the whole body for other metabolically active lesions, and to assist biopsy planning. The study demonstrated intensely increased FDG uptake within the left temporal lobe lesion without evidence of hypermetabolic lesions elsewhere on the whole-body acquisition. The brain lesion was excised, and histopathology and molecular testing were consistent with ALK-positive histiocytosis.

Diagnostic accuracy of bone scan at different PSA levels in biochemical recurrence of prostate cancer.

OBJECTIVE: To determine the diagnostic accuracy of Bone Scan at different PSA levels for detecting skeletal metastases in men with biochemical recurrence of prostate cancer. METHODS: We conducted a retrospective review of the statewide RIS-PACS to identify 251 men with biochemical recurrence who underwent both a Bone Scan and Ga68 PSMA PET/CT (within 2 months of each other) between September 2019 and December 2022 at a single institution. The Ga68 PSMA PET/CT report was considered to be the reference standard. RESULTS: The median age was 72 years (IQR 67-76) with a median PSA level of 1 ng/ml (IQR 0.25-2.8). Using Ga68 PSMA PET/CT as the reference standard, 68/251 patients (25%) were positive for osseus metastases. Overall sensitivity and specificity of Bone Scan was 51% (95% CI 40-64%) and 99% (95% CI 98-100%) respectively. Using PSA banding, a PSA threshold of 20 ng/ml provided the greatest discriminatory benefit with sensitivity of the Bone Scan below the threshold being 46% (95% CI 33-59%) and above the threshold being 89% (95% CI 68-100%). Specificity remained consistently high both below and above this threshold. CONCLUSION: Bone Scan provides greater diagnostic accuracy for detecting skeletal metastases in biochemical recurrence when the PSA level is above 20 ng/ml. This knowledge is valuable in optimising imaging algorithms in biochemical recurrence, particularly in regions where PSMA PET/CT is less readily available or affordable.

Role of Concurrent Ultrasound Surveillance of Sentinel Node-Positive Node Fields in Melanoma Patients Having Routine Cross-Sectional Imaging.

PURPOSE: In sentinel node-positive (SN+ve) melanoma patients, active surveillance with regular ultrasound examination of the node field has become standard, rather than completion lymph node dissection (CLND). A proportion of these patients now receive adjuvant systemic therapy and have routine cross-sectional imaging (computed tomography [CT] or positron emission tomography [PET]/CT). The role of concurrent ultrasound (US) surveillance in these patients is unclear. The purpose of our study was to describe the modality of detection of nodal recurrence in SN+ve node fields. METHODS: SN+ve melanoma patients who did not undergo CLND treated at a single institution from January 1, 2016 to December 31, 2020 were included. RESULTS: A total of 225 SN+ve patients with a median follow-up of 23 months were included. Of these, 119 (53%) received adjuvant systemic therapy. Eighty (36%) developed a recurrence at any site; 24 (11%) recurred first in the SN+ve field, of which 12 (5%) were confirmed node field recurrence only at 2 months follow-up. The nodal recurrences were first detected by ultrasound in seven (3%), CT in seven (3%), and PET/CT in seven (3%) patients. All nodal recurrences evident on US were also evident on PET/CT and vice versa. CONCLUSIONS: The high rate of recurrences outside the node field and the identification of all US-detected nodal recurrences on concurrent cross-sectional imaging modalities suggest that routine concurrent ultrasound surveillance of the node-positive field may be unnecessary for SN+ve melanoma patients having routine cross-sectional imaging.

Surgical Management and Denosumab for Aneurysmal Bone Cysts of the Spine in an Australian Tertiary Paediatric Centre.

Aneurysmal bone cysts (ABC) are rare osteolytic, benign but often locally aggressive tumours of the long bones or vertebrae. For spinal ABC, surgical management, embolisation or sclerotherapy alone often carry high morbidity and/or high recurrence rates. Interruption of receptor activator of nuclear factor-kappa B ligand (RANKL) signalling holds promise as an effective therapeutic strategy for these tumours. We aimed to review the approach to surgical management and evaluate the efficacy and safety of denosumab for ABC of the spine in children. Retrospective review of 7 patients treated with denosumab using a standardised protocol for ABC of the spine in a tertiary paediatric centre. Surgical intervention was only conducted if there was spinal instability or significant neurological impairment. Denosumab 70 mg/m2 was given 4-weekly for at least 6 months, followed by 2 doses of zoledronate 0.025 mg/kg, aiming to prevent rebound hypercalcaemia. All patients achieved stability of the spine and resolution of neurological impairment, if present. Six patients achieved metabolic remission and have ceased denosumab without recurrence to date; the other showed clinical and radiological improvement without complete metabolic remission. Three patients developed symptomatic hypercalcaemia 5-7 months after cessation of denosumab, requiring additional bisphosphonate treatment. We present our algorithm for the surgical and medical management of paediatric spinal ABC. Denosumab produced a radiological and metabolic response in all patients, with complete remission in most. Follow-up time was not long enough to evaluate the endurance of response after cessation in some patients. Incidence of rebound hypercalcaemia in this paediatric cohort was high, prompting a change to our protocol.

Lack of association between anatomical sites of scalp melanomas and brain metastases does not support direct vascular spread.

Primary scalp melanomas are associated with a higher rate of brain metastasis than primary cutaneous melanomas occurring at other head and neck and body sites, but the reason is unclear. Spread to brain parenchyma via emissary veins draining from the scalp to dural sinuses has been suggested. We sought to examine the locations of metastases from primary scalp and nonscalp head and neck melanomas to determine whether there was anatomical evidence supporting direct venous spread to the brain. Data from patients who developed distant metastases from cutaneous head and neck melanomas (CHNMs) between 2000 and 2018 were analyzed. Anatomical sites of primary scalp melanomas and their respective intracranial metastases were compared. Times to first brain and nonbrain metastases were investigated for scalp and nonscalp primary CHNMs. Of 693 patients with CHNMs, 244 developed brain metastases: 109 (44.7%) had scalp primaries and 135 (55.3%) had nonscalp primaries. There was no significant association between anatomical sites of scalp primary melanomas and brain metastases (Cramer's V = 0.21; Chi-square P = 0.63). Compared with nonscalp CHNMs, scalp melanomas had no greater propensity for the brain as the first distant metastatic site ( P = 0.52) but had a shorter time to both brain metastasis (76.3 vs. 168.5 months; P < 0.001) and nonbrain metastasis (22.6 vs. 35.8 months; P < 0.001). No evidence was found to support a direct vascular pathway for metastatic spread of scalp melanomas to the brain. The increased incidence of brain metastases from scalp melanomas is probably driven by aggressive biological mechanisms.

Denosumab for central giant cell granuloma in an Australian tertiary paediatric centre.

BACKGROUND: Central giant cell granulomas (CGCG) are rare osteolytic, benign but often locally aggressive tumours of bone. Surgical curettage may not be possible in extensive lesions and resection carries high morbidity, especially in growing children, and previous medical therapies have had variable efficacy and high recurrence rates. Interruption of receptor activator of nuclear factor-kappa B ligand (RANKL) signalling holds promise as an effective therapeutic strategy for these tumours. AIMS: To evaluate the efficacy and safety of our protocol for denosumab treatment of CGCG in children. METHODS: Retrospective review of 4 patients treated with denosumab using a standardised protocol for CGCG in a tertiary paediatric centre. Denosumab 70 mg/m2 was given 4-weekly, followed by 2 doses of zoledronate 0.025 mg/kg, aimed at preventing rebound hypercalcaemia. RESULTS: Treatment of CGCG resulted in metabolic remission in all patients, but recurrence, detected by positron emission tomography (PET), occurred at 6 months in three patients and 12 months in one patient. Three patients developed symptomatic hypercalcaemia 4-5 months and one patient asymptomatic hypercalcaemia 7 months after cessation of denosumab, with 3 requiring additional bisphosphonate treatment. CONCLUSIONS: Denosumab produced a radiological and metabolic response in our patients, but metabolic recurrence occurred in all patients. PET imaging was effective for monitoring treatment response and early detection of recurrence. Incidence of rebound hypercalcaemia in this paediatric cohort was high. We present proposed changes to our protocol with the aim of producing sustained remission and preventing rebound hypercalcaemia.

Reducing Radiation Exposure to Paediatric Patients Undergoing [18F]FDG-PET/CT Imaging.

PURPOSE: To investigate the possibility of reducing the injected activity for whole-body [18F]FDG-PET/CT studies of paediatric oncology patients and to assess the usefulness of time-of-flight (TOF) acquisition on PET image quality at reduced count levels. PROCEDURES: Twenty-nine paediatric oncology patients (12F/17M, 3-18 years old (median age 13y), weight 45±20 kg, BMI 19±4 kg/m2), who underwent routine whole-body PET/CT examinations on a Siemens Biograph mCT TrueV system with TOF capability (555ps) were included in this study. The mean injected activity was 156 ± 45 MBq (3.8 ± 0.8 kg/MBq) and scaled to patient weight. The raw data was collected in listmode (LM) format and pre-processed to simulate reduced levels of [18F]FDG activity (75, 50, 35, 20 and 10% of the original counts) by randomly removing events from the original LM data. All data were reconstructed using the vendor-specific e7-tools with standard OSEM only, with OSEM plus resolution recovery (PSF). The reconstructions were repeated with added TOF (TOF) and PSF+TOF. The benefit of TOF together with the reduced count levels was evaluated by calculating the gains in signal-to-noise ratio (SNR) in the liver and contrast-to-noise ratio (CNR) in all PET-positive lesions before and after TOF employed at every simulated reduced count level. Finally, the PSF+TOF images at 50, 75 and 100% of counts were evaluated clinically on a 5-point scale by three nuclear medicine physicians. RESULTS: The visual inspection of the reconstructed images did not reveal significant differences in image quality between 75 and 100% count levels for PSF+TOF. The improvements in SNR and CNR were the greatest for TOF reconstruction and PSF combined. Both SNR and CNR gains did increase linearly with the patients BMI for both OSEM only and PSF reconstruction. These benefits were observed until reducing the counts to 50 and 35% for SNR and CNR, respectively. CONCLUSIONS: The benefit of using TOF was noticeable when using 50% or greater of the counts when evaluating the CNR and SNR. For [18F]FDG-PET/CT, whole-body paediatric imaging the injected activity can be reduced to 75% of the original dose without compromising PET image quality.

Rest tremor correlates with reduced contralateral striatal dopamine transporter binding in Parkinson's disease.

INTRODUCTION: In vivo dopamine transporter imaging is a useful tool for distinguishing nigrostriatal pathologies (e.g. Parkinson's disease) from other causes of tremor. However, while many of the motoric features of Parkinson's disease (e.g. bradykinesia, rigidity, hypomimia) correlate well with reduced striatal dopamine transporter binding, the same relationship has not been demonstrated for tremor. We investigated the relationship between striatal dopamine transporter binding and quantitative measures of tremor. METHODS: 23 participants with Parkinson's disease underwent standardised clinical assessment including structured, videotaped clinical examination, tremor neurophysiology study of both upper limbs using accelerometry and surface EMG, and Technitium-99 m TRODAT-1 brain SPECT imaging. Normalised striatal uptake values were calculated. Tremor EMG and accelerometry time series were processed with Fourier transformation to identify peak tremor power within a window of 3-10Hz and to calculate the tremor stability index (TSI). RESULTS: Spearman correlation analyses revealed an association between tremor power and contralaterally reduced striatal uptake in a number of recording conditions. This association was strongest for rest tremor, followed by postural tremor, with the weakest association observed for kinetic tremor. Lower TSI was also associated with lower contralateral striatal uptake in a number of rest and postural conditions. CONCLUSION: These data suggest a relationship between Parkinsonian rest tremor and contralateral reduction in striatal dopamine binding. Use of quantitative neurophysiology techniques may allow the demonstration of clinico-pathophysiological relationships in tremor that have remained occult to previous studies.

Ultrasound Examination of the Lymphatic Drainage Area and Regional Lymph Nodes in Melanoma Patients with In-Transit Metastases.

BACKGROUND: In-transit metastases (ITMs) are cutaneous or subcutaneous regional metastases that may occur in patients with melanoma. ITMs are often multiple and new lesions tend to appear over time. Ultrasonography can detect impalpable subcutaneous tumors. OBJECTIVE: The aim of this study was to assess the value of ultrasound examination in detecting additional, non-palpable ITMs and to determine their relevance. METHODS: Melanoma patients with ITMs who underwent regional ultrasound examination of the skin and subcutaneous tissue between the wide excision scar of the primary melanoma and the regional lymph node field were identified. In most, ultrasound assessment also included the regional lymph node field. Relevant data were collected and analyzed. RESULTS: Twenty-eight patients presenting with a total of 40 ITMs were included. Ultrasound examination identified additional ITMs in 15 patients (54%). No nodal recurrences were detected. Most additional lesions were found closer to the regional lymph nodes than the original ITMs. Management was influenced by the ultrasound findings in nine patients (32%), five of whom had more extensive surgery, three received systemic drug therapy instead of surgery, and in one patient surgery was delayed and follow-up intensified. In one patient, only subcutaneous fat was found in the excised specimen and the ultrasound was classified as false-positive. CONCLUSION: In melanoma patients with ITMs, ultrasonography of the lymphatic drainage area provided valuable information, as additional ITMs were identified in more than half of these patients and management was influenced in one-third.

Oral sucrose for analgesia in children aged between 3 months and 3 years undergoing transurethral bladder catheterisation: A randomised, double-blinded, clinical trial.

AIM: Many children admitted to hospital undergo invasive, painful and stressful procedures, including children who are not toilet trained undergoing transurethral bladder catheterisation (TUBC). Oral sucrose is commonly given to children to reduce procedural pain. In this study, we evaluated the effectiveness of oral sucrose in reducing procedural pain in children aged between 3 months and 3 years undergoing TUBC. METHODS: This study was a randomised, double-blind, placebo-controlled study conducted at Nepean Hospital, Sydney, Australia from June 2005 to June 2010. A total of 40 participants requiring TUBC for diagnostic evaluation were included. The participants were randomly assigned to receive 4 mL of 75% oral sucrose (n = 20) or a placebo (sterilised water) (n = 20). The primary outcomes were changes in two paediatric pain scale scores (the FLACC pain scale and the OUCHER pain scale), assessed by the parent/guardian(s), the doctor performing the TUBC and the nurse assisting. The secondary outcomes were physiological (changes in heart rate) and behavioural pain (crying) indicators. RESULTS: Of the outcome measures, 65% favoured the oral sucrose group, 31% favoured the placebo group, and 4% found no difference between the oral sucrose and placebo groups. CONCLUSION: While the trends favouring the sucrose group in this study were encouraging, as the results were not statistically significant, there was insufficient evidence to demonstrate the effectiveness of oral sucrose in reducing procedural pain in children aged between 3 months and 3 years undergoing TUBC.

FDG PET-CT in pediatric Langerhans cell histiocytosis.

OBJECTIVE: Langerhans cell histiocytosis (LCH) in pediatric patients presents with single-system or multisystem disease. Accurate staging is essential for selecting the most appropriate therapy ranging from local surgery to chemotherapy. METHODS: A retrospective review was undertaken of reported fludeoxyglucose (FDG) positron emission tomography - computed tomography (PET-CT) scans performed in children with LCH from June 2006 to February 2017. Findings were compared with a reference standard of biopsy or informed clinical follow-up. RESULTS: One hundred nine scans were performed in 33 patients (age 7 weeks to 18 years). Nineteen patients had single-system, bone unifocal disease; seven patients had single-system, bone multifocal disease; four patients had single-system, skin unifocal disease; two patients had multisystem disease; and one patient had single-system, lymph node disease. Twenty-six scans were performed to stage biopsy-proven LCH, and 83 scans were performed during follow-up to assess treatment response or recurrence after therapy completion. At staging, FDG PET-CT detected all sites of biopsy-proven LCH (except where bone unifocal disease had been resected). There was one false-positive thymic finding that resolved without therapy. The per-patient false-positive rate of FDG PET-CT at staging was 4% (1/26). During follow-up, five LCH recurrences and one case of progressive disease on therapy occurred, all positive on FDG PET-CT. During follow-up two patients had FDG PET-CT scans with false-positive findings and one patient with a magnetic resonance imaging false-positive finding. The per-scan false-positive rate of FDG PET-CT during follow-up was 2% (2/83). CONCLUSIONS: FDG PET-CT is highly sensitive for the staging and follow-up of pediatric patients with LCH, and has a very low false-positive rate.

Parkinsonism in PGK1 deficiency implicates the glycolytic pathway in nigrostriatal dysfunction.

BACKGROUND: Phosphoglycerate kinase-1 deficiency is caused by X-linked recessive mutations in PGK-1 and associated with haemolytic anaemia, rhabdomyolysis, myopathy and nervous system involvement. Some cases have been rarely associated with juvenile Parkinsonism however the causal relationship between PGK1 deficiency and nigrostriatal dysfunction causing Parkinsonism has not been determined. OBJECTIVE AND METHODS: To investigate the nigrostriatal system using 99mTc-TRODAT-1 SPECT binding and report the phenotype of three affected males with early onset levodopa responsive Parkinsonism harbouring the c.491 A > T/p.D164V pathogenic variant. RESULTS: All patients initially presented with infantile-onset encephalopathic and stroke-like episodes, haemolytic anaemia and epilepsy. Two patients had an early-onset and one juvenile-onset levodopa responsive Parkinsonism with motor fluctuations. 99mTc-TRODAT-1 SPECT showed severe bilateral reduced putaminal uptake in the three patients. None of the patients had structural lesions that could explain either pre- or postsynaptic dopaminergic dysfunction. CONCLUSION: These cases provide strong evidence of a causal relationship between PGK1 deficiency and nigrostriatal pathology causing Parkinsonism. These findings have potential implications for our understanding of the pathophysiology of nigrostriatal degeneration in sporadic PD.

Early mercaptoacetyltriglycine(MAG-3) diuretic renography results after pyeloplasty.

OBJECTIVE: To describe the drainage and functional outcome of paediatric pyeloplasty, 1 week after stent removal 7-9 weeks after pyeloplasty using diuretic renography. PATIENTS AND METHODS: Between 2009 and 2014, we assessed the functional and drainage outcomes according to mercaptoacetyltriglycine MAG-3 diuretic renograms from 66 children (69 kidneys) who underwent modified dismembered Anderson-Hynes pyeloplasty for pelvi-ureteric junction (PUJ) obstruction. Stents were left in place for 6-8 weeks and postoperative renal units were evaluated with MAG-3 renogram 1 week after stent removal. Surgical success was defined by improvement of drainage (half clearance time [T/2] < 20 min), stable or improved function on the postoperative MAG-3 renogram and by decreased pyelocaliceal dilatation on ultrasonography (US) at 1 year. RESULTS: Of the 69 kidneys with a preoperative median range T/2 of 33.4 (7.6-200) min, 60 (87%) had improved drainage curves, with a median (range) T/2 of 6.9 (1.6-19) min. Thirteen percent (9/69) had persistent impaired drainage, with a median (range) T/2 of 36 (24-108) min. Of these nine children, one girl was found to have a persistent obstructive pattern (T/2 = 30 min) associated with a decreased split renal function (SRF; from 42 to 33%) and persistent hydronephrosis (at 28 mm). Redo pyeloplasty was performed 2 months after the initial procedure (and 18 days after stent removal) and renal function recovered to 47%. The remaining eight patients were free of symptoms; hydronephrosis improved at 1 year (anteroposterior diameter decreased from 28 to 18.5 mm; P = 1.94) and SRF remained stable (44.5 vs 48.5% after repair; P = nonsignificant). In the 29% of kidneys (20/69) that had preoperative impaired SRF, postoperative renal function improved in 75% (from 27.5 to 43%; P < 0.001), remained unchanged in 2% and one kidney (0.2%) deteriorated. The median (range) postoperative follow-up was 18 (12-90) months. CONCLUSIONS: There is no agreement regarding the 'gold standard' investigation to use after pyeloplasty for PUJ obstruction. Improvement in hydronephrosis on US is slow and often takes > 12 months. Based on animal studies, it is possible that missed recurrent obstruction will cause irreversible loss of renal function after 6 weeks; therefore, early postoperative assessment is desirable, but there have been few reports on urinary drainage changes with early diuretic renography after pyeloplasty. Most of the renal units had improved drainage on diuretic renography 7 weeks after pyeloplasty and 1 week after stent removal. An early diuretic renogram is a reliable method of documenting surgical success after pyeloplasty.

The Role of [18F]FDG-PET/CT in Predicting Malignant Transformation of Plexiform Neurofibromas in Neurofibromatosis-1.

Background. Malignant peripheral nerve sheath tumours (MPNSTs) are difficult to diagnose and treat and contribute to significant morbidity and mortality for patients with Neurofibromatosis-1 (NF-1). FDG-PET/CT is being increasingly used as an imaging modality to discriminate between benign and malignant plexiform neurofibromas. Objectives. To assess the value of FDG-PET/CT in differentiating between benign and malignant peripheral nerve lesions for patients with Neurofibromatosis-1. Methods. A systematic review of the literature was performed prior to application of stringent selection criteria. Ultimately 13 articles with 796 tumours were deemed eligible for inclusion into the review. Results. There was a significant difference between mean SUVmax of benign and malignant lesions (1.93 versus 7.48, resp.). Sensitivity ranged from 89 to 100% and specificity from 72 to 94%. ROC analysis was performed to maximise sensitivity and specificity of SUVmax cut-off; however no clear value was identified (range 3.1-6.1). Significant overlap was found between the SUVmax of benign and malignant lesions making differentiation of lesions difficult. Many of the studies suffered from having a small cohort and from not providing histological data on all lesions which underwent FDG-PET/CT. Conclusion. This systematic review is able to demonstrate that FDG-PET/CT is a useful noninvasive test for discriminating between benign and malignant lesions but has limitations and requires further prospective trials.

Voxel-based analysis of normal cerebral [18F]FDG uptake during childhood using statistical parametric mapping.

The changing pattern of relative cerebral (18)F-fluoro-2-deoxy-D-glucose (FDG) uptake that occurs during normal childhood development is not completely understood. Using SPM8 we undertook a voxel-based analysis of dedicated cerebral FDG scans in 28 children ranging in age from 11 months to 16 years to examine the effects of age on regional FDG uptake. The subjects included were children with suspected or proven extracranial malignancies without central nervous system metastases and no previous or current therapies or medical conditions likely to interfere with cerebral metabolism. The included cerebral FDG scans were considered to represent normal cerebral FDG distribution in a child of their age at the time of the scan. When normalised to whole brain mean uptake, the voxel-based analysis showed increasing FDG uptake with age in the premotor and prefrontal cortices, insula cortex, cingulate cortex, basal ganglia, thalamus, cerebellum and in small areas of the inferior temporal lobes and left Heschl's gyrus. These findings correlate with previous published analysis of the same data that used qualitative and maximal standardised uptake value (SUV(max)) analysis techniques. This data provides more regionally specific information and further supports the conclusion that relative cerebral FDG uptake in children has not reached a typical adult pattern by approximately one year of age but in fact changes throughout childhood. The results speak to the importance of using age-matched data or adjusting for age in the statistical analysis of studies comparing paediatric cerebral FDG scans to a control dataset to avoid bias due to different age distributions in the groups of subjects studied. The areas of increasing FDG uptake with age probably relate to underlying neuronal processes linked to normal neurodevelopment including key resting state networks.

Normal cerebral FDG uptake during childhood.

PURPOSE: Current understanding of cerebral FDG uptake during childhood originates from a small number of studies in patients with neurological abnormalities. Our aim was to describe cerebral FDG uptake in a dataset of FDG PET scans in children more likely to represent a normal population. METHODS: We reviewed cerebral FDG PET scans in children up to 16 years of age with suspected/proven extracranial malignancies and the following exclusions: central nervous system metastases, previous malignancies, previous chemotherapy or radiotherapy, development of cerebral metastases during therapy, neurological conditions, taking antiepileptic medication or medications likely to interfere with cerebral metabolism, and general anaesthesia within 24 h. White matter, basal ganglia, thalamus and the cerebellar cortex were analysed using regional SUV(max), and the cerebral cortex, basal ganglia, thalamus and cerebellum were analysed using a regional relative uptake analysis in comparison to maximal cortical uptake. RESULTS: Scans from 30 patients (age range 11 months to 16 years, mean age 10 years 5 months) were included. All regions showed increasing SUV(max) with age. The parietal, occipital, lateral temporal and medial temporal lobes showed lower rates of increasing FDG uptake causing changing patterns of regional FDG uptake during childhood. The cortical regions showing the most intense uptake in early childhood were the parietal and occipital lobes. At approximately 7 years of age these regions had relatively less uptake than the frontal lobes and at approximately 10 years of age these regions had relatively less uptake than the thalamus. CONCLUSION: Relative FDG uptake in the brain has not reached an adult pattern by 1 year of age, but continues to change up to 16 years of age. The changing pattern is due to different regional rates of increasing cortical FDG uptake, which is less rapid in the parietal, occipital and temporal lobes than in the frontal lobes.

18F-FDG PET/CT compared to conventional imaging modalities in pediatric primary bone tumors.

BACKGROUND: F-Fluoro-2-deoxy-D: -glucose (FDG) positron emission tomography (PET) is useful in adults with primary bone tumors. Limited published data exist in children. OBJECTIVE: To compare hybrid FDG positron emission tomography/computed tomography (PET/CT) with conventional imaging (CI) modalities in detecting malignant lesions, predicting response to chemotherapy and diagnosing physeal involvement in pediatric primary bone tumors. MATERIALS AND METHODS: Retrospective analysis of PET/CT and CI reports with histopathology or follow-up > 6 months as reference standard. Response parameters and physeal involvement at diagnosis were compared to histopathology. RESULTS: A total of 314 lesions were detected in 86 scans. Excluding lung lesions, PET/CT had higher sensitivity and specificity than CI (83%, 98% and 78%, 97%, respectively). In lung lesions, PET/CT had higher specificity than CI (96% compared to 87%) but lower sensitivity (80% compared to 93%). Higher initial SUV(max) and greater SUV(max) reduction on PET/CT after chemotherapy predicted a good response. Change in tumor size on MRI did not predict response. Both PET/CT and MRI were very sensitive but of low specificity in predicting physeal tumor involvement. CONCLUSION: PET/CT appears more accurate than CI in detecting malignant lesions in childhood primary bone tumors, excluding lung lesions. It seems better than MRI at predicting tumor response to chemotherapy.

18F-FDG PET/CT in paediatric lymphoma: comparison with conventional imaging.

PURPOSE: In children with Hodgkin's disease and non-Hodgkin's lymphoma, the ability of (18)F-fluoro-2-deoxy-D-glucose PET/CT and conventional imaging (CI) to detect malignant lesions and predict poor lesion response to therapy was assessed and compared. METHODS: A retrospective review of findings reported on PET/CT and CI was performed using a lesion-based analysis of 16 lymph node and 8 extra-nodal regions. Lesions were defined by histopathological findings or follow-up > 6 months. RESULTS: The study included 209 PET/CT scans with a valid CI comparator. A total of 5,014 regions (3,342 lymph node, 1,672 extra-nodal) were analysed. PET/CT performed significantly better than CI in the detection of malignant lesions with sensitivity and specificity of 95.9 and 99.7% compared to 70.1 and 99.0%, respectively. For predicting poor lesion response to therapy, PET/CT had fewer false-positive lesions than CI. The specificity for predicting poor lesion response to treatment for PET/CT was 99.2% compared to 96.9% for CI. PET/CT was the correct modality in 86% of lesions with discordant findings. CONCLUSION: PET/CT is more accurate than CI in detecting malignant lesions in childhood lymphoma and in predicting poor lesion response to treatment. In lesions with discordant findings, PET/CT results are more likely to be correct.