[18F]-Fluorodeoxyglucose positron emission tomography in children with neurofibromatosis type 1 and plexiform neurofibromas: correlation with malignant transformation.

The objective of this study was to investigate the predictive value of [18F]-fluorodeoxyglucose positron emission tomography (FDG-PET) in detecting malignant transformation of plexiform neurofibromas in children with neurofibromatosis type 1 (NF1). An electronic search of the medical records was performed to determine patients with NF1 who had undergone FDG-PET for plexiform neurofibroma between 2000 and 2011. All clinical, radiologic, pathology information and operative reports were reviewed. Relationship between histologic diagnosis, radiologic features and FDG-PET maximum standardized uptake value (SUV(max)) was evaluated. This study was approved by the Institutional Review Board of our institution. 1,450 individual patients were evaluated in our Multidisciplinary Neurofibromatosis Program, of whom 35 patients underwent FDG-PET for suspected MPNST based on change or progression of clinical symptoms, or MRI findings suggesting increased tumor size. Twenty patients had concurrent pathologic specimens from biopsy/excision of 27 distinct lesions (mean age 14.9 years). Pathologic interpretation of these specimens revealed plexiform and atypical plexiform neurofibromas (n = 8 each), low grade MPNST (n = 2), intermediate grade MPNST (n = 4), high grade MPNST (n = 2), GIST (n = 1) and non-ossifying fibroma (n = 1). SUV(max) of plexiform neurofibromas (including typical and atypical) was significantly different from MPNST (2.49 (SD = 1.50) vs. 7.63 (SD = 2.96), p < 0.001). A cutoff SUV(max) value of 4.0 had high sensitivity and specificity of 1.0 and 0.94 to distinguish between PN and MPNST. FDG-PET can be helpful in predicting malignant transformation in children with plexiform neurofibromas and determining the need for biopsy and/or surgical resection.

Natural history of vesicoureteral reflux in girls after age 5 years.

PURPOSE: Expectations concerning the likelihood that vesicoureteral reflux will resolve during a given interval are predominantly based on experience with children younger than 5 years. We assess the natural course of vesicoureteral reflux in girls older than 5 years. MATERIALS AND METHODS: We reviewed the diagnostic and followup cystograms, medical records and renal imaging studies of 200 girls with vesicoureteral reflux, of whom 97 were diagnosed before age 60 months and 103 were diagnosed at or after age 60 months. Vesicoureteral reflux was considered to have resolved when a followup radionuclide cystogram demonstrated no reflux. RESULTS: Vesicoureteral reflux demonstrated at or after age 60 months by a radionuclide or radiographic examination (index study) resolved in 43% of cases during a mean followup interval of 41 months. The yearly percent chance of resolution approached or exceeded 20% through age 11 years. For girls with moderate vesicoureteral reflux on the index study unilateral moderate vesicoureteral reflux was associated with a higher overall percent chance of resolution and a shorter time from index study to resolution. Evidence of new or progressive parenchymal injury was not indicated in any of 92 girls who underwent serial renal ultrasonograms. CONCLUSIONS: Vesicoureteral reflux resolution continues after age 5 years at a rate similar to that in younger children. Continued medical management in the anticipation of spontaneous resolution is safe and appropriate for most patients.

Assessment of the clinical significance of asymptomatic lower extremity uptake abnormality in young athletes.

UNLABELLED: This study was undertaken to evaluate our hypothesis that most asymptomatic lower extremity uptake abnormalities are of no clinical consequence and to assess whether these findings should affect patient care. METHODS: One hundred consecutive young athletes referred for bone scintigraphy by a sports medicine clinic because of low back pain were evaluated for the presence of asymptomatic bone scan abnormalities in the lower extremities. The patients were then reexamined by the referring sports medicine physician, who had full knowledge of the bone scan results. Scintigraphic findings were correlated with the clinical evaluation at the time of scintigraphy and on follow-up evaluations ranging from 8 to 14 mo later. RESULTS: Asymptomatic lower extremity abnormalities were present in 34% of patients. There were abnormalities of the feet in 30 patients (focal uptake in 26 patients, diffuse uptake in 10 patients), the tibia in 13 patients (2 focal uptake, 11 diffuse uptake), and the femur in 2 patients (both with diffuse uptake). None of the regions of abnormal lower extremity uptake was symptomatic at the time of initial evaluation. There was no change in the clinical management of any patient because of the scan findings. None of the patients was advised to restrict the activity level because of the asymptomatic scan findings. None of the regions of scan abnormality became symptomatic on follow-up evaluation. CONCLUSION: This study shows that asymptomatic bone scintigraphic abnormalities of the feet, as well as diffuse abnormalities of the tibia, are common in young athletes. These findings are most likely of no clinical consequence and do not require a change in the activity level. Focal abnormalities of the femur or tibia are not commonly seen in asymptomatic young athletes.

Reproducibility of renal length measurements with 99mTc-DMSA SPECT.

UNLABELLED: Renal length measurements are used in evaluating several abnormalities of the pediatric genitourinary tract. This study assesses reproducibility of renal length measurements obtained with 99mTc-dimercaptosuccinic acid (DMSA) SPECT. METHODS: The lengths of 98 kidneys of 51 children (age range, 1-16 y; mean age, 5.4 y) who underwent 99mTc-DMSA SPECT were measured independently by 2 observers. Renal length was calculated by converting pixels between points at the superior and inferior renal margins on a summated coronal image to centimeters. Lengths were measured for kidneys as they appeared in situ and after realignment along their long axes. SPECT reconstruction, choice of display parameters, positioning of points used for measuring, and alignment were performed independently by each observer. Interobserver variability, interobserver correlation, and mean differences between observers' measurements (expressed as measurement of observer 2 - measurement of observer 1) were calculated. RESULTS: Correlation between the observers' measurements was highly significant for both nonaligned and aligned studies (r = 0.95 and 0.97, respectively; both, P < 0.0001). Interobserver variability expressed as 1 SD was 3.6 mm for nonaligned studies and 2.8 mm for aligned studies. The mean difference between the 2 observers' measurements for nonaligned studies was 2.0 +/- 4.8 mm (P < 0.0001) with a range of -11 to 14 mm. For aligned studies the mean difference between the 2 observers' measurements was -0.1 +/- 4.0 mm (P = 0.88) with a range of -20 to 10 mm. Differences between observers were not dependent on absolute renal length (P = 0.68 for nonaligned studies; P = 0.40 for aligned studies). CONCLUSION: The variability in renal length measurements determined by 99mTc-DMSA SPECT is similar to that reported previously using sonography. Because the interobserver differences in renal length are similar to annual renal growth rates during childhood, caution should be applied when incorporating renal length measurements determined by 99mTc-DMSA SPECT into management algorithms. Additional studies are required to further establish interobserver variability, to assess intraobserver variability, and to evaluate means of improving standardization.

Effect of early emptying on quantitation and interpretation of liquid gastric emptying studies of infants and young children.

UNLABELLED: This study assesses the effect of emptying that occurs during feeding on quantitation and interpretation of liquid gastric emptying studies of infants and young children. METHODS: Forty-nine 99mTc-sulfur colloid liquid gastric emptying studies of 44 children (22 boys, 22 girls; mean age, 20 mo; age range, 2-46 mo) fed orally or by gastrostomy tubes were evaluated. Gastric residuals quantitated by 2 commonly used methods, the first of which does not account for early emptying and the second of which does, were compared. With the first method, residual relative to activity in the stomach at the start of imaging (Rg) was quantified by comparing activity in a region of interest (ROI) drawn about the stomach on the final image to activity in an ROI drawn about only the stomach at the start of imaging. With the second method, residual relative to total dose (Rt) was quantified by comparing activity in the same final ROI to activity in an ROI that included stomach and small bowel at the start of imaging. Studies were interpreted independently for Rg and Rt considering a value >70% as evidence of delayed emptying. RESULTS: Rt was lower than Rg by 15%-16% for the entire population, for patients fed orally, and for patients fed by gastrostomy tube. These differences reached statistical significance (P < 0.0001). In 31 of 49 studies, R1 was lower than Rg by > or =10%. In 8 studies, emptying classified as delayed on the basis of Rg was classified as nondelayed on the basis of Rt. Clinical decisions based on Rt did not require later management changes that would have indicated that treatment of gastric dysmotility had been postponed in any patient. CONCLUSION: Emptying that occurs during feeding should be factored into quantitation of liquid gastric emptying in infants and young children. Not recognizing and accounting for early emptying results in overestimated gastric residuals and can lead to classification of emptying as delayed in children whose residuals of the total administered dose are within a recognized range of normal.