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OBJECTIVE The purpose of this study was to automate volume measurement of pediatric kidneys using Technetium-99m-dimercaptosuccinic acid (99mTc DMSA) SPECT. Assessment of renal size is essential in making an accurate clinical diagnosis and in evaluating normal and abnormal renal growth. Existing techniques for measuring renal length and volume are often observer-dependent and are limited by interobserver variability. MATERIALS AND METHODS An automated method using 99mTc DMSA SPECT was developed to measure renal length, volume, and 2D/3D split renal functions. An adaptive threshold was used for segmentation of renal images. To improve measurement accuracy of renal volumes, a boundary-weighted integration and a linear correction from phantom experiments were applied. Using the new automated software, we evaluated 620 normal kidneys in 310 patients aged 1 to 21 years. RESULTS In all, 99.4% of renal volume measurement was inter-/intraobserver reproducible without manual intervention. Correlations between renal size (volume and length) and growth parameters (age and body weight) were evaluated by nonlinear regression modeling. Body weight was found to be the best predictor of kidney volume and length (P < 0.0001). Normal ranges were established according to body weight. CONCLUSIONS Automatic renal volume measurement with 99mTc DMSA SPECT demonstrates high observer reproducibility, and it is useful for achieving accurate assessment of renal growth using sequential measurements. The renal growth models generated by this study will aid physicians in evaluating and monitoring renal growth.

Estimates of radiation absorbed dose to organs of the nuclear medicine patient are a requirement for administered activity optimization and for stochastic risk assessment. Pediatric patients, and in particular the newborn child, represent that portion of the patient population where such optimization studies are most crucial owing to the enhanced tissue radiosensitivities and longer life expectancies of this patient subpopulation. In cases where whole-body CT imaging is not available, phantom-based calculations of radionuclide S values--absorbed dose to a target tissue per nuclear transformation in a source tissue--are required for dose and risk evaluation. In this study, a comprehensive model of electron and photon dosimetry of the reference newborn child is presented based on a high-resolution hybrid-voxel phantom from the University of Florida (UF) patient model series. Values of photon specific absorbed fraction (SAF) were assembled for both the reference male and female newborn using the radiation transport code MCNPX v2.6. Values of electron SAF were assembled in a unique and time-efficient manner whereby the collisional and radiative components of organ dose--for both self- and cross-dose terms--were computed separately. Dose to the newborn skeletal tissues were assessed via fluence-to-dose response functions reported for the first time in this study. Values of photon and electron SAFs were used to assemble a complete set of S values for some 16 radionuclides commonly associated with molecular imaging of the newborn. These values were then compared to those available in the OLINDA/EXM software. S value ratios for organ self-dose ranged from 0.46 to 1.42, while similar ratios for organ cross-dose varied from a low of 0.04 to a high of 3.49. These large discrepancies are due in large part to the simplistic organ modeling in the stylized newborn model used in the OLINDA/EXM software. A comprehensive model of internal dosimetry is presented in this study for the newborn nuclear medicine patient based upon the UF hybrid computational phantom. Photon dose response functions, photon and electron SAFs, and tables of radionuclide S values for the newborn child--both male and female--are given in a series of four electronic annexes available at stacks.iop.org/pmb/57/1433/mmedia. These values can be applied to optimization studies of image quality and stochastic risk for this most vulnerable class of pediatric patients.

Despite the clinical and pathologic indicators implicating injury to the basal ganglia in children with hyperkinetic movement disorders, we were previously unable to identify lesions in these structures by means of cranial computed tomography or magnetic resonance imaging. We evaluated regional cerebral perfusion measured by single photon emission computed tomography (SPECT) with technetium 99m hexamethyl propylene amine oxime as a technique to localize functional cerebral abnormalities in eleven children who had a movement disorder after hypothermic cardiac surgery. Perfusion defects of the deep gray matter were noted in six of these eleven patients and cortical perfusion defects in nine. For both cortical and subcortical defects a strong right-sided predilection was present. Our findings suggest functional brain injury not detectable by conventional cranial computed tomography and magnetic resonance imaging in these patients. We speculate that these perfusion defects might relate to the behavioral and developmental sequelae in survivors of this syndrome. SPECT may identify subclinical injury in patients at risk for future neurodevelopmental problems and contribute to our understanding of the mechanisms of cerebral injury in the patient operated on for cardiac disease.

Objectives . This study was conducted to determine the prevalence of myocardial perfusion abnormalities at rest and exercise and to assess exercise capacity in children after the arterial switch operation. Background . There have been sporadic reports of myocardial ischemia or sudden death in children after the arterial switch operation for transposition of the great arteries, possibly related to inadequate coronary perfusion due to kinking or stenosis of the translocated coronary arteries. Methods . Myocardial perfusion at rest and peak exercise was assessed using the scintigraphic agent technetium-99m methoxyisobutyl isonitrile (sestamibi). Exercise capacity was determined with a modified Brace protocol. Ambulatory etectrocardiographic (ECG) Holter monitoring was performed. Ventricular function, contractility and wall motion were assessed echocardiographically. Results . Twenty-three children (aged 4.2 to 7.9 years) underwent evaluation. Abnormalities were found on the rest perfusion scans in 22 children (95.6%). The left ventricular myocardium was divided into 13 segments for analysis. Of 299 rest segments, 225 (75.3%) were normal, 11 (3.7%) showed mild defects, 45 (15%) moderate defects and 18 (6%) severe defects at rest. At peak exercise, 237 segments (79.3%) were normal, 24 (8%) showed mild defects, 33 (11%) moderate defects and 5 (1.7%) severe defects. Compared with rest studies, myocardial perfusion grade at exercise was unchanged in 246 segments (82.3%), improved in 42 (14%) and worsened in 11 (3.7%). All patients had normal exercise tolerance without symptoms or ischemic ECG changes. No ventricular tachycardia was seen on Holter monitoring. All patients had a shortening fraction ≥27%. Left ventricular contractility was normal in 12 children in whom it was assessed. Regional wall motion was normal in 17 children with adequate echocardiographic images for this analysis. Conclusions . Myocardial perfusion scan abnormalities assessed by technetium-99m sestamibi are common after an arterial switch operation. These abnormalities are of uncertain clinical significance and generally lessen with exercise. The normal exercise tolerance without symptoms or ECG changes suggests that myocardial perfusion is adequate during the physiologic stress of exercise in children up to 8 years after an arterial switch operation.

A recent survey of pediatric hospitals showed a large variability in the activity administered for diagnostic nuclear medicine imaging of children. Imaging guidelines, especially for pediatric patients, must balance the risks associated with radiation exposure with the need to obtain the high-quality images necessary to derive the benefits of an accurate clinical diagnosis. Methods: Pharmacokinetic modeling and a pediatric series of nonuniform rational B-spline–based phantoms have been used to simulate 99mTc-dimercaptosuccinic acid SPECT images. Images were generated for several different administered activities and for several lesions with different target-to-background activity concentration ratios; the phantoms were also used to calculate organ S values for 99mTc. Channelized Hotelling observer methodology was used in a receiver-operating-characteristic analysis of the diagnostic quality of images with different modeled administered activities (i.e., count densities) for anthropomorphic reference phantoms representing two 10-y-old girls with equal weights but different body morphometry. S value–based dosimetry was used to calculate the mean organ-absorbed doses to the 2 pediatric patients. Using BEIR VII age- and sex-specific risk factors, we converted absorbed doses to excess risk of cancer incidence and used them to directly assess the risk of the procedure. Results: Combined, these data provided information about the tradeoff between cancer risk and diagnostic image quality for 2 phantoms having the same weight but different body morphometry. The tradeoff was different for the 2 phantoms, illustrating that weight alone may not be sufficient for optimally scaling administered activity in pediatric patients. Conclusion: The study illustrates implementation of a rigorous approach for balancing the benefits of adequate image quality against the radiation risks and also demonstrates that weight-based adjustment to the administered activity is suboptimal. Extension of this methodology to other radiopharmaceuticals would yield the data required to generate objective and well-founded administered activity guidelines for pediatric and other patients.

New consensus guidelines for pediatric administered radiopharmaceutical doses have been recently established and, in late 2010, were approved by the Society of Nuclear Medicine, the Society for Pediatric Radiology, and the American College of Radiology.

To determine the minimum dose of technetium 99m ((99m)Tc) mercaptoacetyltriglycerine (MAG3) needed to perform dynamic renal scintigraphy in the pediatric population without loss of diagnostic quality or accurate quantification of renal function and to investigate whether adaptive noise reduction could help further reduce the minimum dose required.Approval for this retrospective study was obtained from the institutional review board, with waiver of informed consent. A retrospective review was conducted in 33 pediatric patients consecutively referred for a (99m)Tc-MAG3 study. In each patient, a 20-minute dynamic study was performed after administration of 7.4 MBq/kg. Binomial subsampling was used to simulate studies performed with 50%, 30%, 20%, and 10% of the administered dose. Four nuclear medicine physicians independently reviewed the original and subsampled images, with and without noise reduction, for image quality. Two observers independently performed a quantitative analysis of renal function. Subjective rater confidence was analyzed by using a logistic regression model, and the quantitative analysis was performed by using the paired Student t test.Reducing the administered dose to 30% did not substantially affect image quality, with or without noise reduction. When the dose was reduced to 20%, there was a slight but significant decrease (P = .0074) in image quality, which resolved with noise reduction. Reducing the dose to 10% caused a decrease in image quality (P = .0003) that was not corrected with noise reduction. However, the dose could be reduced to 10% without a substantial change in the quantitative evaluation of renal function independent of the application of noise reduction.Decreasing the dose of (99m)Tc-MAG3 from 7.4 to 2.2 MBq/kg did not compromise image quality. With noise reduction, the dose can be reduced to 1.5 MBq/kg without subjective loss in image quality. The quantitative evaluation of renal function was not substantially altered, even with a theoretical dose as low as 0.74 MBq/kg.

The technology revolution in image acquisition, instrumentation, and methods has resulted in vast data sets that far outstrip the human observers’ ability to view, digest, and interpret modern medical images by using traditional methods. This may require a paradigm shift in the radiologic interpretation process. As human observers, radiologists must search for, detect, and interpret targets. Potential interventions should be based on an understanding of human perceptual and attentional abilities and limitations. New technologies and tools already in use in other fields can be adapted to the health care environment to improve medical image analysis, visualization, and navigation through large data sets. This historical psychophysical and technical review touches on a broad range of disciplines but focuses mainly on the analysis, visualization, and navigation of image data performed during the interpretive process. Advanced postprocessing, including three-dimensional image display, multimodality image fusion, quantitative measures, and incorporation of innovative human-machine interfaces, will likely be the future. Successful new paradigms will integrate image and nonimage data, incorporate workflow considerations, and be informed by evidence-based practices. This overview is meant to heighten the awareness of the complexities and limitations of how radiologists interact with images, particularly the large image sets generated today. Also addressed is how human-machine interface and informatics technologies could combine to transform the interpretation process in the future to achieve safer and better quality care for patients and a more efficient and effective work environment for radiologists. © RSNA, 2011 Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11091276/-/DC1

In this study, an automated analysis of pulmonary ventilation (AAPV) was developed to visualize the ventilation in pediatric lungs using dynamic Xe-133 scintigraphy. AAPV is a software algorithm that converts a dynamic series of Xe- 133 images into four functional images: equilibrium, washout halftime, residual, and clearance rate by analyzing pixelbased activity. Compared to conventional methods of calculating global or regional ventilation parameters, AAPV provides a visual representation of pulmonary ventilation functions.

Significant progress has been made in radiation protection for children during the last 10 years. This includes increased awareness of the need for radiation protection for pediatric patients with international partnerships through the Alliance for Radiation Safety in Pediatric Imaging. This paper identifies five areas of significant progress in radiation safety for children: the growth of the Alliance; the development of an adult radiation protection campaign Image Wisely™; increased collaboration with government agencies, societies and the vendor community; the development of national guidelines in pediatric nuclear medicine, and the development of a size-based patient dose correction factor by the American Association of Physicists in Medicine, Task Group 204. However, many challenges remain. These include the need for continued education and change of practice at adult-focused hospitals where many pediatric CT exams are performed; the need for increased emphasis on appropriateness of pediatric imaging and outcomes research to validate the performance of CT studies, and the advancement of the work of the first pediatric national dose registry to determine the “state of the practice” with the final goal of establishing ranges of optimal CT technique for specific scan indications when imaging children with CT.

Dose reduction has been a work in progress in pediatric imaging for nearly a decade. A 1996 report indicated that the long-term risk of carcinogenesis due to ionizing radiation in atomic bomb survivors was higher than had been previously estimated. For solid tumors, representing about 75% of excess

OBJECTIVE: Our objective was to evaluate screening for vesicoureteral reflux (VUR) among siblings of patients with VUR, in terms of cost, radiation exposure, and number of febrile urinary tract infections (fUTIs) averted. METHODS: We constructed a Markov model to evaluate 2 competing management options, that is, universal screening (cystographic evaluation of all siblings without symptoms) and usual care (cystographic evaluation of siblings only after fUTIs). Published data were used to inform all model inputs. Costs were estimated by using a societal perspective. RESULTS: Universal screening yielded 2980 fUTIs, whereas usual care yielded 6330. Therefore, universal screening for VUR in a cohort of 100 000 siblings 1 year of age without symptoms resulted in the prevention of 1 initial fUTI per 3360 siblings, at an excess cost of $55 600 per averted fUTI, in comparison with usual care. These estimates were heavily dependent on screening age and the effectiveness of antibiotic prophylaxis; prevention of a single fUTI would require screening of 166 siblings 5 years of age and 694 siblings 10 years of age. Similarly, if prophylaxis was ineffective in preventing fUTIs, then up to 10 000 siblings would need to be screened for prevention of a single fUTI. CONCLUSIONS: Prevention of a single fUTI would require screening of 30 to 430 siblings 1 year of age without symptoms, at an estimated excess cost of $56 000 to $820 000 per averted fUTI. These estimates are heavily dependent on screening age and the effectiveness of antibiotic prophylaxis.

Radiological imaging is the mainstay of diagnosing ureteropelvic junction obstruction. Current established radiological modalities can potentially differentiate the varying degrees of obstruction but they are limited in functionality, applicability and/or comprehensiveness. Of particular concern is that some tests require radiation, which has long-term consequences, especially in children.We investigated the novel use of Genhance™ 680 dynamic fluorescence imaging to assess ureteropelvic junction obstruction in 20 mice that underwent partial or complete unilateral ureteral obstruction. Ultrasound, mercaptoacetyltriglycine renography, magnetic resonance imaging and fluorescence imaging were performed.Our model of partial and complete obstruction could be distinguished by ultrasound, mercaptoacetyltriglycine renography and magnetic resonance imaging, and was confirmed by histological analysis. Using fluorescence imaging distinct vascular and urinary parameters were identified in the partial and complete obstruction groups compared to controls.Fluorescence imaging is a feasible alternative radiological imaging modality to diagnose ureteropelvic junction obstruction. It provides continuous, detailed imaging without the risk of radiation exposure.

Use of copper radioisotopes in antibody radiolabeling is challenged by reported loss of the radionuclide from the bifunctional chelator used to label the protein. The objective of this study was to investigate the relationship between the thermodynamic stability of the (64)Cu-complexes of five commonly used bifunctional chelators (BFCs) and the biodistribution of an antibody labeled with (64)Cu using these chelators in tumor-bearing mice.The chelators [S-2-(aminobenzyl)1,4,7-triazacyclononane-1,4,7-triacetic acid (p-NH(2)-Bn-NOTA): 6-[p-(bromoacetamido)benzyl]-1, 4, 8, 11-tetraazacyclotetradecane-N, N', N'', N'''-tetraacetic acid (BAT-6): S-2-(4-aminobenzyl)-1,4,7,10-tetraazacyclododocane tetraacetic acid (p-NH(2)-Bn-DOTA): 1,4,7,10-tetraazacyclododocane-N, N', N", N"'-tetraacetic acid (DOTA): and 1-N-(4-aminobenzyl)-3,6,10,13,16,19-hexaazabicyclo[6.6.6]eicosane-1,8-diamine (SarAr)] were conjugated to the anti-GD2 antibody ch14.18, and the modified antibody was labeled with (64)Cu and injected into mice bearing subcutaneous human melanoma tumors (M21) (n = 3-5 for each study). Biodistribution data were obtained from positron emission tomography images acquired at 1, 24 and 48 hours post-injection, and at 48 hours post-injection a full ex vivo biodistribution study was carried out.The biodistribution, including tumor targeting, was similar for all the radioimmunoconjugates. At 48 h post-injection, the only statistically significant differences in radionuclide uptake (p0.05) were between blood, liver, spleen and kidney. For example, liver uptake of [(64)Cu]ch14.18-p-NH(2)-Bn-NOTA was 4.74 ± 0.77 per cent of the injected dose per gram of tissue (%ID/g), and for [(64)Cu]ch14.18-SarAr was 8.06 ± 0.77 %ID/g. Differences in tumor targeting correlated with variations in tumor size rather than which BFC was used.The results of this study indicate that differences in the thermodynamic stability of these chelator-Cu(II) complexes were not associated with significant differences in uptake of the tracer by the tumor. However, there were significant differences in tracer concentration in other tissues, including those involved in clearance of the radioimmunoconjugate (e.g., liver and spleen).

It has been shown that warming patients prior to and during (18)F-FDG uptake by controlling the room temperature can decrease uptake by brown adipose tissue (BAT). The aim of this study is to determine if this effect is subject to seasonal variation.A retrospective review was conducted of all patients referred for whole-body (18)F-FDG PET between December 2006 and December 2008. After December 2007, all patients were kept in the PET injection room at a constant 24 degrees C for 30 min before and until 1 h following FDG administration. Patients over 22 years of age and those who received pre-medication known to reduce FDG uptake by BAT were excluded. One hundred and three patients were warmed to 24 degrees C prior to scanning. The number of patients showing uptake by BAT in this group was compared to a control group of 99 patients who underwent PET prior to December 2007 when the injection room temperature was 21 degrees C.Uptake by BAT occurred in 9% of studies performed after patient warming (24 degrees C), compared to 27% of studies performed on the control group (21 degrees C) (p0.00001). The effect of warming on decreasing FDG accumulation in BAT was statistically significant in the winter (p0.005) and summer (p0.001). However, in the spring and autumn, though the effect of warming on decreasing FDG accumulation in BAT was evident, it was not statistically significant (p0.05).Maintaining room temperature at a constant 24 degrees C for 30 min prior to and 1 h after IV tracer administration significantly decreases FDG uptake by BAT in children. This effect is greatest in the summer and winter.

Planar scintigraphy using (99m)Tc-labeled methylene diphosphonate ((99m)Tc-MDP) has been established as a method for evaluating mandibular growth and asymmetry. However, (99m)Tc-MDP single photon emission computed tomography (SPECT) provides improved image contrast and quantitative capability potentially allowing the clinician to make a more accurate assessment of the stage of activity of normal and asymmetric mandibular growth. The purpose of this study was to utilize (99m)Tc-MDP SPECT in normal subjects to develop a standardized approach to imaging the mandible that could subsequently be used to evaluate patients with potential for mandibular growth abnormalities.Thirty-two patients (22 females, 10 males, 8-25 years of age, mean of 14 years) having (99m)Tc-MDP bone scans (7.4 MBq/kg, maximum of 518 MBq) for indications not involving the head were asked to have an additional SPECT that included the mandibular condyles. Internal (clivus) and external (source of known activity included within the field of view) standards were both investigated. Two- and three-dimensional (2-D and 3-D) regions of interest (ROI) were drawn over each condyle and the clivus in a single slice containing the maximum pixel value within the structure. A 3-D ROI was also drawn about the external standard. Maximum and average pixel values within the 2-D and 3-D ROIs were recorded.Correlation analysis indicated that essentially the same information was obtained whether the maximum or average pixel value within a 2-D or 3-D ROI was used. The right to left ratio provided a parameter that can be used to assess the magnitude of mandibular metabolic asymmetry. Use of an external standard provides the potential for quantifying condylar uptake for assessment of the activity of mandibular growth. Normal ranges for different age groups were determined for condylar uptake using both internal and external standards.(99m)Tc-MDP SPECT provides a quantitative method for assessing mandibular condylar uptake as a reflection of the activity of mandibular growth. The maximum pixel value of a 2-D ROI using external standardization and the right to left ratio of the condylar uptake provide the potential for quantitative evaluation of patients with mandibular asymmetry. These parameters will be further evaluated in an upcoming clinical investigation.

As part of our on-going effort to develop (64)Cu-based radiopharmaceuticals for PET (positron emission tomography) imaging of multidrug resistance in cancer, we prepared a tetramethylfuranone-functionalized diiminedioxime ligand, TMFPreH (TMFPreH = 4-[3-(4-Hydroxyimino-2,2,5,5-dimethyl-dihydro-furan-3-ylideneamino)-propylimino]-2,2,5,5-tetramethyl-dihydro-furan-3-one oxime) and its Cu(II) and Ni(II) complexes. When the copper(II) complex was prepared from Cu(ClO(4))(2) in ethanol, it was isolated as a Cu(II)-bridged dimer, but when it was prepared from Cu(OAc)(2) and heated in acetone, an unusual example of an acetone adduct of the ligand is formed by reduction of one of the imine double bonds by the solvent. The Ni(II) complex is square pyramidal with the perchlorate counterion at the apex.

To assess whether thallium-201 thallous chloride (Tl) can detect childhood tumors and whether diagnostic effectiveness improves with combined blood flow imaging, 28 children (1.0-18.6 years) were studied using single photon emission computed tomography (SPECT): Tl (1.3-1.8 mCi intravenously), followed in 13 of the patients by technetium-99m-hexamethylpropyleneamine oxime (99mTc-HMPAO; 8-18 mCi intravenously). Tl-uptake was markedly increased with histologically confirmed recurrent brain tumors (N = 12). Tl-avid tumors comprised several histologic types, including 6 astrocytomas/gliomas as well as nonastrocytic neoplasms, such as medulloblastoma and ependymoma. A questionable false-positive study was observed with a treated medulloblastoma. Tl failed to detect 5 tumors (i.e., 2 medulloblastomas, 1 ependymoma, 1 malignant schwannoma, and initially 1 low-grade astrocytoma). The sensitivity and specificity of 201Tl-SPECT for detection of childhood brain tumors was 76.9% and 93.3%, respectively. The mean tumor-to-normal brain ratio for Tl was 2.5 +/- 0.5 (N = 7). In some of the patients, 201Tl-SPECT allowed a more precise assessment of the functional state of the tumor than was possible with computed tomography and magnetic resonance imaging. HMPAO distribution was variously normal, increased or decreased at the site of tissue abnormality, and abnormal blood flow was demonstrated in the remaining neuraxis, in 3 of the 7 patients. Changes in tissue perfusion did not correlate with Tl findings, but were evaluated in only one false-negative study.

The aim of this study was to determine if warming patients prior to and during (18)F-FDG uptake by controlling the room temperature could decrease uptake by brown adipose tissue (BAT).A group of 40 children underwent (18)F-FDG PET after being kept in the injection room at a constant temperature of 24 degrees C for half an hour before and 1 hour after intravenous tracer administration. The rate of uptake by BAT in this group was compared to the uptake in a control group of 45 patients who underwent PET when the injection room temperature was 21 degrees C.Uptake by BAT occurred in 5% of studies in the temperature-controlled room compared to 31% of studies performed when the injection room temperature was 21 degrees C (p0.002).Maintaining room temperature at a constant 24 degrees C, half an hour prior to and during the period of FDG uptake significantly decreases accumulation of FDG in BAT in children.

The rationale of this study was to investigate the feasibility of three-dimensional (3D) methods to analyze 18F-fluoro-deoxy-glucose (FDG) uptake in children with anaplastic astrocytoma (AA) in a multi-institutional trial, to compare 3D and two-dimensional (2D) methods and explore data associations with progression-free survival (PFS). 3D tumor volumes from pretreatment MR images (fluid attenuation inversion recovery and postgadolinium) of children with recurrent AA on a phase I trial of imatinib mesylate were coregistered to FDG positron emission tomography (PET) images. PET data were normalized. Four metrics were defined: the maximum ratio (maximum pixel value within the 3D tumor volume, normalized), the total ratio (cumulative pixel values within the tumor volume, normalized) and tumor mean ratio (total pixel value divided by volume, normalized). 2D analysis methods were compared. Cox proportional hazards models were used to estimate the association between these methods and PFS. Strongest correlations between 2D and 3D methods were with analyses using postcontrast T1 images for volume of interest (VOI). The analyses suggest 3D maximum tumor and mean tumor ratios, whether normalized by gray matter or white matter, were associated with PFS. This study of a series of pretreatment AA patients suggests that 3D PET methods using VOIs based on postcontrast T1 correlate with 2D methods and are related to PFS. These methods yield an estimate of metabolically active tumor burden and may add prognostic information after tumor grade is determined. Future rigorous multi-institutional protocols with larger numbers of patients will be required for validation.

The renal and hemodynamic effects of dopamine were measured during the immediate postoperative period in six infants following repair of congenital cardiac defects. Dopamine was infused at rates of 5, 10, and 15 micrograms/kg/min. Cardiac index (CI) increased significantly at a dopamine infusion rate of 15 micrograms/kg/min. The glomerular filtration rate (GFR) and urine output increased at dopamine infusion rates of 5 and 10 micrograms/kg/min and returned to baseline at 15 micrograms/kg/min. No significant changes occurred in right atrial pressure (RAP), left atrial pressure (LAP), systemic artery pressure, systemic vascular resistance (SVR), or pulmonary vascular resistance (PVR). Heart rate (HR) increased slightly at a dopamine infusion rate of 15 micrograms/kg/min. Pulmonary artery pressure (PAP) increased significantly in only one patient. These data demonstrate that infants require high doses of dopamine to produce the hemodynamic effects seen in adults and that these higher doses may be used without adverse renal effects.

Purpose: Skeletal positron emission tomography (PET) with fluorine-18 ( 18 F) sodium fluoride 18 F NaF) is an alternative to technetium-99m ( 99m Tc)methylene diphosphonate (MDP) scintigraphy. Experience with pediatric PET is sparse, primarily in oncology. This study assesses the role of 18 F NaF in evaluating young patients with back pain. Methods: Ninety-four 18 F NaF PET scans were performed in 94 patients (27 males, 67 females; mean age, 15 years; range, 4-26 years) with back pain. Three-dimensional PET acquisition was performed 30 minutes after administration of 18 F NaF (2.1 MBq/kg; maximum, 148 MBq). Radiation doses are presented for 18 F NaF and 99m Tc MDP. Results: 18 F NaF PET revealed a possible cause of back pain in 55% (52/94). Fifteen patients had 2 or more potential sources of back pain. Diagnoses by PET were pars interarticularis/pedicle stress (34%), spinous process injury (16%), vertebral body ring apophyseal injury (14%), stress at a transitional vertebra-sacral articulation (7%), and sacroiliac joint inflammation/stress (3%). Comparing 18 F NaF PET with 99m Tc MDP scintigraphy, time between injection and scanning was shorter (0.5 hours vs 3 hours), radiation dosimetry was similar (3.5 mGy vs 2.8 mGy effective dose for a 55-kg patient for 18 F NaF and 99m Tc MDP, respectively), and cost of radiopharmaceutical was higher. Conclusions: 18 F NaF bone PET can detect a variety of skeletal abnormalities in young patients with back pain. Relative to 99m Tc MDP, images are of higher resolution. Total time from tracer administration to completion is shorter, and radiation dosimetry is similar. Higher cost for 18 F NaF may be offset by enhanced patient throughput.

To evaluate the dose from the computed tomographic (CT) portion of positron emission tomography (PET)/CT to determine minimum CT acquisition parameters that provide adequate attenuation correction.Measurements were made with a PET/CT scanner or a PET scanner, five anthropomorphic phantoms (newborn to medium adult), and an ionization chamber. The CT dose was evaluated for acquisition parameters (10, 20, 40, 80, 160 mA; 80, 100, 120, 140 kVp; 0.5 and 0.8 second per rotation; 1.5:1 pitch). Thermoluminescent dosimetry was used to evaluate the germanium 68/gallium 68 rod sources. A phantom study was performed to evaluate CT image noise and the adequacy of PET attenuation correction as a function of CT acquisition parameters and patient size.The volumetric anthropomorphic CT dose index varied by two orders of magnitude for each phantom over the range of acquisition parameters (0.30 and 21.0 mGy for a 10-year-old with 80 kVp, 10 mAs, and 0.8 second and with 140 kVp, 160 mAs, and 0.8 second, respectively). The volumetric anthropomorphic CT dose index for newborn phantoms was twice that for adult phantoms acquired similarly. The rod source dose was 0.03 mGy (3-minute scan). Although CT noise varied substantially among acquisition parameters, its contribution to PET noise was minimal and yielded only a 2% variation in PET noise. In a pediatric phantom, PET images generated by using CT performed with 80 kVp and 5 mAs for attenuation correction were visually indistinguishable from those generated by using CT performed with 140 kVp and 128 mAs. With very-low-dose CT (80 kVp, 5 mAs) for the adult phantom, undercorrection of the PET data resulted.For pediatric patients, adequate attenuation correction can be obtained with very-low-dose CT (80 kVp, 5 mAs, 1.5:1 pitch), and such correction leads to a 100-fold dose reduction relative to diagnostic CT. For adults undergoing CT with 5 mAs and 1.5:1 pitch, the tube voltage needs to be increased to 120 kVp to prevent undercorrection.

This article presents an automated, patient-specific method for the detection of epileptic seizure onset from noninvasive electroencephalography. We adopt a patient-specific approach to exploit the consistency of an individual patient's seizure and nonseizure electroencephalograms. Our method uses a wavelet decomposition to construct a feature vector that captures the morphology and spatial distribution of an electroencephalographic epoch, and then determines whether that vector is representative of a patient's seizure or nonseizure electroencephalogram using the support vector machine classification algorithm. Our completely automated method was tested on noninvasive electroencephalograms from 36 pediatric subjects suffering from a variety of seizure types. It detected 131 of 139 seizure events within 8.0+/-3.2 seconds of electrographic onset, and declared 15 false detections in 60 hours of clinical electroencephalography. Our patient-specific method can be used to initiate delay-sensitive clinical procedures following seizure onset, for example, the injection of a functional imaging radiotracer.

We investigated the feasibility of using (191m)Ir (half-life, 5 s) to measure rapid dynamic alterations in differential renal blood flow.A nonobstructive constant renal pelvic pressure model was used. The renal pelves of 6 New Zealand White rabbits were drained by use of bilateral catheters, and increased hydrostatic pressure was achieved by raising 1 catheter to 16, 25, 30, or 35 cm above the level of the renal pelvis. The contralateral kidney served as the control. (191m)Ir first-pass angiograms were obtained at baseline, after the induction of elevated pressure in the renal pelvis, and after the pressure was returned to normal. A minimum of 3 sequential angiograms were obtained at each point.The differential blood flow values (mean +/- SD) were 47.5% +/- 7.3% at baseline, decreased to 42.3% +/- 2.6% when the renal pelvic pressure was elevated (P = 0.001), and returned to 51.1% +/- 4.0% after the pressure was returned to normal (P = 0.0017). There was no significant difference between baseline and postcompression values (P = 0.4807).It is possible to use (191m)Ir first-pass angiography to evaluate rapid dynamic changes in differential renal blood flow in an experimental animal model.

Aneurysmal bone cyst is an uncommon nonneoplastic lesion that occurs predominantly during the first 2 decades of life. Angiographic- and tissue-phase imaging provided more striking evidence of this unexpected lesion than skeletal-phase imaging in a 13-year-old girl with pain in the right buttock and posterior thigh.

Skeletal scintigraphy showed a disproportionately small pelvis in a 15-year-old girl with a slipped capital femoral epiphysis and a history of therapeutic pelvic irradiation at the age of 18 months. This case illustrates the hypoplasia of flat bones and the predisposition to physeal injury that can result from radiation damage to chondroblasts of the growing skeleton.

Symptoms are commonly nonspecific in children with acute pyelonephritis; therefore, other diagnoses may be considered first. Skeletal scintigraphy revealed abnormal tracer distribution in the left kidney of a 7-year-old girl suspected of having acute osteomyelitis. A diagnosis of acute pyelonephritis was suggested and later supported by computed tomography and urine culture.

Objective: Chronic acalculous cholecystitis previously has been diagnosed by hepatobiliary scan stimulated with intravenous octapeptide of cholecystokinin. This compound may soon be unavailable in the United States. The goal of this study was to describe the characteristics of children with chronic acalculous cholecystitis diagnosed by hepatobiliary scintigraphy with oral Lipomul challenge, and to evaluate their clinical response to cholecystectomy. Methods: Retrospective chart review of patients with no gall stones detected by abdominal ultrasound or computed tomography with gallbladder ejection fraction (GBEF)

Lumbosacral transitional vertebrae can alter the biomechanics of weight transfer at the affected spinal segment. Low-back pain may result. This study assessed what skeletal scintigraphy reveals about stress associated with a lumbosacral transitional vertebra in young patients with low-back pain.The study population included 48 patients (30 male, 18 female; age range, 6-19 y; mean age, 15.7 y) with low-back pain and a lumbosacral transitional vertebra. Skeletal scintigraphy was correlated with plain radiographs in all, CT in 12, and MRI in 11.High uptake was shown at the articulation between the transverse process of a lumbosacral transitional vertebra and the sacrum in 39 (81%) of the patients. In 23 (59%) of the 39 patients with high uptake, this finding was shown only by SPECT. In 13 (81%) of the 16 for which the high uptake was shown by planar imaging, the anterior projection was more valuable than the posterior projection. In 9 (23%) of the 39 patients with high uptake at the transverse-sacral articulation, the lumbosacral transitional vertebra had not been noted in a radiographic report before skeletal scintigraphy but was identified through reevaluation or repetition of radiographs after skeletal scintigraphy. Radiographs showed sclerosis along the transverse-sacral articulation in only 8 (21%) of the 39 patients with high uptake. Findings indicating stress or motion at the joint were shown by CT in 6 (55%) of 11 and by MRI in 5 (63%) of 8 patients with high uptake at the transverse-sacral articulation who underwent these examinations.Skeletal scintigraphy often indicates stress at the transverse-sacral articulation of young patients with low-back pain and a lumbosacral transitional vertebra. Showing evidence of stress is best accomplished using SPECT. Changes are usually not radiographically evident, but there is a trend for MRI and CT to show findings that imply stress or motion at the articulation. The unique ability of skeletal scintigraphy to provide this physiologic information supports its use in these patients.

Os calcaneus secundarius is an uncommon anatomic variant that usually has no symptoms. The authors describe a patient with foot pain in whom plain radiographs and computed tomography suggested an os calcaneus secundarius. Skeletal scintigraphy, by showing high uptake at the corresponding site, supported its contributory role in explaining the patient's symptoms.

The emergence of MRI has challenged the long-standing primacy of skeletal scintigraphy in pediatric cases of suspected acute hematogenous osteomyelitis (AHO) with nondiagnostic radiographs. This study evaluated a strategy in which skeletal scintigraphy is the primary and MRI a supplemental test.We reviewed the records of 213 children (age range, 8 mo-18 y; mean age, 67 mo) with musculoskeletal symptoms and nondiagnostic radiographs who were referred for skeletal scintigraphy because of the possibility of AHO. MRI was performed when diagnostic uncertainty persisted after skeletal scintigraphy or when abscess was suspected.Diagnosis was made using skeletal scintigraphy without referral for MRI in 179 (84%) of the children, including 79 (92%) of 86 with a final diagnosis of AHO. In no instance was the diagnosis of AHO indicated only by MRI. Treatment and diagnosis were accomplished without referral for MRI in 146 (69%) of all cases and 46 (53%) of the AHO cases. Abscesses that required drainage were found in 3 (6%) of 48 cases of major-long-bone AHO. Each of these 3 had exhibited a slow therapeutic response before MRI. Drainable abscesses were found in 5 (20%) of 25 cases affecting the pelvis, which was the other preponderant location of AHO. These were found with pelvic foci both when MRI was performed at diagnosis and when MRI was performed during treatment.An imaging strategy in which skeletal scintigraphy is the first test used when AHO is suspected but radiographs are negative remains highly effective. This approach can be most strongly advocated when symptoms are poorly localized or are localized to major long bones. MRI should be performed after skeletal scintigraphy shows major-long-bone AHO if treatment response is slow. Skeletal scintigraphy is also an appropriate first test for suspected radiographically occult pelvic AHO. Because of the association of abscesses with pelvic AHO, however, the use of MRI should be strongly considered after pelvic AHO is detected, and MRI might be substituted diagnostically for skeletal scintigraphy when symptoms are well localized to the pelvis.

Malignant pleural mesothelioma is an aggressive primary neoplasm for which early detection and accurate staging are known diagnostic challenges. The role of (18)F-FDG dual-head gamma-camera coincidence imaging ((18)F-FDG-CI) is yet to be defined. The purpose of this study was to evaluate the usefulness of (18)F-FDG-CI in the assessment of malignant pleural mesothelioma using histopathology as the gold standard.Fifteen consecutive patients with CT scan evidence of pleural thickening, fluid, plaques, or calcification underwent (18)F-FDG imaging 1.5 h after the intravenous administration of 370 MBq (18)F-FDG. Imaging was performed with a dual-head gamma camera equipped with 2.54-cm-thick NaI crystals operating in coincidence mode. Using an iterative algorithm, whole-body images were reconstructed as transaxial, sagittal, and coronal images. No attenuation correction was applied. The results of (18)F-FDG-CI scans were compared with CT and with histopathologic diagnosis.Eleven of 15 patients had histologically proven malignant mesotheliomas (10 epithelial, 1 sarcomatoid). All 11 primary tumors were detected by (18)F-FDG, and absence of disease was confirmed in the 4 patients who were disease free. Thirty-four lesions were biopsied; among these, 29 were found to be positive for tumor. (18)F-FDG was true-positive in 28 lesions, true-negative in 4, false-negative in 1 (0.5 cm in diameter), and false-positive in 1 (inflammatory pleuritis). The smallest lesion detected was 0.8 cm. For biopsied lesions, overall sensitivity, specificity, and accuracy for (18)F-FDG-CI were 97%, 80%, and 94% respectively, compared with 83%, 80%, and 82% for CT. Twenty-one of 29 positive lesions involved the pleura, lung parenchyma, or chest wall and were all (18)F-FDG avid. In the mediastinum, (18)F-FDG-CI detected 7 of 8 biopsy-positive lesions (88%), whereas CT was positive in 6 of 8 lesions (75%). (18)F-FDG identified extrathoracic metastases in 5 patients, excluding them from surgical therapy.These preliminary results suggest that (18)F-FDG-CI appears to be an accurate method to diagnose and to define the extent of disease in patients with diffuse malignant pleural mesothelioma.

Nuclear medicine is important in the diagnosis, staging, and long-term surveillance of a number of pediatric cancers. Skeletal scintigraphy is used to evaluate primary skeletal cancers, such as osteosarcoma and Ewing sarcoma, and nonskeletal cancers such as neuroblastoma, lymphoma, medulloblastoma, rhabdomyosarcoma, and retinoblastoma. Metaiodobenzylguanidine scintigraphy is valuable in examinations of children with neuroblastoma. The therapeutic response of primary bone and brain tumors can be assessed using Tl-201 and Tc-99m MIBI scintigraphy. Imaging strategies for staging and monitoring the therapeutic response of Hodgkin's lymphoma include Ga-67 citrate scintigraphy. Pediatric oncologic applications of positron emission tomography are being investigated extensively.

Demonstration of cortical defects by renal cortical scintigraphy provides supportive evidence of acute pyelonephritis or renal scarring in the appropriate clinical settings. The presented case illustrates the potential for a small nonfunctioning or poorly functioning obstructed upper pole of a duplex kidney to mimic a pyelonephritic cortical defect and underscores the importance of the correlation between renal cortical scintigraphy and anatomic imaging studies.

Sir, The article by Chawla et al. [1] calculates effective doses for [F-18]FDG PET/CT studies performed at their hospital. This paper provides interesting data with respect to the numbers of PET/CT scans performed in their patients and an estimate of the resulting cumulative dose. However, a careful reading discloses that the effective dose from the PET radiopharmaceutical does not represent optimal clinical practice in 2010 and that it also no longer represents clinical practice at the authors’ hospital. The CT doses attributed to PET/CT represent the full diagnostic CT doses in use at their hospital. The authors state that it was their practice to perform the diagnostic CT required by the patient as part of the PET/CT scan. Therefore, the only added effective dose from the PET/CT scan is due to the addition of PET imaging. The amount of [F-18]FDG (administered activity) that a pediatric patient receives is usually calculated from a reference adult administered activity. The authors’ administered activity of 0.21 mCi/kg (7.8 MBq/kg) indicates that they used a reference activity of 15 mCi (555 MBq), which is commonly used at adult hospitals. However, a survey of North American children’s hospitals in 2008 indicated the median administered activity at these specialty hospitals surveyed was 0.145 mCi/kg (5.4 MBq/kg), corresponding to a reference activity of 10.1 mCi (373 MBq). An FDG administered activity of 0.14 mCi/kg (5.2 MBq/kg) has been used or recommended by other authors [2–5]. The authors indicate in a single sentence in the Discussion section that, after completion of PET/CT studies in this study’s patient cohort, they reduced the administered activity at their hospital to 0.14 mCi/kg. At an administered activity of 0.14 mCi/kg, the effective dose attributable to [F-18]FDG is reduced by 33%. Recent studies indicate that administered activities can be reduced further in pediatric patients younger than 5 to 10 years of age and for brain imaging [6, 7]. In the authors’ estimation of an average effective dose of 24.8 mSv per PET/CT, 80% of this dose is due to the CT acquisition. In general, the CT acquisition was performed with a rather high technique over the entire body. In contrast to the presented cohort, the CT component of the PET/CT study can be performed using any of three approaches. One approach is to perform a full diagnostic CT scan, usually with intravenous contrast agent, integrated into the PET/CT protocol. The authors appear to have used this approach. In a patient with neoplasm, this diagnosticquality CT scan would typically be the only diagnostic CT scan performed at this time point in the patient’s care. The added effective dose for the CT part of the PET/CT study at this time point is, therefore, zero. A second approach to the use of CT during PET/CT is to perform a reduced dose localization CT scan during free breathing as part of the PET/CT scan. This scan is typically performed at less than half of the exposure settings used for a diagnostic CT scan. This results in an effective dose attributable to CT of about 4–6 mSv. M. J. Gelfand (*) : S. E. Sharp Department of Radiology, Cincinnati Children’s Medical Center, 3333 Burnet Ave., Cincinnati, OH 45215-3039, USA e-mail: Michael.gelfand@cchmc.org

Background/Purpose: We have demonstrated previously that postnatal lung growth can be accelerated by continuous intrapulmonary distension with perfluorocarbon (PFC). The purpose of this study was to examine the effect of PFC distension on long-term lung function and to determine if shorter periods of lung distension would be sufficient to stimulate growth. Methods: Eight neonatal lambs underwent a right thoracotomy. The superior segment of the right upper lobe of the experimental group (n = 5) was isolated and distended with PFC to an intrabronchial pressure of 7 to 10 mm Hg. The inferior segment was removed. After a 7-day distension period (the maximum period of exposure currently allowed for humans), the experimental animals underwent removal of the intrabronchial catheter and surgical closure of the bronchial stump. Control animals (n = 3) underwent right upper lobe inferior segmentectomy alone. Animals were allowed to breathe spontaneously and reach 3 to 6 months of age. Before death, all animals were evaluated by chest radiographs and ventilation-perfusion scans. Pulmonary venous blood gas levels were obtained. Lungs were harvested and airway fixed for morphometric analysis. Results: Chest radiographs of the experimental group showed variable amounts of intrapleural and interstitial PFC but were otherwise normal. Results of ventilation/perfusion (VQ) scans of all experimental animals were normal. On retrieval, the right upper lobe of experimental animals appeared slightly hyperinflated compared with controls. Right upper lobe pulmonary vein Pao 2 to left pulmonary vein Pao 2 ratio was comparable in experimental and control animals (1.2 ± .41 v 0.92 ± .15). DNA to protein ratios were slightly higher in the right upper lobes of experimental animals, however, the difference was not statistically significant (.64 ± .11 v .42 ± .03). On histological evaluation, the airway epithelium and alveoli of the right upper lobe of experimental animals appeared normal. Lung morphometry results showed no statistically significant differences in alveloar number between experimental and control animals. Conclusions: From these preliminary data we conclude that (1) lung architecture is preserved in juvenile animals subjected to intrapulmonary PFC distension as neonates, (2) lung function is preserved in the lobar segment after PFC distension, and (3) intrapulmonary PFC distension appears to be safe at 3 to 6 months follow-up. However, 7 days of PFC distension is insufficient to promote lung growth.

Nonossifying fibroma (NOF) is a common benign lesion in adolescents. NOF typically is replaced with normal bone during growth and is not clinically significant. In the presented case, fracture occurred through an NOF in the proximal tibial metadiaphysis of a 14-year-old male basketball player. Skele

Sixteen children who had focal cortical resections for medically intractable epilepsy were preoperatively evaluated with 99m technetium-labelled hexamethylpropyleneamineoxime single photon emission computed tomography ( 99m Tc-HMPAO SPECT). Video-EEG monitoring was performed in all patients. Outcome was assessed according to the criteria of Engel et al. [1], at a mean follow up length of 13.4 ± 8.7 months, in all patients. Interictal SPECT showed appropriate localization in 11/15 cases, of whom nine had a class 1 outcome and two had class 2 and 4 outcomes. Interictal SPECT did not correlate with ictal EEG in 4/15 patients, of whom two had a class 1 outcome, and two had class 3 and 4 outcomes. Two postictal studies obtained in group I showed good correlation with the area of ictal EEG onset, and both patients had a class 1 outcome. Interictal HMPAO SPECT imaging, when positively correlated with the ictal EEG focus or with the site of surgery determined by other means, may have prognostic value for outcome of cortical resections for epilepsy in children. The use of ictal and post-ictal studies shows promise for further improving prognostic information in this population.

Skeletal tracer localization in the rectus abdominis muscle of a 17-year-old girl whose training regimen included vigorous abdominal exercise but who had no abdominal soreness is described. The case illustrates that bone tracers may localize to skeletal muscle without associated symptoms. This is consistent with bone tracer localization in skeletal muscle reflecting subtle fiber abnormalities rather than necrosis.