Nuclear Medicine in the First Year of Life

EANM procedural recommendations for managing the paediatric patient in diagnostic nuclear medicine

PURPOSE

The manuscript aims to characterize the principles of best practice in performing nuclear medicine procedures in paediatric patients. The paper describes all necessary technical skills that should be developed by the healthcare professionals to ensure the best possible care in paediatric patients, as it is particularly challenging due to psychological and physical conditions of children.

METHODS

We performed a comprehensive literature review to establish the most relevant elements of nuclear medicine studies in paediatric patients. We focused the attention to the technical aspects of the study, such as patient preparation, imaging protocols, and immobilization techniques, that adhere to best practice principles. Furthermore, we considered the psychological elements of working with children, including comforting and distraction strategies.

RESULTS

The extensive literature review combined with practical conclusions and recommendations presented and explained by the authors summarizes the most important principles of the care for paediatric patient in the nuclear medicine field.

CONCLUSION

Nuclear medicine applied to the paediatric patient is a very special and challenging area, requiring proper education and experience in order to be performed at the highest level and with the maximum safety for the child.

Role of Functional SPECT and PET in Renal Emergencies

Renal scintigraphy is a centerpiece of nuclear medicine and is also commonly applied for (peri-)acute care. In this regard, referrals by the treating physician include: I.) acute obstructions caused by gradual and infiltrative tumor growth or renal off-target effects under anti-tumor treatment, II.) functional issues in infants, for example, structural abnormalities such as duplex kidneys or uroliths in adults, which can also trigger III.) Infections of renal parenchyma. Renal radionuclide imaging is also requested due to IV.) acute trauma to the abdomen, for example, to assess renal scarring or upon further follow-up after reconstructive surgery. We will discuss clinical applications of (peri-)acute renal scintigraphy, along with future prospects on the use of more advanced nuclear imaging techniques such as renal positron emission tomography.

Update on Pediatric Nuclear Medicine in Acute Care

Various radiopharmaceuticals are available for imaging pediatric patients in the acute care setting. This article focuses on the common applications used on a pediatric patient in acute care. To confirm the clinical diagnosis of brain death, brain scintigraphy is considered accurate and has been favorably compared with other methods of detecting the presence or absence of cerebral blood flow. Ventilation-perfusion lung scans are easy and safe to perform with less radiation exposure than computed tomography pulmonary angiography and remain an appropriate procedure to perform on children with suspected pulmonary embolism as a first imaging test in a hemodynamically stable patient with no history of lung disease and normal chest radiograph. 99mTc-pertechnetate scintigraphy (Meckel's scan) is the best noninvasive procedure to establish the diagnosis of ectopic gastric mucosa in Meckel's diverticulum. 99mTcred blood cell scintigraphy generally is useful for assessing lower GI bleeding in patients from any cause. Hepatobiliary scintigraphy is the most accurate diagnostic imaging modality for acute cholecystitis. 99mTc-dimercaptosuccinic acid scintigraphy is the simplest, and the most reliable and sensitive method for the early diagnosis of focal or diffuse functional cortical damage. 99mTcmercaptoacetyltriglycine scintigraphy is used to evaluate for early and late complications of renal transplantation. Bone scintigraphy is a sensitive and noninvasive technique for diagnosis of bone disorders such as osteomyelitis and fracture. 18F-fluorodeoxyglucose-positron emission tomography could be valuable in the evaluation of fever of unknown origin in pediatric patients, with better sensitivity and significantly less radiation exposure than a gallium scan. Moving forward, further refinement of pediatric radiopharmaceutical administered activities, including dose reduction, greater radiopharmaceutical applications, and updated consensus guidelines is warranted, with the use of radionuclide imaging likely to increase.

Evaluation of radiation dose to pediatric models from whole body PET/CT imaging

Positron emission tomography (PET)/computed tomography (CT) is a well-known modality for the diagnosis of various diseases in children and adult patients. On the other hand, younger patients are more radiosensitive than adults, so there are concerns about the level of ionizing radiation exposure in pediatric whole body PET/CT imaging. In this regard, comprehensive specific radiation dosimetry for whole body PET/CT imaging is highly desired for different ages, sizes, and shapes. Therefore, in this study, organ absorbed doses were evaluated for pediatric voxel models from 4 to 14 years old and compared with those of ICRP phantoms. Monte Carlo calculation was performed to evaluate S-value, absorbed dose, and effective dose from ¹⁸ F-FDG radiotracers and whole body CT scan for different computational models, including 4- to 14-year-old phantoms. The results showed that the S-value and, therefore, absorbed dose of ¹⁸ F-FDG strongly depended on the phantom anatomy. These variations were justified by the distance between source and target organs. Moreover, on average, the absorbed doses from whole body CT scans were 13.5 times lower than those from ¹⁸ F-FDG for all organs. According to the results, various anatomies and ages should be considered for accurate dose evaluation. These data can be used for specific risk assessment of the pediatric population in clinical nuclear imaging.

Radiation Dose to Pediatric Patients From Radiopharmaceuticals

Nuclear medicine provides methods and techniques in that has benefited pediatric patients and their referring physicians for over 40 years. Nuclear medicine provides qualitative and quantitative information about overall and regional function of organs, systems, and lesions in the body. This involves applications in many organ systems including the skeleton, the brain, the kidneys and the heart as well as in the diagnosis and treatment of cancer. The practice of nuclear medicine requires the administration of radiopharmaceuticals which expose the patient to very low levels of ionizing radiation. Advanced approaches in the estimation of radiation dose from the internal distribution of radiopharmaceuticals in patients of various sizes and shapes have been developed in the past 20 years. Although there is considerable uncertainty in the estimation of the risk of adverse health effects from radiation at the very low exposure levels typically associated with nuclear medicine, some considers it prudent to be more cautious when applied to children as they are generally considered to be at higher risk than adults. Standard guidelines for administered activities for nuclear medicine procedures in children have been established including the North American consensus guidelines and the Paediatric Dosage Card developed by the European Association of Nuclear Medicine. As we move into the future, these guidelines would likely be reviewed in response to changes in clinical practice, a better understanding of radiation dosimetry as applied to children as well as new clinical applications, new advancements in the field with respect to both instrumentation and image reconstruction and processing.

A review of current imaging techniques used for the detection of occult bony fractures in young children suspected of sustaining non-accidental injury

Non-accidental injuries remain a leading cause of preventable morbidity and mortality in young children. The accurate identification of the full spectrum of injuries in children presenting with suspected abuse is essential to ensure the appropriate protective intervention is taken. The identification of occult bone fractures in this cohort is important as it raises the level of concern about the mechanism of injury and maintaining the child's safety. Radiographic imaging remains the modality of choice for skeletal assessment; however, current studies report concerns regarding the ability of radiographs to detect certain fractures in the acute stage. As such, alternative modalities for the detection of fractures have been proposed. This article reviews the current literature regarding fracture detectability and radiation dose burden of imaging modalities currently used for the assessment of occult bony injury in young children in whom non-accidental injury is suspected.

A comparison of subadult skeletal and dental development based on living and deceased samples

OBJECTIVES

A fundamental assumption in biological anthropology is that living individuals will present with different growth than non-survivors of the same population. The aim is to address the question of whether growth and development data of non-survivors are reflective of the biological consequences of selective mortality and/or stress.

MATERIALS AND METHODS

The study compares dental development and skeletal growth collected from radiographic images of contemporary samples of living and deceased individuals from the United States (birth to 20 years) and South Africa (birth to 12 years). Further evaluation of deceased individuals is used to explore differential patterns among manners of death (MOD).

RESULTS

Results do not show any significant differences in skeletal growth or dental development between living and deceased individuals. However, in the South African deceased sample the youngest individuals exhibited substantially smaller diaphyseal lengths than the living sample, but by 2 years of age the differences were negligible. In the US sample, neither significant nor substantial differences were found in dental development or diaphyseal length according to MOD and age (>2 years of age), though some long bones in individuals <2 years of age did show significant differences. No significant differences were noted in diaphyseal length according to MOD and age in the SA sample.

DISCUSSION

The current findings refute the idea that contemporary deceased and living individuals would present with differential growth and development patterns through all of ontogeny as well as the assumptions linking short stature, poor environments, and MOD.

Pediatric Solid Gastric Emptying Scintigraphy: Normative Value Guidelines and Nonstandard Meal Alternatives

INTRODUCTION

Adult standards for gastric emptying scintigraphy, including the type of meal and range of normative values for percent gastric emptying, are routinely used in pediatric practice, but to date have not been validated. The purpose of this study is to determine whether the use of adult criteria for gastric emptying scintigraphy is valid for children and whether alternative nonstandard meals can also be offered based on these criteria.

METHODS

This retrospective study analyzed patients (n = 1,151 total) who underwent solid-phase gastric emptying scintigraphy. Patients were stratified into normal and delayed gastric emptying cohorts based on adult criteria, i.e., with normal gastric emptying defined as ≤10% gastric retention at 4 hours. Patients were further stratified based on the type of meal, namely complete or partial adult standard meals or alternative cheese-based meals. Percent gastric retention values at 1, 2, 3, and 4 hours were compared.

RESULTS

The median (95% upper reference limit) percentage gastric retention values for the complete standard meal were 72% (93%) at 1 hour, 39% (65%) at 2 hours, 15% (33%) at 3 hours, and 6% (10 %) at 4 hours. By comparison, the values for cheese-based meals were 60% (87%) at 1 hour, 29% (61%) at 2 hours, 10% (30%) at 3 hours, and 5% (10%) at 4 hours. Consumption of at least 50% of the standard meal yielded similar retention percentages; 68% (89%) at 1 hour, 32% (57%) at 2 hours, 10% (29%) at 3 hours, and 5% (10%) at 4 hours. There were no significant age- or sex-specific differences using the adult criteria.

DISCUSSION

The adult normative standards for gastric emptying scintigraphy are applicable for use in the pediatric population. These same standards can be also be applied to nonstandard meal options, including cheese-based alternative meals and partial standard meals.

Activity estimation and biokinetic analysis of 99mTc-DMSA in renal infant patients using a gamma camera

Biokinetic data from the administration of radiopharmaceuticals is essential in nuclear medicine dosimetry. It has particular significance in children, as their metabolism is very different from adults. Biokinetic models for paediatric patients could therefore need to be adapted to better reflect their absorption, retention and excretion functions, when compared to adults. Obtaining quality in vivo infant or paediatric biokinetic data is then essential to improve the available reference models, which in turn can lead to the optimization of paediatric procedures and protocols in clinical practice. This study analyses the biokinetic behaviour of ^99mTc-dimercaptosuccinic acid (DMSA), in 8 infants aged 4 months to 2 years old, through an imaging study using a gamma camera, and compares the obtained values with those obtained with the reference ICRP biokinetic model. The in vivo data was treated using an adapted methodology from the MIRD 16 pamphlet. Activity curves for the liver, the kidney and the whole body, were built, and new effective absorption, retention and excretion half-lives were estimated, and compared with the reference biokinetic parameters of ICRP 128. The obtained residence time in the kidneys of 2.56 h, has a deviation of 30.8% to the ICRP 128 value of 3.70 h. The obtained maximum uptake in the kidneys was of 0.22/A₀, which compares to the value of 0.31/A₀ for ICRP. The obtained biokinetic parameters were used to estimate the absorbed dose. The obtained dose values are smaller than the reference ICRP 128 ones by 32.1% in the kidneys, and 18.4% in the liver.

PATIENT-SPECIFIC DOSIMETRY FOR PEDIATRIC IMAGING OF 99mTc-DIMERCAPTOSUCCINIC ACID WITH GATE MONTE CARLO CODE

In this study, radiation absorbed dose of 99mTc-dimercaptosuccinic acid (DMSA) in critical organs was calculated using Monte Carlo simulation. Ten child patients with genitourinary abnormalities were imaged using a series of planar, SPECT and MRI, after injection with 99mTc-DMSA. Patient-specific organ segmentation was performed on MRI and used as input in GATE. Organs with substantial uptake included kidneys, bladder and liver. The mean organ absorbed dose coefficients (mGy/MBq) were 0.063, 0.058, 0.018, 0.016, 0.013 and 0.010 for the right kidney, left kidney, bones, urinary bladder wall, liver and gonads, respectively. The absorbed dose coefficients in the remainder of the body was 0.012 mGy/MBq. The authors implemented an image-based Monte Carlo method for patient-specific 3D absorbed dose calculation. This study also demonstrates the possibility to obtain patient-specific attenuation map from MRI to be used for the simulations of radiation transport and energy deposition in phantom using Monte Carlo methods.

Nuclear Medicine in Pediatric Nephro-Urology: An Overview

In the context of ante-natally diagnosed hydronephrosis, the vast majority of children with a dilated renal pelvis do not need any surgical treatment, as the dilatation resolves spontaneously with time. Slow drainage demonstrated at Tc-99m-mercaptoacetyltriglycine (MAG3) renography does not necessarily mean obstruction. Obstruction is defined as resistance to urinary outflow with urinary stasis at the level of the pelvic-ureteric junction (PUJ) which, if left untreated, will damage the kidney. Unfortunately this definition is retrospective and not clinically helpful. Therefore, the identification of the kidney at risk of losing function in an asymptomatic patient is a major research goal. In the context of renovascular hypertension a DMSA scan can be useful before and after revascularisation procedures (angioplasty or surgery) to assess for gain in kidney function. Renal calculi are increasingly frequent in children. Whilst the vast majority of patients with renal stones do not need functional imaging, DMSA scans with SPECT and a low dose limited CT can be very helpful in the case of complex renal calculi. Congenital renal anomalies such as duplex kidneys, horseshoe kidneys, crossed-fused kidneys and multi-cystic dysplastic kidneys greatly benefit from functional imaging to identify regional parenchymal function, thus directing further management. Positron emission tomography (PET) is being actively tested in genito-urinary malignancies. Encouraging initial reports suggest that F-18-fluorodeoxyglucose (FDG) PET is more sensitive than CT in the assessment of lymph nodal metastases in patients with genito-urinary sarcomas; an increased sensitivity in comparison to isotope bone scans for skeletal metastatic disease has also been reported. Further evaluation is necessary, especially with the promising advent of PET/MRI scanners. Nuclear Medicine in paediatric nephro-urology has stood the test of time and is opening up to new exciting developments.

Detection of salivary aspiration using radionuclide salivagram SPECT/CT in patients with COPD exacerbation: a preliminary study

BACKGROUND

The aim of this prospective study was to assess the utility of radionuclide salivagram for detecting salivary aspiration in AECOPD patients and to evaluate the adding value of SPECT/CT to planar imaging.

METHODS

52 consecutive AECOPD patients underwent radionuclide salivagram SPECT/CT and water swallow test between April 2012 and March 2014. All images were interpreted independently by two experienced nuclear medicine physicians. Final diagnosis was made by consensus of two readers. The radionuclide salivagram and water swallow test results were compared using kappa values. The relationship between radionuclide salivagram results and exacerbation frequency was evaluated with the Person χ² test.

RESULTS

Salivary aspiration was diagnosed by radionuclide salivagram in 17 of 52 patients. Aspiration into the right main bronchus and branch was seen in 8 patients, bilateral main bronchi in 6 patients, and left lung field in 3 patients. SPECT/CT provided more accurate information on the extent and location of salivary aspiration, in 11 cases, SPECT/CT demonstrated aspiration of pulmonary segment bronchus and the following areas. Moreover, SPECT/CT revealed salivary aspiration corresponding to aspiration pneumonia in 8 cases. There was general agreement between the radionuclide salivagram and water swallow test results (Kappa =0.712; 95% CI, 0.504-0.920; P<0.001). The incidence of frequent exacerbations was greater among subjects with positive salivagram than among those with negative salivagram results (RR =3.43; 95% CI, 1.90-6.19; P<0.001).

CONCLUSIONS

Radionuclide salivagram is an objective method for detecting salivary aspiration in AECOPD patients. Moreover, SPECT/CT can identify more precise location of salivary aspiration and suggest a possible role for saliva in the pathophysiology of aspiration pneumonia.

Assessment of radiation dose in nuclear cardiovascular imaging using realistic computational models

PURPOSE

Nuclear cardiology plays an important role in clinical assessment and has enormous impact on the management of a variety of cardiovascular diseases. Pediatric patients at different age groups are exposed to a spectrum of radiation dose levels and associated cancer risks different from those of adults in diagnostic nuclear medicine procedures. Therefore, comprehensive radiation dosimetry evaluations for commonly used myocardial perfusion imaging (MPI) and viability radiotracers in target population (children and adults) at different age groups are highly desired.

METHODS

Using Monte Carlo calculations and biological effects of ionizing radiation VII model, we calculate the S-values for a number of radionuclides (Tl-201, Tc-99m, I-123, C-11, N-13, O-15, F-18, and Rb-82) and estimate the absorbed dose and effective dose for 12 MPI radiotracers in computational models including the newborn, 1-, 5-, 10-, 15-yr-old, and adult male and female computational phantoms.

RESULTS

For most organs, (201)Tl produces the highest absorbed dose whereas (82)Rb and (15)O-water produce the lowest absorbed dose. For the newborn baby and adult patient, the effective dose of (82)Rb is 48% and 77% lower than that of (99m)Tc-tetrofosmin (rest), respectively.

CONCLUSIONS

(82)Rb results in lower effective dose in adults compared to (99m)Tc-labeled tracers. However, this advantage is less apparent in children. The produced dosimetric databases for various radiotracers used in cardiovascular imaging, using new generation of computational models, can be used for risk-benefit assessment of a spectrum of patient population in clinical nuclear cardiology practice.

Radiation doses for pediatric nuclear medicine studies: comparing the North American consensus guidelines and the pediatric dosage card of the European Association of Nuclear Medicine

BACKGROUND

Estimated radiation dose is important for assessing and communicating the risks and benefits of pediatric nuclear medicine studies. Radiation dose depends on the radiopharmaceutical, the administered activity, and patient factors such as age and size. Most radiation dose estimates for pediatric nuclear medicine have not been based on administered activities of radiopharmaceuticals recommended by established practice guidelines. The dosage card of the European Association of Nuclear Medicine (EANM) and the North American consensus guidelines each provide recommendations of administered activities of radiopharmaceuticals in children, but there are substantial differences between these two guidelines.

OBJECTIVE

For 12 commonly performed pediatric nuclear medicine studies, two established pediatric radiopharmaceutical administration guidelines were used to calculate updated radiation dose estimates and to compare the radiation exposure resulting from the recommendations of each of the guidelines.

MATERIALS AND METHODS

Estimated radiation doses were calculated for 12 common procedures in pediatric nuclear medicine using administered activities recommended by the dosage card of the EANM (version 1.5.2008) and the 2010 North American consensus guidelines for radiopharmaceutical administered activities in pediatrics. Based on standard models and nominal age-based weights, radiation dose was estimated for typical patients at ages 1, 5, 10 and 15 years and adult. The resulting effective doses were compared, with differences greater than 20% considered significant.

RESULTS

Following either the EANM dosage card or the 2010 North American guidelines, the highest effective doses occur with radiopharmaceuticals labeled with fluorine-18 and iodine-123. In 24% of cases, following the North American consensus guidelines would result in a substantially higher radiation dose. The guidelines of the EANM dosage card would lead to a substantially higher radiation dose in 39% of all cases, and in 62% of cases in which patients were age 5 years or younger.

CONCLUSION

For 12 commonly performed pediatric nuclear medicine studies, updated radiation dose estimates can guide efforts to reduce radiation exposure and provide current information for discussing radiation exposure and risk with referring physicians, patients and families. There can be substantial differences in radiation exposure for the same procedure, depending upon which of these two guidelines is followed. This discordance identifies opportunities for harmonization of the guidelines, which may lead to further reduction in nuclear medicine radiation doses in children.

Gender-based differences in pediatric nuclear medicine

Gender-based differences commonly encountered in pediatric nuclear medicine reflect both basic embryologic differences of the sexes, which are evident from infancy, and evolving physiological changes due to gender, which occur as the pediatric patient grows, undergoes puberty, and matures to adulthood. It is important for a nuclear medicine physician or radiologist to know both the gender and the age of a patient when interpreting her or his studies. It is also important that the reading physician be familiar with the normally evolving physiological changes that are specific for that patient's stage of development. It is particularly important that the reading physician consider such changes when comparing serial studies of the patient that are acquired during the patient's transitions through her or his different significant stages of development. Many pediatric nuclear medicine imaging protocols are modifications or adaptations of the protocols for adult imaging. Physicians reading pediatric studies must routinely incorporate knowledge on age and gender that is relevant to the patient for any given study. The age-defined gender-based subtleties of potential findings in pediatric nuclear medicine studies are often underrecognized. However, they are often of interest and at times important in the workup of both benign entities and pathologic processes of the pediatric patient.

Select the optimized effective dose to reduce nuclear radiations in pediatric nuclear medicine

Many techniques and research models on calculating and reducing the nuclear radiation dose on pediatric nuclear medicine procedure have been developed and reported in recent years. However, most those models either utilized simple shapes to present the organs or used more realistic models to estimate the nuclear dose applied on pediatric patients. The former are too simple to provide accurate estimation results, and the latter are too complicated to intensively involve complex calculations. In this study, a simple but practical model is developed to enable physicians to easily and quickly calculate and select the average optimal effective nuclear dose for the given age and body-size of the pediatric patients. This model is built based on one research result reported by Frederic Fahey, et al and it can be easily implemented in most common pediatric nuclear medicine procedures. This is the first research of using fuzzy inference system to calculate the optimal effective dose applied in the nuclear medicine for pediatric patients.

Japanese consensus guidelines for pediatric nuclear medicine. Part 1: Pediatric radiopharmaceutical administered doses (JSNM pediatric dosage card). Part 2: Technical considerations for pediatric nuclear medicine imaging procedures

The Japanese Society of Nuclear Medicine has recently published the consensus guidelines for pediatric nuclear medicine. This article is the English version of the guidelines. Part 1 proposes the dose optimization in pediatric nuclear medicine studies. Part 2 comprehensively discusses imaging techniques for the appropriate conduct of pediatric nuclear medicine procedures, considering the characteristics of imaging in children.

Evaluation of radiation dose to anthropomorphic paediatric models from positron-emitting labelled tracers

PET uses specific molecules labelled with positron-emitting radionuclides to provide valuable biochemical and physiological information. However, the administration of radiotracers to patients exposes them to low-dose ionizing radiation, which is a concern in the paediatric population since children are at a higher cancer risk from radiation exposure than adults. Therefore, radiation dosimety calculations for commonly used positron-emitting radiotracers in the paediatric population are highly desired. We evaluate the absorbed dose and effective dose for 19 positron-emitting labelled radiotracers in anthropomorphic paediatric models including the newborn, 1-, 5-, 10- and 15-year-old male and female. This is achieved using pre-calculated S-values of positron-emitting radionuclides of UF-NCI paediatric phantoms and published biokinetic data for various radiotracers. The influence of the type of anthropomorphic model, tissue weight factors and direct human- versus mouse-derived biokinetic data on the effective dose for paediatric phantoms was also evaluated. In the case of (18)F-FDG, dosimetry calculations of reference paediatric patients from various dose regimens were also calculated. Among the considered radiotracers, (18)F-FBPA and (15)O-water resulted in the highest and lowest effective dose in the paediatric phantoms, respectively. The ICRP 103 updated tissue-weighting factors decrease the effective dose in most cases. Substantial differences of radiation dose were observed between direct human- versus mouse-derived biokinetic data. Moreover, the effect of using voxel- versus MIRD-type models on the calculation of the effective dose was also studied. The generated database of absorbed organ dose and effective dose for various positron-emitting labelled radiotracers using new generation computational models and the new ICRP tissue-weighting factors can be used for the assessment of radiation risks to paediatric patients in clinical practice. This work also contributes to a better understanding of the factors influencing patient-specific radiation dose calculation.

Imaging, radiation exposure, and attributable cancer risk for neonates with necrotizing enterocolitis

PURPOSE

Neonates with necrotizing enterocolitis (NEC) receive numerous radiologic investigations that potentially increase their lifetime cancer mortality risk. We evaluated our radiologic practice pattern for patients with NEC and estimated cumulative radiation exposure and lifetime cancer risk.

METHODS

Infants with NEC in a tertiary care NICU had patient demographics, imaging, treatments/interventions, and outcomes analyzed over 3 years. The number and type of imaging were recorded, including NEC-related imaging (thoraco-abdominal "babygrams" and abdominal radiographs), and all other imaging modalities. Patients were stratified by birth weight: group 1 (<750 g); group 2 (751-1500 g); and group 3 (>1501 g). Pre-existing normative data were used to calculate radiation exposure, absorption, and attributable cancer risk from NEC-related imaging.

RESULTS

Sixty-four neonates with 72 episodes of NEC were identified. Overall survival was 75.0%. When stratified by birth weight, mean abdominal radiographs and babygrams comprised 51%, 60%, and 74% of total imaging, giving median mGy doses of 2.1, 0.4, and 0.2, respectively. Compared to normative data, radiation dosing, and median cumulative cancer lifetime mortality risk increased by an average of 4.3× from baseline, with two cases documenting a 20-fold increase.

CONCLUSION

Neonates with NEC are exposed to significant amounts of radiation directly attributable to disease surveillance. Non-radiologic surveillance methods could significantly reduce radiation exposure and cancer risk in these infants.

Utility of salivagram in pulmonary aspiration in pediatric patients: comparison of salivagram and chest radiography

OBJECTIVE

The purpose of our study was to correlate the results of the radionuclide salivagram with the corresponding chest radiography findings on patients being evaluated for salivary aspiration to determine the utility of the salivagram.

MATERIALS AND METHODS

We identified 222 patients younger than 21 years who underwent salivagram and chest radiography within 3 months of each other. Salivagrams were blindly interpreted by two readers and chest radiographs were blindly interpreted by two other readers. The kappa coefficient with 95% CI was used to measure the level of interobserver agreement. Multivariate logistic regression was applied to determine whether age, sex, and neurologic diagnosis were predictors of a positive salivagram, with the odds ratio used to estimate association.

RESULTS

Interobserver agreement on salivagram interpretation was excellent (κ = 0.988; p < 0.0001; 95% CI, 0.968-1.000). Interobserver agreement on chest radiography interpretation was excellent (κ = 0.905; p < 0.0001; 95% CI, 0.845-0.965). The salivagram was positive for aspiration in 55 patients (25%). Chest radiography was positive in 54 patients (24%). When the interpretations of the salivagram (normal or abnormal) were compared with interpretations of the chest radiograph (normal or abnormal), there were 213 agreements and nine disagreements (intermethod agreement κ = 0.891; p < 0.0001; 95% CI, 0.831-0.952). Independent of age (p = 0.80) and sex (p = 0.31), patients with a neurologic diagnosis had odds of a positive salivagram 5.6 times higher than other diagnoses (odds ratio = 5.6; 95% CI, 2.5-13.1; p < 0.0001).

CONCLUSION

Infants with abnormal findings on salivagrams also had a high rate of abnormal findings on chest radiographs, which may indicate that some of the lung disease may be due to aspirated saliva. Salivagrams may be useful in children at risk of aspiration to identify those in whom intervention may help minimize the consequences of aspiration.

Comparison between the radionuclide salivagram and videofluoroscopic swallowing study methods for evaluating patients with aspiration pneumonia

OBJECTIVE

A videofluoroscopic swallowing study (VFSS) is generally used to assess dysphagia and aspiration, although false-negative results may be obtained. Saliva aspiration may cause false-negative VFSS findings in elderly people. A radionuclide salivagram can be useful in detecting saliva aspiration. We therefore compared these two methods for the evaluation of patients with aspiration pneumonia.

METHODS

We prospectively enrolled 50 patients with aspiration pneumonia into this study. All patients underwent VFSS, and were evaluated on the Penetration-Aspiration Scale. A salivagram was performed on the day after VFSS and each patient received 1 mL Tc-99 m DTPA sublingually. Both dynamic and delayed images were obtained.

RESULTS

Aspiration was observed in 34% of patients by salivagram and in 42% by VFSS. The frequency of tests that were positive for aspiration pneumonia using a combination of the two methods was 52%. Five patients with positive aspiration findings on salivagram were negative on VFSS. The association between VFSS and salivagram findings was significant but the total agreement was 72%. The frequency of aspiration pneumonia was significantly associated with an abnormal salivagram finding.

CONCLUSIONS

A salivagram may be a useful method for the evaluation of aspiration in elderly people, and a combination of the VFSS and salivagram methods could enable a more effective investigation of aspiration pneumonia.

Minimizing and communicating radiation risk in pediatric nuclear medicine

The value of pediatric nuclear medicine is well established. Pediatric patients are referred to nuclear medicine from nearly all pediatric specialties including urology, oncology, cardiology, gastroenterology, and orthopedics. Radiation exposure is associated with a potential, small, risk of inducing cancer in the patient later in life and is higher in younger patients. Recently, there has been enhanced interest in exposure to radiation from medical imaging. Thus, it is incumbent on practitioners of pediatric nuclear medicine to have an understanding of dosimetry and radiation risk to communicate effectively with their patients and their families. This article reviews radiation dosimetry for radiopharmaceuticals and also CT given the recent proliferation of PET/CT and SPECT/CT. It also describes the scientific basis for radiation risk estimation in the context of pediatric nuclear medicine. Approaches for effective communication of risk to patients' families are discussed. Lastly, radiation dose reduction in pediatric nuclear medicine is explicated.

Internal photon and electron dosimetry of the newborn patient--a hybrid computational phantom study

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.