Ultrasound diagnosis of hypertrophic pyloric stenosis - Time to change the criteria.

Introduction: Ultrasound is the examination of choice for the diagnosis of hypertrophic pyloric stenosis (HPS). A correct diagnosis is dependent on the technique and measurement accuracy. However, in the world literature there is a wide range of values suggested for the diagnosis of this condition. The current minimum measurements used to diagnose HPS seem excessively large, and therefore, we set out to redefine these values. Methods: A retrospective study was performed on 607 patients (615 scans) being investigated for HPS. The length and transverse diameter of the pyloric canal, and thickness of the pyloric muscle were measured. All results were correlated with clinical and surgical findings. Results: In this study, the muscle thickness in the normal group was <2.0 mm than in HPS infants having a muscle thickness of 2.0-5.0 mm. All the pyloric canal lengths in the normal group were <5.0 mm than in those with HPS having a length of 10.0-24.0 mm. The transverse diameters ranged from 6.0 to 11.0 mm in the normal group compared with those with HPS having a diameter between 8.0 and 16.0 mm. Conclusions: The current criteria for sonographic diagnosis of HPS should be redefined. The canal length is the single most important discriminator, with a clear separation between normal and abnormal. The commonly used 16.0-mm measurement is too long and should be reduced to 10.0 mm (without the risk of false positives). In many cases, the muscle thickness in those with HPS is as low as 2.0 mm, considerably less than the 3.0 mm that is currently used. The transverse diameter is not a useful discriminator for HPS. The use of current values will delay the diagnosis and timely treatment of this condition.

Comparison of glomerular filtration rates determined using two- and single-blood sample methods with a three-blood sample technique for 2922 paediatric studies.

OBJECTIVE: Several different methods for measuring glomerular filtration rates (GFRs) have been developed in search of a more accurate and simplified technique. Currently, the main methods used are the slope-intercept and distribution volume techniques. In this work, 2922 GFR studies have been retrospectively reanalysed as two- and single-blood sample methods and compared with the three-blood sample data. PATIENTS AND METHODS: Paediatric GFR data from 1/1/1993 to 4/12/2018 using the three-blood sample technique have been reanalysed as two- and single-blood sample methods. The timing of blood sampling was also reviewed. RESULTS: Both the two- and the single-sample methods provide accurate estimates of GFR in children for all levels of renal function provided that the blood samples are collected at the appropriate times post administration of the tracer. For the highest accuracy, blood for the two-blood samples method should be collected at 2 and 4 h and at 2 h for the single-blood sample method. The relationship between renal clearance and the 2-h volume of distribution (V120) is linear with a line of best fit: GFR (ml/min) = 3.108 × V120 - 2.557. CONCLUSION: Both the two- and the single-sample techniques can be used to measure GFR in children with the same accuracy as the three-blood sample. With the collection of only a single-blood sample, there are benefits to all involved: patients, families, and nuclear medicine personnel. In addition, institutions have a choice as to which technique to use and for which patients.

Radioiodine (131I) therapy in a child with autism spectrum disorder: A complex and demanding task.

In January 2017, an 11.5-year-old male child with autism was referred for radioiodine (RAI) therapy post total thyroidectomy for papillary thyroid carcinoma. The treatment required swallowing a RAI capsule and remaining isolated (48-72 h). Initially, obstacles to a successful treatment seemed insurmountable as he had complex needs and behavioral issues due to his autism, mild intellectual disability, and family environment. His mother was adamant that he would not be able to swallow the capsule and comply with the required isolation period. A multidisciplinary team was formed to explore options for successful treatment. Each option considered had its own risks and challenges. Behavioral therapy was considered to be the only possible option. It was pursued with regular, frequent contact between the child, his parents, and members of the team for counseling and behavioral modification, familiarization of the child with the staff, procedures, trial visits, and admission. The patient was successfully treated in October 2017.

Radioiodine (131I) therapies performed in a paediatric hospital: facilities and procedures.

Radioiodine (131I) therapies on younger children with thyroid cancer and neuroblastoma can be challenging as they are required to be isolated for a period of time due to radiation safety concerns. At our hospital these therapies are performed in a purpose-built child-friendly therapy room. Nursing staff are able to provide personal care during the isolation period with minimum radiation exposure. Patients are provided with various age-appropriate entertainment items such as iPad, X-Box, DVD, craft and books to keep them entertained while in isolation. Parents can communicate freely with their child via the audio-visual system located in the Ward Parent Lounge and can also stay in the shielded part of the ante room of the therapy room. Nursing staff can communicate with the patient via a similar audio-visual system located in the nurses station so that they only need to enter the therapy room when they are required to provide personal patient care. All persons entering the therapy room are monitored with personal digital dosimeters. Patients accept the isolation period with minimal aggravation and the personal radiation exposures to staff, parents and visitors are well below the general public annual limit of 1000 µSv. The design and facilities of the therapy room with its child-friendly surroundings and support network makes the experience of the isolation period easier and positive for both patients and parents. For Graves' disease, the patients are treated as outpatients in the Department of Nuclear Medicine and are discharged within a short time after the radioiodine administration.

A review of paediatric administered radiopharmaceutical activities to determine compliance with prescription guidelines.

OBJECTIVE: Attempts are underway to standardize paediatric administered activities, but equally important is knowing the actual activities administered to patients. In this work, paediatric administered activities are reviewed to determine compliance with the institution-prescribed guidelines. PATIENTS AND METHODS: Paediatric administered activities for common studies at our institution, August 2011 to January 2017, have been analysed to determine their deviations from the set guideline tolerance of 10% from prescribed activities. RESULTS: The results for technetium-99m hydroxy diphosphonate (Tc-HDP), technetium-99m mercaptoacetyl triglycine (Tc-MAG3) and technetium-99m dimercaptosuccinic acid (Tc-DMSA), are presented here. Tc-MAG3 mean activities were close to the tolerance guideline at 10.3% SD. For Tc-HDP and Tc-DMSA, the prescribed guidelines were reviewed and reduced in May 2014 and September 2015, respectively. SDs for these studies over the two acquisition periods were different (8.9 and 6.6%, respectively, for Tc-HDP and 11.8 and 14.2%, respectively, for Tc-DMSA).The administered activities (dispensed minus residual activities) to patients depend on prescribed activities and dispensing and injecting techniques. Deviations from the prescribed activities are primarily because of issues related to residual activities, particularly with small activities prescribed in young patients. Small activities in small volumes make residual activities significant. The skill and experience of the nuclear medicine staff are essential in minimizing deviations from prescribed activities. CONCLUSION: It is important to measure residual to accurately determine the administered activities. If precautions are taken with dispensing and injecting techniques, it is possible to administer activities close to 10% of the prescribed activities. The regular review of the administered activities is essential to ensure that patients are not unnecessarily irradiated.

Effective doses and standardised risk factors from paediatric diagnostic medical radiation exposures: Information for radiation risk communication.

INTRODUCTION: In the paediatric medical radiation setting, there is no consistency on the radiation risk information conveyed to the consumer (patient/carer). Each communicator may convey different information about the level of risk for the same radiation procedure, leaving the consumer confused and frustrated. There is a need to standardise risks resulting from medical radiation exposures. In this study, paediatric radiographic, fluoroscopic, CT and nuclear medicine examination data have been analysed to provide (i) effective doses and radiation induced cancer risk factors from common radiological and nuclear medicine diagnostic procedures in standardised formats, (ii) awareness of the difficulties that may be encountered in communicating risks to the layperson, and (iii) an overview of the deleterious effects of ionising radiation so that the risk communicator can convey with confidence the risks resulting from medical radiation exposures. METHODS: Paediatric patient dose data from general radiographic, computed tomography, fluoroscopic and nuclear medicine databases have been analysed in age groups 0 to <5 years, 5 to <10 years, 10 to <15 years and 15 to <18 years to determine standardised risk factors. RESULTS: Mean, minimum and maximum effective doses and the corresponding mean lifetime risks for general radiographic, fluoroscopic, CT and nuclear medicine examinations for different age groups have been calculated. For all examinations, the mean lifetime cancer induction risk is provided in three formats: statistical, fraction and category. CONCLUSION: Standardised risk factors for different radiological and nuclear medicine examinations and an overview of the deleterious effects of ionising radiation and the difficulties encountered in communicating the risks should facilitate risk communication to the patient/carer.

Shielding of medical imaging X-ray facilities: a simple and practical method.

The most widely accepted method for shielding design of X-ray facilities is that contained in the National Council on Radiation Protection and Measurements Report 147 whereby the computation of the barrier thickness for primary, secondary and leakage radiations is based on the knowledge of the distances from the radiation sources, the assumptions of the clinical workload, and usage and occupancy of adjacent areas. The shielding methodology used in this report is complex. With this methodology, the shielding designers need to make assumptions regarding the use of the X-ray room and the adjoining areas. Different shielding designers may make different assumptions resulting in different shielding requirements for a particular X-ray room. A more simple and practical method is to base the shielding design on the shielding principle used to shield X-ray tube housing to limit the leakage radiation from the X-ray tube. In this case, the shielding requirements of the X-ray room would depend only on the maximum radiation output of the X-ray equipment regardless of workload, usage or occupancy of the adjacent areas of the room. This shielding methodology, which has been used in South Australia since 1985, has proven to be practical and, to my knowledge, has not led to excess shielding of X-ray installations.

Diagnostic reference levels of paediatric computed tomography examinations performed at a dedicated Australian paediatric hospital.

INTRODUCTION: Diagnostic Reference Levels (DRL) of procedures involving ionizing radiation are important tools to optimizing radiation doses delivered to patients and in identifying cases where the levels of doses are unusually high. This is particularly important for paediatric patients undergoing computed tomography (CT) examinations as these examinations are associated with relatively high-dose. METHODS: Paediatric CT studies, performed at our institution from January 2010 to March 2014, have been retrospectively analysed to determine the 75th and 95th percentiles of both the volume computed tomography dose index (CTDIvol ) and dose-length product (DLP) for the most commonly performed studies to: establish local diagnostic reference levels for paediatric computed tomography examinations performed at our institution, benchmark our DRL with national and international published paediatric values, and determine the compliance of CT radiographer with established protocols. RESULTS: The derived local 75th percentile DRL have been found to be acceptable when compared with those published by the Australian National Radiation Dose Register and two national children's hospitals, and at the international level with the National Reference Doses for the UK. The 95th percentiles of CTDIvol for the various CT examinations have been found to be acceptable values for the CT scanner Dose-Check Notification. Benchmarking CT radiographers shows that they follow the set protocols for the various examinations without significant variations in the machine setting factors. CONCLUSION: The derivation of DRL has given us the tool to evaluate and improve the performance of our CT service by improved compliance and a reduction in radiation dose to our paediatric patients. We have also been able to benchmark our performance with similar national and international institutions.

Diagnostic reference levels for common paediatric fluoroscopic examinations performed at a dedicated paediatric Australian hospital.

INTRODUCTION: Diagnostic reference levels (DRL) of procedures involving ionising radiation are important tools for optimising radiation doses delivered to patients and to identify cases where the levels of dose are unusually high. This is particularly important for paediatric patients undergoing fluoroscopic examinations as these examinations can be associated with a high radiation dose. In this study, a large amount of paediatric fluoroscopic data has been analysed to: establish local DRL, identify the most significant factors determining radiation dose to patients, and modify fluoroscopic techniques to optimise the examination protocols. METHODS: Paediatric fluoroscopic studies performed at our institution from April 2010 to May 2015 have been retrospectively analysed to determine range, mean, 75th and 95th percentiles of Dose-Area Product (DAP) and fluoroscopic screening time for Micturating Cystourethrography (MCU), Airway, Airway and Swallow, Barium Swallow and Meal, Barium Follow Through and Barium Enema studies. RESULTS: Currently, no Australian paediatric fluoroscopic DRL data are available for comparison and thus our data can only be compared with international published data. No major changes to examination protocols or modification to fluoroscopic techniques were found necessary as our data compared well with the international published values. CONCLUSION: The dose delivered to patients depend on a number of factors particularly the experience of the operators. However, DRL are also important, as shown in this study, as they enable best practice by providing feedback to the operators on their performance and benchmarking the institution with other institutions.

Measurement uncertainty analysis of low-dose-rate prostate seed brachytherapy: post-implant dosimetry.

The minimal dose covering 90 % of the prostate volume--D 90--is arguably the most important dosimetric parameter in low-dose-rate prostate seed brachytherapy. In this study an analysis of the measurement uncertainties in D 90 from low-dose-rate prostate seed brachytherapy was conducted for two common treatment procedures with two different post-implant dosimetry methods. The analysis was undertaken in order to determine the magnitude of D 90 uncertainty, how the magnitude of the uncertainty varied when D 90 was calculated using different dosimetry methods, and which factors were the major contributors to the uncertainty. The analysis considered the prostate as being homogeneous and tissue equivalent and made use of published data, as well as original data collected specifically for this analysis, and was performed according to the Guide to the expression of uncertainty in measurement (GUM). It was found that when prostate imaging and seed implantation were conducted in two separate sessions using only CT images for post-implant analysis, the expanded uncertainty in D 90 values were about 25 % at the 95 % confidence interval. When prostate imaging and seed implantation were conducted during a single session using CT and ultrasound images for post-implant analysis, the expanded uncertainty in D 90 values were about 33 %. Methods for reducing these uncertainty levels are discussed. It was found that variations in contouring the target tissue made the largest contribution to D 90 uncertainty, while the uncertainty in seed source strength made only a small contribution. It is important that clinicians appreciate the overall magnitude of D 90 uncertainty and understand the factors that affect it so that clinical decisions are soundly based, and resources are appropriately allocated.

Background ionising radiation: a pictorial perspective.

Ionising radiation from natural sources, known as background radiation, has existed on earth since the earth's formation. The exposure of humans and other living creatures to this radiation is a feature of the earth's environment which is continuing and inescapable. The word "radiation" brings fear to many people: a fear of the unknown, as human's senses cannot detect the presence of ionising radiation. In this study, a catalogue of images of the distribution of radioactivity in every day objects and foods has been produced using an imaging plate from a computed radiography cassette. The aim of the study is that by visually demonstrating that every day objects and foods are radioactive would alleviate the fear of "radiation" by becoming aware that we live in a radioactive environment and even our body is radioactive.

Uncertainties in effective dose estimates of adult CT head scans: the effect of head size.

PURPOSE: This study is an extension of a previous study where the uncertainties in effective dose estimates from adult CT head scans were calculated using four CT effective dose estimation methods, three of which were computer programs (CT-EXPO, CTDOSIMETRY, and IMPACTDOSE) and one that involved the dose length product (DLP). However, that study did not include the uncertainty contribution due to variations in head sizes. METHODS: The uncertainties due to head size variations were estimated by first using the computer program data to calculate doses to small and large heads. These doses were then compared with doses calculated for the phantom heads used by the computer programs. An uncertainty was then assigned based on the difference between the small and large head doses and the doses of the phantom heads. RESULTS: The uncertainties due to head size variations alone were found to be between 4% and 26% depending on the method used and the patient gender. When these uncertainties were included with the results of the previous study, the overall uncertainties in effective dose estimates (stated at the 95% confidence interval) were 20%-31% (CT-EXPO), 15%-30% (CTDOSIMETRY), 20%-36% (IMPACTDOSE), and 31%-40% (DLP). CONCLUSIONS: For the computer programs, the lower overall uncertainties were still achieved when measured values of CT dose index were used rather than tabulated values. For DLP dose estimates, head size variations made the largest (for males) and second largest (for females) contributions to effective dose uncertainty. An improvement in the uncertainty of the DLP method dose estimates will be achieved if head size variation can be taken into account.

On the uncertainties in effective dose estimates of adult CT head scans.

Estimates of the effective dose to adult patients from computed tomography (CT) head scanning can be calculated using a number of different methods. These estimates can be used for a variety of purposes, such as improving scanning protocols, comparing different CT imaging centers, and weighing the benefits of the scan against the risk of radiation-induced cancer. The question arises: What is the uncertainty in these effective dose estimates? This study calculates the uncertainty of effective dose estimates produced by three computer programs (CT-EXPO, CTDosimetry, and ImpactDose) and one method that makes use of dose-length product (DLP) values. Uncertainties were calculated in accordance with an internationally recognized uncertainty analysis guide. For each of the four methods, the smallest and largest overall uncertainties (stated at the 95% confidence interval) were: 20%-31% (CT-EXPO), 15%-28% (CTDosimetry), 20%-36% (ImpactDose), and 22%-32% (DLP), respectively. The overall uncertainties for each method vary due to differences in the uncertainties of factors used in each method. The smallest uncertainties apply when the CT dose index for the scanner has been measured using a calibrated pencil ionization chamber.

Uncertainties of exposure-related quantities in mammographic x-ray unit quality control.

Breast screening programs operate in many countries with mammographic x-ray units subject to stringent quality control tests. These tests include the evaluation of quantities based on exposure measurements, such as half value layer, automatic exposure control reproducibility, average glandular dose, and radiation output rate. There are numerous error sources that contribute to the uncertainty of these exposure-related quantities, some of which are unique to the low energy x-ray spectrum produced by mammographic x-ray units. For each of these exposure-related quantities, the applicable error sources and their magnitudes vary, depending on the test equipment used to make the measurement, and whether or not relevant corrections have been applied. This study has identified and quantified a range of error sources that may be used to estimate the combined uncertainty of these exposure-related quantities, given the test equipment used and corrections applied. The uncertainty analysis uses methods described by the International Standards Organization's Guide to the Expression of Uncertainty in Measurement. Examples of how these error sources combine to give the uncertainty of the exposure-related quantities are presented. Using the best test equipment evaluated in this study, uncertainties of the four exposure-related quantities at the 95% confidence interval were found to be +/-1.6% (half value layer), +/-0.0008 (automatic exposure control reproducibility), +/-2.3% (average glandular dose), and +/-2.1% (radiation output rate). In some cases, using less precise test equipment or failing to apply corrections, resulted in uncertainties more than double in magnitude.