Robert D. MacDougall

Managing Radiation Dose from Thoracic Multidetector Computed Tomography in Pediatric Patients: Background, Current Issues, and Recommendations

This review includes an overview of the fundamental physics and dose metrics of multidetector computed tomography (MDCT), a brief summary of research concerning health effects of ionizing radiation with an emphasis on risks to children, research of dose optimization, and practical recommendations that can be implemented immediately at the radiologists own center. It is hoped that by combining results of recent research, this review will provide valuable information for the practicing radiologist. The sections of this review were designed such that each section can be read independently or skipped depending on the level of expertise of the reader.

Size-based protocol optimization using automatic tube current modulation and automatic kV selection in computed tomography

Size-based diagnostic reference ranges (DRRs) for contrast-enhanced pediatric abdominal computed tomography (CT) have been published in order to establish practical upper and lower limits of CTDI, DLP, and SSDE. Based on these DRRs, guidelines for establishing size-based SSDE target levels from the SSDE of a standard adult by applying a linear correction factor have been published and provide a great reference for dose optimization initiatives. The necessary step of designing manufacturer-specific CT protocols to achieve established SSDE targets is the responsibility of the Qualified Medical Physicist. The task is straightforward if fixed-mA protocols are used, however, more difficult when automatic exposure control (AEC) and automatic kV selection are considered. In such cases, the physicist must deduce the operation of AEC algorithms from technical documentation or through testing, using a wide range of phantom sizes. Our study presents the results of such testing using anthropomorphic phantoms ranging in size from the newborn to the obese adult. The effect of each user-controlled parameter was modeled for a single-manufacturer AEC algorithm (Siemens CARE Dose4D) and automatic kV selection algorithm (Siemens CARE kV). Based on the results presented in this study, a process for designing mA-modulated, pediatric abdominal CT protocols that achieve user-defined SSDE and kV targets is described. PACS numbers: 87.57.Q-, 87.57.qp, 87.53.Bn.Size‐based diagnostic reference ranges (DRRs) for contrast‐enhanced pediatric abdominal computed tomography (CT) have been published in order to establish practical upper and lower limits of CTDI, DLP, and SSDE. Based on these DRRs, guidelines for establishing size‐based SSDE target levels from the SSDE of a standard adult by applying a linear correction factor have been published and provide a great reference for dose optimization initiatives. The necessary step of designing manufacturer‐specific CT protocols to achieve established SSDE targets is the responsibility of the Qualified Medical Physicist. The task is straightforward if fixed‐mA protocols are used, however, more difficult when automatic exposure control (AEC) and automatic kV selection are considered. In such cases, the physicist must deduce the operation of AEC algorithms from technical documentation or through testing, using a wide range of phantom sizes. Our study presents the results of such testing using anthropomorphic phantoms ranging in size from the newborn to the obese adult. The effect of each user‐controlled parameter was modeled for a single‐manufacturer AEC algorithm (Siemens CARE Dose4D) and automatic kV selection algorithm (Siemens CARE kV). Based on the results presented in this study, a process for designing mA‐modulated, pediatric abdominal CT protocols that achieve user‐defined SSDE and kV targets is described. PACS numbers: 87.57.Q‐, 87.57.qp, 87.53.Bn

Ionizing radiation from computed tomography versus anesthesia for magnetic resonance imaging in infants and children: patient safety considerations

In the context of health care, risk assessment is the identification, evaluation and estimation of risk related to a particular clinical situation or intervention compared to accepted medical practice standards. The goal of risk assessment is to determine an acceptable level of risk for a given clinical treatment or intervention in association with the provided clinical circumstances for a patient or group of patients. In spite of the inherent challenges related to risk assessment in pediatric cross-sectional imaging, the potential risks of ionizing radiation and sedation/anesthesia in the pediatric population are thought to be quite small. Nevertheless both issues continue to be topics of discussion concerning risk and generate significant anxiety and concern for patients, parents and practicing pediatricians. Recent advances in CT technology allow for more rapid imaging with substantially lower radiation exposures, obviating the need for anesthesia for many indications and potentially mitigating concerns related to radiation exposure. In this review, we compare and contrast the potential risks of CT without anesthesia against the potential risks of MRI with anesthesia, and discuss the implications of this analysis on exam selection, providing specific examples related to neuroblastoma surveillance imaging.

Quality of pediatric abdominal CT scans performed at a dedicated children’s hospital and its referring institutions: a multifactorial evaluation

BackgroundPediatric patients requiring transfer to a dedicated children’s hospital from an outside institution may undergo CT imaging as part of their evaluation. Whether this imaging is performed prior to or after transfer has been shown to impact the radiation dose imparted to the patient. Other quality variables could also be affected by the pediatric experience and expertise of the scanning institution.ObjectiveTo identify differences in quality between abdominal CT scans and reports performed at a dedicated children’s hospital, and those performed at referring institutions.Materials and methodsFifty consecutive pediatric abdominal CT scans performed at outside institutions were matched (for age, gender and indication) with 50 CT scans performed at a dedicated freestanding children’s hospital. We analyzed the scans for technical parameters, report findings, correlation with final clinical diagnosis, and clinical utility. Technical evaluation included use of intravenous and oral contrast agents, anatomical coverage, number of scan phases and size-specific dose estimate (SSDE) for each scan. Outside institution scans were re-reported when the child was admitted to the children’s hospital; they were also re-interpreted for this study by children’s hospital radiologists who were provided with only the referral information given in the outside institution’s report. Anonymized original outside institutional reports and children’s hospital admission re-reports were analyzed by two emergency medicine physicians for ease of understanding, degree to which the clinical question was answered, and level of confidence in the report.ResultsMean SSDE was lower (8.68) for children’s hospital scans, as compared to outside institution scans (13.29, P = 0.03). Concordance with final clinical diagnosis was significantly lower for original outside institution reports (38/48, 79%) than for both the admission and study children’s hospital reports (48/50, 96%; P = 0.005). Children’s hospital admission reports were rated higher than outside institution reports for completeness, ease of understanding, answering of clinical question, and level of confidence of the report (P < 0.001).ConclusionPediatric abdominal CT scans performed and interpreted at a dedicated children’s hospital are associated with higher technical quality, lower radiation dose and a more clinically useful report than those performed at referring institutions.

Operational and Dosimetric Aspects of Pediatric PET/CT

No consistent guidelines exist for the acquisition of a CT scan as part of pediatric PET/CT. Given that children may be more vulnerable to the effects of ionizing radiation, it is necessary to develop methods that provide diagnostic-quality imaging when needed, in the shortest time and with the lowest patient radiation exposure. This article describes the basics of CT dosimetry and PET/CT acquisition in children. We describe the variability in pediatric PET/CT techniques, based on a survey of 19 PET/CT pediatric institutions in North America. The results of the survey demonstrated that, although most institutions used automatic tube current modulation, there remained a large variation of practice, on the order of a factor of 2–3, across sites, pointing to the need for guidelines. We introduce the approach developed at our institution for using a multiseries PET/CT acquisition technique that combines diagnostic-quality CT in the essential portion of the field of view and a low-dose technique to image the remainder of the body. This approach leads to a reduction in radiation dose to the patient while combining the PET and the diagnostic CT into a single acquisition. The standardization of pediatric PET/CT provides an opportunity for a reduction in the radiation dose to these patients while maintaining an appropriate level of diagnostic image quality.

Selecting appropriate gastroenteric contrast media for diagnostic fluoroscopic imaging in infants and children: a practical approach

In our experience, questions about the appropriate use of enteric contrast media for pediatric fluoroscopic studies are common. The purpose of this article is to provide a comprehensive review of enteric contrast media used for pediatric fluoroscopy, highlighting the routine use of these media at a large tertiary care pediatric teaching hospital.

How we read pediatric PET/CT: indications and strategies for image acquisition, interpretation and reporting

PET/CT plays an important role in the diagnosis, staging and management of many pediatric malignancies. The techniques for performing PET/CT examinations in children have evolved, with increasing attention focused on reducing patient exposure to ionizing radiation dose whenever possible and minimizing scan duration and sedation times, with a goal toward optimizing the overall patient experience.This review outlines our approach to performing PET/CT, including a discussion of the indications for a PET/CT exam, approaches for optimizing the exam protocol, and a review of different approaches for acquiring the CT portion of the PET/CT exam. Strategies for PACS integration, image display, interpretation and reporting are also provided.Most practices will develop a strategy for performing PET/CT that best meets their respective needs. The purpose of this article is to provide a comprehensive overview for radiologists who are new to pediatric PET/CT, and also to provide experienced PET/CT practitioners with an update on state-of-the art CT techniques that we have incorporated into our protocols and that have enabled us to make considerable improvements to our PET/CT practice.

Development of a tool to aid the radiologic technologist using augmented reality and computer vision

This technical innovation describes the development of a novel device to aid technologists in reducing exposure variation and repeat imaging in computed and digital radiography. The device consists of a color video and depth camera in combination with proprietary software and user interface. A monitor in the x-ray control room displays the position of the patient in real time with respect to automatic exposure control chambers and image receptor area. The thickness of the body part of interest is automatically displayed along with a motion indicator for the examined body part. The aim is to provide an automatic measurement of patient thickness to set the x-ray technique and to assist the technologist in detecting errors in positioning and motion before the patient is exposed. The device has the potential to reduce the incidence of repeat imaging by addressing problems technologists encounter daily during the acquisition of radiographs.

Sinus Computed Tomography Imaging in Pediatric Cystic Fibrosis: Added Value?

Study Objective To evaluate the prevalence of computed tomography (CT) sinus imaging in a pediatric cystic fibrosis (CF) population, determine changes in Lund Mackay (LM) scores over time, and estimate radiation exposure. Study Design Case series with chart review. Setting Tertiary care children’s hospital. Subjects and Methods In total, 202 pediatric patients with CF who underwent endoscopic sinus surgery (ESS) were included. The total number of CT scans was calculated for each patient, with specific focus on the indications for and subsequent outcomes of the sinus CT scan subgroup. Results Patients underwent a total of 1718 CT scans, 832 of which were sinus CT scans (mean of 4.2 sinus scans per patient). Disease evaluation (54%) and preoperative planning (35%) were the most common indications. Otolaryngologists were more likely to order imaging for preoperative evaluation, and those scans were more likely to result in surgery compared with those requested by other physicians (P < .001). Ninety CT scans (10.8%) led to no change in management. There was no significant difference in LM scores between patients admitted to the hospital or prescribed antibiotics and those who were not. There was also no significant change in LM score following ESS after adjusting for age and sex (P = .23). Conclusion Based on LM scores, all sinus CT scans in patients with CF reveal moderate to severe sinus disease. Effort should be made to minimize radiation exposure in patients with CF by limiting sinus CT scans to the preoperative context or for evaluation of potential sinusitis complications.

Urology mythbusters: Radiation and radiophobia

In this episode of Mythbusters we critically examine the premise that there is strong biological and epidemiologic evidence that radiation exposure at levels associated with modern genitourinary diagnostic imaging increases the risk of subsequent malignancy, especially in children.