Estimation of the Risk of Cancer Associated with Pediatric Cranial Computed Tomography.

Background: The role of Computed Tomography (CT) in the medical diagnosis of diseases has greatly expanded, despite the potential risk of cancer following exposures to ionising radiation (X-Ray) from this modality. This risk is particularly of great concern in children, who are more radiosensitive and have many years to manifest radiation effect than adults. Aims: To estimate risk of cancer induction from Pediatric cranial CT. Materials and Methods: A total of 203 patients, who were referred from various pediatric clinics and wards for cranial CT in a teaching hospital in the South Western Nigeria between the year 2011 and 2013 were considered. All patients were grouped into four age (year) groups: less than 1, 1-5, 5-10 and 10-15. A mathematical method was used to estimate the risk of cancer from the effective dose(ED) calculated from volume computed tomography dose index (CTDIvol), dose length product (DLP) and standard conversion factor. Results: The range of CTDIvol (mGy) received by all patients was 10–250 mGy while majority of the patients received 50–100. The range of DLP (mGy.cm) received by all patients and majority of patients was 500–5000 and 2001–2500 respectively. The range of ED (mSv) received by all patients and majority of the patients was 1–25 and 5–10 respectively. The risk estimated with respect to patients’ age showed that patient in the age group 1–5 years have the highest risk of cancer induction while the risk based on gender showed no significant difference. Conclusion: Over 60% of pediatric patients received more than the recommended values of CTDIvol, DLP and ED from cranial CT. Urgent steps must be taken to ensure compliant with international recommended precautions for dose reduction in pediatric medical imaging.

Towards Routine Clinical Use of Radial Stack-of-Stars 3D Gradient-Echo Sequences for Reducing Motion Sensitivity

PURPOSE: To describe how a robust implementation of a radial 3D gradient-echo sequence with stack-of-stars sampling can be achieved, to review the imaging properties of radial acquisitions, and to share the experience from more than 5000 clinical patient scans. MATERIALS AND METHODS: A radial stack-of-stars sequence was implemented and installed on 9 clinical MR systems operating at 1.5 and 3 Tesla. Protocols were designed for various applications in which motion artifacts frequently pose a problem with conventional Cartesian techniques. Radial scans were added to routine examinations without selection of specific patient cohorts. RESULTS: Radial acquisitions show significantly lower sensitivity to motion and allow examinations during free breathing. Elimination of breath-holding reduces failure rates for non-compliant patients and enables imaging at higher resolution. Residual artifacts appear as streaks, which are easy to identify and rarely obscure diagnostic information. The improved robustness comes at the expense of longer scan durations, the requirement for fat suppression, and the nonexistence of a time-to-center value. Care needs to be taken during the configuration of receive coils. CONCLUSION: Routine clinical use of radial stack-of-stars sequences is feasible with current MR systems and may serve as substitute for conventional fat-suppressed T1-weighted protocols in applications where motion is likely to degrade the image quality.

Image Quality in Pediatric Imaging in Association with Use of Sedation and General Anaesthesia

Introduction: The accuracy of image interpretations of CT and MRI studies is absolutely dependent on the quality of the images produced. Motion artifacts which result from the patients' movement during image acquisitions may lead to misinterpretation, wrong diagnosis or inconclusive examinations. In pediatric age groups, most of CT and MRI examinations require sedation or general anesthesia to achieve the degree of cooperation or immobilisation to complete the procedures successfully. Methods: The patients were randomly chosen among children, from newborn to 12 years of age who underwent sedation and general anesthesia for CT scan and and MRI in the University of Malaya Medical Centre between September 2001 and August 2003. The quality of MRI and CT images were evaluated by radiologists using a three-point scale: 1-no motion artifact; 2-minor motion artifacts and 3-major motion artifacts. Results: Among sedated children, 75.5% and 41% had good CT and MRI images respectively. In general, the anesthesia group, 100% had good CT images and 85.7% had good MRI images. Children who received sedation (33.5%) had severe motion artifacts whereas none of the anesthetised children had severe motion artifacts. Conclusion: General anesthesia is much better for good quality images in both MRI and CT examinations; however it is associated with a higher cost and longer hospital stay. Combination of oral chloral hydrate and intravenous midazolam was found to be the most effective sedative agent in terms of CT/MRI image quality.