Radiation doses and risks from paediatric computed tomography

The use of computed tomography (CT) worldwide has increased dramatically since its introduction. In Australia, more than two million CT services are funded by Medicare every year and the rate of imaging is increasing beyond population growth. CT imaging currently accounts for the largest source of ionising radiation exposure to the population from all diagnostic procedures. There is a small, theoretical risk of carcinogenesis attributable to low doses of ionising radiation based on epidemiological evidence at higher doses and dose rates. The doses from CT examinations fall into this low dose range. Recognition of the potential radiation risks combined with the high utilisation of CT imaging has led to greater awareness of population health risks. Furthermore, the exposure risks from radiation are higher for children than for adults due to their increased radiosensitivity and greater prospective life expectancy. There is only limited information on Australian paediatric CT imaging rates, doses and risks. This thesis aims to assess the medical radiation exposure of children in Australia from CT examinations. An experimental method for paediatric CT organ dosimetry was developed using a physical anthropomorphic phantom representing a child and high sensitivity thermoluminescent dosemeters. Radiation doses for typical paediatric CT clinical protocols performed at the Royal Children’s Hospital (RCH) in Melbourne were quantified. An analysis of indirect dose computation methods was undertaken to identify a robust and reliable method for paediatric CT organ dosimetry feasible for clinical implementation. A practical method for assessing doses and scan parameters from a local dose survey was developed to enable identification of areas for dose optimisation. Local diagnostic reference levels were established based on the dose distributions from RCH patient data across all paediatric age groups. The first comprehensive analysis of CT imaging frequency and trends for the Australian paediatric population was undertaken. Finally, cancer risk projections for incidence and mortality from paediatric CT scanning have been made for the Australian population

Systems Radiology and Personalized Medicine

Medicine has evolved into a high level of specialization using the very detailed imaging of organs. This has impressively solved a multitude of acute health-related problems linked to single-organ diseases. Many diseases and pathophysiological processes, however, involve more than one organ. An organ-based approach is challenging when considering disease prevention and caring for elderly patients, or those with systemic chronic diseases or multiple co-morbidities. In addition, medical imaging provides more than a pretty picture. Much of the data are now revealed by quantitating algorithms with or without artificial intelligence. This Special Issue on “Systems Radiology and Personalized Medicine” includes reviews and original studies that show the strengths and weaknesses of structural and functional whole-body imaging for personalized medicine

Medical Robotics

The first generation of surgical robots are already being installed in a number of operating rooms around the world. Robotics is being introduced to medicine because it allows for unprecedented control and precision of surgical instruments in minimally invasive procedures. So far, robots have been used to position an endoscope, perform gallbladder surgery and correct gastroesophogeal reflux and heartburn. The ultimate goal of the robotic surgery field is to design a robot that can be used to perform closed-chest, beating-heart surgery. The use of robotics in surgery will expand over the next decades without any doubt. Minimally Invasive Surgery (MIS) is a revolutionary approach in surgery. In MIS, the operation is performed with instruments and viewing equipment inserted into the body through small incisions created by the surgeon, in contrast to open surgery with large incisions. This minimizes surgical trauma and damage to healthy tissue, resulting in shorter patient recovery time. The aim of this book is to provide an overview of the state-of-art, to present new ideas, original results and practical experiences in this expanding area. Nevertheless, many chapters in the book concern advanced research on this growing area. The book provides critical analysis of clinical trials, assessment of the benefits and risks of the application of these technologies. This book is certainly a small sample of the research activity on Medical Robotics going on around the globe as you read it, but it surely covers a good deal of what has been done in the field recently, and as such it works as a valuable source for researchers interested in the involved subjects, whether they are currently “medical roboticists” or not

Personalised advanced 3D dosimetry in peptide receptor radionuclide therapy

Peptide Receptor Radionuclide Therapy is one of the most efficient therapies against Neuro endocrine tumours. In clinical practice, absorbed dose calculations are computed based on the Medical Internal Radiation Dose (MIRD) schema which is not planned or optimised for patient-specific characteristics. This PhD project has aimed to assess the impact that advanced personalised 3D dosimetry can have within a Molecular Radiotherapy (MRT) treatment with an image-based dosimetry component. For this purpose, the impact of image registration algorithms has been studied, comparing rigid and non-rigid schemes. Results showed that nonrigid algorithms performed better than rigid equivalents in aligning images to the same frame of reference. The non-rigid algorithm was then used to investigate a workflow which involved dose maps instead of SPECT images, because such analysis has not previously been reported in the literature. Raydose, a Monte Carlo-based software package, was used to perform 3D personalised dosimetry; the results were compared against the calculations carried out with OLINDA/EXM, a MIRD-based software system. Differences were statistically significant only for kidneys and lesions (p-value<0.005). Finally, a new segmentation method for tumour delineation is described and its performance compared with a manual segmentation performed by expert 2 physicians. JACCARD analysis showed that the two methods do not have a good overlap (mean JACCARD coefficient = 0.29). From visual assessment, the proposed approach obtained better results than the manual segmentation according to the target tissue characteristics. Furthermore, quantitative analysis showed that the manual segmentation significantly overestimates the volume by 3.7 ± 13.3 cc (p-value<0.05), while it significantly underestimates the dose by -2.67 ± 6.8 Gy (p-value<0.05) compared to the proposed method. This study has demonstrated the importance of assessing accurate personalised 3D absorbed dose distribution to lesions and organs at risk. It also has the potentia

Deep Learning in Medical Image Analysis

The accelerating power of deep learning in diagnosing diseases will empower physicians and speed up decision making in clinical environments. Applications of modern medical instruments and digitalization of medical care have generated enormous amounts of medical images in recent years. In this big data arena, new deep learning methods and computational models for efficient data processing, analysis, and modeling of the generated data are crucially important for clinical applications and understanding the underlying biological process. This book presents and highlights novel algorithms, architectures, techniques, and applications of deep learning for medical image analysis

Investigating the ability to use the CT scan projection radiograph to monitor adolescent idiopathic scoliosis

Introduction: Adolescent idiopathic scoliosis (AIS) is a spinal deformity that causes the spine to bend laterally. Patients with AIS undergo frequent X-ray examinations to monitor the progression of the deformity through the measurement of the Cobb angle, increasing the risk of developing radiation-induced cancer. The aim of this study was to investigate the use of scan projection radiograph (SPR) in computed tomography (CT) to assess AIS by quantifying radiation dose from the SPR acquisitions and comparing it to those of digital radiography (DR) and a dedicated scoliosis imaging system (EOS) and by evaluating the accuracy of Cobb angle measurements on SPR images using a bespoke validated phantom. Methods: A dosimetry phantom representing a 10-year-old child and thermoluminescent dosimeters were used for measuring organ dose to calculate effective dose (ED) and effective risk (ER). Twenty-seven CT SPR protocols were used. A comparison was made to doses from imaging protocols using DR and the EOS system. The effectiveness of a scoliosis shawl for selected projections was also tested. To test the accuracy of Cobb angle measurements on SPR images, a scoliotic phantom was constructed and validated. Poly-methyl methacrylate (PMMA) and plaster of Paris (PoP) were used to represent human soft tissue and bone tissue, respectively, to construct a phantom exhibiting a 15° lateral curve of the spine. The phantom was validated by comparing the Hounsfield unit (HU) of its vertebrae with those of a human and an animal. Additionally, comparisons of signal-to-noise ratio (SNR) to those from a commercially available phantom were made. The angle of the curve in the phantom was measured directly to confirm that it was 15°. The constructed phantom was scanned in CT SPR mode, and the resulting images were visually evaluated against set criteria to determine their suitability for Cobb angle measurements. Those deemed of insufficient quality were excluded. Cobb angle measurements were then performed on the remaining images (n = 10) by 13 observers.Results: EOS had the lowest ED and ER when it was used to irradiate the phantom in AP positions. Five SPR AP imaging protocols and seven PA imaging protocols delivered significantly lower radiation dose and risk than their corresponding imaging positions in DR (p < 0.05). The scoliosis shawl significantly lowered the ED and ER of SPR and DR AP imaging protocols (p < 0.05). The validation of the PoP phantom revealed that the HU of the PoP vertebrae was 628 (SD= 56), human vertebrae was 598 (SD= 79) and sheep vertebra was 605 (SD= 83). The SNR values of the two phantoms correlated strongly (r = 0.93 [(p < 0.05]). The measured scoliosis angle was 14 degrees. When the phantom was imaged using SPR, the difference between the measured Cobb angle and the known angle was, on average, –2.75° (SD = 1.46°). The agreement among the observers was good (p = 0.861, 95% CI [0.70–0.95]) and comparable to similar studies on other imaging modalities which are used for Cobb angle estimation.Conclusion: EOS had the lowest dose. Where this technology is not available, there is a potential for organ dose (OD) reduction in AIS imaging using CT SPR compared with DR. The PoP phantom has physical characteristics (in terms of spinal deformity) and radiological characteristics (in terms of HU and SNR values) of the spine of a 10-year-old child with AIS. CT SPR images can be used for AIS assessment with the 5° margin of error that is clinically acceptable. A few SPR imaging protocols (CT4, 8 and 11) had the lower radiation risk compared with the DR and provided the most accurate Cobb angle measurements.Implications for practice: The bespoke phantom can be used to investigate new X-ray imaging techniques and technology in the assessment of scoliosis and has utility for the optimisation of X-ray imaging techniques in 10-year-old children. Overall, the outcome is promising for patients and health providers because it provides an opportunity to reduce patient dose and achieve clinically acceptable Cobb angle measurements whilst using existing CT technology

Automated analysis and visualization of preclinical whole-body microCT data

In this thesis, several strategies are presented that aim to facilitate the analysis and visualization of whole-body in vivo data of small animals. Based on the particular challenges for image processing, when dealing with whole-body follow-up data, we addressed several aspects in this thesis. The developed methods are tailored to handle data of subjects with significantly varying posture and address the large tissue heterogeneity of entire animals. In addition, we aim to compensate for lacking tissue contrast by relying on approximation of organs based on an animal atlas. Beyond that, we provide a solution to automate the combination of multimodality, multidimensional data.* Advanced School for Computing and Imaging (ASCI), Delft, NL * Bontius Stichting inz Doelfonds Beeldverwerking, Leiden, NL * Caliper Life Sciences, Hopkinton, USA * Foundation Imago, Oegstgeest, NLUBL - phd migration 201

Mastering Endo-Laparoscopic and Thoracoscopic Surgery

This is an open access book. The book focuses mainly on the surgical technique, OR setup, equipments and devices necessary in minimally invasive surgery (MIS). It serves as a compendium of endolaparoscopic surgical procedures. It is an official publication of the Endoscopic and Laparoscopic Surgeons of Asia (ELSA). The book includes various sections covering basic skills set, devices, equipments, OR setup, procedures by area. Each chapter cover introduction, indications and contraindications, pre-operative patient’s assessment and preparation, OT setup (instrumentation required, patient’s position, etc.), step by step description of surgical procedures, management of complications, post-operative care. It includes original illustrations for better understanding and visualization of specific procedures. The book serves as a practical guide for surgical residents, surgical trainees, surgical fellows, junior surgeons, surgical consultants and anyone interested in MIS. It covers most of the basic and advanced laparoscopic and thoracoscopic surgery procedures meeting the curriculum and examination requirements of the residents