There have been reports on the use of Ultrasound (US) for monitoring fracture repair and for measuring muscle volume. Change in muscle mass is a useful bio-marker for monitoring the use and disuse of muscle, and the affects of age, disease and injury. The main modality for imaging bone is X-ray and for muscle volume Magnetic Resonance (MR). Previous studies have shown US to have advantages over X-ray and MR. US can image all stages of the fracture repair process and can detect signs of healing 4-6 weeks before X-ray allowing earlier detection of possible complications. Compared to MR, US is less resource intensive, easier to access and also has fewer exclusion criteria for patients. Despite these advantages, the limited field of view that US can provide results in high operator dependency for scan interpretation and also for length and volume measurements. Three-dimensional Ultrasound (3D US) has been developed to overcome these limitations and has been used to provide extended field of view images of the foetus and the heart and to obtain accurate volume measurements for organs. In this thesis it is hypothesized that 3D US can provide a more comprehensive method of imaging fracture repair than X-ray and is also a viable alternative to MR for determining muscle volumes in vivo. Initially, an electromagnetically (EM) tracked 3D US system was evaluated for clinical use using phantom-based experiments. It was found that the presence of metal objects in or near the EM field caused distortion and resulted in errors in the volume measurements of phantoms of up to ±20%. An optically tracked system was also evaluated and it was found that length measurements of a phantom could be made to within ±1.3%. Fracture repair was monitored in five patients with lower limb fractures. Signs of healing were visible earlier on 3D US with a notable, although variable, lag between callus development on X-ray compared to 3D US. 3D US provided a clearer view of callus formation and the changes in density of the callus as it matured. Additional information gained by applying image processing methods to the 3D US data was used to develop a measure of callus density and to identify the frequency dependent appearance of the callus. Volume measurements of the rectus femoris quadricep muscle were obtained using 3DUS from eleven healthy volunteers and were validated against volume measurements derived using MR. The mean difference between muscle volume measurements obtained using 3D US and MR was 0.53 cm3 with a standard deviation of 1.09 cm3 and 95% confidence intervals of 0.20 - 1.27 cm3 In conclusion, 3D US demonstrates great potential as a tool for imaging components of the musculoskeletal system and as means of measuring callus density.

<p>There have been several advancements in radiofrequency (RF) coil development for magnetic resonance imaging (MRI) to improve both image quality and patient comfort. Notable to these improvements is the trend towards lightweight and flexible coils allowing for the conformation around a variety of anatomies and body sizes. This allows for a more comfortable patient experience and enhanced signal reception. Despite these improvements, flexible supine coils for dedicated breast imaging, or larger stretchable coil arrays for closer proximity of placement and imaging at degrees of flexion, are not available. Conventional breast coils are rigid and typically require prone positioning which creates uncomfortable pressure points along the sternum. Also, these coils do not encompass the axilla or areas in the upper chest wall. Additionally, surgical planning is performed in the supine position, making it challenging to localize lesions from prone MRI scans. To address these issues, two novel RF coil technologies are presented. Firstly, a flexible, lightweight, 60-channel supine breast coil has been constructed. This coil provides shorter scan times, greater coverage of the breasts, axilla, upper chest wall, and torso while also providing enhanced patient comfort over conventional breast coils. The second RF coil technology is a 20-channel stretchable, multipurpose coil. This coil addresses limitations of conformability around curved surfaces while allowing for the imaging of joints at a bend. Due to the stretchability, this coil exhibited enhanced signal and image quality for a variety of body sizes and anatomies, such as ankles and wrists, when compared to a flexible commercial coil.</p>