83 Planning Radiation Therapy When planning radiation therapy of brain tumours from MR scans of the head, it is necessary to apply to most effective dose of radiation to the tumour, yet cause least damage to the surrounding tissue. This is a complex task demanding 3D visualization. An interactive system is being developed to produce 3D representations of the head, by combining the information from a series of cross-sectional images. Segmentation techniques are used to semi-automatically identify the tumour and other anatomical structures. One approach is for the clinician to select a point within an area of interest, such as the tumour. The system then locates the surrounding points which possess similar characteristics, within a given range of variability. This is repeated for other regions, and other images, to produce a 3D model. Given this model, an optimal treatment plan can be generated.
84 Merging Medical Images Different types of medical image yield different information. For example, MR scans provide soft tissue information, yet nothing regarding bones. The converse is true of computed tomography (CT) scans. When planning surgery, information from both CT and MR scans may be needed. Machine vision techniques can be used to collate information from the different scans, thus producing a single 3D image showing the relationship between single 3D image showing the relationship between important features. This has been achieved, for example, by interactively labelling matching features in the original images. Bone is identified in the CT scan by locating areas with grey levels above a certain threshold value. Identifying tissue structures in the MR scan requires more sophisticated segmentation techniques. This process is now being developed to use known anatomical relationships to automatically match 3D models derived from different medical images
90 What is PET/CT?PET/CT is a new imaging tool that combines two scan techniques in one exam - a PET scan and a CT scan. PET/CT is mainly used for diagnosis, staging or restaging malignant disease and metastases and evaluation of treatment response. It may also be used to differentiate dementia verses Alzheimer's disease. The two procedures together provide information about the location, nature of and the extent of the lesion. In other words, it answers questions like : Where is the tumor, how big is it, is it malignant, benign or due to inflammatory change, and has the cancer spread?
107 HIPThe knee is a region and the knee is a joint. As a joint it is made up of uh... how many bones? Mmm... well, mmm, that depends if you want to count the fibula in on the action. Yeah, let's do that because it anchors the lateral ligament complex. The femur, and tibia are obvious. Add the patella and the fibula, that's four.
108 TIBIA/FIBULAThe shin is the region of the tibia. At the proximal (in proximity to the body) is the knee. At the distal end (distant from the body) is the ankle.
109 ANKLEThe ankle is a region and the ankle is a joint, but the joint isn't the same region as the region. Huh? What folks call the ankle (singular) is actually two distinctly different joints. What they call ankle motion is actually motion of both those joints.
110 FOOT1 Calcaneus 2 Talus 3 Navicular 4 Medial cuneiform 5 Intermediate cuneiform 6 Lateral cuneiform 7 Cuboid 8 First metatarsal 9 Second metatarsal 10 Third metatarsal 11 Fourth metatarsal 12 Fifth metatarsal 13 Proximal phalanx of great toe 14 Distal phalanx of great toe 15 Proximal phalanx of second toe 16 Middle phalanx of second toe 17 Distal phalanx of second toe