A three dimensional analysis of soft tissue and bone changes following orthognathic surgery

Introduction: This report investigates the ability of surgeons to achieve predicted surgical movements in five different groups of patients, and analyses both the predictions and the changes in two dimensions using scale space analyses (Campos 1991). The report then progresses to the three dimensional analysis of the bone, the soft tissues and the ratio of soft tissue to bone following surgery, using a colour coded techniques (Fright and Linney, 1991) to illustrate the changes. The average soft tissue scans from each group of patients were averaged and compared to a control group at the preoperative, three months and 1 year postoperative stages (Fright, 1991) Data Acquisition: Bone measurements were recorded from lateral skull radiographs preoperatively and 48 hrs postoperatively, and CT scans preoperatively and 1 year postoperatively. Soft tissue measurements from an optical scanner, preoperatively, three months and 1 year postoperatively. Patients 1) Control group: 30 females and 30 males 2) Skeletal class 2 patients: 15 Females and 2 Males 3) Skeletal class 3 patients: 9 Females and 7 Males 4) Cleft Palate Patients a) Unilateral cleft lip and palate: I 6 Females: 2 left and 4 right sided clefts 7 Males: 3 left and 4 right sided clefts b) Bilateral cleft lip and palate: 5 Males and 1 Female c) Clefts of the Hard and Soft palate: 5 Females. Results: Prediction: There was a surprisingly poor match between the predicted and achieved movements in both the horizontal and vertical direction in all patient groups. The scale space analysis provided an efficient method of illustrating profile changes. Soft tissue movements There were definite patterns of change and relapse in the patient groups. The relapse being most marked in the cleft palate patients. Bone movements and soft tissue to bone ratios Definite patterns of movement for the maxilla and the mandible became apparent for both the bone and soft tissue to bone ratio of movement in each group. For maxillary impactions in the skeletal 2 group there was a 1:1 ratio of movement of the soft tissue to bone in the midline increasing to 1.25:1 in the canine region and 1.5:1 in the paranasal region. Conclusions: There is a need to develop a technique to aid the the surgeons in carrying out planned surgical movements. The colour coded method was shown to be a simple, efficient and easily understandable way of analysing surgical change. Diagnosis of surgical requirements was aided by the ability to objectively compare the individual to a control group. The prediction of surgical change should be greatly aided by adapting the current database to include the distinct patterns of movement in the bone and ratio of movements of the soft tissues to the bone

Issues in Contemporary Orthodontics

Issues in Contemporary Orthodontics is a contribution to the ongoing debate in orthodontics, a discipline of continuous evolution, drawing from new technology and collective experience, to better meet the needs of students, residents, and practitioners of orthodontics. The book provides a comprehensive view of the major issues in orthodontics that have featured in recent debates. Abroad variety of topics is covered, including the impact of malocclusion, risk management and treatment, and innovation in orthodontics

Shape classification: towards a mathematical description of the face

Recent advances in biostereometric techniques have led to the quick and easy acquisition of 3D data for facial and other biological surfaces. This has led facial surgeons to express dissatisfaction with landmark-based methods for analysing the shape of the face which use only a small part of the data available, and to seek a method for analysing the face which maximizes the use of this extensive data set. Scientists working in the field of computer vision have developed a variety of methods for the analysis and description of 2D and 3D shape. These methods are reviewed and an approach, based on differential geometry, is selected for the description of facial shape. For each data point, the Gaussian and mean curvatures of the surface are calculated. The performance of three algorithms for computing these curvatures are evaluated for mathematically generated standard 3D objects and for 3D data obtained from an optical surface scanner. Using the signs of these curvatures, the face is classified into eight 'fundamental surface types' - each of which has an intuitive perceptual meaning. The robustness of the resulting surface type description to errors in the data is determined together with its repeatability. Three methods for comparing two surface type descriptions are presented and illustrated for average male and average female faces. Thus a quantitative description of facial change, or differences between individual's faces, is achieved. The possible application of artificial intelligence techniques to automate this comparison is discussed. The sensitivity of the description to global and local changes to the data, made by mathematical functions, is investigated. Examples are given of the application of this method for describing facial changes made by facial reconstructive surgery and implications for defining a basis for facial aesthetics using shape are discussed. It is also applied to investigate the role played by the shape of the surface in facial recognition

SYNCHROTRON RADIATION INLINE PROPAGATION BASED PHASE CONTRAST COMPUTERIZED TOMOGRAPHY (PC-CT) OF HUMAN PROSTATE SAMPLE

The human prostate is an accessory male reproductive gland located below the neck of the urinary bladder. Benign prostatic hyperplasia (BPH) and prostate cancer are the frequently encountered pathological conditions of the prostate. It is estimated that 50% of men will develop BPH by age 50 with the incidence increasing to 90% by age 90. Prostate cancer is the second most common cause of cancer in men worldwide after lung cancer. In this study, we examined the ability of synchrotron radiation propagation phase-contrast computerized tomography (PC-CT) in comparison to ultrasound (US), magnetic resonance imaging (MRI) and histology, to characterize and differentiate various structural features and pathological lesions in 61 prostate tissues from 13 human patients collected during trans-urethral resection of the prostate. We compared the PC-CT, MRI, US and histology images of the same tissues from the same plane to determine if different structures like blood vessels, dilated acini etc. could be observed with each modality. The PC-CT was found to be a powerful imaging technique compared to MRI and US in identifying and resolving small structures located near each other. With PC-CT imaging, the same structures could be correctly identified almost 4 times and 15 times more often than MRI and US respectively. While comparing the ability to identify and resolve the nearby structures in PC-CT images reconstructed from 100%, 50% and 25% of the number of total projections collected (i.e. 2250 projections over 180 degree rotation of a sample on imaging stage), the ranking was as follows: 100% PC-CT>50% PC-CT>25% PC-CT (p<0.05). Radiation data recorded during a previous study while imaging dog cadavers with PC-CT were also analyzed. It was found that the average effective radiation dose imparted in a medium-sized dog during PC-CT imaging of one view of 7.8 mm height with 2000 projections in the biomedical imaging and therapy – insertion device (BMIT-ID) beamline of Canadian light source (CLS) beamline was 1,481.7 mSv, which is very high compared to the standard clinical CT examination deposits in human clinical medicine. The dose could be reduced by performing sparse view imaging i.e. 50% projection PC-CT or 25% projection PC-CT, but these amounts are still hazardous, such that a similar protocol used in human would have the potential to induce cancer later in life in approximately 0.5 % of the patients. For PC-CT imaging of human prostate in situ, a human positioning device was also designed. Due to the limitation in the weight-bearing capacity of the stage in the beamline, the positioning device was designed to be able to hold only a human pelvis or pelvis phantom up to 50 kg of weight in an upright position. The results from this work demonstrate that the synchrotron radiation-based inline PC-CT is a promising technique that offers closer-to-histology grade non-invasive diagnostic imaging of prostate tissue. Further study in conducting in-vivo prostate imaging to reduce the radiation dose is the next step to move forward in this direction

Three-dimensional breast assessment by multiple stereophotogrammetry after breast reconstruction with latissimus dorsi flap

Introduction: Numerous methods exist for the assessment of the female breast. Traditionally, a subjective approach was taken for surgical planning and evaluation of the postoperative outcome. Several objective methods have been developed to support this procedure, among which are laser scanning, MRI, mammography, ultrasound and photography. Recently, 3D imaging technology has been developed. Material & Method: 3D breast assessment by multiple stereophotogrammetry was examined. A custom-made imaging system with eight digital cameras arranged in four camera pods was utilised. This system was used for breast capture, resulting in eight images obtained by the cameras. The merging of these images and 3D image construction was carried out by C3D software and the volume assessment of the 3D images was made using breast analysis tool (BAT) software, developed by Glasgow University. A validation study was conducted. Nine plaster models were investigated and their volume determined by 3D stereophotogrammetry and water displacement method. Water displacement was considered to be the gold standard for comparison. The plaster models were specially made in order to represent a variety of shapes and sizes of the female breast. Each plaster model was examined 10 times by each method. Further, the volumes of the breasts of six female volunteer live models were investigated by the same two methods and the results compared. A special focus was placed on the reproducibility of the assessment. Each live model was captured with the 3D capture system three times at two different time points after retaking a special pose in a custom-made positioning frame. Altogether, each live model was captured six times, resulting in six 3D images, each of which was measured three times with BAT software. A patient study was conducted in 44 patients after unilateral immediate breast reconstruction with Latissimus dorsi flap and no contra-lateral surgery. Each patient underwent 3D imaging with the multiple stereophotogrammetry system. During capture, the special pose in the custom-made positioning frame was taken by the patient’s leaning forward almost horizontally with the upper body for the breasts to rise off the chest wall to enable full breast coverage by the cameras. 3D images were constructed with C3D software and volumes measured with BAT. For each patient, one 3D image was constructed and measured four times with BAT software. In addition to the volume determination, a shape analysis was conducted. For this purpose, 10 landmarks were determined according to recommendations in the literature. Two landmarks, sternal notch and xiphoid, were marked, forming an imaginary midline between each other and four landmarks on each breast, i.e. the medial and lateral ends of the infra-mammary fold, and the most prominent and most inferior breast points were utilised for symmetry assessment between the right and left breasts. Each landmark was recorded four times by the operator on the 3D image and three-dimensional coordinates obtained. By assessment of the left and right breasts a breast asymmetry score was calculated. Firstly, breast asymmetry was assessed objectively on the 3D images through the centroid size, which was determined as the square root of the sum of squared Euclidian distances from each landmark to the centroid. The centroid was the geometric mean of the landmarks. Secondly, asymmetry was assessed through breast volume by application of BAT software. Thirdly, asymmetry was examined through the landmarks themselves by investigation of the mismatch of the landmark configuration of one breast and its relabelled and matched reflection. The non-operated and reconstructed sides were compared and landmarks were recorded by the operator in three dimensions in four repeated tests. A decomposition of the total landmark asymmetry into its factors was conducted by fixation of the surface of the non-operated side and translation, rotation and scaling of the surface of the reconstructed side. For comparison, a subjective breast assessment was conducted by six expert observers who rated the results after breast reconstruction by subjective qualitative assessment of the symmetry in 2D images of the same 44 patients in six poses. For this purpose the Harris scale was utilised, providing a score of 1 to 4 for poor to excellent symmetry. Results: The results revealed that differences in the obtained volumes in the plaster models were not significant. In contrast, differences in the breast volumes measured in the live models were significant. The examination of the reproducibility revealed that overall reproducibility obtained by stereophotogrammetry was better than that obtained by water displacement. No correlation between breast size and reproducibility of the measurements was found. The results of the patient study demonstrated that the reproducibility of the landmarks was within 5 mm. There was a non-significant difference of the centroid sizes between both breasts. There was a significant difference of the volumes between the two breasts, with the non-operated side being larger than the reconstructed side. Volume was considered to be a more accurate measure for comparison of both breasts than centroid size as it was based on thousands of data points for the calculation as opposed to only four points of the centroid size. The statistical analysis of the landmark data provided a mathematical formula for determination of the breast asymmetry score. The average asymmetry score, derived by landmark assessment as the degree of mismatch between both sides, was 0.052 with scores ranging from 0.019 (lowest score) to 0.136 (highest score). The decomposition of the landmark-based asymmetry revealed that location was the most important factor contributing to breast asymmetry, ahead of intrinsic breast asymmetry, orientation and scale. When investigating the subjective assessment, the inter-observer agreement was good or substantial. There was moderate agreement on the controls and fair to substantial intra-observer agreement. When comparing the objective and subjective assessments, it was found that the relationship between the two scores was highly significant. Conclusion: We concluded that 3D breast assessment by multiple stereophotogrammetry was reliable for a comparative analysis and provided objective data to breast volume, shape and symmetry. A breast asymmetry score was developed, enabling an objective measurement of breast asymmetry after breast reconstruction. 3D breast assessment served as an objective method for comparison to subjective breast assessment

Examining the taphonomic challenges to the 3D digitisation of fragmented bone

The utilisation of 3D digitisation and visualisation has grown considerably since 2008 and is becoming an increasingly useful tool for the digital documentation and metric analysis of archaeological artefacts and skeletal remains. It provides public access to rare and fragile specimens of palaeontological and palaeopathological importance whilst reducing the physical impact on these remains. Research in engineering and computer vision provides some insight into the impact of surface properties such as colour, specularity, reflectance and shape on the quality of the recorded 3D image, but within the archaeological and palaeontological disciplines comparable work has not yet been developed. If archaeology and anthropology are to provide long term reliable data from archaeological and palaeontological specimens in a way that doesn’t require repeated re-digitisation, we need to understand the impacts that the taphonomic histories of such samples have on our ability to 3D record them. Understanding the relationship of these taphonomic histories and the surface and optical properties will promote informed choices about the suitability of recording techniques. This thesis considers the taphonomic processes that affect the preservation of bone over archaeological, forensic and palaeontological timescales and the effect this has on the quality of 3D digital models. The digital refit of fragmentary bone samples is considered in relation to the effect of taphonomic alterations to bone. Conclusions regarding the key taphonomic factors and 3D digital model quality are drawn and areas of further work are identified.Arts and Humanities Research Counci