Cone-beam computed tomography (CBCT) is an imaging technique used in conjunction with radiation therapy. CBCT is used to verify the position of tumours just prior to radiation treatment session. The accuracy of the radiation treatment of thoracic and upper abdominal tumours is heavily affected by respiratory movement. Blurring artefacts, due to the movement during a CBCT scanning, cause misregistration between the CBCT image and the planning image. There has been growing interest in the use of motion-compensated CBCT for correcting the breathing-induced artefacts. A wide range of iterative reconstruction methods have been developed for CBCT imaging. The direct motion compensation technique has been applied to algebraic reconstruction technique (ART), simultaneous ART (SART), ordered-subset SART (OS-SART) and conjugate gradient least squares (CGLS). In this thesis a dual modality imaging of electrical impedance tomography (EIT) and CBCT is proposed for the first time. This novel dual modality imaging uses the advantages of high temporal resolution of EIT imaging and high spatial resolution of the CBCT method. The main objective of this study is to combine CBCT with EIT imaging system for motion-compensated CBCT using experimental and computational phantoms. The EIT images were used for extracting motion for a motion-compensated CBCT imaging system. A simple motion extraction technique is used for extracting motion data from the low spatial resolution EIT images. This motion data is suitable for input into the direct motion-compensated CBCT. The performance of iterative algorithms for motion compensation was also studied. The dual modality CBCT-EIT is verified using experimental EIT system and computational CBCT phantom data.

Introduction: Salivary gland obstructive conditions are common and may necessitate imaging of the glands for diagnosis and management purposes. Many imaging options are available but all have limitations. Sialography is considered the gold standard for examining obstructive conditions of the parotid and submandibular glands but it is largely influenced by the imaging technique to which it is coupled. Cone beam computed tomography (cbCT) is a relatively new and very promising imaging modality that has overcome many of the inherent limitations of other imaging modalities used in the past for sialography. Materials and methods: A RANDO®Man imaging phantom was used to determine the effective radiation doses from the series of plain film images that represent the current standard of practice for sialography. Similar experiments were then undertaken to determine the effective radiation doses from cbCT when varying the field-of-view (FOV) size and center, x-ray tube peak kilovoltage (kVp) and milliamperage (mA). Next, cbCT image quality, measured using the signal-difference-to-noise-ratio (SDNR) was used to determine those technical factors that optimized image quality. Finally, using the optimized image acquisition parameters, a prospective clinical study was conducted to test the diagnostic efficacy of cbCT sialography compared to plain film sialography. Results: Effective radiation doses were comparable between the plain film image series and cbCT examinations of the parotid and submandibular glands when a 6” FOV was chosen, and when the x-ray tube was operating at 80 kVp and 10 mA. We also found that these exposure settings optimized the image SDNR. Finally, we demonstrated that the diagnostic capabilities of cbCT sialography were superior to plain film sialography with regards to detecting sialoliths and strictures, and when differentiating normal salivary glands from those with changes secondary to inflammation. Conclusion: We have successfully developed a three dimensional (3D) sialography technique for imaging the parotid and submandibular salivary glands using cbCT that balances radiation effective dose with image quality. We also demonstrated the superior diagnostic capabilities of the new technique in a clinical setting.

Introduction: Salivary gland obstructive conditions are common and may necessitate imaging of the glands for diagnosis and management purposes. Many imaging options are available but all have limitations. Sialography is considered the gold standard for examining obstructive conditions of the parotid and submandibular glands but it is largely influenced by the imaging technique to which it is coupled. Cone beam computed tomography (cbCT) is a relatively new and very promising imaging modality that has overcome many of the inherent limitations of other imaging modalities used in the past for sialography. Materials and methods: A RANDO®Man imaging phantom was used to determine the effective radiation doses from the series of plain film images that represent the current standard of practice for sialography. Similar experiments were then undertaken to determine the effective radiation doses from cbCT when varying the field-of-view (FOV) size and center, x-ray tube peak kilovoltage (kVp) and milliamperage (mA). Next, cbCT image quality, measured using the signal-difference-to-noise-ratio (SDNR) was used to determine those technical factors that optimized image quality. Finally, using the optimized image acquisition parameters, a prospective clinical study was conducted to test the diagnostic efficacy of cbCT sialography compared to plain film sialography. Results: Effective radiation doses were comparable between the plain film image series and cbCT examinations of the parotid and submandibular glands when a 6” FOV was chosen, and when the x-ray tube was operating at 80 kVp and 10 mA. We also found that these exposure settings optimized the image SDNR. Finally, we demonstrated that the diagnostic capabilities of cbCT sialography were superior to plain film sialography with regards to detecting sialoliths and strictures, and when differentiating normal salivary glands from those with changes secondary to inflammation. Conclusion: We have successfully developed a three dimensional (3D) sialography technique for imaging the parotid and submandibular salivary glands using cbCT that balances radiation effective dose with image quality. We also demonstrated the superior diagnostic capabilities of the new technique in a clinical setting.

<p>The daily uncertainty concerning tumor localization is one of the major problems during the course of radiation therapy. Image guided-radiation therapy (IGRT) can be used to improve the localization and adjustment of the planning target volume. The aim of this work was to evaluate both the IGRT technique used for prostate cancer patients at the department of the Karolinska University Hospital and an alternative on-line adaptive radiation therapy (ART) method with an On-Board Imager (OBI).</p><p>In the first part of the thesis 2D and 3D image registration with an OBI were compared. Ten prostate cancer patients were involved in the analyses. Two different statistical tests were used to determine significant systematic deviations between the two methods. The second part concerns daily dose verifications and dose plan reoptimization of one intensity modulated radiation therapy (IMRT) prostate cancer patient treated with IGRT. The study was based on cone-beam computed tomography (CBCT) images acquired at 6 different treatment fractions. The risk of developing late rectal and bladder toxicity was quantified using normal tissue complication probability (NTCP) calculations. Additional measurements on an Alderson phantom were performed to verify the accuracy of using the CBCT images for dose calculations.</p><p>A statistically significant difference between the 2D-2D and the 3D-3D match applications could be observed in lateral and longitudinal direction. However, the effect differed among the patients. The phantom measurements showed small dose deviations between the CT and CBCT image, with a mean dose increase to the prostate and seminal vesicles (SV) of 2.5 %. The daily dose to the prostate and SV of the IMRT patient showed to be satisfactory. The daily dose to the rectum did not exceed the prescribed rectal dose except at one treatment fraction and the highest risk of developing late rectal toxicity was about 10.4 %. Large daily bladder dose variations were observed and at two treatment fractions the bladder dose restrictions were exceeded. With a reoptimization process of the dose plan, the dose to the bladder could be reduced while conserving the dose to the target.</p><p>This work shows that for these specific patient cases appropriate doses to the prostate and SV can be delivered with IGRT. However, introducing a suitable ART method could lead to a reduction of inter-fractional rectal and bladder dose variations.</p>

The daily uncertainty concerning tumor localization is one of the major problems during the course of radiation therapy. Image guided-radiation therapy (IGRT) can be used to improve the localization and adjustment of the planning target volume. The aim of this work was to evaluate both the IGRT technique used for prostate cancer patients at the department of the Karolinska University Hospital and an alternative on-line adaptive radiation therapy (ART) method with an On-Board Imager (OBI). In the first part of the thesis 2D and 3D image registration with an OBI were compared. Ten prostate cancer patients were involved in the analyses. Two different statistical tests were used to determine significant systematic deviations between the two methods. The second part concerns daily dose verifications and dose plan reoptimization of one intensity modulated radiation therapy (IMRT) prostate cancer patient treated with IGRT. The study was based on cone-beam computed tomography (CBCT) images acquired at 6 different treatment fractions. The risk of developing late rectal and bladder toxicity was quantified using normal tissue complication probability (NTCP) calculations. Additional measurements on an Alderson phantom were performed to verify the accuracy of using the CBCT images for dose calculations. A statistically significant difference between the 2D-2D and the 3D-3D match applications could be observed in lateral and longitudinal direction. However, the effect differed among the patients. The phantom measurements showed small dose deviations between the CT and CBCT image, with a mean dose increase to the prostate and seminal vesicles (SV) of 2.5 %. The daily dose to the prostate and SV of the IMRT patient showed to be satisfactory. The daily dose to the rectum did not exceed the prescribed rectal dose except at one treatment fraction and the highest risk of developing late rectal toxicity was about 10.4 %. Large daily bladder dose variations were observed and at two treatment fractions the bladder dose restrictions were exceeded. With a reoptimization process of the dose plan, the dose to the bladder could be reduced while conserving the dose to the target. This work shows that for these specific patient cases appropriate doses to the prostate and SV can be delivered with IGRT. However, introducing a suitable ART method could lead to a reduction of inter-fractional rectal and bladder dose variations.

Objective: The purpose of this study is to determine the relationship between cone beam CT (CBCT) voxel size and tooth root fracture detection. Materials and Methods: Vertical and horizontal root fractures were induced in a total of 30 teeth, and 15 teeth were left intact. Teeth were imaged with projection digital radiography and the Kodak 9000 3D CBCT system with a native voxel size of 76 &mu;m. The CBCT voxels were then downsampled to 100 &mu;m, 200 &mu;m and 300 &mu;m. Five blinded observers evaluated both sets of images with a 1 week washout interval between each set of observations. Results: CBCT outperformed the projection images for fracture detection for all voxel sizes except 300 &mu;m (p&lt;0.05). No significant differences were found between the different voxel sizes (p&gt;0.05). Conclusion: Although voxel size does not impact the interpretation of root fractures, in vitro, CBCT outperformed projection imaging for voxel sizes less than 300 &mu;m.

Objective: The purpose of this study is to determine the relationship between cone beam CT (CBCT) voxel size and tooth root fracture detection. Materials and Methods: Vertical and horizontal root fractures were induced in a total of 30 teeth, and 15 teeth were left intact. Teeth were imaged with projection digital radiography and the Kodak 9000 3D CBCT system with a native voxel size of 76 &mu;m. The CBCT voxels were then downsampled to 100 &mu;m, 200 &mu;m and 300 &mu;m. Five blinded observers evaluated both sets of images with a 1 week washout interval between each set of observations. Results: CBCT outperformed the projection images for fracture detection for all voxel sizes except 300 &mu;m (p&lt;0.05). No significant differences were found between the different voxel sizes (p&gt;0.05). Conclusion: Although voxel size does not impact the interpretation of root fractures, in vitro, CBCT outperformed projection imaging for voxel sizes less than 300 &mu;m.

Imaging of the osseous structures of the temporomandibular joint is best accomplished using computed tomography (CT). Cone beam CT offers a reduced radiation dose and improved spatial resolution compared to multislice helical CT. This study evaluates comparative dosimetry for temporomandibular joint imaging using two different cone beam CT systems, the Hitachi CB MercuRay and Kodak 9000 3D. These systems demonstrate differing properties with respect to field-of view sizes, operational technique factors, and spatial resolution. The Kodak 9000 3D unit offers an effective radiation dose reduction of greater than ten-fold compared with the Hitachi CB MercuRay, depending on kVp and mA. A subsequent clinical study evaluating the effect of spatial resolution on the ability to detect osseous changes related to temporomandibular joint degenerative disease found no significant difference in diagnostic efficacy between high and low spatial resolution images, however, observers consistently associated high spatial resolution with superior image quality.

Imaging of the osseous structures of the temporomandibular joint is best accomplished using computed tomography (CT). Cone beam CT offers a reduced radiation dose and improved spatial resolution compared to multislice helical CT. This study evaluates comparative dosimetry for temporomandibular joint imaging using two different cone beam CT systems, the Hitachi CB MercuRay and Kodak 9000 3D. These systems demonstrate differing properties with respect to field-of view sizes, operational technique factors, and spatial resolution. The Kodak 9000 3D unit offers an effective radiation dose reduction of greater than ten-fold compared with the Hitachi CB MercuRay, depending on kVp and mA. A subsequent clinical study evaluating the effect of spatial resolution on the ability to detect osseous changes related to temporomandibular joint degenerative disease found no significant difference in diagnostic efficacy between high and low spatial resolution images, however, observers consistently associated high spatial resolution with superior image quality.

Objectives: With increasing utilization of cone beam computed tomography for diagnosis and treatment planning of complex dentomaxillofacial rehabilitation, more incidental findings of pathology in the maxillary sinus have been identified by clinicians. Part one of this article discusses the association between age, gender, ethnicity and dentition status in relation to prevalence of sinus pathology. The aim of this study is to expand the current knowledge base in regards to the prevalence of maxillary sinus pathologies in patients of Temple University Kornberg School of Dentistry and to determine if smoking and allergies have relationship with the prevalence of pathology. Materials and Methods: : Three hundred and sixty-three cone beam computed tomography scans taken were evaluated at Temple University Kornberg School of Dentistry Department of Oral and Maxillofacial Radiology between 2009 to July 31, 2013. Scans were classified into 1 of 5 categories based upon the type of sinus pathology detected. The categories of sinus findings were: healthy, mucosal thickening &gt; 3-4 mm, polypoidal mucosal thickening, partial opacification and complete opacification. Medical health questionnaires were reviewed for patient's social history such as smoking and systemic factors such as allergies. Chi-square statistical analysis using SAS was done to examine the relationship. Results: This study included a total of 363 subjects subdivided by gender into 203 females and 160 males. The subjects were further subdivided by ethnicity into 217 Caucasians, 86 African Americans, 35 Asians, and 25 Hispanics. Also, 129 of the subjects had a history of smoking, 98 had seasonal allergies, and 50 had environmental allergies. In addition 129 of the subjects had at least 1 type of sinus pathology. Chi-square analyses showed that there was no relationship between the prevalence of sinus pathology and allergy or smoking status. History of allergies was marginally higher in females and significantly higher in African Americans (p=0.007). History of smoking was higher in older subjects (p=0.0004), males (p=0.01) and Caucasians (p&lt;0.0001). Conclusions: This CBCT cross sectional study shows that there is no statistically significant correlation between prevalence of sinus pathology and smoking or allergy status. Further cohort studies are needed to determine if smoking or allergies may or may not contribute to sinus pathology. / Oral Biology