Helical Computed Tomography System Research Articles

Three-dimensional Maxillofacial Morphology Measurements in Japanese Adults with Normal Occlusion.

Accurate orthodontic analysis and diagnosis based on anatomical landmarks is essential to the success of orthodontic treatment. Helical computed tomography (CT) has evolved markedly, and dentists can now quickly obtain 3-dimensional (3D) reconstruction data using this imaging modality. The planning of orthodontic treatment had traditionally been based on cephalometric analysis using 2D landmarks. This study aimed to collect 3D morphological data using CT images to establish new landmarks for analysis and diagnosis in orthodontic treatment. Twenty male and 20 female adult Japanese dry skulls with of normal occlusion were selected. The skulls were scanned using a multidetector helical CT system (SIEMENS, Volume Zoom Plus 4, Germany). Models were reconstructed using 3D measurement software (Simplant, Dentsply Sirona, Tokyo, Japan) and 45 landmarks determined. Three-dimensional measurement for a total of 30 items representing these landmarks was then performed. The results provided 3D standard values for maxillofacial morphology in adult Japanese individuals with normal occlusion. These measurement items should allow the disadvantages of 2D cephalometric analysis to be overcome.

P049] Moving forward to personalized pediatric dosimetry on computed tomography applications

Purpose Personalized dosimetry is of high interest in pediatric applications where exposure to ionizing radiation is widely debated. This study intends to create an organ dose database for pediatric reference individuals undergoing computed tomography (CT) examinations. The data will permit quick estimates of organ effective doses for patients of different age, gender, and examination procedure. Methods The GATE MC toolkit [1] was used for modeling a multislice helical CT system. The energy spectrum was calculated using Spektr software, and consequently imported in GATE as a gamma-particle point source with an almost continuous helical movement. To validate our results, simulations were performed with the standard CTDI head/body phantoms. A thin-walled ionization chamber was simulated according to the manufacturer specifications at 1 center, and 4 peripheral positions. Five pediatric computational models in the 5–15 y age-range [2] , [3] , were used to simulate realistic helical chest protocols and compare the variations on absorbed dose/organ. Results The CT scanner model was validated against experimental CTDI measurements with differences being lower than ∼18%. The simulated dose variations for the different pediatric phantoms are presented. Indicatively, normalized absorbed doses for selected organs inside the scan coverage varied between 25–35%, and 43–51% for 5 vs. 8, and 8 vs. 11 years-old girls respectively. Conclusions This is an ongoing study for the creation of a CT dosimetry pediatric database and for the quantification of the differences on the absorbed doses in tissue/organ level, using several models with variations in anatomical features. Every patient could be matched to the best anatomical model of this database (according to characteristics such as weight, height, age, gender) to provide more accurate and patient-specific organ doses.

SU‐F‐J‐194: Development of Dose‐Based Image Guided Proton Therapy Workflow

Purpose:To implement image‐guided proton therapy (IGPT) based on daily proton dose distribution.Methods:Unlike x‐ray therapy, simple alignment based on anatomy cannot ensure proper dose coverage in proton therapy. Anatomy changes along the beam path may lead to underdosing the target, or overdosing the organ‐at‐risk (OAR). With an in‐room mobile computed tomography (CT) system, we are developing a dose‐based IGPT software tool that allows patient positioning and treatment adaption based on daily dose distributions. During an IGPT treatment, daily CT images are acquired in treatment position. After initial positioning based on rigid image registration, proton dose distribution is calculated on daily CT images. The target and OARs are automatically delineated via deformable image registration. Dose distributions are evaluated to decide if repositioning or plan adaptation is necessary in order to achieve proper coverage of the target and sparing of OARs. Besides online dose‐based image guidance, the software tool can also map daily treatment doses to the treatment planning CT images for offline adaptive treatment.Results:An in‐room helical CT system is commissioned for IGPT purposes. It produces accurate CT numbers that allow proton dose calculation. GPU‐based deformable image registration algorithms are developed and evaluated for automatic ROI‐delineation and dose mapping. The online and offline IGPT functionalities are evaluated with daily CT images of the proton patients.Conclusion:The online and offline IGPT software tool may improve the safety and quality of proton treatment by allowing dose‐based IGPT and adaptive proton treatments.Research is partially supported by Mevion Medical Systems.

Comparison of the diagnostic quality of computed tomography images of normal ocular and orbital structures acquired with and without the use of general anesthesia in the cat

To compare the diagnostic quality of computed tomography (CT) images of normal ocular and orbital structures acquired with and without the use of general anesthesia in the cat. Eleven privately owned cats with nasal disease presenting to a single referral hospital. All cats received a complete ophthalmic examination. A 16 multislice helical CT system was utilized to acquire images of the skull and neck with and without the use of general anesthesia. Images were acquired before and after the administration of intravenous iodinated contrast. Images of normal ocular and orbital structures were evaluated via consensus by two board-certified radiologists. Visibility of ocular and orbital structures, degree of motion, and streak artifact were assessed and scored for each image set in the transverse, dorsal, and sagittal planes. The use of general anesthesia did not significantly affect the diagnostic quality of images. No motion artifact was observed in any CT image. Streak artifact was significantly increased in scans performed in the transverse orientation but not in the dorsal orientation or sagittal orientation and did not affect the diagnostic quality of the images. Contrast enhancement did not significantly enhance the visibility of any ocular or orbital structures. Diagnostic CT images of normal ocular and orbital structures can be acquired without the use of general anesthesia in the cat.

THORACIC COMPUTED TOMOGRAPHY IN FELINE PATIENTS WITHOUT USE OF CHEMICAL RESTRAINT

Computed tomography (CT) and thoracic radiography were performed in nonsedated, nonanesthetized, cats with thoracic disease. The final diagnosis was obtained with echocardiography, cytology, histopathology, necropsy, or response to therapy. For CT imaging, cats were in a positioning device using a 16 multislice helical CT system. Fifty-four cats had CT imaging of which 50 had thoracic radiography. The most common diagnoses were lung neoplasia, lower airway disease, and cardiomyopathy (nine each). Other disease groups included mediastinal mass (eight), infection (seven), trauma (four), and hernia (three). CT provided additional correct diagnoses in 28% (14/50) and additional information in 74% (37/50) of the cats. Additional correct diagnoses achieved only with CT were most common for cats with lower airway disease. The most common additional findings with CT were lung nodules (n=4), lung masses (n=4), bronchiectasis (n=4), and mediastinal lymphadenopathy (n=3). Survey CT led to a significant different diagnosis or different prognosis in 20 of the 50 cats that were imaged both modalities. Contrast CT was performed in 19 cats, most commonly in cats with lung neoplasia (n=6), a mediastinal mass (n=4) or an infection (n=3), and provided additional correct diagnosis in two cats not achieved with survey CT. Thoracic CT using a positioning device in diseased awake cats is feasible, safe, and clinically useful.

Dynamic Computed Tomography Myelography for the Investigation of Cervical Degenerative Disease

Dynamic computed tomography (CT) myelography was conducted in 15 patients with cervical degenerative disease to assess the lesions responsible for their symptoms. CT myelography was performed using a multi-detector row helical CT system in dynamic positions (flexion or extension or both) in addition to the neutral position. Fine sagittal reconstructed images could be obtained in addition to axial images. This method provided static information including cervical vertebral body deformities, and good contrast images of the spinal cord, nerve roots, and cerebrospinal fluid space. In addition, laterality of the offending lesion and changes exaggerated by cervical motion were clearly shown in both axial and sagittal images. Ten of 15 patients demonstrated dynamic changes including dynamic canal stenosis or spinal cord impingement. The operative strategies were changed based on dynamic CT myelography findings in three of the 15 patients. Dynamic CT myelography can provide the axial and sagittal images required for flexion-extension studies, and in combination with conventional imaging modalities, provides valuable information for determining treatment strategies and objectives.

Intra- and perinodular hemodynamics of hepatocellular carcinoma: CT observation during intra-arterial contrast injection.

It is imperative to understand the intraand perinodular hemodynamics of hepatocellular carcinoma (HCC) for precise imaging diagnosis and determination of treatment strategies. For this purpose, the combination of computed tomography (CT) and selective arteriography, such as CT during hepatic arteriography (CTHA) and CT during arterial portography (CTAP), is most valuable and precise. We introduced CTAP as a part of an arteriographic examination for preoperative evaluation of HCC in the 1980s [1], and, after the development of helical CT system, simultaneous performance of CTAP and CTHA became possible [2]. In this article, the intraand peritumoral hemodynamics analyzed by CTHA and CTAP are compared with histology.

The Results of Serial Dynamic Enhanced Computed Tomography in Patients With Carotid-Cavernous Sinus Fistulas

Purpose: To assess serial dynamic enhanced computed tomography (serial DE-CT) as a diagnostic tool for carotid-cavernous sinus fistula (CCF). Methods: Serial DE-CT was performed in seven patients (ages 31–74) with CCF. Contrast material was injected intravenously at a dose of 60 mL with an injection speed of 4 mL per second. Serial axial images of the cavernous sinus were undertaken every 3 seconds using a helical computed tomography system. This relatively low-risk technique provides direct evidence of the arteriovenous shunt in the cavernous sinus. Results: In early imaging after the injection, enhancement of the cavernous sinus on the side of the CCF was noted at the arterial phase in all patients, whereas early enhancement of the cavernous sinus was not observed on the contralateral uninvolved side. Conclusions: These findings suggest the usefulness of serial DE-CT as a diagnostic tool for the initial diagnosis of both high- and low-flow CCFs.