Cone Beam Computed Tomography Slices Research Articles

Real-Time In Vivo Characterization of Primary Liver Tumors With Diffuse Optical Spectroscopy During Percutaneous Needle Interventions: Feasibility Study in Woodchucks.

This study presents the first in vivo real-time optical tissue characterization during image-guided percutaneous intervention using near-infrared diffuse optical spectroscopy sensing at the tip of a needle. The goal of this study was to indicate transition boundaries from healthy tissue to tumors, namely, hepatic carcinoma, based on the real-time feedback derived from the optical measurements. Five woodchucks with hepatic carcinoma were used for this study. The woodchucks were imaged with contrast-enhanced cone beam computed tomography with a flat panel detector C-arm system to visualize the carcinoma in the liver. In each animal, 3 insertions were performed, starting from the skin surface toward the hepatic carcinoma under image guidance. In 2 woodchucks, each end point of the insertion was confirmed with pathologic examination of a biopsy sample. While advancing the needle in the animals under image guidance such as fluoroscopy overlaid with cone beam computed tomography slice and ultrasound, optical spectra were acquired at the distal end of the needles. Optical tissue characterization was determined by translating the acquired optical spectra into clinical parameters such as blood, water, lipid, and bile fractions; tissue oxygenation levels; and scattering amplitude related to tissue density. The Kruskal-Wallis test was used to study the difference in the derived clinical parameters from the measurements performed within the healthy tissue and the hepatic carcinoma. Kurtoses were calculated to assess the dispersion of these parameters within the healthy and carcinoma tissues. Blood and lipid volume fractions as well as tissue oxygenation and reduced scattering amplitude showed to be significantly different between the healthy part of the liver and the hepatic carcinoma (P < 0.05) being higher in normal liver tissue. A decrease in blood and lipid volume fractions and tissue oxygenation as well as an increase in scattering amplitude were observed when the tip of the needle crossed the margin from the healthy liver tissue to the carcinoma. The kurtosis for each derived clinical parameter was high in the hepatic tumor as compared with that in the healthy liver indicating intracarcinoma variability. Tissue blood content, oxygenation level, lipid content, and tissue density all showed significant differences when the needle tip was guided from the healthy tissue to the carcinoma and can therefore be used to identify tissue boundaries during percutaneous image-guided interventions.

Pelvic lymph node displacement in high-risk prostate cancer patients treated with image guided intensity modulated radiation therapy with 2 independent target volumes

PurposeTo evaluate the displacement of the pelvic lymph node (PLN) target when using cone beam computed tomography (CBCT) for localization of the prostate in patients treated with simultaneous integrated boost. Methods and materialsHigh-risk prostate cancer patients treated with image guided intensity modulated radiation therapy with simultaneous integrated boost receiving 60 Gy in 20 fractions to the prostate and proximal seminal vesicles (PTV60) and 44 Gy in the same 20 fractions to the PLN (PTV44) were studied. Two hundred weekly CBCTs of 50 patients were retrospectively reviewed to assess the displacement of the iliac vessels compared with the simulation computed tomography. For each CBCT, possible displacements were analyzed at 3 levels of PTV44: a superior, middle, and inferior slice, making a total of 600 slices reviewed. Geographical miss (GM) was defined when any part of the iliac vessels on the CBCT was outside of the PTV44 contour. ResultsGM was found in 7 of the 600 CBCT slices, all in different patients. All GMs were of ≤5 mm. Four GMs occurred on the middle slice and 3 on the superior slice. In 3 cases, the GM was related to shifts ≥7 mm applied to the prostate. ConclusionsOur review suggests that for high-risk prostate cancer, the chance of not appropriately covering the PLN target after adjusting the prostate is low. GM was uncommon and in the order of only a few millimeters when it occurred.

Aneurysmal bone cyst of the mandible: Report of a case with a review of the literature

Aneurysmal bone cyst (ABC), is a rare benign osteolytic bone neoplasm of bone tissue characterized by several sponge-like blood or serum filled, generally non-endothelialized spaces of various diameters that can contain osteoid tissue and osteoclast-like giant cells. In this article, we describe a case of ABC in the mandibular corpus region with clinical, radiological and pathological findings and review the literature concerning the case. A 23-year-old male patient attended to our clinic with the complaint of a mild-pain on the left posterior lower jaw since two months. The superior margin of the lesion was extending between the apical third parts of the roots of the teeth 35-38. Cone beam computed tomography (CBCT) was performed. CBCT Slices revealed an expansile lesion with hydraulic-appearing outer margins above the mandibular canal. Excisional surgical treatment was performed after raising a mucoperiosteal flap and finalized with curette of lesion under local anesthesia. Diagnosis of aneurysmal bone cyst was confirmed by histopathological evaluation. The patient was pain free after six months follow-up, and panoramic radiography showed no evidence of recurrence. The ABC is most common in those regions of the skeleton where there is a relatively high venous pressure and high marrow content. Clinical presentation of the ABC varies from a small, indolent, asymptomatic lesion to rapidly growing, expansile, destructive lesion causing pain, swelling, deformity, neurologic symptoms, pathologic fracture, and perforation of the cortex. As the radiologic and clinical presentation of ABC is extremely variable, histopathologic examination is placed a great emphasis on for the diagnosis.

Characteristics and Dimensions of the Sinus Membrane in Patients Referred for Single-Implant Treatment in the Posterior Maxilla: A Cone Beam Computed Tomographic Analysis

The purpose of the present study was to evaluate the thickness and anatomic characteristics of the sinus membrane using cone beam computed tomography (CBCT) in patients evaluated for implant surgery in the posterior maxilla. The study included 131 consecutive patients referred for dental implant placement in the posterior maxilla. A total of 138 CBCT images was obtained using fields of view of 4 × 4 cm, 6 × 6 cm, or 8 × 8 cm. Reformatted sagittal CBCT slices were analyzed with regard to the thickness and characteristics of the sinus membrane at single-tooth gaps in the posterior maxilla. Factors that might influence the dimensions of the sinus membrane, such as age, sex, endodontic status, and the season, were analyzed. The mean thickness of the maxillary sinus mucosa varied between 2.1 and 2.69 mm in the three locations analyzed. Fewer than half of the evaluated sinuses exhibited a healthy mucosa (49 of 138, or 35.51%). Most of the pathologic findings were flat, shallow thickenings (63 of 138, or 45.65%). Sex did not influence the thickness of the sinus membrane at the root tips of the premolars or at single-tooth gaps, but there was a statistically significant correlation in the region of the maxillary molars. No other evaluated factors had a statistically significant effect on the dimensions of the antral mucosa. In the present study, sex was the only factor influencing the dimension of the sinus membrane, whereas patient age, season, and the endodontic status of neighboring teeth had no significant effect on the thickness of the antral mucosa. Future studies should address which types of mucosal thickening require interdisciplinary therapy.

Identification of occlusal prematurity by clinical examination and cone-beam computed tomography

The aim of this study was to evaluate the ability to identify occlusal prematurity by images from paraxial slices of cone-beam computed tomography (CBCT). For such purpose, a pilot study was performed in which 16 asymptomatic young patients were subjected to a clinical examination, including a careful occlusal analysis and then individual deprogrammer devices ("Lucia's JIG") were fabricated. Premature contacts were clinically identified in centric relation (CR) for each patient by jaw manipulation and interocclusal marking with articulating paper (Accufilm). Subsequently, these devices were adjusted in CR and used during the tomographic exams in such a way that CBCT in CR could be obtained. After routine processing, the images were analyzed in order to identify occlusal prematurity on the displayed images by 30 professionals divided according to areas of activity (occlusion specialist, general practitioner and radiologist; n=10 per area) and time of professional experience (less than 5, between 5 and 10, and over 10 years). By comparing the premature contacts identified in the clinical analysis and CBCT images, an agreement index between these two variables was calculated. Data were analyzed statistically by ANOVA and Scott-Knott test (α=0.05). The results showed that the identification of occlusal prematurity by paraxial CBCT slices was proven to be a method of average reliability.

Construction of orthodontic setup models on a computer

Orthodontic setup models are usually limited to the display of teeth, with no information about the roots. The purpose of this article is to present a method for visualizing the tooth roots in setup models by integrating information from cone-beam computed tomography and a laser scanner. The reproducibility of the integration was evaluated. The records of 5 patients were used in this study. Three-dimensional digital models were generated from the dental casts. Tooth models were generated from the cone-beam computed tomography slices. The 3-dimensional models were superimposed on the crowns of the teeth in the tooth models and integrated. The integrated 3-dimensional tooth model and 3-dimensional setup model were registered. The reproducibility of the integration was evaluated for each tooth. Unpaired Student t tests were performed on the data between the anterior and posterior teeth, and between the right and left teeth. The discrepancy among the integrated 3-dimensional models at the final positions after we used this technique was 0.025 ± 0.007 mm. There was a significant difference in the distance between the anterior and posterior teeth (P<0.05). However, the average distances between the anterior and posterior teeth were small: 0.023 ± 0.007 and 0.028 ± 0.007 mm, respectively. No significant difference was found between the right and left teeth (P= 0.831). The methods presented in this study provide a reproducible visualization of tooth roots in virtual setup models by registering accurate crown models to cone-beam computed tomography scans.

Characteristics and Dimensions of the Schneiderian Membrane and Apical Bone in Maxillary Molars Referred for Apical Surgery: A Comparative Radiographic Analysis Using Limited Cone Beam Computed Tomography

Introduction The purpose of the present study was to evaluate the thickness and the anatomic characteristics of the Schneiderian membrane and cortical bone using limited cone beam computed tomography (CBCT) scannning in patients referred for planning of apical surgery of maxillary molars. Methods This controlled study included 2 cohorts of patients (n = 50 for each group). For patients in group 1 (with apical pathology), 3 measurements in millimeters were performed using coronal and sagittal CBCT slices: the dimension of the apical lesion in the axis of the root, the width of the cortical bone in the axis of the root, and the thickness of the Schneiderian membrane perpendicular to the underlying cortical bone. For the analysis of CBCT scans of group 2 (without apical pathologies), 2 measurements were performed using coronal and sagittal CBCT slices: the width of the cortical bone in the axis of the root and the thickness of the Schneiderian membrane perpendicular to the underlying cortical bone. Results For group 1, the periapical lesions evaluated measured between 0.27 and 7.41 mm in diameter, the apical bone separating the apical lesions from the maxillary sinus ranged from 0.13 to 7.83 mm, and the dimensions of the Schneiderian membrane ranged from 0.25 to 13.98 mm. The apical bone was generally thicker in patients with periapical lesions. Regarding the dimensions of the Schneiderian membrane, the values were statistically significantly higher for the patients in group 1 compared with group 2. Conclusions The study showed that the Schneiderian membrane in the vicinity of roots with apical lesions tends to be significantly thicker when compared with the roots of teeth without apical pathoses.

CBCT fractal dimension changes at the apex of immediate implants placed using undersized drilling

To evaluate, on the base of cone beam computed tomography (CBCT) fractal dimension, bone quality changes surrounding the apical portion of immediate implants placed under higher insertion torque utilizing an undersized drilling technique. Three patients were enrolled in this study. Single implants were placed into fresh extraction sockets in the anterior maxilla and provisionalized immediately. Adequate stability was ensured on all the implants by a 28.5% undersizing of the apical portion of the osteotomy. Bone quality at the most apical 1.15 mm peri-implant bone portion were measured by CBCT at placement and after 6 months. This analysis was carried out by evaluating the box counting fractal dimension of 15 consecutive CBCT slices related to the most apical part of each implant. All the three implants were successful after an 18-month follow-up period. The mean fractal dimension at the implant apex exhibited a 3% increase 6 months following placement. Within the limitations of an explorative study, an undersized drilling resulting in high insertion torque would seem to induce no adverse changes in radiographic bone quality after 6 months of follow-up. The most favorable entity of drilling undersizing and its effect on peri-implant bone remodeling, should be evaluated on a larger patient population.

Characteristics and dimensions of the Schneiderian membrane: a radiographic analysis using cone beam computed tomography in patients referred for dental implant surgery in the posterior maxilla

To determine the dimensions of the Schneiderian membrane using limited cone beam computed tomography (CBCT) in individuals referred for dental implant surgery, and to determine factors influencing the mucosal thickness. The study included 143 consecutive patients referred for dental implant placement in the posterior maxilla. A total of 168 CBCT images were taken using a limited field of view of 4 × 4 cm, 6 × 6 cm, or 8 × 8 cm. Reformatted coronal CBCT slices were analyzed with regard to the thickness and characteristics of the Schneiderian membrane in nine standardized points of reference. Factors such as age, gender, or status of the remaining dentition that could influence the dimensions of the Schneiderian membrane were evaluated using univariate and multivariate linear regression models. The thickness of the Schneiderian membrane exhibited a wide range, with a minimum value of 0.16 mm and a maximum value of 34.61 mm. The highest mean values, ranging from 2.16 to 3.11 mm, were found for the mucosa located in the mid-sagittal regions of the maxillary sinus. The most frequent mucosal findings diagnosed were flat thickenings of the Schneiderian membrane (62 positive findings, 37%). For the multivariate linear regression model, only gender had a statistically significant influence on the mean overall and mid-sagittal thickness of the sinus mucosa. There is great interindividual variability in the thickness of the Schneiderian membrane. Gender seems to be the most important parameter influencing mucosal thickness in asymptomatic patients. Future studies are needed to assess the therapeutic and prognostic consequences of mucosal alterations in the maxillary sinus.

Comparison of Periapical Radiography and Limited Cone-Beam Computed Tomography in Mandibular Molars for Analysis of Anatomical Landmarks before Apical Surgery

Introduction The purpose of the present study was to evaluate the detectability and dimensions of periapical lesions, the relationship of the mandibular canal to the roots of the respective teeth, and the dimension of the buccal bone by using limited cone-beam computed tomography (CBCT) in comparison to conventional periapical (PA) radiographs for evaluation of mandibular molars before apical surgery. Methods The study comprised 38 molars with 75 roots. The type of PA lesion as diagnosed on PA radiographs was compared with the type of lesion seen on sagittal and coronal CBCT sections. The distances of the apices of the first mandibular molars and basal border of the PA lesion to the coronal lining of the mandibular canal were assessed with PA radiographs and corresponding sagittal and coronal CBCT images. Furthermore, coronal CBCT images were used to measure the distance from the apices to the buccal bone surface and the corresponding width of the cortical bone plate. Results Of 58 detected PA lesions, 15 (25.9%) lesions diagnosed with sagittal CBCT slices were missed with PA radiography. The distance between the apices and the upper border of the mandibular canal was only measurable in 24 of 68 radiographs (35.3%) by using PA images. The cortical bone wall had a mean thickness of 1.7 mm, whereas the total buccal bone wall (cortical and spongious) measured 5.3 mm on average. Conclusions The present study highlights the advantages of using limited CBCT for treatment planning in mandibular molars before apical surgery.

Comparison of Five Cone Beam Computed Tomography Systems for the Detection of Vertical Root Fractures

Introduction This study compared the accuracy of cone beam computed tomography (CBCT) scans made by five different systems in detecting vertical root fractures (VRFs). It also assessed the influence of the presence of root canal filling (RCF), CBCT slice orientation selection, and the type of tooth (premolar/molar) on detection accuracy. Methods Eighty endodontically prepared teeth were divided into four groups and placed in dry mandibles. The teeth in groups Fr-F and Fr-NF were artificially fractured; those in groups control-F and control-NF were not. Groups Fr-F and control-F were root filled. CBCT scans were made using five different commercial CBCT systems. Two observers evaluated images in axial, coronal, and sagittal reconstruction planes. Results There was a significant difference in detection accuracy among the five systems ( p = 0.00001). The presence of RCF did not influence sensitivity ( p = 0.16), but it reduced specificity ( p = 0.003). Axial slices were significantly more accurate than sagittal and coronal slices ( p = 0.0001) in detecting VRF in all systems. Significantly more VRFs were detected among molars than premolars ( p = 0.0001). Conclusions RCF presence reduced specificity in all systems ( p = 0.003) but did not influence accuracy ( p = 0.79) except in one system ( p = 0.012). Axial slices were the most accurate in detecting VRFs ( p = 0.0001).

Commissioning experience with cone‐beam computed tomography for image‐guided radiation therapy

This paper reports on the commissioning of an Elekta cone‐beam computed tomography (CT) system at one of the first U.S. sites to install a “regular,” off‐the‐shelf Elekta Synergy (Elekta, Stockholm, Sweden) accelerator system. We present the quality assurance (QA) procedure as a guide for other users. The commissioning had six elements: (1) system safety, (2) geometric accuracy (agreement of megavoltage and kilovoltage beam isocenters), (3) image quality, (4) registration and correction accuracy, (5) dose to patient and dosimetric stability, and (6) QA procedures. The system passed the safety tests, and agreement of the isocenters was found to be within 1 mm. Using a precisely moved skull phantom, the reconstruction and alignment algorithm was found to be accurate within 1 mm and 1 degree in each dimension. Of 12 measurement points spanning a 9×9×15‐cm volume in a Rando phantom (The Phantom Laboratory, Salem, NY), the average agreement in the x, y, and z coordinates was 0.10 mm, −0.12 mm, and 0.22 mm [standard deviations (SDs): 0.21 mm, 0.55 mm, 0.21 mm; largest deviations: 0.6 mm, 1.0 mm, 0.5 mm] respectively. The larger deviation for the y component can be partly attributed to the CT slice thickness of 1 mm in that direction. Dose to the patient depends on the machine settings and patient geometry. To monitor dose consistency, air kerma (output) and half‐value layer (beam quality) are measured for a typical clinical setting. Air kerma was 6.3 cGy (120 kVp, 40 mA, 40 ms per frame, 360‐degree scan, S20 field of view); half value layer was 7.1 mm aluminum (120 kV, 40 mA).We suggest performing items 1, 2, and 3 monthly, and 4 and 5 annually. In addition, we devised a daily QA procedure to verify agreement of the megavoltage and kilovoltage isocenters using a simple phantom containing three small steel balls. The frequency of all checks will be reevaluated based on data collected during about 1 year.PACS number: 87.53.Xd

Automatic localization of the prostate for on-line or off-line image-guided radiotherapy

With higher radiation dose, higher cure rates have been reported in prostate cancer patients. The extra margin needed to account for prostate motion, however, limits the level of dose escalation, because of the presence of surrounding organs at risk. Knowledge of the precise position of the prostate would allow significant reduction of the treatment field. Better localization of the prostate at the time of treatment is therefore needed, e.g. using a cone-beam computed tomography (CT) system integrated with the linear accelerator. Localization of the prostate relies upon manual delineation of contours in successive axial CT slices or interactive alignment and is fairly time-consuming. A faster method is required for on-line or off-line image-guided radiotherapy, because of prostate motion, for patient throughput and efficiency. Therefore, we developed an automatic method to localize the prostate, based on 3D gray value registration. A study was performed on conventional repeat CT scans of 19 prostate cancer patients to develop the methodology to localize the prostate. For each patient, 8-13 repeat CT scans were made during the course of treatment. First, the planning CT scan and the repeat CT scan were registered onto the rigid bony structures. Then, the delineated prostate in the planning CT scan was enlarged by an optimum margin of 5 mm to define a region of interest in the planning CT scan that contained enough gray value information for registration. Subsequently, this region was automatically registered to a repeat CT scan using 3D gray value registration to localize the prostate. The performance of automatic prostate localization was compared to prostate localization using contours. Therefore, a reference set was generated by registering the delineated contours of the prostates in all scans of all patients. Gray value registrations that showed large differences with respect to contour registrations were detected with a chi(2) analysis and were removed from the data set before further analysis. Comparing gray value registration to contour registration, we found a success rate of 91%. The accuracy for rotations around the left-right, cranial-caudal, and anterior-posterior axis was 2.4 degrees, 1.6 degrees, and 1.3 degrees (1 SD), respectively, and for translations along these axes 0.7, 1.3, and 1.2 mm (1 SD), respectively. A large part of the error is attributed to uncertainty in the reference contour set. Automatic prostate localization takes about 45 seconds on a 1.7 GHz Pentium IV personal computer. This newly developed method localizes the prostate quickly, accurately, and with a good success rate, although visual inspection is still needed to detect outliers. With this approach, it will be possible to correct on-line or off-line for prostate movement. Combined with the conformity of intensity-modulated dose distributions, this method might permit dose escalation beyond that of current conformal approaches, because margins can be safely reduced.

Open-Bite Malocclusion, Its Causes and Treatment

In relation to an impacted third molar, which is the most frequently impacted tooth, external root resorption (ERR) or dental caries can be seen on the distal surface of the adjacent second molar. The purpose of this study was to investigate the risk factors for ERR in second molars associated with impacted third molars using cone-beam computed tomography (CBCT).In this cross-sectional study, the presence of ERR on the adjacent second molar was investigated retrospectively on sagittal and axial CBCT slices of patients who underwent CBCT examination for diagnostic reasons (surgical removal of third molars, orthodontic assessments, and so on) between 2013 and 2017 at the Necmettin Erbakan University Faculty of Dentistry, Konya, Turkey. The primary outcome variable was ERR (yes or no). Predictor variables included demographic (age and gender) and radiographic (impacted tooth angulation and tooth type) parameters. Given that there are multiple observations per patient (1 to 4 impacted teeth), 1 third molar per patient was selected at random for study inclusion. Statistical analysis was performed using descriptive statistics, the Mann-Whitney U test, and the Pearson χ2 test. Logistic regression analysis was used to determine the risk factors for ERR in second molars. The Cohen κ test was used to test intraobserver agreement. The significance level was set at P < .05.Two hundred patients were analyzed, and of the 200 impacted third molars evaluated, 42 (21%) showed ERR. The severity of resorption increased with aging (P < .05). Logistic regression analysis indicated that tooth type and inclination of the third molars could predict the occurrence of ERR associated with an impacted third molar (P < .05).Mesioangular and horizontal inclinations and impacted mandibular third molars posed a greater risk of ERR lesions in adjacent second molars than other inclinations (distoangular and vertical) and maxillary third molars.