Cone-beam Computed Tomography Protocols Research Articles

Low-dose, standard, and high-resolution cone beam computed tomography for alveolar bone measurements related to implant planning: An exvivo study in human specimens.

To evaluate the performance of low-dose cone beam computed tomography (CBCT) protocols with regard to linear bone measurements in the posterior mandible for implant planning compared with higher dose protocols. Forty-two edentulous posterior sites in human cadaveric mandibles were imaged in three CBCT scanners using three or four protocols with varying exposure parameters to achieve lower dose. Co-registration was performed to generate sagittal and cross-sectional image sections representative of the implant site. Three observers measured bone height, from the alveolar crest to the mandibular canal, and width, three mm from the top of the alveolar crest. Intra- and interobserver reproducibility were assessed for the cases rated as nonmeasurable as well as for completed measurements. The measurements were analyzed using paired t-tests for differences among the CBCT protocols and the frequency distribution of nonmeasurable cases with a Pearson Chi-square test. Reproducibility for registering nonmeasurable cases varied among observers; however, no consistent significant differences were found in the frequency distribution of these cases among observers, units, and protocols. Intraclass correlation coefficients (ICC) were >0.9 for all measurements of bone height and width. Mean differences of <0.5 mm were found regardless of protocol; however, one observer did in some cases produce larger differences. Linear bone measurements did not differ significantly and could be performed with excellent reliability, using low-dose CBCT protocols compared with standard and high-resolution ones. Varying approaches for rating nonmeasurable cases were found, indicating differences in diagnostic strategies related to implant planning among observers.

Assessment of cone-beam CT technical image quality indicators and radiation dose for optimal STL model used in visual surgical planning.

The aim of this study was to identify cone-beam computed tomography (CBCT) protocols that offer an optimal balance between effective dose and 3D model for orthognathic virtual surgery planning, using CT as a reference, and to assess whether such protocols can be defined based on technical image quality metrics. Eleven CBCT (VISO G7, Planmeca Oy, Helsinki, Finland) scan protocols were selected out of 32 candidate protocols, based on effective dose and technical image quality measurements. Next, an anthropomorphic RANDO SK150 phantom was scanned using these 11 CBCT protocols and 2 CT scanners for bone quantity assessments. The resulting DICOM files were converted into STL models that were used for bone volume and area measurements in the predefined orbital region to assess the validity of each CBCT protocol for VSP. The highest CBCT bone volume and area of the STL models were obtained using normal dose protocol (F2) and ULD protocol (J13) which resulted in 48% and 96% of the mean STL bone volume and 48% and 95% of the bone area measured on CT scanners, respectively. The optimal normal dose CBCT protocol" F2" offered optimal bone area and volume balance for STL. The optimal CBCT protocol can be defined exhibited similar using CNR and MTF values that were similar with of those of the reference CT scanners'. CBCT scanner with selected protocols can offer a viable alternative to CT scanners for acquiring STL models for VSP at a lower effective dose.

Evaluation of normal organ doses for extended kV- CBCT protocol in para-aortic region treatment using nanoDot dosimeter

Extended cone beam computed tomography (CBCT) imaging protocol was used to extend the longitudinal coverage by acquiring double CBCT which allows an overlapping of doubled doses from the two orbits. The aim of this study was to evaluate the absorbed doses of three normal organs; bladder, small bowel, and rectum in the overlapped region for extended CBCT imaging protocol with 125 kV and 592 mAs of Ethos™ machine in para-aortic lymph node treatment using nanoDot™ dosimeters placed on the Rando phantom. The nanoDot™ correction factor (CFOSLD) and an organ depth dose correction factor (CFDepth) were used to calculate the absorbed doses of each organ. The result showed that the absorbed dose for bladder, small bowel and rectum were 18.71 ± 0.99, 19.57 ± 0.05 and 20.93 ± 0.74 mGy, respectively, which are lower than the radiation tolerance doses. However, the overlapping dose from the extended CBCT protocol should be considered to estimate the imaging dose throughout the treatment course for managing the use of extended CBCT to verify patient positioning before treatment. Additionally, the results can be used to determine the radiation dose in treatment planning to keep the additional imaging dose to the patient as low as reasonably achievable.

Accuracy of linear measurements for implant planning based on low-dose cone beam CT protocols: a systematic review and meta-analysis.

The aim of this systematic review was to verify the accuracy of linear measurements performed on low-dose CBCT protocols for implant planning, in comparison with those performed on standard and high-resolution CBCT protocols. The literature search included four databases (Pubmed, Web of Science, Embase, and Scopus). Two reviewers independently screened titles/abstracts and full texts according to eligibility criteria, extracted the data, and examined the methodological quality. Risk of bias assessment was performed using the Quality Assessment Tool For In Vitro Studies. Random-effects meta-analysis was used for pooling measurement error data. The initial search yielded 4684 titles. In total, 13 studies were included in the systematic review, representing a total of 81 samples, while 9 studies were included in the meta-analysis. The risk of bias ranged from medium to low. The main results across the studies indicate a strong consistency in linear measurements performed on low-dose images in relation to the reference methods. The overall pooled planning measurement error from low-dose CBCT protocols was -0.24 mm (95% CI, -0.52 to 0.04) with a high level of heterogeneity, showing a tendency for underestimation of real values. Various studies found no significant differences in measurements across different protocols (eg, voxel sizes, mA settings, or dose levels), regions (incisor, premolar, molar) and types (height vs. width). Some studies, however, noted exceptions in measurements performed on the posterior mandible. Low-dose CBCT protocols offer adequate precision and accuracy of linear measurements for implant planning. Nevertheless, diagnostic image quality needs must be taken into consideration when choosing a low-dose CBCT protocol.

A quantitative CBCT pipeline based on 2D antiscatter grid and grid-based scatter sampling for image-guided radiation therapy.

Quantitative accuracy is critical for expanding the role of cone beam CT (CBCT) imaging from target localization to quantitative treatment monitoring and plan adaptations in radiation therapy. Despite advances in CBCT image quality improvement methods, quantitative accuracy gap between CBCT and multi-detector CT (MDCT) remains. In this work, a physics-driven approach was investigated that combined robust scatter rejection, raw data correction and iterative image reconstruction to further improve CBCT image quality and quantitative accuracy, referred to as quantitative CBCT (qCBCT). QCBCT approach includes tungsten 2D antiscatter grid hardware, residual scatter correction with grid-based scatter sampling, image lag, and beam hardening correction for offset detector geometry linac-mounted CBCT. Images were reconstructed with iterative image reconstruction to reduce image noise. qCBCT was evaluated using a variety of phantoms to investigate the effect of object size and its composition on image quality, and image quality was benchmarked against clinical CBCT and gold standard MDCT images used for treatment planning. QCBCT provided statistically significant improvement in CT number accuracy and reduced image artifacts when compared to clinical CBCT images. When compared to gold standard MDCT, mean HU errors in qCBCT and clinical CBCT were 17±9 and 38±29 HU, respectively. Magnitude of phantom size dependent HU variations were comparable between MDCT and qCBCT images. With iterative reconstruction, contrast-to-noise ratio improved by 25% when compared to clinical CBCT protocols. Combination of novel scatter suppression techniques and other data correction methods in qCBCT provided CT number accuracy comparable to gold standard MDCT used for treatment planning. This approach may potentially improve CBCT's promise in fulfilling the tasks that demand high quantitative accuracy, such as online dose calculations and treatment response assessment, in image guided radiation therapy.

Evaluation of 2- and 3-dimensional anatomic parameters of C-shaped root canals with cone beam computed tomography, microcomputed tomography, and nanocomputed tomography

The objective of this study was to evaluate 2-dimensional (2D) and 3D morphometric parameters of C-shaped root canals on cone beam computed tomography (CBCT) and microcomputed tomography (microCT) images using nanocomputed tomography (nanoCT) as the reference standard. Sixty mandibular molars with C-shaped canals were individually scanned using nanoCT and microCT. Cone beam computed tomography acquisitions were then performed with 4 CBCT systems, using high and standard resolutions. The 2D parameters of roundness and major and minor diameters were obtained in the cross sections of the root canals at 1, 2, and 3 mm from the root apex. The 3D parameters of surface area, volume, and structure model index were measured considering the entire extension of the root canals. Absolute error (AE) in measurement was calculated against the nanoCT values. Data were statistically analyzed with the Shapiro-Wilk test and analysis of variance (α=0.05). No significant differences in AE were discovered for the 2D parameters among microCT and the CBCT scans. The AE values for the 3D parameters of volume and surface area were significantly smaller in microCT compared to all CBCT units (P < .05). Significantly lower AE values for surface area were observed in high resolution compared to standard resolution for all CBCT units (P < .05). Structure model index did not differ significantly among microCT and all CBCT protocols. Cone beam computed tomography images showed accuracy for evaluating 2D parameters and over- and underestimation for 3D parameters.

Creation of Dimicleft radiological cleft phantom skulls using reversed virtual planning technique.

The aim of this technical report was to develop customized pediatric phantoms for cone-beam computed tomography (CBCT)-related research in cleft patients. Six human pediatric skulls (age: 5-10 years) were recruited. A cone-beam computed tomography (CBCT) scan was taken for each skull, followed by virtual modeling through the process of segmentation. An artificial cleft was designed and printed to be applied onto the skull for the creation of an artificial cleft. The skulls were covered with non-radiopaque tape and immersed in melted Mix-D soft tissue equivalent material. The resulting phantoms covered with Mix-D were assessed radiologically by two expert radiologists. These phantoms were referred to as Dimicleft pediatric skull phantoms. Dimicleft phantoms were able to appropriately mimic in vivo circumstances. No gaps existed between Mix-D and bony tissue. Virtual planning allowed the optimal designing of an artificial cleft onto the phantom. The artificially created cleft was suitable to determine the size, location, and extent of the cleft. Dimicleft phantoms could act as a viable alternative to other commercially available options for assessing image quality and optimizing CBCT protocols in cleft patients for diagnostics and three-dimensional treatment planning.

Testing of Different Scanning Protocols Used for Precise 3D-printing of Mandibular Models.

Multidetector computed tomography (MDCT) is often necessary to manufacture 3D-printed medical models (MMs) required for mandibular restoration due to trauma or malignant tumor. Although cone-beam computed tomography (CBCT) is a preferable method of mandibular imaging, additional scanning is often unjustified. To test whether a single radiologic protocol could be used for mandibular reconstructions, the human mandible was scanned with 6 MDCT and 2 CBCT protocols and later 3D-printed using a fused-deposition modelling technique. Then, we assessed linear measures on the mandible and compared them with MDCT/CBCT digital scans and 3D-printed MMs. Our data revealed that CBCT0.25 was the most precise protocol for manufacturing 3D-printed mandibular MMs, which is expected considering its voxel size. However, we noted that CBCT0.35 and Dental2.0H60s MDCT protocols were of comparable accuracy, indicating that this MDCT protocol could be a single radiologic protocol used to scan both donor and recipient regions required for mandibular reconstruction.

Assessment of organ and size-specific effective doses from cone beam CT (CBCT) in image-guided radiotherapy (IGRT) based on body mass index (BMI)

The ability of radiation therapy to deliver radiation doses accurately to tumour targets, while sparing normal tissues, has advanced remarkably over recent decades. A development that has been key to achieving this improvement has been the application of image-guidance that facilitates more precise delivery of the prescribed dose to the treatment site. A recent international survey showed that kV cone beam CT (CBCT) is the imaging modality used most widely for image guided radiation therapy (IGRT) procedures. However, IGRT will deliver additional radiation doses to patients that should be considered. The aims of this study were to (1) estimate organ and size-specific effective doses resulting from kV-CBCT chest and pelvis scans based on body mass index (BMI) of the patient, and (2) investigate the influence of patient size on imaging dose. A validated Monte Carlo model developed with BEAMnrc/EGSnrc was employed to simulate kV spectra generated by Varian on-board imaging (OBI) system. Organ and size-specific effective doses were assessed for adult phantoms in the National Cancer Institute (NCI) phantom library using DOSXYZnrc/EGSnrc code. The library has been reconstructed from images of CT patients, and contains 100 male and 93 female phantoms of a wide range of sizes. The phantoms were grouped into six categories based on body mass index (BMI) as classified by the world health organization. For all sizes, average doses to organs that lay fully or partially inside the field of the chest and pelvic scans were in the range of (0.20–3.06 mGy/100 mAs) and (0.17–4.47 mGy/100 mAs), and size-specific effective doses were (0.63 – 1.78 mSv/100 mAs) and (0.30 – 1.17 mSv/100 mAs), respectively. Patient size played a significant role in determining the imaging doses resulting from both scans. In general, organ and effective doses of chest and pelvic scans of thin patients were about 2–3 times larger than those of obese patients, with the impact of patient size on pelvis doses being slightly higher than on chest ones. Results of this study suggests that patient size should be taken into consideration when estimation and optimization of the imaging doses resulting from CBCT. Although development of patient size-specific CBCT protocols is a practical approach that can account for patient size, it has not been implemented worldwide. Results from this investigation might be used as a simple approach to obtain an estimation of the imaging doses for patients of various sizes based on BMI.

Effects of the cone-beam computed tomography protocol on the accuracy and image quality of root surface area measurements: An in vitro study.

The objective of this study was to evaluate and compare the accuracy and image quality of root surface area (RSA) measurements obtained with various cone-beam computed tomography (CBCT) protocols, relative to the gold standard of micro-computed tomography (CT), in an in vitro setting. Four dry human skulls were scanned using 8 different protocols, with voxel sizes of 0.15 mm, 0.3 mm, and 0.4 mm. Three-dimensional models of the selected teeth were constructed using CBCT and micro-CT protocols, and the RSA was automatically measured by the image-processing software. The absolute difference in the percentage of the RSA (%ΔRSA) was calculated and compared across the 8 CBCT protocols using repeated-measures analysis of variance. Finally, image quality scores of the RSA measurements were computed and reported in terms of percent distribution. No significant differences were observed in the %ΔRSA across the 8 protocols (P>0.05). The deviation in %ΔRSA ranged from 1.51% to 4.30%, with an increase corresponding to voxel size. As the voxel size increased, the image quality deteriorated. This decline in quality was particularly noticeable at the apical level of the root, where the distribution of poorer scores was most concentrated. Relative to CBCT protocols with voxel sizes of 0.15 mm and 0.3 mm, the protocols with a voxel size of 0.4 mm demonstrated inferior image quality at the apical levels. In spite of this, no significant discrepancies were observed in RSA measurements across the different CBCT protocols.

Ultra-low-dose CBCT: new cornerstone of paranasal sinus imaging.

This study evaluates the clinical image quality (IQ) and usability of a sinonasal ultra-low-dose (ULD) cone-beam computed tomography (CBCT) scan. The results are compared to those of a high resolution (HR) CBCT scan to identify the strengths and weaknesses of a ULD CBCT protocol. Sixty-six anatomical sites in 33 subjects were imaged twice using two imaging modalities: HR CBCT (Scanora 3Dx scanner; Soredex, Tuusula, Finland) and ULD CBCT (Promax 3D Mid scanner; Plandent, Helsinki, Finland). IQ, opacification and obstruction, structural features and operative usability were assessed. The overall IQ in subjects with 'no or minor opacification' was excellent: 100% (HR CBCT) and 99% (ULD CBCT) of ratings were evaluated as sufficient for every structure. Increased opacification reduced the quality of both imaging modalities, resulting conchtoethmoidectomy, frontal sinusotomy, sphenotomy and posterior ethmoidectomy in cases with greater opacification. IQ of paranasal ULD CBCT is sufficient for clinical diagnostics and should be considered for surgical planning. We recommend it as the primary imaging protocol for all patients who meet imaging criteria due to recurrent or chronic nasal symptoms. Additional or conventional imaging might be needed for patients with extensive chronic rhinosinusitis and/or indications of frontal sinus involvement.

Do cone-beam computed tomography low-dose protocols affect the evaluation of the temporomandibular joint?

There is no established acquisition protocol based on scientific evidence for the acquisition of cone-beam computed tomography (CBCT) exams to evaluate the temporomandibular joint (TMJ). To evaluate the influence of acquisition protocols and jaw positioning on the diagnostic accuracy of TMJ condylar morphological alterations (CMA), dimension, position and excursion. Thirty-six TMJs on 18 dry skulls were imaged using a CBCT unit (OP300 Maxio, Instrumentarium, Tuusula, Finland) at two exposure settings (4.5 and 6.3mA), three voxel resolutions (0.085, 0.125 and 0.280 mm), three jaw positions (concentric, anteriorised and posteriorised) and three jaw excursions (normoexcursion, hyperexcursion and hypoexcursion). The macroscopic anatomy examination and high-resolution CBCT images were used as ground truth for CMA. Twenty-five TMJs had at least one CMA with 11 healthy TMJs serving as controls. Three experienced oral and maxillofacial radiologists evaluated the parasagittal images for the presence of CMA, position and excursion and measured dimensions. The area under the ROC curve, sensitivity and specificity were calculated. Weighted Kappa (α=0.05) was used to determine intra- and interexaminer reliability and comparisons between dependent variables analysed by Analysis of Variance at an a prior level of significance of 0.05. The agreement of the evaluation of the position and excursion with the reference standard was high, independent of the protocol (range, 0.75-0.91). Various combinations of acquisition protocols and jaw position did not influence the CMA evaluation. Erosion was overdiagnosed in protocols with larger voxel sizes and the detection of osteophytes greater in images with smaller voxel sizes. The anteroposterior dimension was greater in the open jaw position (p < .05). CBCT protocols using reduced radiation exposure from the CBCT machine evaluated in this study can be used to assess condylar morphology, dimension, position and excursion, without compromising diagnostic performances for these parameters.

Comparison of subjective image analysis and effective dose between low-dose cone-beam computed tomography machines.

To compare the cone-beam computed tomography (CBCT) image quality and effective dose between low-dose scanning and standard manufacturer-recommended protocols among different CBCT units. Three human-equivalent phantoms were scanned using the ultra-low-dose (ULD), low dose (LD), and standard dose (STD) modes of ProMax 3D Mid (Planmeca Oy, Helsinki, Finland) and Orthophos SL (Sirona, Bensheim, German) for the CBCT images. The quality of the dental anatomical images was assessed by four experienced oral and maxillofacial radiologists using a 5-point Likert scale. OnDemand3D (Cybermed Co., Seoul, Korea) was used as the third-party software for viewing. The percentage of absolute agreement was calculated to determine intra- and interrater agreements among the observers. The effective doses for all CBCT scanning protocols were also calculated. The STD protocol yielded a higher image quality than did the ULD and LD protocols in both ProMax 3D Mid and Orthophos SL. The ULD and LD protocols demonstrated an "acceptable-to-good" sense of visual perception of the CBCT images. The visibility scores significantly differed between the ULD and LD and the STD protocols in ProMax 3D Mid and Orthophos SL, except for the 120-kVp setting in ProMax 3D Mid. The average intra- and interrater agreement scores ranged from 0.63 to 0.89 and from 0.44 to 0.76, respectively. The ULD and LD protocols reduced the radiation dose sixfold compared with the STD protocol. High-tube-voltage protocols could remarkably reduce the imaging dose without degrading the image quality. Specifically, ULD and LD CBCT protocols may be adopted as routine practice for diagnosis and treatment planning.

Diagnostic efficacy of 3 imaging modalities in the detection of fractured endodontic instruments: an in vitro study

<h3>Objectives</h3> To compare the diagnostic efficacy of periapical radiography (PAR) and cone beam computed tomography (CBCT) without and with a metal artifact reduction algorithm (MARA) in the detection of fractured endodontic instruments in unfilled and filled root canals that were straight and curved. <h3>Study Design</h3> In total, 144 root canals from 48 mandibular molars were divided into 4 groups: the control group with empty canals, the fracture group with a fractured instrument, the fill group with root canal filling, and the fracture/fill group with a fractured instrument and root canal filling. The teeth were examined with PAR using a complementary metal oxide semiconductor sensor and CBCT without and with MARA to evaluate the diagnostic efficacy of the 3 techniques in the detection of fractured instruments. Three examiners evaluated the radiographs. <h3>Results</h3> Overall, PAR exhibited significantly better diagnostic outcomes than CBCT without MARA. PAR yielded significantly better results than both CBCT protocols in the presence of root filling and in straight canals. In the absence of filling and in curved canals, there were no statistically significant differences among the 3 techniques. <h3>Conclusions</h3> PAR was the imaging technique that best detected fractured instruments in filled and unfilled straight root canals.

Implementation of a comprehensive set of optimised CBCT protocols and validation through imaging quality and dose audit.

Cone-beam computed tomography (CBCT) for radiotherapy treatment verification has increased in frequency; therefore, it is crucial to optimise image quality and radiation dose to patients. The aim of this study was to implement optimised CBCT protocols for the Varian TrueBeams for most tumour sites in adult patients. A combination of patient size-specific CBCT protocols from the literature and developed in-house was used. Scans taken before and after optimisation were compared by senior radiographers and physicists to evaluate how changes affected image quality and clinical usability for online image registration. The change in dose for each new CBCT protocol was compared to the Varian default. A clinical audit was performed following implementation to evaluate the changes in imaging dose for all patients receiving a CBCT during that period. Ten CBCT protocols were introduced including head and neck and patient-size-specific thorax and pelvis/abdomen protocols. Scans from 102 patients with images before and after optimisation were assessed, none of the scans showed image quality changes compromising clinical usability and for some image quality was improved. Between November 2020 and June 2021, 1185 patients had CBCTs using the new protocols. The imaging dose was reduced for 52% of patients, remained the same for 37% and increased for 12%. This study showed that substantial dose reductions and image quality improvements can be achieved with simple changes in the default settings of the Varian TrueBeam CBCT without affecting the radiographers' confidence in online image registration. This study represents a comprehensive assessment and optimisation of CBCT protocols for most sites, validated on a large cohort of patients.

Cone beam computed tomography (CBCT) in pediatric dentistry

Objective: The aims of this systematic review of the literature were to investigate the uses of cone beam computed tomography (CBCT) in pediatric dentistry and, if possible, identify the indications.&#x0D; Material and methods: A literature search was conducted using the PubMed and Scopus electronic databases and the keywords "CBCT and pediatric dentistry". This search provided us with 1518 references. The selected publications were all clinical articles written in French or English and referring to a pediatric population. After screening, 461 eligible full text articles remained.&#x0D; Results: In total, there were 169 references that met the inclusion criteria. Different topics, mainly relating to orthodontics, anatomy, and cleft lips and palate, were discussed. There was large variability in the information concerning the&#x0D; technical parameters. The radiographic protocols that we analyzed showed a large heterogeneity.&#x0D; Conclusions: The level of evidence provided by our work is limited because only two randomized double-blind controlled studies are included. Two indications can be distinguished: for orthodontics and for the rehabilitation of cleft lips and palate. There are a multitude of radiographic protocols. More research is needed to identify other potential clinical indications as well as to determine a standard CBCT protocol for children and adolescents.

ULTRA-LOW DOSE CONE-BEAM CT INCREASES POSITIVE DIAGNOSIS RATE OF PERIPHERAL NODULE BRONCHOSCOPY WHILE IMPROVING RADIATION SAFETY

TYPE: Late Breaking Abstract TOPIC: Procedures PURPOSE: Cone-beam CT (CBCT) can be used during electromagnetic navigation bronchoscopy (ENB) to improve accuracy and safety of biopsy. Although the added value of CBCT is recognized, there are concerns about radiation exposure. We investigate the impact of a ultra-low-dose CBCT protocol. METHODS: A single institution, retrospective, comparative study of CBCT-ENB for biopsies using two radiation protocols (standard (Gp1) vs ultra-low-dose (Gp2)). We estimated the total E, E attributed to CBCT (E1) and E attributed to fluoroscopy (E2) per lesion from the dose-area-product (conversion factor 0.16 mSv/Gy·cm2). Secondary outcomes were number of CBCT runs and positive diagnosis (PD) rate. RESULTS: From Jan 2015-22, 386 patients (mean age 68.3) underwent CBCT-ENB for biopsy of 452 pulmonary lesions (mean size 19.5 mm): Gp1 121 patients with 138 lesions, Gp2 258 patients with 306 lesions. Total E was 4.85 mSv (Gp1) vs 1.72 mSv (Gp2) (64.5% decrease, p<0.01). E1 was 3.57 mSv (Gp1) vs 1.46 mSv (Gp2) (p<0.01) and E2 was 1.28 mSv (Gp1) vs 0.29 mSv (Gp2) (p<0.01). The number of CBCT runs increased from 3.65 to 5.68 (55.6% increase, p<0.01, dose-per-CBCT-run 0.98 mSv vs 0.26 mSv). PD rate increased from 61.7% to 72.0% (16.7% increase, p=0.05). CONCLUSIONS: The ultra-low dose protocol reduced radiation exposure compared to standard dose protocol. This allowed for more CBCT runs, more accurate tool positioning, and an improved diagnostic rate. CLINICAL IMPLICATIONS: Ultra-low dose CBCT not only reduces radiation exposure, but allows more iterative CBCT runs and improved diagnostic rate and should be adopted more widely. DISCLOSURE: Funded student internship at Philips Image Guided Therapy Systems (Best, The Netherlands) (applies to submitter). Two co-authors are employee's of Philips Image Guided Therapy Systems (Best, The Netherlands). KEYWORD: Interventional pulmonology

PO-1605 Low dose cone beam CT protocols for image-guided breast and pediatric treatments

PO-1605 Low dose cone beam CT protocols for image-guided breast and pediatric treatments

Imaging furcation defects with low-dose cone beam computed tomography

Different cone beam computed tomography (CBCT) protocols have shown promising results for imaging furcation defects. This study evaluates the suitability of low-dose (LD)-CBCT for this purpose. Fifty-nine furcation defects of nine upper and 16 lower molars in six human cadavers were measured by a high-dose (HD)-CBCT protocol, a LD-CBCT protocol, and a surgical protocol. HD-CBCT and LD-CBCT measurements were made twice by two investigators and were compared with the intrasurgical measurements, which served as the reference. Furcation defect volumes generated from HD-CBCT and LD-CBCT imaging were segmented by one rater. Cohen’s kappa and intraclass correlation coefficient (ICC) values were calculated to determine intra- and interrater reliability. The level of significance was set at α = 0.05. In total, 59 furcation defects of nine upper and 16 lower human molars were assessed. Comparing CBCT furcation defect measurements with surgical measurements revealed a Cohen’s kappa of 0.5975 (HD-and LD-CBCT), indicating moderate agreement. All furcation defects identified by HD-CBCT were also detected by LD-CBCT by both raters, resulting in a Cohen’s kappa of 1. For interrater agreement, linear furcation defect measurements showed an ICC of 0.992 for HD-CBCT and 0.987 for LD-CBCT. The intrarater agreement was 0.994(r1)/0.992(r2) for HD-CBCT and 0.987(r1)/0.991(r2) for LD-CBCT. The intermodality agreement was 0.988(r1)/0.991(r2). Paired t-test showed no significant differences between HD-CBCT and LD-CBCT measurements. LD-CBCT is a precise and reliable method for detecting and measuring furcation defects in mandibular and maxillary molars in this experimental setting. It has the potential to improve treatment planning and treatment monitoring with a far lower radiation dose than conventional HD-CBCT.

In vitro measurements of radiation exposure with different modalities (computed tomography, cone beam computed tomography) for imaging the petrous bone with a pediatric anthropomorphic phantom

BackgroundVarious imaging modalities, such as multi-detector computed tomography (CT) and cone beam CT are commonly used in infants for the diagnosis of hearing loss and surgical planning of implantation hearing aid devices, with differing results.ObjectiveWe compared three different imaging modalities available in our institution, including a high-class CT scanner, a mid-class CT scanner and an angiography system with a cone beam CT option, for image quality and radiation exposure in a phantom study.Materials and methodsWhile scanning an anthropomorphic phantom imitating a 1-year-old child with vendor-provided routine protocols, organ doses, surface doses and effective doses were determined for these three modalities with thermoluminescent dosimeters. The image quality was evaluated using the signal difference to noise ratio (SDNR) and the spatial resolution of a line-pair insert in the phantom head. The dose efficiency, defined as the ratio of SDNR and effective dose, was also compared.ResultsThe organ and surface doses were lowest with the high-class CT protocol, but the image quality was the worst. Image quality was best with the cone beam CT protocol, which, however, had the highest radiation exposure in this study, whereas the mid-class CT was in between.ConclusionBased on our results, high-end CT should be used for surgical planning because it has the lowest dose, while the image quality is still sufficient for this purpose. However, if highest image quality is needed and required, e.g., by ENT surgeons, the other modalities should be considered.