Dose calculation and treatment plan optimization including imaging dose from kilovoltage cone beam computed tomography

AbstractObjectiveCone beam computed tomography (CBCT) images contain more scatter than a conventional computed tomography (CT) image and therefore provide inaccurate Hounsfield units (HUs). Consequently, CBCT images cannot be used directly for dose calculation. The aim of this study is to enable dose calculations to be performed with the use of CBCT images taken during radiotherapy and potentially avoid the necessity of re-planning.MethodologyA phantom and prostate cancer patient with a metallic prosthetic hip replacement were imaged using both CT and CBCT. The multilevel threshold algorithm was used to categorise pixel values in the CBCT images into segments of homogeneous HU. The variation in HU with position in the CBCT images was taken into consideration and the benefit of using a larger number of materials than typically used in previous work has been explored. This segmentation method relies upon the operator dividing the CBCT data into a set of volumes where the variation in the relationship between pixel values and HUs is small. A field-in-field treatment plan was generated from the CT of the phantom. An intensity-modulated radiation therapy plan was generated from CT images of the patient. These plans were then copied to the segmented CBCT datasets with identical settings and the doses were recalculated and compared.ResultsIn the phantom study,γevaluation showed that the percentage of points falling in planning target volume, rectum and bladder withγ<1 (3%/3 mm) was 100%. In the patient study, increasing the number of bins to define the material type from seven materials to eight materials required 50% more operator time to improve the accuracy by 0·01% using pencil beam and collapsed cone and 0·05% when using Monte Carlo algorithms.ConclusionThe segmentation of CBCT images using the method in this study can be used for dose calculation. For a simple phantom, 2 values of HU were needed to improve dose calculation accuracy. In challenging circumstances such as that of a prostate patient with hip prosthesis, 5 values of HU were found to be needed, giving a reasonable balance between dose accuracy and operator time.

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Long-term stability of the Hounsfield unit to electron density calibration curve in cone-beam computed tomography images for adaptive radiotherapy treatment planning

Journal of Radiotherapy in Practice ◽

10.1017/s1460396915000321 ◽

2015 ◽

Vol 14 (4) ◽

pp. 410-417 ◽

Cited By ~ 2

Author(s):

Akihiro Takemura ◽

Shogo Tanabe ◽

Mei Tokai ◽

Shinichi Ueda ◽

Kimiya Noto ◽

...

Keyword(s):

Computed Tomography ◽

Treatment Planning ◽

Electron Density ◽

Cone Beam Computed Tomography ◽

Treatment Plan ◽

Dose Calculation ◽

Hounsfield Unit ◽

Cone Beam ◽

Computed Tomography Images ◽

Calibration Curves

AbstractAimTo use cone-beam computed tomography (CBCT) images for treatment planning, the Hounsfield unit (HU)-electron density (ED) calibration table for CBCT should be stable. The purpose of this study was to verify the stability of the HU values for the CBCT system over 1 year and to evaluate the effects of variation in HU-ED calibration curves on dose calculation.Materials and MethodsA tissue characterisation phantom was scanned with the field of view (FOV) of size S (FOV-S) and FOV of size M (FOV-M) using the CBCT system once a month for 1 year. A single field treatment plan was constructed on digital phantom images to validate the dose distribution using mean HU-ED calibration curves and possible variations.ResultsHU values for each material rod over the observation period varied with trend. The HU value of the cortical bone rod decreased by about 100 HU for the FOV-S and by about 300 HU for the FOV-M. Possible variation in the HU-ED calibration curves produced a ≤17·9% dose difference in the dose maximum in the treatment plan.ConclusionsThe CBCT system should be calibrated periodically for consistent dose calculation.

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Variations in vertical mucosal thickness at edentulous ridge according to site and gender measured by cone-beam computed tomography

International Journal of Implant Dentistry ◽

10.1186/s40729-021-00319-w ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Motohiro Munakata ◽

Koudai Nagata ◽

Minoru Sanda ◽

Ryota Kawamata ◽

Daisuke Sato ◽

...

Keyword(s):

Computed Tomography ◽

Cone Beam Computed Tomography ◽

Treatment Plan ◽

Cone Beam ◽

Alveolar Ridge ◽

Marginal Bone Loss ◽

Mandibular Molar ◽

Mucosal Thickness ◽

And Gender ◽

Edentulous Patients

Abstract Background The vertical thickness of the peri-implant mucosa is associated with the amount of post treatment marginal bone loss. However, the variations in mucosal thickness at the different edentulous sites have been sparsely documented. The purpose of the study was to conduct a survey of the frequency distribution of variations in mucosal thickness at the different sites of the edentulous alveolar ridge and to compare them according to gender. Our study included 125 partially edentulous patients having a total of 296 implant sites. Cone-beam computed tomography (CBCT) scans were obtained by placing a diagnostic template with a radiopaque crown indicator on the ridge to determine the mucosal thickness at the crest of the alveolar ridge. Results The mucosal thickness was 3.0±1.3 mm in the maxilla, which was significantly greater than the mucosal thickness of 2.0±1.0 mm in the mandible (p<0.001). In both the maxilla and the mandible, the mucosa was the thickest in the anterior region, followed by the premolar and molar regions. Sites were further classified into two groups based on whether the mucosal thickness was greater than 2 mm. In the mandible, more than half of the sites showed a mucosal thickness of 2 mm or less. Conclusions Although this study was a limited preoperative study, the vertical mucosal thickness at the edentulous ridge differed between the maxillary and mandibular regions. The majority of sites in the mandibular molar region had a mucosal thickness of less than 2 mm. Practitioners might be able to develop an optimal dental implant treatment plan for long-term biologic and esthetic stability by considering these factors.

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A comprehensive evaluation of angular range and separation on image quality, image registration, and imaging dose for cone beam computed tomography in radiotherapy

Medical Dosimetry ◽

10.1016/j.meddos.2018.02.003 ◽

2019 ◽

Vol 44 (1) ◽

pp. 67-73 ◽

Cited By ~ 1

Author(s):

Kuo Men ◽

Jianrong Dai

Keyword(s):

Computed Tomography ◽

Image Quality ◽

Image Registration ◽

Cone Beam Computed Tomography ◽

Comprehensive Evaluation ◽

Cone Beam ◽

Angular Range ◽

Quality Image ◽

Imaging Dose

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TU-C-AUD-07: Analysis On the Use of Megavoltage Cone-Beam Computed-Tomography Images for Dose Calculation

Medical Physics ◽

10.1118/1.2761356 ◽

2007 ◽

Vol 34 (6Part17) ◽

pp. 2551-2551

Author(s):

M Johnson ◽

B Reitz ◽

O Gayou ◽

D Parda ◽

M Miften

Keyword(s):

Computed Tomography ◽

Cone Beam Computed Tomography ◽

Dose Calculation ◽

Cone Beam ◽

Computed Tomography Images

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Poster - Thurs Eve-27: Method of estimating imaging dose to patients from on-line cone-beam computed tomography using patient size data

Medical Physics ◽

10.1118/1.2965946 ◽

2008 ◽

Vol 35 (7Part2) ◽

pp. 3406-3406

Author(s):

B Schaly ◽

EK Osei ◽

R Barnett

Keyword(s):

Computed Tomography ◽

Cone Beam Computed Tomography ◽

Cone Beam ◽

Patient Size ◽

On Line ◽

Imaging Dose ◽

Size Data

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Can diagnostic changes caused by cone beam computed tomography alter the clinical decision in impacted lower third molar treatment plan?

Dentomaxillofacial Radiology ◽

10.1259/dmfr.20200412 ◽

2020 ◽

pp. 20200412

Author(s):

Lucas Moreira Mendonça ◽

Hugo Gaêta-Araujo ◽

Pedro Bastos Cruvinel ◽

Ingrid Wenzel Tosin ◽

Marcelo Rodrigues Azenha ◽

...

Keyword(s):

Computed Tomography ◽

Logistic Regression ◽

Cone Beam Computed Tomography ◽

Treatment Plan ◽

Third Molar ◽

Clinical Decision ◽

Cone Beam ◽

Diagnostic Features ◽

Operative Complications ◽

Post Operative Complications

Objectives: This study observed whether changes in diagnosis caused by analysis of three-dimensional images can lead to alterations in the treatment plans of impacted lower third molars (ILTMs). Methods: Sets of panoramic (PAN) – cone beam computed tomography (CBCT) of 218 patients were assessed for ILTM classification, contact with mandibular canal, contact and resorption of the lower second molar (LSM), intraoperative planning and post-operative expectations. Results: Percentage agreement and McNemar test compared PAN vs CBCT assessments. Logistic regression analyzed the dependency of change in surgical planning considering the changes in diagnostic features; descriptive statistics was used to observe the expectation of post-operative complications and paresthesia. Differences were found between PAN vs CBCT for classification of impaction and positioning, LSM relationship, choice for crown and root sectioning and expectation of post-operative complications (all with p < 0.001). Logistic regression indicated that the change in diagnosis caused by CBCT examination did not change the clinical decision to extract ILTM but altered the planning of intraoperative steps such as osteotomy, crown sectioning and relaxing incision. The expectation of post-operative complications decreased when professionals planned the ILTM removal using tri-dimensional images. Conclusions: We concluded that changes in the diagnosis after CBCT examination can lead to alterations in the treatment plan of impacted lower third molar.

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