Background: While many clinical computed tomography (CT) protocols use helical scanning, the traditional method for measuring the volume CT Dose Index (CTDI) requires modifying the helical protocol to perform a single axial rotation. This modification can present challenges and mismatched settings across various scanner models.
Purpose: This study investigates the generalizability of a helical methodology for estimating CTDI across a diverse range of participants, CT scanner models, and protocol parameters.
Methods: A web-based platform collected axial and helical CTDI measurements from 24 medical physicists who submitted 569 data sets obtained using four CT protocols on scanners from seven CT manufacturers. Various parameters were tested for tube voltage (70-140 kVp), rotation time (0.25-1.50 s), beam width (8-80 mm), and pitch (0.29-3.0) settings. Measurements from the two methodologies were assessed for reproducibility using three repeated exposures and then compared to each other and to the scanner-displayed CTDI. Agreement between the methodologies was assessed using Bland-Altman analysis, linear regression, paired t-tests, and a paired two one-sided tests (TOST) procedure with equivalence margins of 5% of the mean protocol CTDI. The impact of beam width and pitch on measurement accuracy was assessed using linear regression analysis and an independent t-test.
Results: This study demonstrated better measurement reproducibility with the helical method (p < 0.05) and excellent concordance between helical and axial measurements (CCC > 0.99), with an average difference of -0.61 mGy (limits of agreement: -4.54 and 3.32). The TOST analysis confirmed that the measurement methods were statistically equivalent within the defined equivalence margins. The number of measurements that differed from the displayed CTDI by more than ± 20% was 10 for the axial method and 22 for the helical method. We did not identify a linear correlation between measurement accuracy and beam width or pitch (R< 0.06). However, differences between axial and helical methods were significant for protocols with beam widths up to 40 mm versus those greater than 40 mm, as well as for protocols with pitch factors up to 1.0 compared to those greater than 1.0 (p < 0.001).
Conclusion: Utilizing the same equipment currently used for measuring CTDI and a simple measurement setup, the helical method offers an alternative measurement methodology that can be seamlessly implemented by medical physicists and adopted by regulatory and accrediting bodies for routine quality control of CT scanners.
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http://dx.doi.org/10.1002/mp.17543 | DOI Listing |
BMC Oral Health
December 2024
Department of Orthodontics, Institute of Craniofacial Deformity, Yonsei University College of Dentistry, 50-1 Yonsei-Ro, Seodaemun-Gu, Seoul, 03722, Republic of Korea.
Background: This case report details a true hemifacial hyperplasia with temporomandibular joint ankylosis case managed through a multidisciplinary approach involving department of oral and maxillofacial surgery, orthodontics, and prosthodontics.
Case Presentation: A 42-year-old female patient presented with a chief complaint of limited mouth opening. Clinically, the patient exhibited severe facial asymmetry due to hyperplasia of the left facial region.
Surg Radiol Anat
December 2024
School of Dentistry, Federal University of Rio Grande do Sul, UFRGS. Rua Ramiro Barcelos 2492, Porto Alegre, RS, 90035-003, Brazil.
Purpose: This study utilized cone-beam computed tomography images to assess the potential of maxillary sinus (MS) and piriform aperture (PA) measurements in sex prediction and to identify possible correlations between these structures and the MS ostium.
Methods: A total of 204 images were selected and divided into two groups: 102 for constructing and testing the formula, and 102 for validation. In each subgroup, the images were equally divided for 11 measurements by two examiners in the MS (height, width, length, and total width), PA (height and width), and maxillary ostium diameter.
Nanomaterials (Basel)
November 2024
Nanotechnology Group, USAL-Nanolab, Departamento de Física Fundamental, Universidad de Salamanca (USAL), E-37008 Salamanca, Spain.
The ability to manufacture complex 3D structures with nanometer-scale resolution, such as Fresnel Zone Plates (FZPs), is crucial to achieve state-of-the-art control in X-ray sources for use in a diverse range of cutting-edge applications. This study demonstrates a novel approach combining Electron Beam Lithography (EBL) and cryoetching to produce silicon-based FZP prototypes as a test bench to assess the strong points and limitations of this fabrication method. Through this method, we obtained FZPs with 100 zones, a diameter of 20 µm, and an outermost zone width of 50 nm, resulting in a high aspect ratio that is suitable for use across a range of photon energies.
View Article and Find Full Text PDFDiagnostics (Basel)
November 2024
Department of Oral and Maxillofacial Radiology, Faculty of Dentistry, Giresun University, 28200 Giresun, Turkey.
Objectives: Since the formation of skeletal malocclusions is closely linked to general craniofacial development, it is crucial to understand the anatomy and growth patterns of the skull base. This study aimed to assess the morphometry of the occipital condyle (OC) on CBCT scans of Class III skeletal malocclusion subjects and compare the findings with those of skeletal Class I malocclusion subjects.
Methods: A retrospective analysis was performed on CBCT images based on predefined inclusion and exclusion criteria.
Cancers (Basel)
November 2024
Radiotherapy and Radiation Dosimetry, National Physical Laboratory, Teddington TW11 0LW, UK.
: Spatial fractionation of proton fields as sub-millimeter beamlets to treat cancer has shown better sparing of healthy tissue whilst maintaining the same tumor control. It is critical to ensure primary standard dosimetry is accurate and ready to support the modality's clinical implementation. : This work provided a proof-of-concept, using the National Physical Laboratory's Primary Standard Proton Calorimeter (PSPC) to measure average absorbed dose-to-water in a pMBRT field.
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