Computed tomography (CT) is one of the most important imaging methods in clinical medical practice. Students of medicine have an opportunity to learn about its principles during the classes of the medical biophysics. For a high-quality understanding of the function of CT and to increase the curriculum attractiveness, it is advisable to include such clinical equipment or its simulator in the practical lessons. However, regarding operational safety and related maintenance, CT devices are very expensive and demanding. Therefore, the aim of this work was to create a cheap, operationally easy, and safe CT simulator. The device simulates the principle of CT by transmitting visible light through cubes with a built-in filter of defined attenuation simulating various human tissues. During hands-on training, students first measure radiation intensities without a sample (I0) and with single cubes (Ii). In the second task, students measure a matrix consisting of four different cubes, irradiating the matrix from different directions and simulating the CT principle. Based on the measurements, the students calculate the linear attenuation of each cube and the corresponding CT numbers and compare the results. The simulator's control is intuitive, provided measurement results are consistent and automatically fed into an interactive report that compares the measured data with the students' calculations, verifies the results, and finally stores them in the database. The main benefit of the study is to bring cheap and effective tools for the demonstration of the CT principle, which can operate each student during the practical lessons, followed by supporting teaching materials.
1Analyzing radiation absorption difference of dental substance by using Dual CT
Analyzing radiation absorption difference of dental substance by using Dual CT
60Computed Tomography as a Core Analysis Tool: Applications, Instrument Evaluation, and Image Improvement Techniques
In recent years, the use of computerized tomography (CT) to characterize two-phase fluid flow through porous media has become increasingly popular. This paper describes a different application of CT: it use as a core analysis tool. The advantages and disadvantages of the different technological generations of commercial medical CT scanners available as core analysis instruments are also discussed. Additionally, methods are presented for improving images and reducing CT-number errors inherent in the scanning of high-density rock samples on instruments whose software was designed for the scanning of the low-density human patients.
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7Regional Deprivation and Non-Cancer Related Computed Tomography Use in Pediatric Patients in Germany: Cross-Sectional Analysis of Cohort Data.
BackgroundConflicting findings were observed in recent studies assessing the association between patients’ area-level socio-economic status and the received number of computed tomography (CT) examinations in children. The aim was to investigate the association between area-level socio-economic status and variation in CT examination practice for pediatric patients in Germany.MethodsData from Radiology Information Systems for children aged 0 to < 15 years without cancer who had at least one CT examination between 2001 and 2010 were extracted in 20 hospitals across Germany. The small-area German Index of Multiple Deprivation (GIMD) was used to assess regional deprivation. The GIMD scores were classified into least, medium and most deprived areas and linked with the patient’s last known postal code. A multinomial logistic regression model was used to assess the association between patients’ CT numbers and regional deprivation adjusting for age, sex, and location of residence (urban/rural).ResultsA total of 37,810 pediatric patients received 59,571 CT scans during the study period. 27,287 (72%) children received only one CT, while n = 885 (2.3%) received six or more. Increasing numbers of CT examinations in non-cancer patients were significantly associated with higher regional deprivation, which increased, although CI overlap, for higher CT categories: ‘2–3 CT’ odds ratio (OR) = 1.45, 95%CI: 1.40–1.50; ‘4–5 CT’ OR = 1.48, 95%CI: 1.38–1.59; ‘6+CT’ OR = 1.54, 95%CI: 1.41–1.69. In addition, male sex, higher age categories, and specific body regions were positively associated with increased numbers of CT examinations.ConclusionWe observed a positive association between regional deprivation and CT numbers in non-cancer pediatric patients. Limitations of the ecological approach and the lack of differentiation of CT details have to be acknowledged. More information on CT indications is necessary for a full assessment of this finding. In addition, further work on ways to assess socio-economic status more accurately may be required.
Read more1Physical analysis of breast cancer using dual-source computed tomography
Physical analysis of breast cancer using dual-source computed tomography
Inter- and intra-individual radiation dose variability in oncologic chest and abdominal computed tomography.
Computed tomography (CT) plays a central role in oncologic imaging, yet repeated examinations contribute substantially to cumulative radiation exposure. This study aimed to evaluate inter- and intra-individual radiation dose variability in chest and abdominal CT and the impact of CT device model and protocol standardization. In this retrospective single-center study, 42441 CT scans from 4986 adult oncologic patients were analyzed. Dose metrics (CTDIvol, DLP, SSDE, effective dose) were extracted using automated dose monitoring. Inter- and intra-individual radiation dose variability was assessed across four CT device models and various protocol subtypes. Intra-individual radiation dose variability was calculated relative to the lowest dose per patient and compared across CT devices and protocol subtypes. Radiation dose varied substantially between devices, with CTDIvol differences of up to 2.4-fold in chest CT (2.98-7.26 mGy) and 1.7-fold in abdominal CT (5.26-8.77 mGy). The median intra-individual radiation dose variability was 93.7% (IQR 19.8-142.0%) in non-contrast chest CT, 66.3% (31.1-105.4%) in contrast-enhanced chest CT, 19.8% (11.8-32.3%) in non-contrast abdominal CT, and 28.2% (16.6-41.0%) in contrast-enhanced abdominal CT. When consecutive scans were performed on the same scanner, intra-individual radiation dose variability decreased to 14.7% (IQR 8.1-33.1%), 18.1% (9.5-31.3%), 11.7% (7.8-19.8%), and 15.3% (8.3-24.7%), respectively, indicating substantial device-specific effects. Significant radiation dose variability persists in oncologic CT, both between and within patients, despite the use of standardized protocols. Device-adapted dose management and consistent device use may improve dose consistency, support optimization in oncologic imaging, and reduce radiation exposure. · Substantial radiation dose variability persists across CT devices despite protocol standardization.. · Intra-individual radiation dose variability is significant and highest in non-contrast chest CT.. · Consistent use of the same scanner reduces intra-individual radiation dose variability significantly.. · Internal diagnostic reference levels may improve radiation dose consistency and minimize exposure.. · Moradians AF, Rosok D, Serger R et al. Inter- and intra-individual radiation dose variability in oncologic chest and abdominal computed tomography. Rofo 2026; DOI 10.1055/a-2786-2534.
Read more3Morphometric Evaluation of Coccyx with Microcomputed Tomography (Micro CT) and Computed Tomography (CT) Technology
Aim: We investigated the coccyx anatomy accurately in detail by microcomputed tomography (micro CT) and computed tomography (CT) to contribute to the data related to the coccyx anatomy and the potential clinical contribution of these datas in the treatment of coccyx’s pathologies. Material and Methods: Twenty coccyges from embalmed cadavers were examined with a micro CT device. The inferior part of the sacrum and coccyx together with the surrounding soft tissue was removed safely. The tissue was scanned with a micro CT device, and all parameters were measured with micro CT image viewer programs. CT images of 29 patients without coccyx pathology were measured with OsiriX programs. Measured morphometric parameters with micro CT and CT were evaluated using statistical methods. Results: Generally, the morphometric parameters as mean values were larger in males than in females. Mean values for vertical length and coccyx width were higher for CT compared with micro CT images. Coccyx was more flat in the frontal plane in females. There were statistically significant differences between the micro CT and CT images regarding mean vertical length, width, lateral deviation angle, and sacrococcygeal angle and length of the vertebrae (p < 0.05). There were no statistically significant differences in number and width of the vertebrae (p > 0.05). Conclusion: We suggest that examining the normal coccyx morphology will help to better understand and treat the pathologic conditions of the coccyx. We believe our findings will contribute to the data related to the coccyx anatomy.
Read more20Discrepancy between DXA and CT-based assessment of spine bone mineral density.
Discrepancy between DXA and CT-based assessment of spine bone mineral density.
1RELATIONS OF ANISOTROPIC ELASTIC MODULI TO DENSITY AND CT NUMBER IN BOVINE CORTICAL BONE
It would be useful to be able to determine the mechanical properties of bone using a noninvasive technique such as computed tomography (CT). However, in contrast to cancellous bone tissue, quantifying the elastic modulus of cortical bone from bone density and CT number has not been investigated extensively. This study measured the elastic moduli of cortical bone from eight bovine femora in the longitudinal, circumferential, and radial directions using mechanical compressive testing. Before testing, the CT number and wet apparent bone density were obtained. The experimentally determined coefficient of determination between CT number and bone density was around 0.6. Bone density was a good predictor of the elastic modulus of cortical bone in the longitudinal direction (r2 > 0.79), but it could not be used to predict the elastic moduli in the circumferential (r2 < 0.4) and radial (r2 < 0.22) directions. The coefficient of determination between CT number and the elastic modulus in the longitudinal direction was higher than 0.41. However, the correlations between CT number and elastic moduli were weak in the circumferential (r2 < 0.21) and radial (r2 < 0.19) directions. Moreover, the elastic modulus was much higher in the longitudinal direction than the circumferential and radial directions, and hence cortical bone can be considered a transversely isotropic property.
Read moreThe clinical value of computed tomography Hounsfield unit for diagnosing palpable inguinal lymph node metastasis in patients with penile cancer.
Computed tomography (CT) Hounsfield units (HUs) of pathologically confirmed metastatic inguinal lymph nodes (ILNs) were proved to be higher than negative ones. We designed this study to explore the clinical value of CT HU for diagnosing palpable ILN metastasis in patients with penile cancer. A total of 32 patients with penile cancer, including 84 palpable ILNs, were recruited in this study. They all performed 5-mm layer pelvic contrast-enhanced CT (CE-CT) before treatment. The palpable ILNs were matched with CT image. By using radiologic software PACS, the layer with a maximum cross-sectional area of target lymph node was selected, and the short axis was defined as diameter. We outlined the edge of target lymph nodes, and the software automatically calculated its area, maximum CT HU, and average CT HU. All target ILNs were biopsied by surgery to confirm the presence of metastasis. Compared with non-metastatic ILNs, metastatic ILNs had larger diameter, area, maximum non-contrast CT (NC-CT) HU, maximum arterial-phase CE-CT (ACE-CT) HU, average NC-CT HU, and average ACE-CT HU, with statistically significant differences (P < 0.05). Receiver operating characteristic analysis showed the all six parameters (maximum NC-CT HU, maximum ACE-CT HU, average NC-CT HU, average ACE-CT HU, diameter, and area) had significant diagnostic value for ILN metastasis, with an area under the curve of 0.847, 0.853, 0.900, 0.919, 0.809, and 0.789, respectively. The average ACE-CT HU (cutoff: 40.5) had the highest accuracy as 0.857, and maximum NC-CT HU (cutoff: 51.5) had the highest sensitivity of 0.897. ILN CT HU was clinically valuable for the diagnosis of palpable ILN metastasis in patients with newly diagnosed penile cancer.
Read more26Effect of different CT scanners and settings on femoral failure loads calculated by finite element models
ABSTRACTIn a multi‐center patient study, using different CT scanners, CT‐based finite element (FE) models are utilized to calculate failure loads of femora with metastases. Previous studies showed that using different CT scanners can result in different outcomes. This study aims to quantify the effects of (i) different CT scanners; (ii) different CT protocols with variations in slice thickness, field of view (FOV), and reconstruction kernel; and (iii) air between calibration phantom and patient, on Hounsfield Units (HU), bone mineral density (BMD), and FE failure load. Six cadaveric femora were scanned on four CT scanners. Scans were made with multiple CT protocols and with or without an air gap between the body model and calibration phantom. HU and calibrated BMD were determined in cortical and trabecular regions of interest. Non‐linear isotropic FE models were constructed to calculate failure load. Mean differences between CT scanners varied up to 7% in cortical HU, 6% in trabecular HU, 6% in cortical BMD, 12% in trabecular BMD, and 17% in failure load. Changes in slice thickness and FOV had little effect (≤4%), while reconstruction kernels had a larger effect on HU (16%), BMD (17%), and failure load (9%). Air between the body model and calibration phantom slightly decreased the HU, BMD, and failure loads (≤8%). In conclusion, this study showed that quantitative analysis of CT images acquired with different CT scanners, and particularly reconstruction kernels, can induce relatively large differences in HU, BMD, and failure loads. Additionally, if possible, air artifacts should be avoided. © 2018 Orthopaedic Research Society. © 2018 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of the Orthopaedic Research Society. J Orthop Res 36:2288–2295, 2018.
Read moreAbstract 661: CT scan reveals that marked loss of muscle, visceral fat or subcutaneous fat after gastrectomy was a poor prognostic marker in advanced gastric cancer
Background: There is increasing interest in the influence of body composition on oncologic outcomes. Using computed tomography (CT) scan, we evaluated the role of skeletal muscle and fat among patients with gastric cancer (GC) who underwent gastrectomy with or without adjuvant chemotherapy, as well as those changes' associations with survival outcomes. Methods: The present study evaluated 136 patients with GC who were enrolled in the CLASSIC trial at Yonsei Cancer Center. Baseline body compositions including skeletal muscle area, Hounsfield units (HU), visceral fat area, and subcutaneous fat area were measured by preoperative CT scan. The L3 region contains the psoas, paraspinal muscles, and abdominal muscles, which were quantified using the pre-established HU thresholds for skeletal muscle tissue (HU: -30~150). Visceral fat and subcutaneous fat areas (HU:-150~-30) were measured using axial slices at the level of the lumbar vertebra (L3). CT before and after the gastrectomy was used to determine the 6-month relative changes in body composition parameters. Continuous variables were dichotomized according to the best cut-off values by Contal and O'Quigley method. Results: Seventy-three patients (53.7%) underwent surgery alone, and 63 patients (46.3%) underwent surgery followed by adjuvant chemotherapy. The median baseline values were 46.8 cm2/m2 for SMI, 47.5 HU, 33.9 cm2/m2 for VFI, and 34.6 cm2/m2 for SFI. The baseline body composition parameters were not associated with disease-free survival (DFS) or overall survival (OS). However, patients with marked loss of skeletal muscle mass (&lt;-11%), visceral fat area (&lt;-48%), or subcutaneous fat (&lt;-47%) after gastrectomy (the value was determined by best cut-off point) had poorer DFS and OS compared to patients with lesser changes. Patients with a marked loss in at least one significant body composition parameter had significantly shorter DFS (hazard ratio: 2.9, 95% confidence interval: 1.7-4.8, P&lt;0.001) and OS (hazard ratio: 2.9, 95% confidence interval: 1.7-5.0, P&lt;0.001). Conclusion: Marked loss in body composition parameters significantly predicted shorter DFS and OS among patients with GC who underwent gastrectomy. Postoperative nutrition and active health care interventions could improve the prognosis of these GC patients. CT data are readily obtainable during routine clinical practice, which makes this approach useful for identifying prognostic biomarkers. Citation Format: Si Won Lee, Hyung Soon Park, Seung Hoon Beom, Sun Young Rha, Woo Jin Hyung, Song-Ee Baek, Minkyu Jung. CT scan reveals that marked loss of muscle, visceral fat or subcutaneous fat after gastrectomy was a poor prognostic marker in advanced gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 661.
Read more71Standardization and Quantitative Imaging With Photon-Counting Detector CT.
Computed tomography (CT) images display anatomic structures across 3 dimensions and are highly quantitative; they are the reference standard for 3-dimensional geometric measurements and are used for 3-dimensional printing of anatomic models and custom implants, as well as for radiation therapy treatment planning. The pixel intensity in CT images represents the linear x-ray attenuation coefficient of the imaged materials after linearly scaling the coefficients into a quantity known as CT numbers that is conveyed in Hounsfield units. When measured with the same scanner model, acquisition, and reconstruction parameters, the mean CT number of a material is highly reproducible, and quantitative applications of CT scanning that rely on the measured CT number, such as for assessing bone mineral density or coronary artery calcification, are well established. However, the strong dependence of CT numbers on x-ray beam spectra limits quantitative applications and standardization from achieving robust widespread success. This article reviews several quantitative applications of CT and the challenges they face, and describes the benefits brought by photon-counting detector (PCD) CT technology. The discussed benefits of PCD-CT include that it is inherently multienergy, expands material decomposition capabilities, and improves spatial resolution and geometric quantification. Further, the utility of virtual monoenergetic images to standardize CT numbers is discussed, as virtual monoenergetic images can be the default image type in PCD-CT due to the full-time spectral nature of the technology.
Read more269Method for transforming CT images for attenuation correction in PET/CT imaging
A tube-voltage-dependent scheme is presented for transforming Hounsfield units (HU) measured by different computed tomography (CT) scanners at different x-ray tube voltages (kVp) to 511 keV linear attenuation values for attenuation correction in positron emission tomography (PET) data reconstruction. A Gammex 467 electron density CT phantom was imaged using a Siemens Sensation 16-slice CT, a Siemens Emotion 6-slice CT, a GE Lightspeed 16-slice CT, a Hitachi CXR 4-slice CT, and a Toshiba Aquilion 16-slice CT at kVp ranging from 80 to 140 kVp. All of these CT scanners are also available in combination with a PET scanner as a PET/CT tomograph. HU obtained for various reference tissue substitutes in the phantom were compared with the known linear attenuation values at 511 keV. The transformation, appropriate for lung, soft tissue, and bone, yields the function 9.6 x 10(-5). (HU+ 1000) below a threshold of approximately 50 HU and a (HU+ 1000)+b above the threshold, where a and b are fixed parameters that depend on the kVp setting. The use of the kVp-dependent scaling procedure leads to a significant improvement in reconstructed PET activity levels in phantom measurements, resolving errors of almost 40% otherwise seen for the case of dense bone phantoms at 80 kVp. Results are also presented for patient studies involving multiple CT scans at different kVp settings, which should all lead to the same 511 keV linear attenuation values. A linear fit to values obtained from 140 kVp CT images using the kVp-dependent scaling plotted as a function of the corresponding values obtained from 80 kVp CT images yielded y = 1.003 x -0.001 with an R2 value of 0.999, indicating that the same values are obtained to a high degree of accuracy.
Read moreEvaluation of radiation treatment planning by computed tomography metal artifact reduction algorithm
Introduction: The objective of this study was to evaluate the usefulness of Computed Tomography(CT) images acquired through repeated subtraction reconstruction algorithms to reduce metal artifacts in CT Treatment Planning System(TPS).Materials and methods: Origin images of Gammex phantom and Rando phantom and non orthopedic metal artifact reduction(O-MAR) images were obtained after high density implantation. O-MAR applied images were also obtained. For evaluation of images, regions of interest(ROI) were set at five tissue rods and three points directly affected by artifacts in Gammex phantom. CT number and noise were compared and analyzed. To investigate dose change according to CT number change of the surrounding artifact, a three virtual cylindrical target volume was formed on Rando phantom CT images. The average dose was then compared and analyzed.Results: CT number difference according to the application of O-MAR showed significant difference among lung and bone rod and 3 ROI directly affected. Noise difference according to O-MAR application was significantly different in rod except for bone rod. In the treatment plan using Rando phantom, non-O-MAR and O-MAR images showed -4.3 ~ 1.9% and -0.4 ~ 2.3% dose differences, respectively.Conclusion: Applying a metal artifact reduction reconstruction algorithm can reduce image distortion due to high density implantation, improve image quality, and correct CT number.
Read more5CT appearance and measurements of the normal thyroid gland in goats
BackgroundGoats are increasingly being kept as companion animals, thus their owners expect advanced medical care, including modern diagnostic imaging. Computed tomography (CT) is now widely used in veterinary medicine, in both clinical practice and for scientific purposes. So far, the CT appearance of various body parts has been described in goats, but reports on thyroid gland CT are still lacking. The thyroid gland in goats may become enlarged due to dietary, genetic or neoplastic disorders. CT examination, as in other animals and humans, could aid in the diagnosis of thyroid diseases in goats and could be used for research purposes. The aim of the study was to present the CT characteristics of the normal caprine thyroid gland, in particular its dimensions, volume and density.ResultsFifty-seven goats were included in the study. None of the animals had clinical, CT, post-mortem or histopathologic abnormalities in the thyroid gland. CT features of the thyroid gland were determined, such as dimensions, volume, density, location and shape. The presence of the thyroid isthmus and ectopic thyroid tissue was also assessed. The gland was visible in every animal as two homogenous, highly attenuating, well-circumscribed lobes located in the most cranial part of the trachea. The mean dimensions of the thyroid lobe were 30.3 × 12.7 × 6.7 mm, the mean density was 80.9 Hounsfield Units (HU) and the mean volume was 1.32 cm3 or 1.39 cm3, depending on the method used. Also, the internal parathyroid glands were visible in some animals.ConclusionsFor the first time, the normal CT appearance of the thyroid gland has been presented. CT clearly shows the thyroid gland in goats and therefore can be used in clinical practice and for research. The results of the current study may serve as a radiological guideline for practitioners and may be the basis for further CT studies on normal and diseased caprine thyroid glands.
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