CT Radiation Dose Research Articles

Patients undergoing multiple 18F-FDG PET/CT exams: Assessment of frequency, dose and disease classification.

To analyse the frequency, demographics, primary disease and cumulative effective dose of patients undergoing two or more 18F-FDG PET/CT examinations in a year. In a retrospective study performed at a tertiary-care hospital, patients who underwent ≥2 18F-FDG PET/CT scans in a calendar year were identified for two consecutive years. The CT radiation dose was calculated using dose-length-product and sex-specific conversion factors. The primary malignancy of patients was retrieved from electronic medical records. 10,714 18F-FDG PET/CT exams were performed for 6,831 unique patients in 2 years, yielding an average of 1.6 exams per patient. The maximum number of 18F-FDG PET/CT examinations any patient underwent in a single year was seven. 20.9% patients had ≥2 18F-FDG PET/CT exams in any single year. Thirty nine percent patients in the cohort were below 60 years age. The median dose for 18F-FDG PET/CT examination was 25.1 mSv and maximum value reaching 1.7 to 2.9 times the median value. Cumulative effective dose (CED) was≥100 mSv in 12-13% of the patients. The cumulative dose for both years combined demonstrated the 25th percentile, 50th percentile and 75th percentile as well as the mean to be over 100 mSv, with the 25th percentile being 109 mSv. The dominant primary malignancies contributing to serial 18F-FDG PET/CTs in decreasing frequency were melanoma, non-Hodgkin's lymphoma (NHL), gastrointestinal cancer, breast cancer and Hodgkin's lymphoma. A sizeable number of patients undergo≥2 18F-FDG PET/CT exams with one out of every eight patients receiving cumulative dose≥100 mSv and that includes patients with long-life expectancy. The study found that one of five patients had≥2 18F-FDG PET/CT exams in a calendar year, one of four patients in two years and one of eight patients received cumulative dose≥100 mSv. Top malignancies associated with serial imaging in decreasing order of frequency included melanoma, non-Hodgkin's lymphoma (NHL), gastrointestinal cancer, breast cancer and Hodgkin's lymphoma.

Demystifying the CT Radiation Dose Sheet.

The radiation dose sheet generated by the CT scanner is a form that displays important information about an examination. It functions as a road map for the examination, detailing what CT examinations were performed and what parameters were used to perform them. One essential element of the radiation dose sheet, the volume CT dose index (CTDIvol), is a commonly used radiation dose index that is displayed on most CT scanners. The CTDIvol is used for quality control and is helpful for comparing the radiation output among different protocols and different scanners. The dose-length product (DLP) is a radiation dose index that builds on the CTDIvol by incorporation of the scan length. The DLP is combined with a conversion coefficient and used to determine the effective dose from the CT examination. Determining the effective dose is a way to estimate the whole-body radiation dose, even if the CT examination is confined to a smaller part of the body. In addition to these values, other data about the study from the CT scanner manufacturer, including the tube voltage and tube current-time product, usually are displayed on CT scanners. These values are major determinants of the image quality and radiation dose. The radiation dose sheet is a useful tool for radiologists, technologists, and physicists, allowing them to comprehend the technical details of a CT examination. The authors describe the components of the radiation dose sheet, the relationships of these components with one another, and the contributions of these components to the radiation dose. ©RSNA, 2022.

Comparison of Application Value of Different Radiation Dose Evaluation Methods in Evaluating Radiation Dose of Adult Thoracic and Abdominal CT Scan.

ObjectiveTo explore the differences among volumetric CT dose index (CTDIvol), body-specific dose assessment (SSDEED) based on effective diameter (ED), and SSDEWED based on water equivalent diameter (WED) in evaluating the radiation dose of adult thoracic and abdominal CT scanning.MethodsFrom January 2021 to October 2021, enhanced chest CT scans of 100 patients and enhanced abdomen CT scans of another 100 patients were collected. According to the body mass index (BMI), they can be divided into groups A and D (BMI < 20 kg/m2), groups B and E (20 kg/m2 ≤ BMI ≤ 24.9 kg/m2), and groups C and F (BMI > 24.9 kg/m2). The CTDIvol, anteroposterior diameter (AP), and the left and rght diameter (LAT) of all the patients were recorded, and the ED, water equivalent diameter (WED), the conversion factor (fsize,ED), (fsize, WED), SSDEED, and SSDEWED were calculated. The differences were compared between the different groups.ResultsThe AP, LAT, ED, and WED of groups B, E, C, and F were higher than those of groups A and D, and those of groups C and F were higher than those of groups B and E (P < 0.05). The fsize,ED and fsize, WED of groups B, E, C, and F are lower than those of groups A and D, and those of groups C and F are lower than those of groups B and E (P < 0.05). CTDIvol, SSDEED, and SSDEWED in groups B, E, C, and F are higher than those in groups A and D, and those in groups C and F are higher than those in groups B and E (p < 0.05). In the same group, patients with chest- and abdomen-enhanced have higher SSDEWED and SSDEED than CTDIvol, patients with chest-enhanced CT scans have higher SSDEWED than SSDEED, and patients with abdomen-enhanced CT scans have higher SSDEED than SSDEWED (P < 0.05).ConclusionCTDIvol and ED-based SSDEED underestimated the radiation dose of the subject exposed, where the patient was actually exposed to a greater dose. However, SSDEWED based on WED considers better the difference in patient size and attenuation characteristics, and can more accurately evaluate the radiation dose received by patients of different sizes during the chest and abdomen CT scan.

COMPARISON OF CBCT AND CT IN TERMS OF DOSE VALUE OF ORGANS AT RISK IN PARANASAL SINUS IMAGING.

Irradiated dose to the organs at risk surrounding the paranasal sinuses was compared in cone beam computed tomography (CBCT) and multi spiral computed tomography with respect to the organs' relative positions to the imaging field. A head and neck Alderson-Rando phantom equipped with thermoluminescence dosemeters pellets was irradiated according to three routine CBCT protocols and one protocol in multi spiral computed tomography. Dose value of organs outside the imaging field as well as those measured dose of organs inside the field were assessed. The highest measured doses were obtained from CT scan for most of the organs investigated in this study, whereas the lowest one was associated with the low-resolution mode of CBCT. Also, statistical analysis showed no significant differences between the dose values of out-of-field organs in all CBCT modes, whereas significant differences were observed between the radiation doses of CT and CBCT modes for all organs at risk inside and outside of the imaging field. CBCT is recommended on the basis of having a lower dose; however, the image qualities were the same in the two employed modalities, so the approach of lower dose can be made.

The Effects of Additional Filtration on Image Quality and Radiation Dose in Cone Beam CT: An In Vivo Preliminary Investigation.

Purpose The aim of this study was to investigate the effect of reduced radiation doses on the image quality of cone-beam computed tomography scans and the suitability of such imaging for orthodontics, oral surgery, dental implantology, periodontology, and endodontology. Materials and Methods Cone-beam computed tomography scans of a live patient were performed using seven attenuation filters with increased thickness to decrease the effective radiation dose from 22.4 to 1.8 μSv, and the effects of different radiation doses on image quality were further analysed. Quantitative image quality was calculated using dedicated measures, such as signal and contrast-to-noise ratio and sharpness. A panel of five certified raters assessed the cone-beam computed tomography scans qualitatively. Nine anatomical structures relevant to dentistry were identified, and the overall acceptance was assessed. Results Linear reduction of the effective radiation dose had a nonlinear effect on image quality. A 5-fold reduction in the effective dose led to acceptable quantitative and qualitative image quality measures, and the identification rate of dental anatomical structures was 80% or greater. The use of less than 40% of the reference dose was unacceptable for all dental specialties. Conclusions The ideal radiation dose for specific diagnostic requirements remains a patient-related and specialty-related decision that must be made on an individual basis. Based on the results of this study, it is possible to reduce exposure in selected patients, and at the same time obtain sufficient quality of images for clinical purposes.

Radiation dose and image quality in abdominal CT: Phantom Study

The purpose of this study was to evaluate and compare the effect of acquisition parameters of the abdominal computed tomography protocol on image quality and dose quantities, including contrast-to-noise ratio (CNR), noise, spatial resolution (SR) as well as volumetric computed tomography dose index (CTDIv).&#x0D; The measurements have been done on a HITACHI 16-slice scanner using two phantoms (PMMA and Catphan 500), two tube voltages of 120KVp and 100KVp have been analyzed while varying the tube current settings from 155 to 300 (mAs) in order to measure the abdominal image quality quantities and dose (CTDIv).&#x0D; The scanning at 100KVp compared to 120KVp has resulted in a dose reduction up to 38% at mAs ranging from 100 to 300, a decrease in CNR of 28%, a slight decrease in spatial resolution accompanied with an increase in noise.&#x0D; This study has shown that despite the increase in noise at low tube voltages, it is possible to reduce the dose without affecting the quantities of spatial resolution and the contrast/noise ratio by lowering the tube voltage from 120KVp to 100KVp.&#x0D; Keywords: Abdominal CT; CTDIv; Image Quality; Phantom.

Differentiation of malignant from benign orbital tumours using dual-energy CT

To investigate the diagnostic accuracy of dual-energy computed tomography (DECT)-derived iodine concentration (IC), effective atomic number (Zeff), and spectral attenuation information for differentiating malignant and benign orbital tumours. Data from 41 patients with orbital tumours from November 2019 to March 2021 were analysed retrospectively. Each patient underwent contrast-enhanced DECT using a 128-section dual-source computed tomography (DSCT) system. Dual-energy information, including IC, normalised iodine concentration (NIC), Zeff, virtual monoenergetic images (VMIs) reconstructed from 40 to 120 keV and slope (k) value were determined. Quantitative measurement of DECT parameters was undertaken by two independent radiologists blinded to clinical data. Differences in parameters were assessed using independent sample t-test. Diagnosis performance was calculated by the receiver operating characteristic (ROC) curve analysis. Radiation doses of conventional CT and DECT were compared by paired t-tests. Forty-one patients with histopathologically confirmed tumours were enrolled, including 10 malignant cases and 21 benign cases. Malignant orbital tumours exhibited significantly greater IC, NIC, Zeff, CT attenuation of VMIs at 40-105 keV, and k values compared to benign orbital tumours (p<0.05). In ROC analyses, 40 keV VMI demonstrated the highest diagnostic performance of single parameters (area under the ROC curve [AUC], 0.940), and combined parameters achieved the best performance (AUC, 0.971; sensitivity, 90%; specificity, 93.55%). Radiation doses were significantly reduced in DECT than conventional CT (p<0.001). Quantitative DECT analysis can be a useful technique, which yields excellent diagnostic accuracy, in the differentiation of malignant and benign orbital tumours with low radiation dose.

Reduced-Dose Deep Learning Reconstruction for Abdominal CT of Liver Metastases.

Background Assessment of liver lesions is constrained as CT radiation doses are lowered; evidence suggests deep learning reconstructions mitigate such effects. Purpose To evaluate liver metastases and image quality between reduced-dose deep learning image reconstruction (DLIR) and standard-dose filtered back projection (FBP) contrast-enhanced abdominal CT. Materials and Methods In this prospective Health Insurance Portability and Accountability Act-compliant study (September 2019 through April 2021), participants with biopsy-proven colorectal cancer and liver metastases at baseline CT underwent standard-dose and reduced-dose portal venous abdominal CT in the same breath hold. Three radiologists detected and characterized lesions at standard-dose FBP and reduced-dose DLIR, reported confidence, and scored image quality. Contrast-to-noise ratios for liver metastases were recorded. Summary statistics were reported, and a generalized linear mixed model was used. Results Fifty-one participants (mean age ± standard deviation, 57 years ± 13; 31 men) were evaluated. The mean volume CT dose index was 65.1% lower with reduced-dose CT (12.2 mGy) than with standard-dose CT (34.9 mGy). A total of 161 lesions (127 metastases, 34 benign lesions) with a mean size of 0.7 cm ± 0.3 were identified. Subjective image quality of reduced-dose DLIR was superior to that of standard-dose FBP (P < .001). The mean contrast-to-noise ratio for liver metastases of reduced-dose DLIR (3.9 ± 1.7) was higher than that of standard-dose FBP (3.5 ± 1.4) (P < .001). Differences in detection were identified only for lesions 0.5 cm or smaller: 63 of 65 lesions detected with standard-dose FBP (96.9%; 95% CI: 89.3, 99.6) and 47 lesions with reduced-dose DLIR (72.3%; 95% CI: 59.8, 82.7). Lesion accuracy with standard-dose FBP and reduced-dose DLIR was 80.1% (95% CI: 73.1, 86.0; 129 of 161 lesions) and 67.1% (95% CI: 59.3, 74.3; 108 of 161 lesions), respectively (P = .01). Lower lesion confidence was reported with a reduced dose (P < .001). Conclusion Deep learning image reconstruction (DLIR) improved CT image quality at 65% radiation dose reduction while preserving detection of liver lesions larger than 0.5 cm. Reduced-dose DLIR demonstrated overall inferior characterization of liver lesions and reader confidence. Clinical trial registration no. NCT03151564 © RSNA, 2022 Online supplemental material is available for this article.

U.S. Diagnostic Reference Levels and Achievable Doses for 10 Pediatric CT Examinations

HomeRadiologyVol. 302, No. 1 Previous CommunicationsFree AccessErratumU.S. Diagnostic Reference Levels and Achievable Doses for 10 Pediatric CT ExaminationsKalpana M. Kanal, Priscilla F. Butler, Mythreyi B. Chatfield, Jered Wells, Ehsan Samei, Michael Simanowith, Dan Golden, Dustin A. Gress, Judy Burleson, William F. Sensakovic, Keith J. Strauss, Donald FrushKalpana M. Kanal, Priscilla F. Butler, Mythreyi B. Chatfield, Jered Wells, Ehsan Samei, Michael Simanowith, Dan Golden, Dustin A. Gress, Judy Burleson, William F. Sensakovic, Keith J. Strauss, Donald FrushKalpana M. KanalPriscilla F. ButlerMythreyi B. ChatfieldJered WellsEhsan SameiMichael SimanowithDan GoldenDustin A. GressJudy BurlesonWilliam F. SensakovicKeith J. StraussDonald FrushPublished Online:Dec 20 2021https://doi.org/10.1148/radiol.2021219027MoreSectionsPDF ToolsImage ViewerAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinked InEmail Originally published in:https://doi.org/10.1148/radiol.2021211241Erratum in:https://doi.org/10.1148/radiol.2021219027Reference 13 was a duplicate of reference 8 and was therefore changed to reference 8. The references were renumbered as follows: Reference 14 is now 13, reference 15 is now 14, reference 14 is now 15, reference 15 is now 16, reference 16 is now 17, reference 17 is now 18, reference 18 is now 19, reference 19 is now 20, reference 20 is now 21, reference 21 is now 22, reference 22 is now 23, reference 23 is now 24, reference 24 is now 25, reference 25 is now 26, reference 26 is now 27, and reference 27 is now 28.Article HistoryPublished online: Dec 20 2021Published in print: Jan 2022 FiguresReferencesRelatedDetailsAccompanying This ArticleU.S. Diagnostic Reference Levels and Achievable Doses for 10 Pediatric CT Examinations26 Oct 2021RadiologyRecommended Articles Radiation Dose for Pediatric CT: Comparison of Pediatric versus Adult Imaging FacilitiesRadiology2019Volume: 291Issue: 1pp. 158-167Pediatric Chest CT Diagnostic Reference Ranges: Development and ApplicationRadiology2017Volume: 284Issue: 1pp. 219-227U.S. Diagnostic Reference Levels and Achievable Doses for 10 Pediatric CT ExaminationsRadiology2021Volume: 302Issue: 1pp. 164-174Pediatric Hepatoblastoma, Hepatocellular Carcinoma, and Other Hepatic Neoplasms: Consensus Imaging Recommendations from American College of Radiology Pediatric Liver Reporting and Data System (LI-RADS) Working GroupRadiology2020Volume: 296Issue: 3pp. 493-497Equivocal Reporting in Pediatric US Does Not Decrease Clinical CertaintyRadiology2016Volume: 282Issue: 1pp. 303-304See More RSNA Education Exhibits A Systematic Approach to Pediatric Neuroimaging in Critical Care: What to Look For, When to Survey, and Why You Should CareDigital Posters2019A Rational Approach to Pediatric MRI OptimizationDigital Posters2020Deep Learning-Based Reconstruction to Facilitate Lower Dose Pediatric CT: Technical Principles, Image Characteristics, and Clinical ApplicationsDigital Posters2020 RSNA Case Collection Primary gastric torsionRSNA Case Collection2021Bowel malrotation and appendicitisRSNA Case Collection2021Pediatric distal forearm fracturesRSNA Case Collection2020 Vol. 302, No. 1 Metrics Downloaded 548 times Altmetric Score PDF download

Low-Dose Abdominal CT for Evaluating Suspected Appendicitis in Adolescents and Young Adults: Review of Evidence.

Due to its excellent diagnostic performance, CT is the mainstay of diagnostic test in adults with suspected acute appendicitis in many countries. Although debatable, extensive epidemiological studies have suggested that CT radiation is carcinogenic, at least in children and adolescents. Setting aside the debate over the carcinogenic risk of CT radiation, the value of judicious use of CT radiation cannot be overstated for the diagnosis of appendicitis, considering that appendicitis is a very common disease, and that the vast majority of patients with suspected acute appendicitis are adolescents and young adults with average life expectancies. Given the accumulated evidence justifying the use of low-dose CT (LDCT) of only 2 mSv, there is no reasonable basis to insist on using radiation dose of multi-purpose abdominal CT for the diagnosis of appendicitis, particularly in adolescents and young adults. Published data strongly suggest that LDCT is comparable to conventional dose CT in terms of clinical outcomes and diagnostic performance. In this narrative review, we will discuss such evidence for reducing CT radiation in adolescents and young adults with suspected appendicitis.

Technical note: Advancing size-specific dose estimates in CT examinations: Dose estimates at longitudinal positions of scans.

American Association of Physicists in Medicine (AAPM) (Report 204) introduced the size-specific dose estimate (SSDE) for the average dose to the center of a fixed-mA scan. International standards establish a method that CT manufacturers and radiation dose index monitoring software may use to calculate SSDE(z) at longitudinal positions of scans with fixed mA or tube current modulation, and its scan range average . We sought to test how accurate SSDE(z) is in tracking the average dose to the transverse slab of an axial image slice (Dslice ), evaluated with Monte Carlo calculation, in the chest and abdominopelvic examinations. We retrospectively identified 65 consecutive adult patients undergoing whole-body CT for transcatheter aortic valve implantation planning. Examination parameters (kV, mA, CTDIvol ) were extracted from the DICOM headers. Patient water equivalent diameter DW (z) was calculated at each image slice, excluding the patient table. A previously validated Monte Carlo simulation (Geant4) program was used to evaluate Dslice from the chest and abdominopelvic examinations. Alternatively, SSDE(z) was calculated at each slice. The results of the two methods were compared with descriptive statistical outcomes (R, version 4.0.2). In chest and abdominopelvic CT examinations, Dslice largely changed with anatomic location and uniformly fell off toward scan range edges. Scan range averages and were consistent within 2.5%-3.1% (median) and 6.3%-10.4% (maximum) in two examinations. On individual image slices, SSDE(z) could be lower or higher than Dslice , with deviation ranging from -18.3% to 85% in two edges (2 × 5cm) of scan range and from -35.2% to 18.7% in the remaining central region of the scan. This study provides critical inputs for quality assurance programs. is useful to track the average dose of all image slices, but further development may be useful for tracking patient dose at the level of individual image slices, especially near a scan range edge.

CHEST CT USAGE IN COVID-19 PNEUMONIA: MULTICENTER STUDY ON RADIATION DOSES AND DIAGNOSTIC QUALITY IN BRAZIL.

We assessed variations in chest CT usage, radiation dose and image quality in COVID-19 pneumonia. Our study included all chest CT exams performed in 533 patients from 6 healthcare sites from Brazil. We recorded patients’ age, gender and body weight and the information number of CT exams per patient, scan parameters and radiation doses (volume CT dose index—CTDIvol and dose length product—DLP). Six radiologists assessed all chest CT exams for the type of pulmonary findings and classified CT appearance of COVID-19 pneumonia as typical, indeterminate, atypical or negative. In addition, each CT was assessed for diagnostic quality (optimal or suboptimal) and presence of artefacts. Artefacts were frequent (367/841), often related to respiratory motion (344/367 chest CT exams with artefacts) and resulted in suboptimal evaluation in mid-to-lower lungs (176/344) or the entire lung (31/344). There were substantial differences in CT usage, patient weight, CTDIvol and DLP across the participating sites.

P216 - The impact of contrast agent on radiation dose in conventional and dual-energy abdominal CT (DECT)

P216 - The impact of contrast agent on radiation dose in conventional and dual-energy abdominal CT (DECT)

P192 - How chest CT radiation dose of patients with confirmed COVID-19 will impact the cancer risk in the future

P192 - How chest CT radiation dose of patients with confirmed COVID-19 will impact the cancer risk in the future

Diagnostic accuracy using low-dose versus standard radiation dose CT in suspected acute appendicitis: prospective cohort study.

Contrast-enhanced CT is the reference standard used in diagnostic imaging for acute appendicitis in adults. The radiation dose has been of concern. This study aimed to assess whether a lower radiation dose would affect the diagnostic accuracy of CT. This was a prospective single-centre cohort study of patients (aged over 16 years) with suspected appendicitis evaluated for enrolment in concurrent APPAC II-III trials. The diagnostic accuracy of contrast-enhanced low- and standard-dose CT was compared with study protocols guiding imaging based on BMI; this enabled direct CT imaging comparison only in patients with a BMI below 30 kg/m2. The on-call CT diagnosis was compared with the final clinical diagnosis. Among all 856 patients investigated, the accuracy of low-dose (454 patients) and standard-dose (402 patients) CT in identifying patients with and without appendicitis was 98·0 and 98·5 per cent respectively. In patients with a BMI under 30 kg/m2, respective values were 98·2 per cent (434 patients) and 98·6 per cent (210 patients) (P = 1·000). The corresponding accuracy for differentiating between uncomplicated and complicated acute appendicitis was 90·3 and 87·6 per cent in all patients, and 89·8 and 88·4 per cent respectively among those with a BMI below 30 kg/m2 (P = 0·663). The median radiation dose in the whole low- and standard-dose CT groups was 3 and 7 mSv respectively. In the group with BMI below 30 kg/m2, corresponding median doses were 3 and 5 mSv (P < 0·001). Low- and standard-dose CT were accurate both in identifying appendicitis and in differentiating between uncomplicated and complicated acute appendicitis. Low-dose CT was associated with a significant radiation dose reduction, suggesting that it should be standard clinical practice at least in patients with a BMI below 30 kg/m2.

Determining the minimal ultra-low dose CT for reliable attenuation correction of 18F-FDG PET-CT: a phantom study.

To investigate minimal required sub milli-Sievert (mSv) ultra-low dose CT and corresponding tube current and voltage for reliable attenuation correction and semi- quantitation in 18F-FDG PET-CT in an effort for radiation dose reduction. Methods: We performed a PET-CT investigational study using a NEMA torso phantom containing six spheres (diameter: 10, 13, 17, 22, 28, 37 mm) filled with a fixed concentration of 60 kBq/ml and a background of 15 kBq/ml of 18F-FDG. Two sets of PET images, separated by 2 hours, were acquired for 3 minutes in a single bed position using 3-D mode with and without time-of-flight in a GE D-690 scanner. Several sets of CT images were acquired for attenuation correction with different combinations of tube voltage (80, 100, 120 kVp) and effective mAs (tube current-time product divided by pitch), using the maximum beam collimation (64 x 0.625 mm). The lowest CT acquisition technique available on this scanner is 10 mA, 0.4 s and 1.375 for the tube current, tube rotation time and pitch, respectively. The CT radiation dose was estimated based on the computed tomography dose index volume (CTDIvol) measurements performed following the standard methodology and the Imaging Performance Assessment of CT Scanners (ImPACT) calculator. Each of the CT techniques was used for attenuation correction to the same PET acquisition, using ordered-subset expectation maximum (OSEM) algorithm with 24 subsets and 2 iterations. The maximal and average radioactivity (kBq/ml) and standardized uptake values (SUV) of the spheres were measured. The minimal ultra-low dose CT for attenuation correction was determined by reproducible SUV measurements (±10%) compared to our reference CT protocol of 100 kVp and 80 mA for 0.5 s rotation. Results: The minimal ultra-low dose of CT for reproducible quantification in all spheres (<10% relative difference) was determined to be 0.3 mSv for a combination of 100 kVp and 10 mA at 0.5 s rotation, 0.984 helical pitch (0.26 mGy measured CTDIvol) . Based on these results we could confidently determine the CT parameters for reliable attenuation correction of PET images while significantly reducing the associated radiation dose. Conclusion: Our phantom study provided guidance in using ultra-low dose CT for precise attenuation correction and semi-quantification of 18F-FDG PET imaging, which can further reduce CT dose and radiation exposure to patients in clinical PET-CT studies. Clinical application: Based on the data, we can further reduce the radiation dose to sub-mSv using an ultra-low dose CT protocol for reliable attenuation correction in clinical 18F-FDG PET-CT studies.

Classification of moving coronary calcified plaques based on motion artifacts using convolutional neural networks: a robotic simulating study on influential factors

BackgroundMotion artifacts affect the images of coronary calcified plaques. This study utilized convolutional neural networks (CNNs) to classify the motion-contaminated images of moving coronary calcified plaques and to determine the influential factors for the classification performance.MethodsTwo artificial coronary arteries containing four artificial plaques of different densities were placed on a robotic arm in an anthropomorphic thorax phantom. Each artery moved linearly at velocities ranging from 0 to 60 mm/s. CT examinations were performed with four state-of-the-art CT systems. All images were reconstructed with filtered back projection and at least three levels of iterative reconstruction. Each examination was performed at 100%, 80% and 40% radiation dose. Three deep CNN architectures were used for training the classification models. A five-fold cross-validation procedure was applied to validate the models.ResultsThe accuracy of the CNN classification was 90.2 ± 3.1%, 90.6 ± 3.5%, and 90.1 ± 3.2% for the artificial plaques using Inception v3, ResNet101 and DenseNet201 CNN architectures, respectively. In the multivariate analysis, higher density and increasing velocity were significantly associated with higher classification accuracy (all P < 0.001). The classification accuracy in all three CNN architectures was not affected by CT system, radiation dose or image reconstruction method (all P > 0.05).ConclusionsThe CNN achieved a high accuracy of 90% when classifying the motion-contaminated images into the actual category, regardless of different vendors, velocities, radiation doses, and reconstruction algorithms, which indicates the potential value of using a CNN to correct calcium scores.

Radiation dose levels of thoracic-lumbar spine CT in pediatric trauma patients and assessment of scan parameters for dose optimization.

CT is frequently used for assessing spinal trauma in children. To establish the local diagnostic reference levels of spine CT examinations in pediatric spinal trauma patients and analyze scan parameters to enable dose optimization. In this retrospective study, we included 192 pediatric spinal trauma patients who underwent spine CT. Children were divided into two age groups: 0-10years (group 1) and 11-17years (group 2). Each group was subdivided into thoracic, thoracolumbar and lumbar CT groups. CT acquisition parameters (tube potential, in kilovoltage [kV]; mean tube current-time product, in milliamperes [mAs]; reference mAs; collimated slice width; tube rotation time; pitch; scan length) and radiation dose descriptors (volume CT dose index [CTDIvol] and dose-length product [DLP]) were recorded. The CTDIvol and DLP values of spine CTs obtained with different tube potential and collimated slice width values were compared for each group. CTDIvol and DLP values of thoracolumbar spine CTs in group 1 and lumbar spine CTs in group 2 were significantly lower in CTs acquired with low tube potential levels (P<0.05). CTDIvol and DLP values of thoracolumbar spine CTs in both groups and lumbar spine CTs in group 2 acquired with high collimated slice width values were significantly lower than in corresponding CTs acquired with low collimated slice width values (P<0.05). Pediatric spine CT radiation doses can be notably reduced from the manufacturers' default protocols while preserving image quality.

An endovaginal MRI array with a forward-looking coil for advanced gynecological cancer brachytherapy procedures: Design and initial results.

To develop an endovaginal MRI array that provides signal enhancement forward into the posterior parametrium and sideways into the vaginal wall, accelerating multiple-contrast detection of residual tumors that survive external beam radiation. The array's enclosure should form an obturator for cervical cancer brachytherapy, allowing integration with MRI-guided catheter placement, CT, and interstitial radiation dose delivery. The endovaginal array consisted of forward-looking and sideways-looking components. The forward-looking element imaged the cervix and posterior endometrium, and the sideways-looking elements imaged the vaginal wall. Electromagnetic simulation was performed to optimize the geometry of a forward-looking coil placed on a conductive-metallic substrate, extending the forward penetration above the coil's tip. Thereafter, an endovaginal array with one forward-looking coil and four sideways-looking elements was constructed and tested at 1.5 Tesla in saline and gel phantoms, and three sexually mature swine. Each coil's tuning, matching, and decoupling were optimized theoretically, implemented with electronic circuits, and validated with network-analyzer measurements. The array enclosure emulates a conventional brachytherapy obturator, allowing use of the internal imaging array together with tandem coils and interstitial catheters, as well as use of the enclosure alone during CT and radiation delivery. To evaluate the receive magnetic field ( ) spatial profile, the endovaginal array's specific absorption-rate (SAR) distribution was simulated inside a gel ASTM phantom to determine extreme heating locations in advance of a heating test. Heating tests were then performed during high SAR imaging in a gel phantom at the predetermined locations, testing compliance with MRI safety standards. To assess array imaging performance, signal-to-noise-ratios (SNR) were calculated in a saline phantom and in vivo. Swine images were acquired with the endovaginal array combined with the scanner's body and spine arrays. Simulated profiles for the forward-looking lobe pattern, obtained while varying several geometric parameters, disclosed that a forward-looking coil placed on a metal-backed substrate could double the effective forward penetration from approximately 25 to ∼40mm. An endovaginal array, enclosed in an obturator enclosure was then constructed, with all coils tuned, matched, and decoupled. The ASTM gel-phantom SAR test showed that peak local SAR was 1.2 W/kg in the forward-looking coil and 0.3 W/kg in the sideways-looking elements, well within ASTM/FDA/IEC guidelines. A 15-min 4 W/kg average SAR imaging experiment resulted inless than2o C temperature increase, also within ASTM/FDA/IEC heating limits. In a saline phantom, the forward-looking coil and sideways-looking array's SNR was four to eight times, over a 20-30mm field-of-view (FOV), and five to eight times, over a 15-25mm FOV, relative to the spine array's SNR, respectively. In three sexually mature swine, the forward-looking coil provided a 5+0.2 SNR enhancement factor within the cervix and posterior endometrium, and the sideways-looking array provided a 4+0.2 SNR gain factor in the vaginal wall, relative to the Siemens spine array, demonstrating that the array could significantly reduce imaging time. Higher SNR gynecological imaging is supported by forward-looking and sideways-looking coils. A forward-looking endovaginal coil for cervix and parametrium imaging was built with optimized metal backing. Array placement within an obturator enhanced integration with the brachytherapy procedure and accelerated imaging for detecting postexternal-beam residual tumors.

Rhinoplasty Pre-Surgery Models by Using Low-Dose Computed Tomography, Magnetic Resonance Imaging, and 3D Printing.

Rhinoplasty and surgical reconstruction of cartilaginous structures still remain a great challenge today. This study aims to identify an imaging strategy in order to merge the information from CT scans and magnetic resonance imaging (MRI) acquisitions and build a 3D printed model true to the patient’s anatomy, for better surgical planning. Using MRI, information can be obtained about the cartilage structures of which the nose is composed. Ten rhinoplasty candidate patients underwent both a low-dose protocol CT scan and a specific MRI for characterization of nasal structures. Bone and soft tissue segmentations were performed in CT, while cartilage segmentations were extrapolated from MRI and validated by both an expert radiologist and surgeon. Subsequently, a 3D model was produced in materials and colors reproducing the density of the three main structures (bone, soft tissue, and cartilage), useful for pre-surgical evaluation. This study has highlighted that the optimization of a CT and MR dedicated protocol has allowed to reduce the CT radiation dose up to 60% compared to standard acquisitions with the same machine, and MR acquisition time of about 20%. Patient-tailored 3D models and pre-surgical planning have reduced the mean operative time by 20 minutes.