Computed Tomography Dose Index Values Research Articles

Comparison of Planer Dose Equilibrium and Computed Tomography Dose Index and Implications for Reported Patient Dose Information

Technical developments are ongoing in CT, and there has been a continually increasing trend in patient prescription, resulting in increased exposure. Currently, doses delivered during CT are generally evaluated using computed tomography dose index (CTDI), which is measured with a 10 cm pencil ionization chamber placed in a 14 cm PMMA phantom. However, shortfalls in CTDI have been identified by the American Association of Physicists in Medicine (AAPM) who have proposed a new method, dose equilibrium (DEq). In this paper, the dose equilibrium was used to estimate the dose in two protocols (thoracic and abdominopelvic) and compared to CTDI values. In addition, a retrospective correction was applied to 20 patient CTDI’s by characterizing the specific DEq profile of the system scans. The results indicated the dose equilibrium estimations of two protocols, thoracic and abdominopelvic, were 29% and 30% respectively, higher than those informed by the CT scanner. In addition, a retrospective dose correction estimation of a random sample of twenty patients demonstrated an annual underestimation in absorbed dose by between 26% and 28%. Continued use of the CTDI method in quality assurance of modern CT could result in greater patient risk. AAPM Task Group 111 presents a more accurate, safer method to estimate dose and its adoption is paramount.

37 Simulation of CTDI using GATE for 2, 16, 64 slices CT system

Introduction Since the introduction of the computed tomography in the clinical application in the 1971’s, the CT has revolutionized the medical imaging techniques. It well known that Doses from CT examinations are higher if we compared with other medical imaging modalities. Many studies considered that CT may be responsible of radiation-induced diseases, especially carcinogenic processes so it’s important to justify and optimize the radiation dose during CT procedures. In this work, we aimed to estimate the computed tomography dose index (CTDI) using the Monte Carlo code Geant4 Application for Tomographic Emission (GATE) for 3 CT acquisition system. Methods CTDI is the most important indicator of the CT radiation dose. We have evaluated the CTDI with the experimental method using a pencil ion chamber and two phantoms PMMA (PolyMethylMethAcrylate) for simulating head and body. A code based on Monte Carlo simulation named GATE was used for modeling CT geometry for the simulation method. A comparison between simulated and measured CTDI was established for the 3 CT system. Result Results of the simulation are presented and good agreements are observed between measured and simulated CTDI. For dual slices (less than 1.18% for head phantom and l.85% for body phantom for all applied voltages). For 16 slices (less than 3.7% for head phantom and 3.8% for body phantom for all applied voltages). For 64 slices (less than 1.7% for head phantom and 2% for body phantom for all applied voltages). These differences observed can be geometry explained by the difficulty to model a precise geometry and the random errors in the simulated CTDI. We demonstrated that the CTDI values can be characterized as functions of the voltage (kVp), the current (mAs) and diameter of phantoms. Conclusion Based on these results, it is possible to optimize the CT parameters in clinical applications using the Monte Carlo code GATE.

Combination of Adaptive Statistical Iterative Reconstruction-V and Lower Tube Voltage During Craniocervical Computed Tomographic Angiography Yields Better Image Quality with a Reduced Radiation Dose

To evaluate image quality and radiation exposure when using the adaptive statistical iterative reconstruction-V (ASIR-V) algorithm for reconstructing craniocervical computed tomographic angiography images acquired at 100 kVp. We randomly divided 121 patients into three groups: group A (conventional protocol), 120 kVp with filtered back projection; group B, 120 kVp with 50% ASIR-V; and group C, 100 kVp with 50% ASIR-V. All patients underwent scans in a 256-slice computed tomography (CT) scanner. Radiation dose (volume CT dose index), dose-length product, and effective dose, objective parameters such as arterial attenuation value, signal-to-noise ratio, contrast-to-noise ratio, and noise obtained at head, neck, and shoulder levels were compared among the groups. Subjective image quality was independently assessed by two radiologists, and interobserver reliability was assessed using kappa analysis. The radiation dose in group C was the lowest (p < 0.01) with a 40% reduction in volume CT dose index, dose-length product, and effective dose values compared to group A, and group C showed higher arterial attenuation than either group A or B (p < 0.01). Additionally, signal-to-noise ratio and contrast-to-noise ratio were higher and noise was lower in groups B and C than group A. Group C had better subjective image quality than groups A and B (p < 0.05), and the interobserver reliability between the two radiologists was high (k = 0.783). Compared to the conventional protocol, using 50% ASIR-V and the 100 kVp protocol during craniocervical computed tomographic angiography yields better objective and subjective image quality at lower radiation doses.

Dose Reduction by Body Mass Index: Different Protocol in low-Dose Chest Computed tomography

We investigated the effects of exposure involving reduction of automatic exposure control value based on body mass index and image quality using the AAPM phantom in low-dose computed tomography (CT). The study was carried out on subclinical, normal persons without lung diseases among students in a single university. The examination was the same as the phantom experiment. Scan protocol conditions in the phantom study were always tube voltage 120 kVp, 30 mA tube current, 0.5 sec rotation time, 360 mm field of view, and dose modulation (Fixed, D-DOM, Z-DOM, D-DOM+automatic current selection (ACS), Z-DOM+ACS). Comparison and analysis was based on D-DOM. In the fixed mode, the volume CT dose index (CTDIvol) and dose length product (DLP) value was 1.94 mGy and 26. 2 mGy·cm, respectively. In D-DoM the respective values were 1.47 mGy and 20.1 mGy·cm. For D-DoM+ACS, the respective values were 1.70 mGy and 23.2 mGy·cm, and the CTDIvol value of Z-DoM and DLP was 1.82 mGy and 24.9 mGy·cm, respectively. For Z-DoM+ACS together, CTDIvol was 2.22 mGy and DLP was 30.4 mGy·cm; in case of ACS, CTDIvol was 2.46 mGy and DLP was 33.2 mGy·cm. Improvement of exposure dose and the image quality of obese patients could result using a protocol that offers more appropriate image quality and minimum dose

Is It Better to Enter a Volume CT Dose Index Value before or after Scan Range Adjustment for Radiation Dose Optimization of Pediatric Cardiothoracic CT with Tube Current Modulation?

ObjectiveTo determine whether the body size-adapted volume computed tomography (CT) dose index (CTDvol) in pediatric cardiothoracic CT with tube current modulation is better to be entered before or after scan range adjustment for radiation dose optimization.Materials and MethodsIn 83 patients, cardiothoracic CT with tube current modulation was performed with the body size-adapted CTDIvol entered after (group 1, n = 42) or before (group 2, n = 41) scan range adjustment. Patient-related, radiation dose, and image quality parameters were compared and correlated between the two groups.ResultsThe CTDIvol after the CT scan in group 1 was significantly higher than that in group 2 (1.7 ± 0.1 mGy vs. 1.4 ± 0.3 mGy; p < 0.0001). Image noise (4.6 ± 0.5 Hounsfield units [HU] vs. 4.5 ± 0.7 HU) and image quality (1.5 ± 0.6 vs. 1.5 ± 0.6) showed no significant differences between the two (p > 0.05). In both groups, all patient-related parameters, except body density, showed positive correlations (r = 0.49–0.94; p < 0.01) with the CTDIvol before and after the CT scan. The CTDIvol after CT scan showed modest positive correlation (r = 0.49; p ≤ 0.001) with image noise in group 1 but no significant correlation (p > 0.05) in group 2.ConclusionIn pediatric cardiothoracic CT with tube current modulation, the CTDIvol entered before scan range adjustment provides a significant dose reduction (18%) with comparable image quality compared with that entered after scan range adjustment.

The benefits of folic acid-modified gold nanoparticles in CT-based molecular imaging: radiation dose reduction and image contrast enhancement

X-ray computed tomography (CT) requires an optimal compromise between image quality and patient dose. While high image quality is an important requirement in CT, the radiation dose must be kept minimal to protect the patients from ionizing radiation-associated risks. The use of probes based on gold nanoparticles (AuNPs) along with active targeting ligands for specific recognition of cancer cells may be one of the balanced solutions. Herein, we report the effect of folic acid (FA)-modified AuNP as a targeted nanoprobe on the contrast enhancement of CT images as well as its potential for patient dose reduction. For this purpose, nasopharyngeal KB cancer cells overexpressing FA receptors were incubated with AuNPs with and without FA modification and imaged in a CT scanner with the following X-ray tube parameters: peak tube voltage of 130 KVp, and tube current–time products of 60, 90, 120, 160 and 250 mAs. Moreover, in order to estimate the radiation dose to which the patient was exposed during a head CT protocol, the CT dose index (CTDI) value was measured by an X-ray electrometer by changing the tube current–time product. Raising the tube current–time product from 60 to 250 mAs significantly increased the absorbed dose from 18 mGy to 75 mGy. This increase was not associated with a significant enhancement of the image quality of the KB cells. However, an obvious increase in image brightness and CT signal intensity (quantified by Hounsfield units [HU]) were observed in cells exposed to nanoparticles without any increase in the mAs product or radiation dose. Under the same Au concentration, KB cells exposed to FA-modified AuNPs had significantly higher HU and brighter CT images than those of the cells exposed to AuNPs without FA modification. In conclusion, FA-modified AuNP can be considered as a targeted CT nanoprobe with the potential for dose reduction by keeping the required mAs product as low as possible while enhancing image contrast.

Using Age and Weight Specific CT Protocol to Estimate Reference Effective Dose to Patients Undergoing CT Examination

In x-ray computed tomography (CT), the most common parameters used to estimate and minimize patient dose is the CT dose index (CTDI) and DLP. The aim of the study is to serve as a reference values during QC for the purposes of QA in other to reduce doses to patients undergoing CT scan using the age and weight specific CT protocol set out by various manufacturers and other international organizations. This was done by recording CTDI and DLP values to patients within a specific age and weight bracket during scanning on the scanning console and on image data. The effective dose values represents an averaged dose to patients, hence the measurements are only an approximation of the dose to patient, these doses may be overestimated or underestimated by a factor of two or more with CTDI and DLP values in comparison with point dose values. CTDI and DLP were used to evaluate CT scanner output and estimating patient regional effective dose in this study. The estimated head CTDI scans base on the various protocol from all the hospitals increase from approximately 2.8mGy in newborns to approximately 8.7mGy in adults. Resulting with a variation of effective dose from 0.67mSv in new born to approximately 1.03mSv in oversize adults. Neonates head CT effective doses are higher than those for the normal adults except oversize adults as shown in Table 4.4. The chest, abdominal and pelvis CTDI values increases from 2.8, 2.5 and 2.7 mGy in neonates of approximately 3.4kg of weight to 19.84, 7.78 and 11.33mGy in adults of approximately 72.5kg of weight respectively. The estimated effective doses for neonates undergoing chest, abdomen and pelvis of the body CT were 0.83, 6.7, 4.87 and 5.52mSv, whereas those for normal-sized adults are 13.31, 4.61 and 5.34mSv respectively. Chest oversize patients’ examinations exceeded the recommended dose levels of 19.84mSv whiles the head, abdomen and pelvis were: 1.03, 7.16 and 5.98mSv respectively. It was concluded that patient body doses could be substantially minimized through careful selection of scanning parameters based on clinical indications of study, patient age, body size, and body region being examined. Additional dose reduction to superficial body regions would require the use of shielding materials.

Evaluating Low-kV Dual-source CT Angiography by High-pitch Spiral Acquisition and Iterative Reconstruction in Pediatric Congenital Heart Disease Patients.

We retrospectively evaluated the qualities of pediatric cardiovascular dual-source computed tomography (DSCT) images reconstructed by sinogram-affirmed iterative reconstruction (SAFIRE) and filtered back projection (FBP). We analyzed the cases of 287 congenital heart disease (CHD) patients < 5 years old, referred to our department in August 2013-March 2015. We divided them into two groups according to tube voltage (70 kVp, n=147; 80 kVp, n=140). All images were acquired by a CARE kV system and reconstructed by FBP and SAFIRE. The attenuation, noise, and signal-to-noise ratio (SNR) at each region of the heart and great vessels were measured. The volume CT dose index and dose-length product values were recorded. Compared to FBP, reconstruction by SAFIRE showed that the attenuation volume was significantly lower by 0.4% except for the ascending aorta (p<0.05), the noise value was lower by about 20% (p<0.05), and the SNR was higher by approx. 25% (p<0.05). The radiation dose in the 70 kVp group was significantly lower than that in the 80 kVp group. No significant differences in SNR were observed between the patient groups. DSCT image acquisition with SAFIRE using the CARE kV system results in low image noise and radiation dose in pediatric patients with CHD.

Commissioning of the Leksell Gamma Knife® Icon™.

The Leksell Gamma Knife (LGK) Icon has been recently introduced to provide Gamma Knife technology with frameless stereotactic treatments which use an additional cone-beam CT (CBCT) imaging system and a motion tracking system (IFMM, Intra-Fraction Motion Management). The system was commissioned for the treatment unit itself as well as the imaging system. The LGK Icon was calibrated using an A1SL ionization chamber. EBT3 radiochromic films were employed to independently check the machine calibration, to measure the relative output factors (ROFs) and to collect dose distributions. Coincidence between CBCT isocenter and radiological focus was evaluated by means of EBT3 films. CBCT image quality was investigated in terms of spatial resolution, contrast-to-noise ratio (CNR), and uniformity for the two presets available (low dose and high dose). Computed Tomography Dose Index (CTDI) was also measured for both presets. The absolute dose rate of the LGK Icon was 3.86 ± 0.09 Gy/min. This result was confirmed by EBT3 readings. ROF were found to be 0.887 ± 0.035 and 0.797 ± 0.032 for the 8 mm and 4 mm collimators, respectively, which are within 2% of the Monte Carlo-derived ROF values. Excellent agreement was found between calculated and measured dose distribution with the gamma pass rate >95% of points for the nine dose distributions analyzed with 3%/1 mm criteria. CBCT isocenter was found to be within 0.2 mm with respect to radiological focus. Image quality parameters were found to be well within the manufacturer's specifications with the high-dose preset being superior in terms of CNR and uniformity. CTDI values were 2.41 mGy and 6.32 mGy, i.e. -3.6% and 0.3% different from the nominal values for the low-dose and high-dose presets, respectively. The LGK Icon was successfully commissioned for clinical use. The use of the EBT3 to characterize the treatment unit was demonstrated to be feasible. The CBCT imaging system operates well within the manufacturer's specifications and provides good geometrical accuracy.

Estimating cancer induction risk from abdominopelvic scanning with 6- and 16-slice computed tomography

Purpose: The biological effects of ionizing radiation (BEIR VII) report estimates that the risk of getting cancer from radiation is increased by about a third from current regulation risk levels. The propose of this study was to estimate cancer induction risk from abdominopelvic computed tomography (CT) scanning of adult patients using 6- and 16-slice CT scanners.Materials and methods: A cross-sectional study on 200 patients with abdominopelvic CT scan in 6- and 16-slice scanners was conducted. The dose-length product (DLP) and volume CT Dose Index (CTDIvol) values from the scanners as well as the effective dose values from the ImPACT CT patient dosimetry calculator with the biological effects of ionizing radiation (BEIR VII) method were used to estimate the cancer induction risk.Results: The mean (and standard deviation) values of CTDIvol and DLP were 6.9 (±1.07) mGy and 306.44 (± 60.57) mGy.cm for 6-slice, and 5.19 (±0.91) mGy and 219.7 (±49.31) mGy.cm for 16-slice scanner, respectively. The range of effective dose in the 6-slice scanner was 2.61–8.15 mSv and, in the 16-slice scanner, it was 1.47–4.72 mSv. The mean and standard deviation values of total cancer induction risk in abdominopelvic examinations were 0.136 ± 0.059% for men and 0.135 ± 0.063% for women in the 6-slice CT scanner. The values were 0.126 ± 0.051% for men and 0.127 ± 0.056% for women in the 16-slice scanner.Conclusions: The cancer induction risk of abdominopelvic scanning was noticeable. Therefore, radiation dose should be minimized by optimizing the protocols and applying appropriate methods.

Radiation Dose Associated with Multi-Detector 64-Slice Computed Tomography Brain Examinations in Khartoum State, Sudan.

SummaryBackgroundRadiation exposure due to computed tomography (CT) has become an important issue, as the number of CT examinations has been increasing worldwide. Radiation doses associated with CT are higher in comparison to other imaging procedures. CT-related radiation doses should be monitored and controlled in order to ensure reduction of radiation exposure and optimization of image quality. The aim of this study was to evaluate radiation doses in adult patient who underwent routine CT brain examinations, and to assess how CT scanning protocols affect patient doses in practice.Material/MethodsA total of 118 patients underwent brain CT at two radiology departments equipped with 64-slice CT scanners, Khartoum, Sudan. Patient doses regarding weighted CT dose index (CTDIw) and dose length product (DLP) values were recorded. Quality control tests were performed for both scanners.ResultsThe mean CTDIw values ranged from 62.9 to 65.8 mGy, DLP values ranged from 1003.7 to 1192.5 mGy, and the effective dose varied from 2.4 to 3.7 mSv.ConclusionsPatient doses in this study was higher compared to previous research, suggesting that patients exposed to unnecessary radiation. Therefore, optimization of radiation doses with the use of specified imaging protocols, well-documented indications for CT, training of technicians, and quality control programs will reduce the necessary radiation doses. Establishment of the diagnostic reference level is recommended for further dose reduction.

Optimizing CT technique to reduce radiation dose: effect of changes in kVp, iterative reconstruction, and noise index on dose and noise in a human cadaver.

For assessment of the effect of varying the peak kilovoltage (kVp), the adaptive statistical iterative reconstruction technique (ASiR), and automatic dose modulation on radiation dose and image noise in a human cadaver, a cadaver torso underwent CT scanning at 80, 100, 120 and 140kVp, each at ASiR settings of 0, 30 and 50%, and noise indices (NIs) of 5.5, 11 and 22. The volume CT dose index (CTDIvol), image noise, and attenuation values of liver and fat were analyzed for 20 data sets. Size-specific dose estimates (SSDEs) and liver-to-fat contrast-to-noise ratios (CNRs) were calculated. Values for different combinations of kVp, ASiR, and NI were compared. The CTDIvol varied by a power of 2 with kVp values between 80 and 140 without ASiR. Increasing ASiR levels allowed a larger decrease in CTDIvol and SSDE at higher kVp than at lower kVp while image noise was held constant. In addition, CTDIvol and SSDE decreased with increasing NI at each kVp, but the decrease was greater at higher kVp than at lower kVp. Image noise increased with decreasing kVp despite a fixed NI; however, this noise could be offset with the use of ASiR. The CT number of the liver remained unchanged whereas that of fat decreased as the kVp decreased. Image noise and dose vary in a complicated manner when the kVp, ASiR, and NI are varied in a human cadaver. Optimization of CT protocols will require balancing of the effects of each of these parameters to maximize image quality while minimizing dose.

MO-FG-CAMPUS-IeP1-03: Establishment of Provincial Diagnostic Reference Levels in Pediatric Imaging

Purpose: To establish provincial diagnostic reference levels (DRLs) in pediatric general radiography and computed tomography (CT) as a tool for the optimization of exposure parameters. Methods: Patient dose survey was conducted in the only pediatric hospital in the province of Nova Scotia. The DRLs were established as the 75th percentile of patient dose distributions in different age groups. For routine radiography projections the DRLs were determined in terms of entrance surface dose (ESD) calculated from the radiation output measurements and the tube current-exposure time product (mAs) recorded for each examination. Patient thickness was measured by the technologist during the examination. The CR and DR systems, employing respectively a fixed technique and phototiming, were evaluated separately; a two-tailed Student's t-test was used to determine the significance of differences between the means of dose distributions. The CT studies included routine head, chest, abdomen/pelvis, and chest/abdomen/pelvis. The volume CT dose index (CTDIvol) and dose-length product (DLP) values were extracted retrospectively from PACS. The correction factors based on the effective diameter of the patient were applied to the CT dosimetry metrics based on the standard phantoms. Results: The provincial DRLs were established in the following age groups: newborn, 1, 5, 10, and 15 year olds. In general radiography the DR systems demonstrated slightly lower dose than the CR for all views, however the differences were not statistically significant (p > 0.05) for all examinations. In CT the provincial DRLs were lower than the published data, except for head DLPs in all age categories. This might be due to the small patient sample size in the survey. Future work will include additional CT data collection over an extended period of time. Conclusion: Provincial DRLs were established in the dedicated children's hospital to provide guidance for the other facilities in examinations of pediatric patients.

Full Dose-Reduction Potential of Statistical Iterative Reconstruction for Head CT Protocols in a Predominantly Pediatric Population.

A statistical iterative reconstruction algorithm provides an effective approach to reduce patient dose by compensating for increased image noise in CT due to reduced radiation output. However, after a point, the degree to which a statistical iterative algorithm is used for image reconstruction changes the image appearance. Our aim was to determine the maximum level of statistical iterative reconstruction that can be used to establish dose-reduced head CT protocols in a primarily pediatric population while maintaining similar appearance and level of image noise in the reconstructed image. Select head examinations (brain, orbits, sinus, maxilla, and temporal bones) were investigated. Dose-reduced head protocols using an adaptive statistical iterative reconstruction were compared for image quality with the original filtered back-projection reconstructed protocols in a phantom by using the following metrics: image noise frequency (change in perceived appearance of noise texture), image noise magnitude, contrast-to-noise ratio, and spatial resolution. Dose-reduction estimates were based on CT dose index values. Patient volume CT dose index and image noise magnitude were assessed in 737 pre- and post-dose-reduced examinations. Image noise texture was acceptable for up to 60% adaptive statistical iterative reconstruction for the soft reconstruction kernel (at both 100 and 120 kV[peak]) and up to 40% adaptive statistical iterative reconstruction for the standard reconstruction kernel. Implementation of 40% and 60% adaptive statistical iterative reconstruction led to an average reduction in the volume CT dose index of 43% for brain, 41% for orbit, 30% for maxilla, 43% for sinus, and 42% for temporal bone protocols for patients between 1 month and 26 years of age, while maintaining an average noise magnitude difference of 0.1% (range, -3% to 5%), improving the contrast-to-noise ratio of low-contrast soft-tissue targets and the spatial resolution of high-contrast bony anatomy, compared with filtered back-projection. The methodology in this study demonstrates maximizing patient dose reduction and maintaining image quality by using statistical iterative reconstruction for a primarily pediatric population undergoing head CT examinations.

Implementation of full/half bowtie filter models in a commercial treatment planning system for kilovoltage cone-beam CT dose estimations.

The purpose of this study was to implement full/half bowtie filter models in a commercial treatment planning system (TPS) to calculate kilovoltage (kV) cone‐beam CT (CBCT) doses of Varian On‐Board Imager (OBI) kV X‐ray imaging system. The full/half bowtie filter models were created as compensators in Pinnacle TPS using MATLAB software. The physical profiles of both bowtie filters were imported and hard‐coded in the MATLAB system. Pinnacle scripts were written to import bowtie filter models into Pinnacle treatment plans. Bowtie filter‐free kV X‐ray beam models were commissioned and the bowtie filter models were validated by analyzing the lateral and percent‐depth‐dose (PDD) profiles of anterior/posterior X‐ray beams in water phantoms. A CT dose index (CTDI) phantom was employed to calculate CTDI and weighted CTDI values for pelvis and pelvis‐spotlight CBCT protocols. A five‐year‐old pediatric anthropomorphic phantom was utilized to evaluate absorbed and effective doses (ED) for standard and low‐dose head CBCT protocols. The CBCT dose calculation results were compared to ion chamber (IC) and Monte Carlo (MC) data for the CTDI phantom and MOSFET and MC results for the pediatric phantom, respectively. The differences of lateral and PDD profiles between TPS calculations and IC measurements were within 6%. The CTDI and weighted CTDI values of the TPS were respectively within 0.25 cGy and 0.08 cGy compared to IC measurements. The absorbed doses ranged from 0 to 7.22 cGy for the standard dose CBCT and 0 to 1.56 cGy for the low‐dose CBCT. The ED values were found to be 36‐38 mSv and 7‐8 mSv for the standard and low‐dose CBCT protocols, respectively. This study demonstrated that the established full/half bowtie filter beam models can produce reasonable dose calculation results. Further study is to be performed to evaluate the models in clinical situations.PACS number(s): 87.57.uq

Revue Des Doses d’Exposition Et Des Methode d’Optimisation En Tomodensitometrie (TDM) De l’Enfant Au Togo

Objectives: To assess the justification of indications of CT scans and the exposure doses of children during CT scans. Methods: Prospective study of 104 CT-sans of children collected over a period of 6 months. Results: Female children were predominant with a sex ratio female / male of 1.2. The predominant age group was the 10 to 15 years (41%). The CT-Scan of the head was the most practiced exam, with 64.42% (67/104). When analyzing information according to the recommendations of the Guide of well practices of French Society of Radiology (SFR) and the French Society of Biophysics and Nuclear Medicine (SFBMN), only 77% of CT-Scans were justified. Almost half (49.04%) of CT-Scans had a CT-Dose Index (CTDI) and Dose Length Product (DLP) greater than the French reference norms defined for each group of age. The average values of CTDI and DLP are above the norms for all CT-scans of the skull, facial bones and sinuses. Conclusion: The doses administered to children by CT-Scans are above accepted norms. Improved practices continue medical training of radiology manipulators and the creation of a regulatory or an agency of radioprotection is necessary.

Nationwide survey of radiation exposure during pediatric computed tomography examinations and proposal of age-based diagnostic reference levels for Japan

Diagnostic reference levels (DRLs) have not been established in Japan. To propose DRLs for CT of the head, chest and abdomen for three pediatric age groups. We sent a nationwide questionnaire by post to 339 facilities. Questions focused on pediatric CT technology, exposure parameters, CT protocols, and radiation doses for age groups <1 year, 1-5 years, and 6-10 years. For the three age groups in the 196 facilities that responded, the 75th percentile values of volume CT dose index based on a 16-cm phantom (CTDIvol 16 [mGy]) for head, chest and abdominal CT were for infants 39.1, 11.1 and 12.0, respectively; for 1-to 5-year-olds 46.9, 14.3 and 16.7, respectively; and for 6-to 10-year-olds 67.7, 15.0 and 17.0, respectively. The corresponding dose–length products (DLP 16 [mGy・cm]) for head, chest and abdominal CT were for infants 526.1, 209.1 and 261.5, respectively; for 1-to 5-year-olds 665.5, 296.0 and 430.8, respectively; and for 6-to 10-year-olds 847.9, 413.0 and 532.2, respectively. The majority of CTDIvol 16 and DLP 16 values for the head were higher than DRLs reported from other countries. For risk reduction, it is necessary to establish DRLs for pediatric CT in Japan.

CT enterography: Diagnostic value of 4th generation iterative reconstruction algorithm in low dose studies in comparison with standard dose protocol for follow-up of patients with Crohn’s disease

PurposeTo compare radiation dose, image quality and diagnostic performance of low dose CT enterography (CTE) protocol combined with iterative reconstruction algorithm (iDose4) with standard dose CTE in follow-up of patients with known Crohn’s disease (CD). Materials and methodThirty-six patients (12 females), with CD underwent a low-dose CTE scan during single venous phase on 256 MDCT scanner, with the following parameters: 120kV, automated mAs dose-modulation, slice thickness 2mm and iDose4 iterative reconstruction algorithm. A control group of thirty-seven patients underwent standard dose CTE examination on the same CT scanner. Two radiologists, blinded to clinical and pathological findings, independently evaluated in each scan, HU values in bowel wall and any presence of CD activity features and disease complications. Image noise and diagnostic quality were evaluated using a 4-point scale. Dose-length product (DLP) and CT-dose-index (CTDI) were recorded and data from both examinations were compared and statistically analyzed. ResultsLow-dose CTE protocol showed high diagnostic quality in assessment of Crohn’s disease obtaining significantly (p≤0.001) lower values of DLP and CTDI (604.98mGy*cm and 12.29mGy) as compared to standard dose examinations (974.85mGy*cm and 19.71mGy), with an overall dose reduction of 37.6%. Noise resulted slightly higher in iDose4 images (SD=15.97) than in standard dose ones (SD=13.61) but this difference was not statistically significant (p=0.064). ConclusionLow-dose CTE combined with iDose4 reconstruction algorithm offers high quality images with significant reduction of radiation dose, and therefore can be considered a useful tool in the management of CD patients, considering their young age and the frequent imaging follow-up required.

National Survey of Radiation Dose and Image Quality in Adult CT Head Scans in Taiwan.

IntroductionThe purpose of the present study was to evaluate the influence of different variables on radiation dose and image quality based on a national database.Materials and MethodsTaiwan’s Ministry of Health and Welfare requested all radiology departments to complete a questionnaire for each of their CT scanners. Information gathered included all scanning parameters for CT head scans. For the present analysis, CT machines were divided into three subgroups: single slice CT (Group A); multi-detector CT (MDCT) with 2-64 slices (Group B); and MDCT with more than 64 slices (Group C). Correlations between computed tomography dose index (CTDI) and signal-to-noise ratio (SNR) with cumulated tube rotation number (CTW(n)) and cumulated tube rotation time (CTW(s)), and sub group analyses of CTDI and SNR across the three groups were performed.ResultsCTDI values demonstrated a weak correlation (r = 0.33) with CTW(n) in Group A. SNR values demonstrated a weak negative correlation (r = -0.46) with CTW(n) in Group C. MDCT with higher slice numbers used more tube potential resulting in higher effective doses. There were both significantly lower CTDI and SNR values in helical mode than in axial mode in Group B, but not Group C.ConclusionCTW(n) and CTW(s) did not influence radiation output. Helical mode is more often used in MDCT and results in both lower CTDI and SNR compared to axial mode in MDCT with less than 64 slices.

Feasibility Study of Using Gemstone Spectral Imaging (GSI) and Adaptive Statistical Iterative Reconstruction (ASIR) for Reducing Radiation and Iodine Contrast Dose in Abdominal CT Patients with High BMI Values.

PurposeTo prospectively investigate the effect of using Gemstone Spectral Imaging (GSI) and adaptive statistical iterative reconstruction (ASIR) for reducing radiation and iodine contrast dose in abdominal CT patients with high BMI values.Materials and Methods26 patients (weight > 65kg and BMI ≥ 22) underwent abdominal CT using GSI mode with 300mgI/kg contrast material as study group (group A). Another 21 patients (weight ≤ 65kg and BMI ≥ 22) were scanned with a conventional 120 kVp tube voltage for noise index (NI) of 11 with 450mgI/kg contrast material as control group (group B). GSI images were reconstructed at 60keV with 50%ASIR and the conventional 120kVp images were reconstructed with FBP reconstruction. The CT values, standard deviation (SD), signal-noise-ratio (SNR), contrast-noise-ratio (CNR) of 26 landmarks were quantitatively measured and image quality qualitatively assessed using statistical analysis.ResultsAs for the quantitative analysis, the difference of CNR between groups A and B was all significant except for the mesenteric vein. The SNR in group A was higher than B except the mesenteric artery and splenic artery. As for the qualitative analysis, all images had diagnostic quality and the agreement for image quality assessment between the reviewers was substantial (kappa = 0.684). CT dose index (CTDI) values for non-enhanced, arterial phase and portal phase in group A were decreased by 49.04%, 40.51% and 40.54% compared with group B (P = 0.000), respectively. The total dose and the injection rate for the contrast material were reduced by 14.40% and 14.95% in A compared with B.ConclusionThe use of GSI and ASIR provides similar enhancement in vessels and image quality with reduced radiation dose and contrast dose, compared with the use of conventional scan protocol.