Automatic Tube Current Modulation Research Articles

A new phantom developed to test the ATCM performance of chest CT scanners

In this study, a new ATCM phantom was developed to test the performance of the automatic tube current modulation (ATCM) of computed tomography (CT) scanners.. Based on the Chinese reference man and Monte Carlo simulations of x-ray attenuation, a more realistic ATCM phantom made of polymethyl methacrylate was developed. The phantom has a length of 20 cm, and it can be used to measure the dose profile along the central axis using 19 real-time MOSFET detectors. The image noise can be calculated slice by slice in the phantom’s center. Test experiments showed that the phantom could initiate tube current modulation under different modulation levels of CT scans, and the actual effects of ATCM could be evaluated with the aid of the dose profile measurements. Using the measured dose profiles and image noise, the preferred dose can easily be identified from a choice of different modulation levels. The new phantom developed in this study can be used to test the ATCM performance of CT scanners, and is useful for further studies of the optimization of CT scan protocols with ATCM.

Mixed reality models based on low-dose computed tomography technology in nephron-sparing surgery are better than models based on normal-dose computed tomography.

Nephron-sparing surgery has been widely applied in the treatment of renal tumors. Previous studies have confirmed the advantages of mixed reality technology in surgery. The study aimed to explore the optimization of mixed reality technology and its application value in nephron-sparing surgery. In this prospective study of 150 patients with complex renal tumors (RENAL nephrometry score ≥7) who underwent nephron-sparing surgery, patients were randomly divided into Group A (the normal-dose mixed reality group, n=50), Group B (the low-dose mixed reality group, n=50), and Group C (the traditional computed tomography image group, n=50). Group A and Group C received the normal-dose computed tomography scan protocol: 120 kVp, 400 mA, and 350 mgI/mL, while Group B received the low-dose computed tomography scan protocol: 80 kVp, automatic tube current modulation, and 320 mgI/mL. All computed tomography data were transmitted to a three-dimensional visualization workstation and underwent modeling and mixed reality imaging. Two senior surgeons evaluated mixed reality quality. Objective indexes and perioperative indexes were calculated and compared. Compared with Group A, the radiation effective dose in Group B was decreased by 39.6%. The subjective scores of mixed reality quality in Group B were significantly higher than those of Group A (Z=-4.186, P<0.001). The inter-observer agreement between the two senior surgeons in mixed reality quality was excellent (K=0.840, P<0.001). The perioperative indexes showed that the mixed reality groups were significantly different from the computed tomography image group (all P<0.017). More cases underwent nephron-sparing surgery in the mixed reality groups than in the computed tomography image group (P<0.0017). Low-dose computed tomography technology can be effectively applied to mixed reality optimization, reducing the effective dose and improving mixed reality quality. Optimized mixed reality can significantly increase the cases of successful nephron-sparing surgery and improve perioperative indexes.

Evaluation of computed tomography dose Reduction and image Quality in Ingenuity TOF PET/CT.

Objectives: The aim of this study is to evaluate the various automatic tube current modulation combined with iterative reconstruction (iDose4) in commercially available positron emission computed tomography/computed tomography (PET/CT, Philips healthcare) imaging scanner. Methods: A Rando phantom was scanned according to the high dose routine protocol (CTDI=19.3 mGy) using Atomic Exposure Control (Dose Right) with two different dose right modulation Z and 3D modulation.At each modulation, four different values of Dose right index 5, 10, 15, 20 and 30 were applied. Raw data were reconstructed with 4 iDose4 levels (0, 2, 4 and 6).Results: We found that no significant difference in image noise (SD) of bone, lung, liver issue between the two ATCM including 3D-DOM and Z-DOM (p>0.05). However, significant difference in SD measurements was found in soft tissue (p < 0.05). A significant image noise improvement on iDose4 L2 images at DRI 5 and Z-DOM modulation represented by a reduction in SD of 10.1%, 18.5%, 12.8% and 17.5% for bone, soft tissue, lung and liver respectively.The greatest reduction of image noise was observed when using iDose4 L6 by 20.9%, 39.3%, 40.7 and 72.7% for bone, soft tissue, lung and liver respectively. Z-DOM and 3D-DOM protocols were observed to lead significant reduction in CTDI vol, DLP and effective dose. The reduction in effective radiation exposure was between 15% and 63% according to the value of DRI used. Conclusion: While maintaining a diagnostic level of image quality, combining AEC software with iDose4 levels can effectively reduce the radiation effective dose significantly (up to 60%) in comparison with constant tube current (AEC-off). The results demonstrate also that no significant reduction in radiation dose exposure between using Z-DOM and 3D-DOM modulation.

A phantom study to optimise the automatic tube current modulation for chest CT in COVID-19

On March 11, 2020, the World Health Organization declared the coronavirus disease 2019 (COVID-19) pandemic. The expert organisations recommend more cautious use of thoracic computed tomography (CT), opting for low-dose protocols. We aimed at determining a threshold value of automatic tube current modulation noise index below which there is a chance to miss an onset of ground-glass opacities (GGO) in COVID-19. A team of radiologists and medical physicists performed 25 phantom CT studies using different automatic tube current modulation settings (SUREExposure3D technology). We then conducted a retrospective evaluation of the chest CT images from 22 patients with COVID-19 and calculated the density difference between the GGO and unaffected tissue. Finally, the results were matched to the phantom study results to determine the minimum noise index threshold value. The minimum density difference at the onset of COVID-19 was 252 HU (p < 0.001). This was found to correspond to the SUREExposure 3D noise index of 36. We established the noise index threshold of 36 for the Canon scanner without iterative reconstructions, allowing for a decrease in the dose-length product by 80%. The proposed protocol needs to be validated in a prospective study.

Assessment of Imaging Protocol and Patients Radiation Exposure in Computed Tomography Colonography

In the screening and identifying of colon and rectum malignancy, computed tomography colonography (CTC) is a highly effective imaging technique, albeit patients receiving a significant effective dose. Accordingly, patient dose evaluation is an important need, seeking to ensure benefits outweigh the projected cancer risk. Objective: For CTC procedures carried out in the Radiology Department, Medical Imaging Operation Services, King Fahad Medical City (KFMC), evaluation is done using the current American College of Radiology (ACR) imaging protocol and concomitant patient-effective doses. Study is carried out on a sample size of 55 CTC procedures, involving 25 males (45%) and 30 females (55%). The patients were classified as follows: two groups based on CT machine; four groups based on the applied protocol; and three groups based on the procedure results. All procedures were carried out using two machines, the products of two different vendors (a GE Healthcare DISCOVERY CT 750 HD 64 slices dual-energy scanner and a Philips Brilliance CT 64 slices scanner). The overall mean, standard deviation (SD), median, and range of the effective dose (in mSv) were 11.57 ± 7.75, 9.25 (2.17–31.93). Automatic tube current modulation (ATCM) shows a significant increase in CTDIvol up to 69% and effective dose (mSv) up to 95% than the manual tube current (mA) compared to the standard protocol. The CT protocol variation results in a three-fold variation in patient-effective dose. The technologist role is crucial in selecting a noise reference based on patient weight and adjusting tube current per slice to avoid overexposure during ATCM protocol.

Individualized protocol for radiation and contrast medium dose reduction in one-stop assessment for kidney transplantation patients

ObjectiveTo compare image quality, radiation, and contrast medium (CM) doses between individualized and conventional scan protocols in combined coronary CT angiography (CCTA) and iliac artery CTA for kidney transplantation patients. Methods148 patients needing assessment for coronary and iliac arteries before kidney transplantation were prospectively enrolled and randomly divided into the conventional and individualized groups. All patients underwent one-stop combined scans on a 256-row CT scanner with automatic tube current modulation, 50 % pre-ASIR-V to control radiation dose. CCTA was performed first using one heartbeat axial scan mode with bolus tracking technique and iliac CTA was performed 3 s after CCTA using a spiral scan. The conventional group (n = 72) used the standard protocol: 100 kVp, 60 mL of 350 mgI/mL CM at 4.5 mL/s flow rate. The individualized group (n = 76) used a body-mass-index (BMI)-dependent protocol: kVp: 80 (BMI < 24) and 100 (BMI ≥ 24) and CM: 19 mgI/kg (BMI < 18); 21 mgI/kg (18 ≤ BMI < 24); and 22 mgI/kg (BMI ≥ 24). Image quality radiation and CM doses of the two groups were compared. ResultsThere was no significant difference in patient demographic data. Compared with the conventional group, the individualized group reduced contrast flow rate (in mL/s) by 14.4 % (3.85 ± 0.72 vs. 4.5), contrast dose (in mL) by 35.8 % (38.53 ± 7.18 vs. 60) and radiation dose (in mSv) by 34.3 % (4.30 ± 1.73 vs. 6.54 ± 1.45). The individualized group had significantly higher subjective image quality score (P ＜ 0.05), lower noise (17.30 ± 4.97 HU vs. 19.13 ± 4.73 HU, P = 0.02) and higher signal-to-noise ratio (22.09 ± 7.41 vs. 19.55 ± 6.18, P = 0.03) for the three main vessels in CCTA compared with the conventional group. There were no differences in both subjective scores and objective measurements in iliac artery CTA between the two groups. ConclusionThe individualized scanning protocol in the one-stop assessment of coronary and iliac arteries before kidney transplantation significantly reduces both radiation and CM doses while maintaining image quality in iliac artery CTA and providing better coronary artery images in CCTA.

Phantom Study on the Effect of Automatic Tube Current Modulation on Image Quality and Radiation Dose of Abdominal CT

Phantom Study on the Effect of Automatic Tube Current Modulation on Image Quality and Radiation Dose of Abdominal CT

A comparison of breast and lung doses from chest CT scans using organ-based tube current modulation (OBTCM) vs. Automatic tube current modulation (ATCM).

PurposeThe purpose of this work was to estimate and compare breast and lung doses of chest CT scans using organ‐based tube current modulation (OBTCM) to those from conventional, attenuation‐based automatic tube current modulation (ATCM) across a range of patient sizes.MethodsThirty‐four patients (17 females, 17 males) who underwent clinically indicated CT chest/abdomen/pelvis (CAP) examinations employing OBTCM were collected from two multi‐detector row CT scanners. Patient size metric was assessed as water equivalent diameter (Dw) taken at the center of the scan volume. Breast and lung tissues were segmented from patient image data to create voxelized models for use in a Monte Carlo transport code. The OBTCM schemes for the chest portion were extracted from the raw projection data. ATCM schemes were estimated using a recently developed method. Breast and lung doses for each TCM scenario were estimated for each patient model. CTDIvol‐normalized breast (nDbreast) and lung (nDlung) doses were subsequently calculated. The differences between OBTCM and ATCM normalized organ dose estimates were tested using linear regression models that included CT scanner and Dw as covariates.ResultsMean dose reduction from OBTCM in nDbreast was significant after adjusting for the scanner models and patient size (P = 0.047). When pooled with females and male patient, mean dose reduction from OBTCM in nDlung was observed to be trending after adjusting for the scanner model and patient size (P = 0.085).ConclusionsOne specific manufacturer’s OBTCM was analyzed. OBTCM was observed to significantly decrease normalized breast relative to a modeled version of that same manufacturer’s ATCM scheme. However, significant dose savings were not observed in lung dose over all. Results from this study support the use of OBTCM chest protocols for females only.

Abdominal CT radiation dose reduction at Siriraj Hospital (Phase III)

OBJECTIVE: To compare the image quality and the radiation dose between fixed tube current (FTC) low dose abdominal CT currently performed at our hospital and new automatic tube current modulation (ATCM) low dose abdominal CT. MATERIALS AND METHODS: We prospectively performed ATCM low dose abdominal CT in 88 participants who had prior FTC low dose CT for comparison. Four experienced abdominal radiologists independently and blindly assessed the quality of FTC and ATCM low dose CT images by using a 5-point-scale satisfaction score (1 = unacceptable, 2 = poor, 3 = average, 4 = good, and 5 = excellent image quality). Each reader selected the preferred image set between FTC and ATCM low dose techniques for each participant. The image noise of the liver and the aorta in both techniques was measured. The volume CT dose index (CTDIvol) of both techniques was compared. RESULTS: The mean satisfaction scores (SD) for FTC and ATCM low dose CT were 4.38 (0.66) and 4.38 (0.64), respectively with the ranges of 3 to 5 in both techniques, which were all acceptable for CT interpretation. The preferred image set between FTC and ATCM low dose techniques of each participant randomly selected by each reader were varied, depending on the readers’ opinions. The mean image noise of the aorta on FTC and ATCM low dose CT accounted for 34.75 and 36.46, respectively, while the mean image noise of the liver was 28.86 and 29.81, respectively. The mean CTDIvol (SD) of FTC and ATCM low dose CT were 8.42 (0.32) and 8.12 (0.43) mGy, respectively. CONCLUSION: FTC and ATCM low dose abdominal CT provided comparable acceptable image quality and showed no clinical significance in radiation dose optimization.

Computed tomography colonography and radiation risk: How low can we go?

Computed tomography colonography (CTC) has become a key examination in detecting colonic polyps and colorectal carcinoma (CRC). It is particularly useful after incomplete optical colonoscopy (OC) for patients with sedation risks and patients anxious about the risks or potential discomfort associated with OC. CTC's main advantages compared with OC are its non-invasive nature, better patient compliance, and the ability to assess the extracolonic disease. Despite these advantages, ionizing radiation remains the most significant burden of CTC. This opinion review comprehensively addresses the radiation risk of CTC, incorporating imaging technology refinements such as automatic tube current modulation, filtered back projections, lowering the tube voltage, and iterative reconstructions as tools for optimizing low and ultra-low dose protocols of CTC. Future perspectives arise from integrating artificial intelligence in computed tomography machines for the screening of CRC.

Radiomics in the evaluation of lung nodules: Intrapatient concordance between full-dose and ultra-low-dose chest computed tomography

PurposeThe purpose of this study was to retrospectively evaluate the quantitative and qualitative intrapatient concordance of pulmonary nodule risk assessment by commercially available radiomics software between full-dose (FD) chest-CT and ultra-low-dose (ULD) chest CT. Materials and methodsBetween July 2013 and September 2015, 68 patients (52 men and16 women; mean age, 65.5±10.6 [SD] years; range: 35–87 years) with lung nodules≥5mm and<30mm who underwent the same day FD chest CT (helical acquisition; 120kV; automated tube current modulation) and ULD chest CT (helical acquisition; 135kV; 10mA fixed) were retrospectively included. Each nodule on each acquisition was assessed by a commercial radiomics software providing a similarity malignancy index (mSI), classifying it as “benign-like” (mSI<0.1); “malignant-like” (mSI>0.9) or “undetermined” (0.1≤mSI≤0.9). Intrapatient qualitative agreement was evaluated with weighted Cohen–Kappa test and quantitative agreement with intraclass correlation coefficient (ICC). ResultsNinety-nine lung nodules with a mean size of 9.14±4.3 (SD) mm (range: 5–25mm) in 68 patients (mean 1.46 nodule per patient; range: 1–5) were assessed; mean mSI was 0.429±0.331 (SD) (range: 0.001–1) with FD chest CT (22/99 [22%] “benign-like”, 67/99 [68%] “undetermined” and 10/99 [10%] “malignant-like”) and mean mSI was 0.487±0.344 (SD) (range: 0.002–1) with ULD chest CT (20/99 [20%] “benign-like”, 59/99 [60%] “undetermined” and 20/99 [20%] “malignant-like”). Qualitative and quantitative agreement of FD chest CT with ULD chest CT were “good” with Kappa value of 0.60 (95% CI: 0.46–0.74) and ICC of 0.82 (95% CI: 0.73–0.87), respectively. ConclusionA good agreement in malignancy similarity index can be obtained between ULD chest CT and FD chest CT using radiomics software. However, further studies must be done with more case material to confirm our results and elucidate the diagnostic capabilities of radiomics software using ULD chest CT for lung nodule characterization by comparison with FD chest CT.

Feasibility of Pediatric Low-Dose Facial CT Reconstructed with Filtered Back Projection Using Adequate Kernels.

PurposeTo evaluate the feasibility of pediatric low-dose facial CT reconstructed with filtered back projection (FBP) using adequate kernels.Materials and MethodsWe retrospectively reviewed the clinical and imaging data of children aged < 10 years who underwent facial CT at our emergency department. The patients were divided into two groups: low-dose CT (LDCT; Group A, n = 73) with a fixed 80-kVp tube potential and automatic tube current modulation (ATCM) and standard-dose CT (SDCT; Group B, n = 40) with a fixed 120-kVp tube potential and ATCM. All images were reconstructed with FBP using bone and soft tissue kernels in Group A and only bone kernel in Group B. The groups were compared in terms of image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). Two radiologists subjectively scored the overall image quality of bony and soft tissue structures. The CT dose index volume and dose-length product were recorded.ResultsImage noise was higher in Group A than in Group B in bone kernel images (p < 0.001). Group A using a soft tissue kernel showed the highest SNR and CNR for all soft tissue structures (all p < 0.001). In the qualitative analysis of bony structures, Group A scores were found to be similar to or higher than Group B scores on comparing bone kernel images. In the qualitative analysis of soft tissue structures, there was no significant difference between Group A using a soft tissue kernel and Group B using a bone kernel with a soft tissue window setting (p > 0.05). Group A showed a 76.9% reduction in radiation dose compared to Group B (3.2 ± 0.2 mGy vs. 13.9 ± 1.5 mGy; p < 0.001).ConclusionThe addition of a soft tissue kernel image to conventional CT reconstructed with FBP enables the use of pediatric low-dose facial CT protocol while maintaining image quality.

Abdominal CT radiation dose reduction at Siriraj Hospital (Phase II)

Objective: To compare radiation dose, radiologists’ satisfaction, and image noise between the standard dose abdominal CT currently performed at our hospital and the new automatic tube current modulation (ATCM) low dose abdominal CT, using various parameters (0%, 10%, 20%, and 30%) of the Adaptive Statistical Iterative Reconstruction (ASiR). Materials and Methods: We prospectively performed the ATCM low dose abdominal CT in 111 participants who had prior standard dose CT for comparison. The ATCM low dose CT images were post processed with 4 parameters (0%, 10%, 20% and 30%) of ASiR on a CT workstation. The volume CT dose index (CTDIvol) of the ATCM low dose and the standard dose CT were compared. Four experienced abdominal radiologists independently assessed the quality of the ATCM low dose CT with the aforementioned ASiR parameters using a 5-point-scale satisfaction score (1 = unacceptable, 2 = poor, 3 = average, 4 = good, and 5 = excellent image quality) by using the prior standard dose CT as a reference of an excellent image quality (5). Each reader selected the preferred ASiR parameter for each participant. The image noise of the liver and the aorta in all 5 techniques (1 prior standard dose and 4 current ATCM low dose techniques) was measured. The correlation between the image quality vs the participants’ body mass index (BMI) and waist circumferences were analyzed. Results: The mean CTDIvol of the ATCM low dose CT was significantly lower than of the standard dose CT (7.29 ± 0.20 vs 11.28 ± 0.23 mGy, p&lt;0.001). The mean satisfaction score for the ATCM low dose CT with 0%, 10%, 20% and 30% ASiR were 4.14, 4.16, 4.17, and 4.26, respectively with the ranges of 3 to 5 in all techniques. The preferred ASiR parameters of each participant randomly selected by each reader were varied, depending on the readers’ opinions. The mean image noise of the aorta on the standard dose CT and the ATCM low dose CT with 0%, 10%, 20%, and 30% ASiR was 30.69, 36.60, 34.05, 31.43, and 29.09, respectively, while the mean image noise of the liver was 24.96, 29.90, 27.86, 25.66, and 23.68, respectively. There was a correlation between the image quality (satisfaction score and image noise) vs the participants’ BMI and waist circumferences. Conclusion: The ATCM low dose CT received acceptable radiologists’ satisfaction with significant radiation dose reduction. The increment of ASiR was helpful in reducing the image noise and had a tendency to increase the radiologists’ satisfaction score.

A study of using a deep learning image reconstruction to improve the image quality of extremely low-dose contrast-enhanced abdominal CT for patients with hepatic lesions.

To investigate the feasibility of using deep learning image reconstruction (DLIR) to significantly reduce radiation dose and improve image quality in contrast-enhanced abdominal CT. This was a prospective study. 40 patients with hepatic lesions underwent abdominal CT using routine dose (120kV, noise index (NI) setting of 11 with automatic tube current modulation) in the arterial-phase (AP) and portal-phase (PP), and low dose (NI = 24) in the delayed-phase (DP). All images were reconstructed at 1.25 mm thickness using ASIR-V at 50% strength. In addition, images in DP were reconstructed using DLIR in high setting (DLIR-H). The CT value and standard deviation (SD) of hepatic parenchyma, spleen, paraspinal muscle and lesion were measured. The overall image quality includes subjective noise, sharpness, artifacts and diagnostic confidence were assessed by two radiologists blindly using a 5-point scale (1, unacceptable and 5, excellent). Dose between AP and DP was compared, and image quality among different reconstructions were compared using SPSS20.0. Compared to AP, DP significantly reduced radiation dose by 76% (0.76 ± 0.09 mSv vs 3.18 ± 0.48 mSv), DLIR-H DP images had lower image noise (14.08 ± 2.89 HU vs 16.67 ± 3.74 HU, p < 0.001) but similar overall image quality score as the ASIR-V50% AP images (3.88 ± 0.34 vs 4.05 ± 0.44, p > 0.05). For the DP images, DLIR-H significantly reduced image noise in hepatic parenchyma, spleen, muscle and lesion to (14.77 ± 2.61 HU, 14.26 ± 2.67 HU, 14.08 ± 2.89 HU and 16.25 ± 4.42 HU) from (24.95 ± 4.32 HU, 25.42 ± 4.99 HU, 23.99 ± 5.26 HU and 27.01 ± 7.11) with ASIR-V50%, respectively (all p < 0.001) and improved image quality score (3.88 ± 0.34 vs 2.87 ± 0.53; p < 0.05). DLIR-H significantly reduces image noise and generates images with clinically acceptable quality and diagnostic confidence with 76% dose reduction. (1) DLIR-H yielded a significantly lower image noise, higher CNR and higher overall image quality score and diagnostic confidence than the ASIR-V50% under low signal conditions. (2) Our study demonstrated that at 76% lower radiation dose, the DLIR-H DP images had similar overall image quality to the routine-dose ASIR-V50% AP images.

Effect on Radiation Dose and Image Quality of the Computed Tomography Tube Current Modulation

In the present study, the radiation dose and image quality between two techniques, namely; automatic tube current modulation (ATCM) and fixed tube current (FTC), in computed tomography (CT) of multiphasic examination of the liver, were evaluated. For this objective, fifty liver CT patients examined were investigated by arterial, portal, venous, and equilibrium measures following scans of hepatic circulatory phases. All stages, except for tube current, a portal, and a venous phase, have been carried out by the FTC, ATCM and correlated with their dosage and image quality, with similar scanning and reconstruction parameters. In these techniques, the CT unit automatically displays , both the radiation dose measurements and the dose index volume (CTDIvol), simultaneously. Also, for quality insurance, the images obtained were quantitatively evaluated by the contrast noise ratio (CNR). The results showed that the averaged of CTDIvol was 26.07 mGy in FTC, and 13.71 mGy in ATCM. As compared with the FTC technique, CTDIvol was reduced by using the ATCM technique. The average value of CNR were(28.93, 29.98) HU in FTC and ATCM, respectively.

Optimization of paranasal sinus CT procedure: Ultra-low dose CT as a roadmap for pre-functional endoscopic sinus surgery.

To assess image quality and radiation dose associated with ultra-low dose CT protocol for patients with benign paranasal sinus diseases undergoing functional endoscopic surgery (FESS). We scanned the head portion of Alderson RANDO phantom on a second generation, dual-source, multidetector-row CT scanner (Siemens Definition Flash) using standard-dose and five low-dose protocols. Two radiologists assessed the image quality for each protocol to determine best ultra-low-dose protocols for imaging patients with benign paranasal sinus diseases undergoing FESS. The ultra-low-dose CT protocols were then used for scanning. Thereafter, 40 adult patients (age range 18-54years, M:F 23:17) were scanned with the four low dose scanning protocols (10 patients per protocol). On both transverse and coronal reformatted CT images, two radiologists assessed visibility of key anatomic landmarks for FESS on a 2-point scale (1=clear and complete visualization; 2=suboptimal visualization). Data were analyzed with descriptive statistics and Cohen's kappa coefficient for interobserver agreement. In phantom study, the lowest dose scan protocol (CTDIvol 2.1mGy, 70kV, 75 mAs) was unacceptable due to poor image quality. For patient studies, both radiologists gave acceptable image quality scores for ultra-low-dose scan protocol with axial scan mode, automatic tube potential selection and tube current modulation (CTDIvol 2.2mGy; DLP 22.9mGy.cm) with up to 60% lower dose compared to prior standard-dose CT (CTDIvol 5.3mGy; DLP 73.5mGy.cm). Ultra-low-dose CT protocol provides sufficient image quality for scanning patients undergoing functional endoscopic surgery for benign paranasal sinus diseases.

Image quality and clinical usefulness of automatic tube current modulation technology in female chest computed tomography screening.

The study was aimed to evaluate the image quality and radiation dose during female chest computed tomography (CT) screening using organ-based tube current modulation technology X-ray combined applications to reduce exposure (XCARE).Five hundred sixty female individuals undergoing chest CT scan were prospectively enrolled and divided into 4 groups based on body mass index (BMI). Then they were randomly and equally divided into control and experimental subgroup and respectively accepted conventional low-dose and XCARE technology spiral CT scan with same parameters. Signal-to-noise ratio and contrast-to-noise ratio were calculated. The quality of the images was evaluated by 2 radiologists using a 5-point scale.Among experimental subgroups of the 4 BMI groups, Signal-to-noise ratios, CT dose index of volume, dose-length product, effective dose, and contrast-to-noise ratio all displayed significant differences, as well as in control subgroups (P < .001). Both the experimental and control subgroups showed an increasing trend in radiation dose with the increasing of BMI. Parameters of image quality and radiation dose displayed no significant differences between control and experimental subgroups in the 4 groups. In multiple linear regression analysis, age and scanning protocol were not associated with radiation dose (P > .05), while BMI was significantly associated with increased CT dose index of volume (P < .05). The display of the lesions for the patients in the control and experimental subgroups of the 4 groups with different BMIs exhibited no statistically significant difference.The same image quality and radiation dose can be obtained using XCARE technology compared to conventional chest CT scans, which can be used regularly in female patients.Advances in knowledge: Using automatic tube current modulation technology to reduce exposure in breast. In this study, we sought a radiation protection method for sensitive tissue in chest CT screening.

Design and use of a phantom for testing and comparing the performance of computed tomography automatic tube current modulation systems

Automatic tube current modulation (ATCM) is now available on all computed tomography (CT) scanners, but there is no standard phantom for testing its operation. For this study, a phantom comprising five elliptical sections of varying diameters in the shape of a pagoda has been made to represent the range of sizes for patients in Thailand and the Far East. ATCM performance can be evaluated in terms of how tube current and image noise vary with changes in the sizes of the sections. Additional rods of different materials with similar properties to human tissues have been inserted to allow the measurement of contrast-to-noise ratios (CNRs) for assessment of image quality. The phantom has been used to test and compare the performance of CT ATCM systems for the major four CT scanner vendors. The results showed that the ATCM systems of Toshiba and GE CT scanners maintained image noise and CNR within narrower ranges by varying tube current aggressively along the scan length, and commencing modulation before the high attenuation sections are reached. In contrast, the ATCM systems of Philips and Siemens scanners adjusted the tube current within narrower ranges, allowed larger variations in image noise and CNR, and commenced modulation at the start of sections with higher attenuation. The phantom can be used to confirm functionality of the system for acceptance testing, as well as providing information on the tradeoff between radiation dose and image quality when setting up clinical protocols during commissioning of new CT scanners. The phantom can also be used on a routine basis to check that performance is maintained, and could be used in the future for selecting protocol settings to give required values of CNR or adjusting protocol settings on different CT scanners to provide similar levels of clinical performance.

Axial or Helical? CT imaging of the thorax for dyspnoea patients with free-breathing using 16 cm wide-detector CT

To compare image quality and radiation dose between fast-helical mode (FHM) and two-axial mode (TAM) in chest computed tomography (CT) with 16 cm wide-detector for emergency patients with dyspnoea. Ninety-six emergency chest CT patients who cannot comply with breathing instructions were prospectively divided randomly into two groups: the FHM group (n=48, helical scan with 80 mm collimation and pitch 0.992:1), the TAM group (n=48, two axial scans with 160 mm collimation). Both groups used 0.28 seconds rotation speed and automatic tube current modulation. All scans were performed in free breathing. CT value, image noise, and signal-to-noise ratio (SNR) were measured on the descending thoracic aorta, lung parenchyma, and paraspinal muscle at the carina level. Two radiologists assessed images for subjective image quality, motion artefacts and diagnostic confidence. The volume CT dose index and dose-length product (DLP) were evaluated and effective dose (ED) was calculated. The TAM group required less exposure time than the FHM group (0.56 versus 1.14 seconds, p<0.001), reduced the frequency of motion artefacts caused by the diaphragm and heart by 50% and provided higher diagnostic confidence score (3.83 versus 3.58, p<0.05). TAM resulted in 24% lower DLP (96.76±31.58 versus 126.99±33.37 mGy·cm) and ED (1.36±0.44 versus 1.78±0.47 mSv) than FHM (p<0.001), but there was no difference in the CT value, image noise, and SNR between the two groups (p>0.05). TAM with 16 cm detector coverage further reduces the exposure time in chest CT for dyspnoea patients and ensures good image quality with 24% radiation dose reduction, compared with fast-helical chest CT with 80 mm collimation.

Relation between age and CT radiation doses: Dose trends in 705 pediatric head CT

PurposeTo evaluate the relationship between patient age and radiation doses associated with routine pediatric head CT performed with automatic tube potential selection and tube current modulation techniques. MethodsWe obtained patient demographics, scan parameters, and radiation dose descriptors (CT dose index volume -CTDIvol and dose length product -DLP) associated with consecutive routine head CT in 705 children (mean age 6.9 ± 5 years). Children were scanned on one of the three multidetector-row CTs (64–128 slices, Siemens) over 6 months period in a tertiary hospital. All head CT exams were performed in helical scan mode using automatic tube potential selection (Care kV) and automatic tube current modulation (Care Dose 4D) techniques. The information was obtained from a radiation dose monitoring software. Data were analyzed using linear correlation and analysis of variance. ResultsMost age-wise median CTDIvol (9−27 mGy; 703/705 pediatric head CT, >99 %) from our institution were lower than the European Diagnostic Reference Levels (EDRL, CTDIvol 24−50 mGy) but median DLP (151−586 mGy cm) from 201/705 children (28 %) was higher than the EDRL (DLP 300−650 mGy cm). Unlike the age-stratified EDRL, a combination of automatic tube potential selection and tube current modulation for pediatric head results in a significant linear correlation between radiation doses and patient age (r2 = 0.66, p < 0.001). ConclusionsRadiation doses for head CT change linearly with children's age. Despite lower CTDIvol and DLP for most children, longer scan length resulted in higher DLP for some pediatric head CT compared to the corresponding EDRL; this result underscores the need to promote clear guidelines for technologists operating CT.