Dose-length Product Research Articles

ANALISIS AUDIT DOSIS SEBAGAI UPAYA OPTIMISASI PADA PEMERIKSAAN CT ABDOMEN INTRAVENOUS (IV) DI RUMAH SAKIT UMUM PUSAT ADAM MALIK MEDAN

Audits are conducted on CT scan examinations using dose metrics to assess the need for optimization in computed tomography procedures. Diagnostic reference levels (DRL) provide an indicator that helps optimize patient medical exposure by adhering to the recommendations of the International Commission on Radiological Protection (ICRP). In the radiology unit at Adam Malik Hospital, efforts were made to reduce the radiation dose given to patients during CT abdominal IV examinations by using the lowest possible radiation dose without compromising image quality. The CT scans were carried out on 1526 patients using a Philips Ingenuity brand CT Scan, type MRC880, serial number 168014, and a built-in phantom as a patient representation. The radiation output was represented by the volumetric computed tomography dose index (CTDIvol) and dose length product (DLP). The physical parameters of tube voltage (kV) and pitch were evaluated to optimize the CT abdominal IV dose. At the same time, the Signal Difference to Noise Ratio (SDNR) was used to analyze image quality for each change in physical parameters. The results of dose audit data for CT abdominal IV patients, when using parameters of 120 kV and 1.1-1.2 pitch, obtained a Q2 value of 1452 mGy.cm higher than I-DRL of 1360 mGy.cm. Data from measurements with a phantom at 100 kV and 1.40-1.48 pitch showed a lower dose than the previous parameters. CT abdominal IV patient dose data with 100 kV and 1.40 -1.48 pitch showed that the DLP value in Q2 was 755 mGy.cm, lower than the previous measurement of 1452 mGy.cm. This means that there was a 52% decrease in dose after changing the parameters of 100 kV and 1.40 -1.48 pitch with image quality remaining optimal. The highest SDNR value of 12 was obtained at 100 kV and 1.48 pitch. The results indicate that it is necessary to establish a new protocol for CT abdominal IV with parameters of 100 kV and 1.40 -1.48 pitch for adult patients over 15 years of age. Keywords: optimization, radiation dose, image quality, CT abdomen

Evolution of CT radiation dose in pediatric patients undergoing hybrid 2-[18F]FDG PET/CT between 2007 and 2021.

To evaluate the evolution of CT radiation dose in pediatric patients undergoing hybrid 2-[18F]fluoro-2-deoxy-D-glucose (2-[18F]FDG) PET/CT between 2007 and 2021. Data from all pediatric patients aged 0-18 years who underwent hybrid 2-[18F]FDG PET/CT of the body between January 2007 and May 2021 were reviewed. Demographic and imaging parameters were collected. A board-certified radiologist reviewed all CT scans and measured image noise in the brain, liver, and adductor muscles. 294 scans from 167 children (72 females (43%); median age: 14 (IQR 10-15) years; BMI: median 17.5 (IQR 15-20.4) kg/m2) were included. CT dose index-volume (CTDIvol) and dose length product (DLP) both decreased significantly from 2007 to 2021 (both p < 0.001, Spearman's rho coefficients -0.46 and -0.35, respectively). Specifically, from 2007 to 2009 to 2019-2021 CTDIvol and DLP decreased from 2.94 (2.14-2.99) mGy and 309 (230-371) mGy*cm, respectively, to 0.855 (0.568-1.11) mGy and 108 (65.6-207) mGy*cm, respectively. From 2007 to 2021, image noise in the brain and liver remained constant (p = 0.26 and p = 0.06), while it decreased in the adductor muscles (p = 0.007). Peak tube voltage selection (in kilovolt, kV) of CT scans shifted from high kV imaging (140 or 120kVp) to low kV imaging (100 or 80kVp) (p < 0.001) from 2007 to 2021. CT radiation dose in pediatric patients undergoing hybrid 2-[18F]FDG PET/CT has decreased in recent years equaling approximately one-third of the initial amount. Over the past 15 years, CT radiation dose decreased considerably in pediatric patients undergoing hybrid imaging, while objective image quality may not have been compromised.

Patients’ radiation dose evaluation during contrast enhanced computed tomography urography procedure

Renal diseases and urinary tract disorders are causing a global burden, with an estimated prevalence of around 13%. Contrast-enhanced computed tomography urography (CE-CTU) is a well-known diagnostic technique for urinary system diseases for initial diagnosis and, very often, for follow-up. CE-CTU procedure exposes patients to high doses of ionizing radiation; hence, justification and optimization of doses are necessary to maximize the benefits and minimize the patients' risks. This study aims to evaluate radiation doses to patients during CE-CTU procedures and estimate the subsequent radiogenic risk. The study included twenty-seven patients who underwent CE-CTU examination in two different hospitals (National Ribat Hospital (NRH) and National Security Fource Hospital (NSFH)), where 16-slice CT machines from different vendors are used. The variables and significance were analyzed using SPSS and Scheffe's statistical tool. Data collected included the age of patients (19–70 years), the radiation dose received by patients: dose length product (DLP, mGy.cm) and volume CT dose index (CTDIvol (mGy)), and tube current-time product (mAs). Patients' dose measurements per CE-CTU procedure given as (mean and range) was: DLP 3098 (647–5301) (mGy.cm) and CTDIvol 44.11 (15–136) (mGy). The results revealed statistically significant differences in DLP (mGy.cm), CTDIvol (mGy), and mAs, and this could be attributed to discrepancies in protocols, machines, and operators among the hospitals and within each hospital. Considering gender, the variables (age, tube current-time product (mAs), and CTDIvol) showed no statistically significant differences. The radiogenic risks from the CE-CTU procedure were ≈1 per 400. Comparison between the two hospitals showed that the variables varied significantly between the hospitals studied, but no significant differences were found based on gender. CE-CTU with contrast medium exposes patients to high doses. Therefore, proper dose optimization is crucial.

Radiation exposure in navigated techniques for AIS: is there a difference between pre-operative CT and intraoperative CT?

Utilization of navigation improves pedicle screw accuracy in adolescent idiopathic scoliosis (AIS). Our center switched from intraoperative CT (ICT) to an optical navigation system that utilizes pre-operative CT (PCT). We aim to evaluate the radiation dose and operative time for low-dose ICT compared to standard and low-dose PCT used for optical navigation in AIS patients undergoing posterior spinal fusion. A single-center matched-control cohort study of 38 patients was conducted. Nineteen patients underwent ICT navigation (O-arm) and were matched by sex, age, and weight to 19 patients who underwent PCT for use with an optical-guided navigation (7D, Seaspine). A total of 418 levels were instrumented and reviewed. PCT was either a standard dose (N = 7) or a low dose (N = 12). The mean volume CT dose index, dose-length product, overall effective dose (ED), ED per level instrumented, and operative time per level were compared. ED per level instrumented was 0.061 ± 0.029mSv in low-dose PCT and 0.14 ± 0.05mSv in low-dose ICT (p < 0.0001). ED per level instrumented was significantly higher in standard PCT (1.46 ± 0.39 vs. 0.14 ± 0.03mSv; p < 0.0001). Mean operative time per level was 31 ± 7min for ICT and 33 ± 3min for PCT (p = 0.628). Low-dose PCT resulted in 0.70mSv exposure per case and 31min per level, standard-dose was 16.95mSv, while ICT resulted in 1.34-1.62mSv and a similar operative time. Use of a standard-dose PCT involves radiation exposure about 9 times higher than ICT and 23 times higher than low-dose PCT per level instrumented. Level III.

Ultra-low-dose CT for attenuation correction: dose savings and effect on PET quantification for protocols with and without tin filter

BackgroundUltra-low-dose (ULD) computed tomography (CT) scans should be used when CT is performed only for attenuation correction (AC) of positron emission tomography (PET) data. A tin filter can be used in addition to the standard aluminium bowtie filter to reduce CT radiation dose to patients. The aim was to determine how low CT doses can be, when utilised for PET AC, with and without the tin filter, whilst providing adequate PET quantification.MethodsA water-filled NEMA image quality phantom was imaged in three configurations with 18F-FDG: (1) water only (0HU); (2) with cylindrical insert containing homogenous mix of sand, flour and water (SFW, approximately 475HU); (3) with cylindrical insert containing sand (approximately 1100HU). Each underwent one-bed-position (26.3 cm) PET-CT comprising 1 PET and 13 CT acquisitions. CT acquisitions with tube current modulation were performed at 120 kV/50 mAs-ref (reference standard), 100 kV/7 mAs-ref (standard ULDCT for PET AC protocol), Sn140kV (mAs range 7–50-ref) and Sn100kV (mAs range 12–400-ref). PET data were reconstructed with μ-maps provided by each CT dataset, and PET activity concentration measured in each reconstruction. Differences in CT dose length product (DLP) and PET quantification were determined relative to the reference standard.ResultsAt each tube voltage, changes in PET quantification were greater with increasing density and reducing mAs. Compared with the reference standard, differences in PET quantification for the standard ULDCT protocol for the three phantoms were ≤ 1.7%, with the water phantom providing a DLP of 7mGy.cm. With tin filter at Sn100kV, differences in PET quantification were negligible (≤ 1.2%) for all phantoms down to 50mAs-ref, proving a DLP of 2.8mGy.cm, at 60% dose reduction compared with standard ULDCT protocol. Below 50mAs-ref, differences in PET quantification were > 2% for at least one phantom (2.3% at 25mAs-ref in SFW; 6.4% at 12mAs-ref in sand). At Sn140kV/7mAs-ref, quantification differences were ≤ 0.6% in water, giving 3.8mGy.cm DLP, but increased to > 2% at bone-equivalent densities.ConclusionsCT protocols for PET AC can provide ultra-low doses with adequate PET quantification. The tin filter can allow 60–87% lower dose than the standard ULDCT protocol for PET AC, depending on tissue density and accepted change in PET quantification.

Low-dose radiation from CT examination induces DNA double-strand breaks and detectable changes of DNA methylation in peripheral blood cells

Background Radiation burden from CT examinations increases rapidly with the increased clinical use frequency. Previous studies have disclosed the association between radiation exposure and increased double-strand breaks (DSBs) and changes in DNA methylation. However, whether the induced DSBs by CT examination recover within 24h and whether a CT examination induces detectable gene-specific methylation changes are still unclear. The aim of the present study was to analyze γ-H2AX in the peripheral blood lymphocyte (PBL) of healthy adults before and after CT examination and to discover the differentially methylated positions (DMPs) along with an analysis of DNA methylation changes caused by CT examination. Materials and Methods Peripheral blood samples of 4 ml were drawn from 20 healthy volunteers at three time points: before CT examination, after CT examination 1h, and after CT examination 24h. γ-H2AX immunofluorescence and Illumina Infinium Human Methylation EPIC BeadChip (850k BeadChip) were used respectively for the test of DSBs and the epigenome-wide DNA methylation analysis. Linear mixed-effect (LME) models were used to evaluate the impacts of doses represented by different parameters and foci on genome-wide DNA methylation. Results The number of γ-H2AX foci per cell at 1h showed linear dose–responses for the radiation doses represented by CT index volume (CTDIvol), dose length product (DLP), and blood absorbed dose, respectively. Residual γ-H2AX foci was observed after CT examination at 24h (p < .001). DMPs and γ-H2AX foci changes could be found within 1h. One CpG site related to PAX5 was significantly changed by using most of the parameters in LME models and did not recover till 24h. Conclusions Residual γ-H2AX foci exist after CT examination at 24h. The DNA methylation changes induced by CT examination may not recover within 24h. The DNA methylation had been changed as early as at 1h. The PAX5-related CpG site may be a potential biomarker of low-dose radiation. Clinical Relevance The biological effects and the cancer risks of CT examination are still unclear. The present study is an effort to document the CT scan-induced events in 24h in vivo. The CT scanning area should be strictly limited, and non-essential repeated operations shouldn’t be performed within 24h.

Assessment and comparison of radiation dose and cancer risk in thoracic diagnostic and radiotherapy treatment planning CT scans

PurposeThis study intends to compare the radiation doses and cancer induction risks from thoracic diagnostic CT (DG-CT) and radiotherapy treatment planning CT (RP-CT) scans. Material and methodsA cross-sectional study on two groups of patients who underwent thoracic CT scans with RP-CT (n = 100) and DG-CT (n = 100) was conducted. The characteristics of the two groups, including age, weight, height, and body mass index were almost similar. To calculate organ and effective doses in a standard 70 kg phantom, the volume CT Dose Index (CTDIv) and dose-length product (DLP) were recorded and utilized with the ImPACT CT Patient Dosimetry Calculator. Patient-specific organ and effective doses were acquired by applying a weight-based correction factor. The lifetime attribute risk (LAR) of cancers was estimated according to the method proposed in Biological Effects of Ionizing Radiation (BEIR VII) which considers age and sex differences. ResultsThe mean ± standard deviation values of CTDIv, DLP, and effective dose were 12.19 ± 3.49 mGy, 568.68 ± 109.42 mGy cm, and 11.46 ± 2.07 mSv for RP-CT, respectively. For DG-CT, these values were 12.33 ± 3.37 mGy, 372.46 ± 99.57 mGy cm, and 7.65 ± 2.07 mSv, respectively. In males, the mean ± SD of cancer incidence risk of all cancers, all solid, and leukemia were 34.57 ± 18.91, 28.79 ± 16.74, 5.77 ± 2.28 per 100,000 individuals, respectively, for DG-CT. These values were 50.77 ± 14.53, 42.37 ± 12.81, and 9.09 ± 1.67 per 100,000 individuals, respectively, for RP-CT. In the female patients, the mean ± SD of cancer incidence risk of all cancers, all solid, and leukemia were 55.04 ± 31.64, 50.77 ± 14.53, 4.32 ± 1.26 per 100,000 individuals, respectively, for DG-CT. These values for RP-CT were 85.46 ± 30.10, 73.49 ± 26.12, and 6.97 ± 1.69 cancers per 100,000 individuals, respectively. ConclusionCancer incidence and mortality risks for RP-CT were higher than for DG-CT scans, highlighting the need for greater optimization of exposure parameters. For individuals, particularly young female patients, the advantages of CT imaging must be balanced against the risks of radiation.

Improvement of Neurovascular Imaging Using Ultra-High-Resolution Computed Tomography Angiography

ObjectiveTo evaluate diagnostic image quality of ultra-high-resolution computed tomography angiography (UHR-CTA) in neurovascular imaging as compared to normal resolution CT-angiography (NR-CTA).Material and MethodsIn this retrospective single-center study brain and neck CT-angiography was performed using an ultra-high-resolution computed tomography scanner (n = 82) or a normal resolution CT scanner (NR-CTA; n = 73). Ultra-high-resolution images were reconstructed with a 1024 × 1024 matrix and a slice thickness of 0.25 mm, whereas NR-CT images were reconstructed with a 512 × 512 matrix and a slice thickness of 0.5 mm. Three blinded neuroradiologists assessed overall image quality, artifacts, image noise, overall contrast and diagnostic confidence using a 4-point Likert scale. Furthermore, the visualization and delineation of supra-aortic arteries with an emphasis on the visualization of small intracerebral vessels was assessed using a cerebral vascular score, also utilizing a 4-point Likert scale. Quantitative analyses included signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), noise and the steepness of gray value transition. Radiation exposure was determined by comparison of computed tomography dose index (CTDIvol), dose length product (DLP) and mean effective dose. Interrater agreement was evaluated via determining Fleiss-Kappa.ResultsUltra-high-resolution CT-angiography (UHR-CTA) yielded excellent image quality with superior quantitative (SNR: p < 0.001, CNR: p < 0.001, steepness of gray value transition: p < 0.001) and qualitative results (overall image quality: 4 (Inter quartile range (IQR) = 4–4); p < 0.001, diagnostic confidence: 4 (IQR = 4–4); p < 0.001) compared to NR-CT (overall image quality: 3 (IQR = 3–3), diagnostic confidence: 3 (IQR = 3–4)). Furthermore, UHR-CT enabled significantly superior delineation and visualization of all vascular segments, from proximal extracranial vessels to the smallest peripheral cerebral branches (e.g., UHR-CTA PICA: 4 (3–4) vs. NR-CTA PICA: 3 (2–3); UHR-CTA P4: 4 (IQR = 3–4) vs. NR-CTA P4: 2 (IQR = 2–3); UHR-CTA M4: 4 (IQR = 4–4) vs. NR-CTA M4: 3 (IQR = 2–3); UHR-CTA A4: 4 (IQR = 3–4) vs. NR-CTA A4: 2 (IQR = 2–3); all p < 0.001). Noteworthy, a reduced mean effective dose was observed when applying UHR-CT (NR-CTA: 1.8 ± 0.3 mSv; UHR-CTA: 1.5 ± 0.5 mSv; p < 0.001).ConclusionUltra-high-resolution CT-angiography improves image quality in neurovascular imaging allowing the depiction and evaluation of small peripheral cerebral arteries. It may thus improve the detection of pathologies in small cerebrovascular lesions and the resulting diagnosis.

Feasibility analysis of low-dose CT with asynchronous quantitative computed tomography to assess vBMD

BackgroundTo explore the feasibility of low-dose computed tomography (LDCT) with asynchronous quantitative computed tomography (asynchronous QCT) for assessing the volumetric bone mineral density (vBMD).Methods416 women patients, categorized into 4 groups, were included and underwent chest CT examinations combined with asynchronous QCT, and CT scanning dose protocols (LDCT or CDCT) were self-determined by the participants. Radiation dose estimations were retrieved from patient protocols, including volume CT dose index (CTDIvol) and dose-length-product (DLP), and then calculated effective dose (ED). Delimiting ED by 1.0 mSv, chest CT examinations were categorized into 2 groups, LDCT group and CDCT group. vBMD of T12-L2 was obtained by transferring the LDCT and CDCT images to the QCT workstation, without extra radiation.ResultsThere was no difference of vBMD among 4 age groups in LDCT group (P = 0.965), and no difference in CDCT group (P = 0.988). In LDCT group and CDCT group, vBMD was not correlated to mAs, CTDIvol and DLP (P > 0.05), respectively. Between LDCT group and CDCT group, there was no difference of vBMD (P ≥ 0.480), while differences of mAs, CTDIvol and DLP.ConclusionThere was no difference of vBMD between LDCT group and CDCT group and vBMD was not correlated to mAs. While screening for diseases such as lung cancer and mediastinal lesions, LDCT combined with asynchronous QCT can be also used to assess vBMD simultaneously with no extra imaging equipment, patient visit time, radiation dose and no additional economic cost.

Reduced-dose CT in detecting solid liver tumors: A comparison of image quality between automatic exposure control and organ effective modulation

PurposeTo evaluate the subjective and objective image quality of solid liver tumors as well as the radiation dose using organ effective modulation (OEM) technology for abdominopelvic computed tomography (CT). Material and methodsA total of 74 patients who underwent contrast-enhanced abdominopelvic CT between January and April 2022 were prospectively enrolled in this study. Patients were randomly assigned to two groups: the non-OEM group underwent CT scans with automatic exposure control (AEC), while the OEM group underwent CT scans with OEM. The radiation dose was compared between the two groups. Objective image quality was quantitatively assessed using image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). Two experienced radiologists independently evaluated the CT images (5, best; 1, worst) by four characteristics including sharpness, contrast, noise, and diagnostic confidence. ResultsThe OEM group presented a significant reduction in volume CT dose index (CTDIvol), dose-length product (DLP), and effective dose (ED) by 11.4%, 12.2%, and 12.2%, respectively (p < 0.05). There were no significant differences between two groups concerning image noise, SNR, and CNR (p > 0.05). Expect for the left and right liver lobes in portal images, OEM was slightly higher than the non-OEM (p < 0.05). The subjective scores of two radiologists demonstrated good agreement (kappa value = 0.84). No statistically significant differences were observed in subjective grading (p > 0.05). ConclusionOEM technology can effectively reduce the radiation dose of abdominopelvic-enhanced CT without affecting the subjective and objective image quality of solid liver tumors.

The image quality and diagnostic performance of CT perfusion-derived CT angiography versus that of conventional CT angiography.

The combination of computed tomography angiography (CTA) and computed tomography perfusion (CTP) evaluation of cerebral perfusion status and vascular conditions can improve the diagnostic accuracy of infarction, ischemia, and vascular occlusion in stroke patients, as well as a comprehensive assessment of cerebral edema, collateral circulation, and blood perfusion in the lesion area. However, the consequent radiation safety and contrast agent nephropathy have aroused increasing concern. The purpose of this study was to assess the image quality and diagnostic accuracy of CTA images derived from CTP data, and to explore the feasibility of replacing conventional CTA. A total of 31 consecutive patients with suspected acute ischemic stroke were retrospectively analyzed. All patients underwent head and neck CTA and brain CTP examinations. All the CTP images were transmitted to the ShuKun artificial intelligence system, which reconstructs CTA derived from CTP (CTA-DF-CTP). The images were divided into 2 groups, including CTA-DF-CTP (Group A) and conventional CTA (Group B). The CT attenuation values, subjective image noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), image quality, CT volume dose index (CTDIvol), dose length product (DLP), and effective radiation dose (ED) were compared between the 2 groups. Moreover, the consistency of vascular stenosis and stenosis degree between the 2 groups were measured and evaluated. There were no significant differences in image noise, SNR, or CNR between Groups A and B (P>0.05). The CT attenuation values of the arteries were higher in Group A than in B [internal carotid artery (ICA) =548±112 vs. 454±85 Hounsfield units (HU), middle cerebral artery (MCA) =453±118 vs. 388±70 HU, and basilar artery (BA) =431±99 vs. 360±83 HU] (P<0.01). The image quality of the 2 groups met the requirement of clinical diagnosis (4.97±0.18 vs. 4.94±0.25). No significant difference was found in subjective evaluation (P>0.05). In Group A compared with Group B, the following reductions were observed: CTDIvol (10.7%; 100.8 vs. 112.9 mGy), DLP (23.0%; 1,613±0 vs. 2,093±88 mGy·cm), and ED (23.0%; 5.00±0.00 vs. 6.49±0.27 mSv). CTA-DF-CTP data provide diagnostic accuracy and image quality similar to those of conventional CTA of head and neck CTA.

A Study of CT-derived Radiation Dose Calculation in Lung Q-SPECT/CT Imaging.

To investigate the amount of effective dose (ED) due to the computed tomography (CT) component of lung perfusion-single-photon emission computed tomography (Q-SPECT)/CT. In this single-center retrospective study, imaging data were collected from the clinic database for the period 2016-2022. The 327 patients identified were aged between 20 and 94 years. Tube voltage, tube current, pitch, gantry rotation time, volume CT dose index, and dose-length product (DLP) were recorded. The DLP was then converted to an ED using the conversion factors. The comparison of the ED between two groups was performed using the Mann-Whitney U non-parametric test. ED (mean ± standard deviation, mSv) was 1.20±0.70 for the pulmonary embolism (PE) (-) and 1.54±1.04 for the PE (+) cases (p<0.05). It was observed that there was a 28% increase in the ED for the PE (+) cases. In addition, each of the PE (-) and PE (+) cases was divided into two groups according to the use of the computed tomography dose reduction (CTDR): without CTDR protocol group (non-CTDR) and with CTDR protocol group (CTDR). For those groups, ED were obtained as 0.87±0.72 and 1.55±0.47 for PE (-) cases (p<0.05); 1.56±1.17 and 1.49±0.54 for PE (+) cases (p>0.05) correspondingly. For a deeper understanding, ED was calculated for all three groups formed with different tube voltage values applied for the non-CTDR and CTDR groups.There was a 42% decrease in the ED for group 1 PE (+) compared to group 2 PE (+) (1.21±0.28, 2.07±0.91, p<0.05) and there was a 41% decrease in the ED for group 1 PE (-) compared to group 2 PE (-) cases (1.17±0.32, 1.97±0.65, p<0.05). It could be concluded that the effective DR protocol is the non-CTDR protocol for the PE (-) cases and the application of the tube voltage at the level of 100 kVp for the PE (+) cases.

Radiation Exposure Dose Reduction according to ECG Window Acquisition Range Setting in Coronary Artery CT Angiography

This study was to reduce the radiation exposure dose of recipients by setting the ECG window acquisition range appropriately during Coronary artery CT Angiography (CCTA) examination. Group 1 (control group) opened ECG window acquisition range to 65% to 75% using the relative delay scan (RDS), which is divided by percentage (%) based on the R-R peak interval of recipient's Average HR, and tested by setting pitch to auto. Group 2 fixed the pitch according to the recipient's HR under the same conditions as Group 1. Group 3 used absolute delay scan (ADS), which is divided by milliseconds (ms) based on the R-R peak interval of recipient's Average HR and fixed the ECG window acquisition range by 60 ms intervals. Group 4 narrowed the scan range from 68% to 73% under the same conditions as Group 1. The values of the mean, minimum, maximum, the volume CT dose index (CTDIvol), and dose length product (DLP) were compared. The exposure dose was reduced by more than 10% when acquired with ADS, not RDS mainly obtained from CCTA. Also, compared to the existing RDS, when the scan range was reduced by half, it was reduced by more than 20%. In conclusion, In CCTA testing, setting the ECG window acquisition range to 5% or 60 ms can reduce radiation exposure without compromising the best phase image acquisition and image quality.

Influence of Body Mass Index and Abdominal Circumference on Radiation Dose During Abdominopelvic Computed Tomography

Background: Contrast-enhanced examinations of the abdomen region have a greater radiation exposure due to the multiphase abdominal computed tomography (CT) protocols. The use of automatic tube current modulation is known to reduce radiation dose and maintain or improve image quality for abdominal CT. However, using automatic tube current modulation can increase radiation dose for individuals with a larger body habitus. Objectives: The study aimed to assess the influence of body mass index and abdominal circumference on the effective dose for routinely performed contrast-enhanced abdomen and pelvis scans. Methods: A total of 160 subjects referred for routine CT abdomen and pelvis were included in the study and categorised into three groups according to their body mass index (BMI) [underweight: &lt;18.5 kg/m2, normal: 18.5-24.9 kg/m2, overweight: 25-29.9 kg/m2 and obese: (≥30 kg/m2]. All the scans were performed on a 128 MDCT scanner by Philips. The effective dose was calculated from the dose length product using region-specific conversion factors. Results: The effective dose was found to be 21.47 ± 2 mSv for the underweight group, 22.75± 2.3 mSv for the normal group, 25.02 ± 2.8 for the overweight group, and 29.7 ± 6.7 mSv for the obese group. Conclusion: The study reported a 32.39 % increase in effective dose for obese patients. The study also reported a significant increase in effective dose as BMI and abdominal circumference increased.

Deep learning imaging reconstruction of reduced-dose 40 keV virtual monoenergetic imaging for early detection of colorectal cancer liver metastases

ObjectiveTo explore whether reduced-dose (RD) gemstone spectral imaging (GSI) and deep learning image reconstruction (DLIR) of 40 keV virtual monoenergetic image (VMI) enhanced the early detection and diagnosis of colorectal cancer liver metastases (CRLM). MethodsThirty-five participants with pathologically confirmed colorectal cancer were prospectively enrolled from March to August 2022 after routine care abdominal computed tomography (CT). GSI mode was used for contrast-enhanced CT, and two portal venous phase CT images were obtained [standard-dose (SD) CT dose index (CTDIvol) = 15.51 mGy, RD CTDIvol = 7.95 mGy]. The 40 keV-VMI were reconstructed via filtered back projection (FBP) and iterative reconstruction (ASIR-V 60 %, AV60) of both SD and RD images. RD medium-strength deep learning image reconstruction (DLIR-M) and RD high-strength deep learning image reconstruction (DLIR-H) were used to reconstruct the 40 keV-VMI. The contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) of the liver and the lesions were objectively evaluated. The overall image quality, lesion conspicuity, and diagnostic confidence were subjectively evaluated, to compare the differences in evaluation results among the different images. ResultsAll 35 participants (mean age: 59.51 ± 11.01 years; 14 females) underwent SD and RD GSI portal venous-phase CT scans. The dose-length product of the RD GSI scan was reduced by 49–53 % lower than that of the SD GSI scan (420.22 ± 31.95) vs (817.58 ± 60.56). A total of 219 lesions were identified, including 55 benign lesions and 164 metastases, with an average size of 7.37 ± 4.14 mm. SD-FBP detected 207 lesions, SD-AV60 detected 201 lesions, and DLIR-M and DLIR-H detected 199 and 190 lesions, respectively. For lesions ≤ 5 mm, there was no statistical difference between SD-FBP vs DLIR-M (χ2McNemar = 1.00, P = 0.32) and SD-AV60 vs DLIR-M (χ2McNemar = 0.33, P = 0.56) in the detection rate. The CNR, SNR, and noise of DLIR-M and DLIR-H 40 keV-VMI images were better than those of SD-FBP images (P < 0.01) but did not differ significantly from those of SD-AV60 images (P > 0.05). When the lesions ≤ 5 mm, there were statistical differences in the overall diagnostic sensitivity of lesions compared with SD-FBP, SD-AV60, DLIR-M and DLIR-H (P＜0.01). There were no statistical differences in the sensitivity of lesions diagnosis between SD-FBP, SD-AV60 and DLIR-M (both P＞0.05). However, the DLIR-M subjective image quality and lesion diagnostic confidence were higher for SD-FBP (both P < 0.01). ConclusionReduced dose DLIR-M of 40 keV-VMI can be used for routine follow-up care of colorectal cancer patients, to optimize evaluations and ensure CT image quality. Meanwhile, the detection rate and diagnostic sensitivity and specificity of small lesions, early liver metastases is not obviously reduced.

Large variation in radiation dose for routine abdomen CT: reasons for excess and easy tips for reduction

ObjectiveTo characterize the use and impact of radiation dose reduction techniques in actual practice for routine abdomen CT.MethodsWe retrospectively analyzed consecutive routine abdomen CT scans in adults from a large dose registry, contributed by 95 hospitals and imaging facilities. Grouping exams into deciles by, first, patient size, and second, size-adjusted dose length product (DLP), we summarized dose and technical parameters and estimated which parameters contributed most to between-protocols dose variation. Lastly, we modeled the total population dose if all protocols with mean size-adjusted DLP above 433 or 645 mGy-cm were reduced to these thresholds.ResultsA total of 748,846 CTs were performed using 1033 unique protocols. When sorted by patient size, patients with larger abdominal diameters had increased dose and effective mAs (milliampere seconds), even after adjusting for patient size. When sorted by size-adjusted dose, patients in the highest versus the lowest decile in size-adjusted DLP received 6.4 times the average dose (1680 vs 265 mGy-cm) even though diameter was no different (312 vs 309 mm). Effective mAs was 2.1-fold higher, unadjusted CTDIvol 2.9-fold, and phase 2.5-fold for patients in the highest versus lowest size-adjusted DLP decile. There was virtually no change in kV (kilovolt). Automatic exposure control was widely used to modulate mAs, whereas kV modulation was rare. Phase was the strongest driver of between-protocols variation. Broad adoption of optimized protocols could result in total population dose reductions of 18.6–40%.ConclusionThere are large variations in radiation doses for routine abdomen CT unrelated to patient size. Modification of kV and single-phase scanning could result in substantial dose reduction.Clinical relevanceRadiation dose-optimization techniques for routine abdomen CT are routinely under-utilized leading to higher doses than needed. Greater modification of technical parameters and number of phases could result in substantial reduction in radiation exposure to patients.Key Points• Based on an analysis of 748,846 routine abdomen CT scans in adults, radiation doses varied tremendously across patients of the same size and optimization techniques were routinely under-utilized.• The difference in observed dose was due to variation in technical parameters and phase count. Automatic exposure control was commonly used to modify effective mAs, whereas kV was rarely adjusted for patient size. Routine abdomen CT should be performed using a single phase, yet multi-phase was common.• kV modulation by patient size and restriction to a single phase for routine abdomen indications could result in substantial reduction in radiation doses using well-established dose optimization approaches.

Dual-Layer Detector Head CT to Maintain Image Quality While Reducing the Radiation Dose in Pediatric Patients.

Radiation exposure in the CT diagnostic imaging process is a conspicuous concern in pediatric patients. This study aimed to evaluate whether 60-keV virtual monoenergetic images of the pediatric cranium in dual-layer CT can reduce the radiation dose while maintaining image quality compared with conventional images. One hundred six unenhanced pediatric head scans acquired by dual-layer CT were retrospectively assessed. The patients were assigned to 2 groups of 53 and scanned with 250 and 180 mAs, respectively. Dose-length product values were retrieved, and noise, SNR, and contrast-to-noise ratio were calculated for each case. Two radiologists blinded to the reconstruction technique used evaluated image quality on a 5-point Likert scale. Statistical assessment was performed with ANOVA and the Wilcoxon test, adjusted for multiple comparisons. Mean dose-length product values were 717.47 (SD, 41.52) mGy×cm and 520.74 (SD, 42) mGy×cm for the 250- and 180-mAs groups, respectively. Irrespective of the radiation dose, noise was significantly lower, SNR and contrast-to-noise ratio were significantly higher, and subjective analysis revealed significant superiority of 60-keV virtual monoenergetic images compared with conventional images (all P < .001). SNR, contrast-to-noise ratio, and subjective evaluation in 60-keV virtual monoenergetic images were not significantly different between the 2 scan groups (P > .05). Radiation dose parameters were significantly lower in the 180-mAs group compared with the 250-mAs group (P < .001). Dual-layer CT 60-keV virtual monoenergetic images allowed a radiation dose reduction of 28% without image-quality loss in pediatric cranial CT.

A retrospective survey to establish institutional diagnostic reference levels for CT urography examinations based on clinical indications: preliminary results.

Objective. To establish institutional diagnostic reference levels (IDRLs) based on clinical indications (CIs) for three- and four-phase computed tomography urography (CTU).Methods. Volumetric computed tomography dose index (CTDIvol), dose-length product (DLP), patients' demographics, selected CIs like lithiasis, cancer, and other diseases, and protocols' parameters were retrospectively recorded for 198 CTUs conducted on a Toshiba Aquilion Prime 80 scanner. Patients were categorised based on CIs and number of phases. These groups' 75th percentiles of CTDIvoland DLP were proposed as IDRLs. The mean, median and IDRLs were compared with previously published values.Results. For the three-phase protocol, the CTDIvol(mGy) and DLP (mGy.cm) were 22.7/992 for the whole group, 23.4/992 for lithiasis, 22.8/1037 for cancer, and 21.2/981 for other diseases. The corresponding CTDIvol(mGy) and DLP (mGy.cm) values for the four-phase protocol were 28.6/1172, 30.6/1203, 27.3/1077, and 28.7/1252, respectively. A significant difference was found in CTDIvoland DLP between the two protocols, among the phases of three-phase (except cancer) and four-phase protocols (except DLP for other diseases), and in DLP between the second and third phases (except for cancer group). The results are comparable or lower than most studies published in the last decade.Conclusions. The CT technologist must be aware of the critical dose dependence on the scan length and the applied exposure parameters for each phase, according to the patient's clinical background and the corresponding imaging anatomy, which must have been properly targeted by the competent radiologist. When clinically feasible, restricting the number of phases to three instead of four could remarkably reduce the patient's radiation dose. CI-based IDRLs will serve as a baseline for comparison with CTU practice in other hospitals and could contribute to national DRL establishment. The awareness and knowledge of dose levels during CTU will prompt optimisation strategies in CT facilities.

Radiation dose analysis of computed tomography coronary angiography in Children with Kawasaki disease.

There is evolving role of computed tomography coronary angiography (CTCA) in non-invasive evaluation of coronary artery abnormalities in children with Kawasaki disease (KD). Despite this, there is lack of data on radiation dose in this group of children undergoing CTCA. To audit the radiation dose of CTCA in children with KD. Study (December 2013-February 2018) was performed on dual source CT scanner using adaptive prospective electrocardiography-triggering. The dose length product (DLP in milligray-centimeters-mGy.cm) was recorded. Effective radiation dose (millisieverts-mSv) was calculated by applying appropriate age adjusted conversion factors as per recommendations of International Commission on Radiological Protection. Radiation dose was compared across the groups (0-1, 1-5, 5-10, and > 10 years). Eighty-five children (71 boys, 14 girls) with KD underwent CTCA. The median age was 5 years (range, 2 mo-11 years). Median DLP and effective dose was 21 mGy.cm, interquartile ranges (IQR) = 15 (13, 28) and 0.83 mSv, IQR = 0.33 (0.68, 1.01) respectively. Mean DLP increased significantly across the age groups. Mean effective dose in infants (0.63 mSv) was significantly lower than the other age groups (1-5 years 0.85 mSv, 5-10 years 1.04 mSv, and > 10 years 1.38 mSv) (P < 0.05). There was no significant difference in the effective dose between the other groups of children. All the CTCA studies were of diagnostic quality. No child required a repeat examination. CTCA is feasible with submillisievert radiation dose in most children with KD. Thus, CTCA has the potential to be an important adjunctive imaging modality in children with KD.

Feasibility and Safety of Percutaneous CT-Guided Bone Biopsies in Patients with Cancer Using a Patient-Mounted Robotic System: A Retrospective Analysis of 40 Consecutive Biopsies

This retrospective study evaluated the feasibility and safety of percutaneous computed tomography (CT)-guided bone biopsies in patients with cancer using a patient-mounted robotic system with steering capabilities. The study included 39 patients (17 women, 22 men; median age, 65.5 years; interquartile range [IQR], 54.8–71.0 years). Forty biopsies were performed in the pelvis, spine, ribs, shoulder, femur, and sternum. The technical success rate was 100%, and the median trajectory length was 55.9 mm (IQR, 47.1–73.6 mm). Intermediate checkpoints were used in 8 biopsies. Median time from the first to final scan was 21 minutes (IQR, 17–37 minutes). The overall procedure time was 30 minutes (IQR, 24–36 minutes). The median dose length product and effective dose were 536.6 mGy⋅cm (IQR, 396.2–837.7 mGy∗cm) and 7.1 mSv (IQR, 4.7–10.8 mSv), respectively. No adverse events occurred. The diagnostic yield for cancer was 72.5%. Percutaneous robotic-assisted bone biopsies demonstrated high technical success, adequate diagnostic yield, and favorable safety profile.