Dose-length Product Reduction Research Articles

OPTIMISASI DOSIS CT DALAM IMAGING UROGRAFI: STUDI RETROSPEKTIF TENTANG PENGARUH PITCH PADA DLP DENGAN EVALUASI SDLCD

This retrospective study aimed to evaluate the influence of pitch on the Dose Length Product (DLP) in CT Scan examinations used in urography imaging. The study utilized the Statistically Defined Low Contrast Detectability (SDLCD) parameter for analysis. Through this retrospective study, successfully optimizing urography images was achieved by optimizing pitch, resulting in a significant reduction in DLP, almost half of the initial value. The retrospective approach allowed for identifying acceptable parameters within the tolerance limits of good urography imaging while minimizing DLP. The findings of this research provide valuable information for optimizing radiation dosage in CT Scan urography while maintaining image quality. The study offers valuable data for radiology practitioners and experts to determine optimal urography CT scan imaging parameters. Moreover, the results can serve as a foundation for further research to improve radiation dose efficiency in medical imaging. Overall, this study makes a significant contribution to the effort of enhancing image quality and reducing radiation dose risk for patients. Keywords: Urography, CT Scan Optimization, DLP, Pitch, LCD.

Dose development in sinonasal imaging over the last decade – a retrospective patient study

BackgroundComputed tomography (CT) has become the primary imaging modality for visualization of the paranasal sinuses. In this retrospective, single center patient study the radiation dose development in the past 12 years in CT imaging of the paranasal sinuses was assessed.MethodsThe computed tomography dose index (CTDIVol) and dose length product (DLP) of a total of 1246 patients (average age: 41 ± 18 years, 361 females, 885 males) were evaluated, who received imaging of the paranasal sinuses either for chronic sinusitis diagnostic, preoperatively or posttraumatically. Scans were performed on three different CT scanners (Somatom Definition AS, Somatom Definition AS+, Somatom Force, all from Siemens Healthineers) and on one CBCT (Morita) ranging from 2010 to 2022. Reconstruction techniques were filtered back projection and three generations of iterative reconstruction (IRIS, SAFIRE, ADMIRE, all from Siemens Healthineers). Group comparisons were performed using either parametrical (ANOVA) or non-parametrical tests (Kruskal-Wallis Test), where applicable.ResultsOver the past 12 years, there was a 73%, 54%, and 66% CTDIVol reduction and a significant (p < 0.001) 72%, 33%, and 67% DLP reduction in assessing the paranasal sinuses for chronic sinusitis, preoperatively and posttraumatically, respectively.ConclusionTechnological developments in CT imaging, both hardware and software based, have led to a significant reduction in dose exposure in recent years. Particularly in imaging of the paranasal sinuses, the reduction of radiation exposure is of great interest due to the often young patient age and radiation-sensitive organs in the area of radiation exposure.

True Non-Contrast Phase versus Virtual-Non Contrast: “Lights and Shadows” of Dual Energy CT Angiography in Peripheral Arterial Disease

(1) Background: The value of dual-energy CT angiography (DE-CTA) in the detection of peripheral arterial disease (PAD) has been widely recognized. We aim to evaluate the diagnostic accuracy of virtual non-contrast (VNC) imaging of DE-CTA compared to true non-contrast phase (TNC). (2) Methods: Our Internal Review Board (IRB) approved prospective study enrolled 40 patients (28 men, 12 women; median age 69 y, range 41–93 y) who underwent lower extremity DE-CTA for symptomatic PAD. Mean attenuation values of TNC and VNC were obtained by placing circular regions of interest (ROI) at five levels from the aortic to the popliteal arterial lumen, reported in Hounsfield units (HU), and compared using a two-sample t-test. The subjective quality of VNC images was assessed by two independent radiologists with 10 and 4 years of CTA-imaging experience according to a 4-point scale and verified by the intra-class correlation coefficient (ICC). Dose Length Product (DLP) values of each DE-CTA examination were also considered. (3) Results: Except for the external iliac artery, VNC attenuation values were significantly lower than the corresponding TNC values at all levels, with a mean difference ranging from 14.1 and 8.7 HU. At qualitative analysis, VNC images were considered excellent to diagnose in 40%, good in 50%, and sufficient in 10% of cases. No cases of non-diagnostic VNC imaging were reported. Avoiding the TNC phase, a mean reduction in DLP of 54% for each DE-CTA was estimated. (4) Conclusions: TNC and VNC images showed comparable reliability and diagnostic accuracy in the detection of PAD. VNC may be considered a promising substitute for TNC from the perspectives of dose reduction and workflow optimization.

Study on a new “One-stop-shop” scan protocol combining brain CT perfusion and head-and-neck CT angiography by using 256-detector CT for stroke patients

PurposeWe sought to evaluate the performance of a new “one-stop-shop” scan protocol combining brain computed tomography perfusion (CTP) and head-and-neck CT angiography (CTA) imaging for acute stroke patients using a 256-detector CT scanner. MethodFrom March to August 2020, 60 patients (30 men and 30 women) aged 22–88 years with suspected acute stroke were enrolled and randomly divided into 2 groups to undergo brain CTP and head-and-neck CTA with a 256-detector CT system. Group A used traditional scan protocol with a separate brain CTP and head-and-neck CT examination that included non–contrast-enhanced and contrast-enhanced acquisitions; group B used the new “one-stop-shop” scan protocol with head-and-neck CTA data inserted into brain CTP scans at the peak time (PT) of the arterial phase. The insertion point of the head-and-neck CTA data was determined by a test bolus. The examination time, contrast dose, radiation dose, and image quality were compared between the groups. ResultsThe total contrast dose was reduced by 40% in group B compared to group A (60 mL vs. 100 mL). The imaging time was 52.5 ± 2.6 s in group B and 74.9 ± 3.3 s in group A, showing a reduction of approximately 43% in group B. There was no significant difference in image quality both quantitatively and qualitatively between the groups (all P > 0.05). Group B had a slight reduction in dose length product (1139.0 ± 45.3 vs. 1211.6 ± 31.9 mGy·cm, P < 0.001). ConclusionsThe proposed “one-stop-shop” scan protocol combining brain CTP and head-and-neck CTA on a 256-detector CT system can reduce imaging time and contrast dose, without affecting image quality or perfusion results, compared to the traditional protocol of separating the examinations.

Estimation of Aortic Valve Calcium Score Based on Angiographic Phase Versus Reduction of Ionizing Radiation Dose in Computed Tomography.

The aim of the study was to evaluate the estimation efficacy of aortic valve calcium score (AVCS) based on the multislice computed tomography (MSCT) angiographic phase. The evaluation of the reduced amount of ionizing radiation dose was performed because of this estimation. The study included 51 consecutive patients who qualified for transcatheter aortic valve implantation (TAVI) (78.59 ± 5.72 years). All subjects underwent MSCT: in the native phase dedicated to AVCS as well as angiographic phases aimed to morphologically assess the aortic ostium and arterial accesses for TAVI. Based on the native phase, an AVCS assessment was performed for axial reconstructions at 3.0 mm and 2.0 mm slice thickness (AVCSnative3.0 and AVCSnative2.0). Based on the angiographic phase AVCS was estimated for axial reconstruction at 0.6 mm slice thickness with increased values of lesion density in aortic valve cusps/aortic valve annulus, which is considered a calcification, from a typical value of 130 HU to 500 HU and 600 HU (AVCSCTA0.6 500 HU and AVCSCTA0.6 600 HU). Mathematical formulations were developed, allowing for AVCS native calculation based on AVCS values estimated based on the angiographic phase: AVCSnative3.0 = 813.920 + 1.510 AVCSCTA0.6 500 HU; AVCSnative3.0 = 1235.863 + 1.817 AVCSCTA0.6 600 HU; AVCSnative2.0 = 797.471 + 1.393 AVCSCTA0.6 500 HU; AVCSnative2.0 = 1228.310 + 1.650 AVCSCTA0.6 600 HU. The amount of a potential reduction in dose length product (DLP) in the case of AVCS estimation was 4.45 ± 1.54%. In summary, relying solely on the angiographic phase of MSCT examination before TAVI, it is possible to conclusively estimate AVCS. This estimation results in a marked reduction in radiation dose in MSCT.

Image quality and radiation dose reduction in chest CT in pulmonary infection

To evaluate the effect of dose reduction with iterative reconstruction (IR) on image quality of chest CT scan comparing two protocols. Fifty-nine patients were enrolled. The two CT protocols were applied using Iterative Reconstruction (ASIR™) 40% but different noise indexes, recording dose-length product (DLP) and volume computed tomography dose index (CTDIvol). The subjective IQ was rated based on the distinction of anatomic details using a 4-point Likert scale based on the European Guidelines on Quality Criteria for CT. For each patient, two single CTs, at enrollment (group 1) and at follow-up after lowering the dose (group 2), were evaluated by two radiologists evaluating, for each examination, five different lung regions (central zone-CZ; peripheral zone-PZ; sub-pleural region-SPR; centrilobular region-CLR; and apical zone-AZ). An inter-observer agreement was expressed by weighted Cohen's kappa statistics (k) and intra-individual differences of subjective image analysis through visual grading characteristic (VGC) analysis. An average 50.4% reduction in CTDIvol and 51.5% reduction in DLP delivered were observed using the dose-reduced protocol. An agreement between observers evaluating group 1 CTs was perfect (100%) and moderate to good in group 2 examinations (k-Cohen ranging from 0.56 for PZ and AZ to 0.70 for SPR). In the VGC analysis, image quality ratings were significantly better for group 1 than group 2 scans for all regions (AUCVGC ranging from 0.56 for CZ to 0.62). However, disagreement was limited to a score 4 (excellent)-to-score 3 (good) IQ transition; apart from a single case in PZ, both the observers scored the IQ at follow-up as 2 (sufficient) starting from a score 4 (excellent). Dose reduction achieved in the follow-up CT scans, although a lower IQ still allows a good diagnostic confidence.

Evaluation of Adaptive Statistical Iterative Reconstruction-V Reconstruction Algorithm vs Filtered Back Projection in the Detection of Hypodense Liver Lesions: Reader Performance and Preferences.

The aim of the study was to evaluate diagnostic accuracy and readers' experience in the detection of focal liver lesions on computed tomography with Adaptive Statistical Iterative Reconstruction-V (ASIR-V) reconstruction compared with filtered back projection (FBP) scans. Fifty-five patients with liver lesions had FBP and ASIR-V scans. Two radiologists independently reviewed both sets of computed tomography scans, identifying and characterizing liver lesions. Adaptive Statistical Iterative Reconstruction-V scans had a reduction in dose length product (P < 0.0001) with no difference in image contrast (P = 0.1805); image noise was less for the ASIR-V scans (P < 0.0001) and contrast-to-noise ratio was better for ASIR-V (P = 0.0002). Both readers found more hypodense liver lesions on the FBP (P = 0.01) scans. Multiple subjective imaging scores were significantly less for the ASIR-V scans for both readers. Although ASIR-V scans were objectively better, our readers performed worse in lesion detection on them, suggesting a need for better education/experience with this technology during implementation.

Initial radiation dose reduction studies in cervical spine multidetector CT

Feasibility studies were performed to evaluate the potential for dose reduction when investigating cervical spine trauma using multidetector CT (MDCT), without reducing fracture detectability. The studies utilised both in vitro phantom work and low-dose (LD) clinical images from archive. Test phantoms were constructed using dry human cervical vertebrae suspended inside tissue equivalent material. Vertebrae were modified with fine osteotomies to simulate fracture lines. A LightSpeed VCT 64-slice scanner (GE Healthcare Medical Systems, Milwaukee, WI) was employed to scan the phantom using a series of tube current (mA) settings and constant tube voltage (kVp). The phantom was also scanned using the manufacturer’s programme for automatic tube current modulation (TCM). The recommended TCM tube current table ranges were found to be set to high values (120–600 mA); therefore further modified TCM exposures were made with lower minimum value of 50 mA. Images were assessed under standard clinical review conditions. Low-dose CT series from clinical PET/CT examinations on clinical archive were also evaluated to explore their suitability to visualise cortices and other bony characteristics. Preliminary indications are that image assessments of critical bony features can be achieved with a high degree of confidence when the radiation dose is reduced by a factor of two. Dose Length Product (DLP), was used for relative comparisons between examinations. Using the standard TCM’s DLP as the reference value, bony features were visualised suitably using 60–80 mA and a tube current of 60 mA would lead to a halving of the total DLP to 130 mGy cm. Just reducing the lower limit of the TCM selection range to 50 mA led to a more than 58% reduction in DLP. Our study demonstrates that there is potential for radiation dose reduction during routine clinical imaging for cervical spine trauma and provides supporting evidence for a clinical study.

Evidence of dose saving in routine CT practice using iterative reconstruction derived from a national diagnostic reference level survey.

To assess the influence and significance of the use of iterative reconstruction (IR) algorithms on patient dose in CT in Australia. We examined survey data submitted to the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) National Diagnostic Reference Level Service (NDRLS) during 2013 and 2014. We compared median survey dose metrics with categorization by scan region and use of IR. The use of IR results in a reduction in volume CT dose index of between 17% and 44% and a reduction in dose-length product of between 14% and 34% depending on the specific scan region. The reduction was highly significant (p < 0.001, Wilcoxon rank-sum test) for all six scan regions included in the NDRLS. Overall, 69% (806/1167) of surveys included in the analysis used IR. The use of IR in CT is achieving dose savings of 20-30% in routine practice in Australia. IR appears to be widely used by participants in the ARPANSA NDRLS with approximately 70% of surveys submitted employing this technique. This study examines the impact of the use of IR on patient dose in CT on a national scale.

Continuous Monitoring of CT Dose Indexes at Dubai Hospital

Experience of continuous monitoring and control of patient doses in CT in Dubai Hospital over a period of approximately 4 years (January 2008 through August 2011) is presented. Dose measurements-in particular, weighted and volumetric CT dose index, dose-length product (DLP), and estimated effective dose-were regularly monitored using head (16 cm diameter) and body (32 cm diameter) CT phantoms. Patient radiation dose indexes were manually recorded during 2008 for common CT examinations: head, chest, and abdomen and pelvis scans. In 2009-2011, these CT dose data were recorded within the radiology information system and the PACS. Dose reduction actions were taken while maintaining a watch on image quality. The effects of these factors were monitored through change in average DLP on a monthly basis and third quartile annually. Adapted diagnostic reference levels were used for comparison. The reduction in adult dose indexes in 2010 as compared with 2008 was 52%, 16.4%, and 34.8% for head, chest, and abdomen and pelvis examinations, respectively. For the pediatric group, the reduction was 45.23%, 39.6%, and 43.34% for head, chest, and abdomen and pelvis examinations, respectively. Substantial reduction in DLP for common examinations of adults and children is shown through a program of continuous monitoring and action. The results indicate the need to introduce local diagnostic reference levels to substitute for the adapted ones.

Attenuation-based automatic kilovolt (kV)-selection in computed tomography of the chest: Effects on radiation exposure and image quality

ObjectivesTo evaluate an automated attenuation-based kV-selection in computed tomography of the chest in respect to radiation dose and image quality, compared to a standard 120kV protocol. Materials and methods104 patients were examined using a 128-slice scanner. Fifty examinations (58±15 years, study group) were performed using the automated adaption of tube potential (100–140kV), based on the attenuation profile of the scout scan, 54 examinations (62±14 years, control group) with fixed 120kV. Estimated CT dose index (CTDI) of the software-proposed setting was compared with a 120kV protocol. After the scan CTDI volume (CTDIvol) and dose length product (DLP) were recorded. Image quality was assessed by region of interest (ROI) measurements, subjective image quality by two observers with a 4-point scale (3 – excellent, 0 – not diagnostic). ResultsThe algorithm selected 100kV in 78% and 120kV in 22%. Overall CTDIvol reduction was 26.6% (34% in 100kV) overall DLP reduction was 22.8% (32.1% in 100kV) (all p<0.001). Subjective image quality was excellent in both groups. ConclusionThe attenuation based kV-selection algorithm enables relevant dose reduction (∼27%) in chest-CT while keeping image quality parameters at high levels.

Carotid CTA: Radiation Exposure and Image Quality with the Use of Attenuation-Based, Automated Kilovolt Selection

CTA is considered the imaging modality of choice in evaluating the supraaortic vessels in many institutions, but radiation exposure remains a matter of concern. The objective of the study was to evaluate a fully automated, attenuation-based kilovolt selection algorithm in carotid CTA in respect to radiation dose and image quality compared with a standard 120-kV protocol. Ninety-eight patients were included: 53 examinations (patient age, 66 ± 12 years) were performed by use of automated adaption of tube potential (80-140 kV) on the basis of the attenuation profile of the scout scan (study group), and 45 examinations (patient age, 67 ± 11 years) were performed by use of a standard 120-kV protocol (control group). CT dose index volume and dose-length product were recorded from the examination protocol. Image quality was assessed by ROI measurements and calculations of SNR and contrast-to-noise ratio. Subjective image quality was evaluated by 2 observers with the use of a 4-point scale (3, excellent; 0, not diagnostic). Subjective image quality was rated as "excellent" or "good" in all examinations (study group, 2.8; control group, 2.8). The algorithm automatically selected 100 kV in 47% and 80 kV in 34%; 120 kV was retained in 19%. An elevation to 140 kV did not occur. Compared with the control group, overall CT dose index volume reduction was 33.7%; overall dose-length product reduction was 31.5%. In the low-kilovolt scans, image noise and mean attenuation of ROIs inside the carotid arteries were significantly higher than in 120-kV scans, resulting in a constant or increased (80-kV group) contrast-to-noise ratio. The attenuation-based, kilovolt selection algorithm enables a dose reduction of >30% in carotid artery CTA while maintaining contrast-to-noise ratio and subjective image quality at adequate levels.

Image Quality and Radiation Dose Comparison between Filtered Back Projection and Adaptive Statistical Iterative Reconstruction in Non-contrast Head CT Studies

Purpose: The goal of the study was to compare the total radiation dose and subjective image quality between conventional Filtered Back Projection (FBP) and Adaptive Statistical Iterative Reconstruction (ASIR) in non-contrast head CT. Method: Forty seven patients underwent non contrast head CT with image reconstruction using 100% FBP. The same set of patients underwent subsequent non contrast head CT within 6 months using combination of ASIR and FBP reconstruction. Institutional Review Board approval was obtained. Objective assessment of total radiation dose was obtained by measuring the dose length product (DLP) and effective radiation dose. Subjective image quality was assessed by 2 attending radiologists who were blinded to the scanning technique. All images were graded for sharpness, image noise and overall image quality on a 5 point Likert scale. Both subjective and objective measurements from the two sets of images were compared. Paired Student’s t-Test was used for statistical analysis. Results: There was a significant reduction in DLP with the application ASIR from 1781.7 (310) to 1098.9 (SD 281.4) mGy-cm (p<0.01), resulting in mean total dose reduction of 38.4%. The total effective dose also showed similar reduction from 3.9 (SD 0.68) to 2.4 (SD 0.62) mSv (P<0.01). Subjective score for image noise was 4.44 (SD 0.43) and 4.40 (SD 0.48), before and after application of ASIR, respectively (p=0.59). Overall image quality scores were 4.87 (SD 0.33) and 4.85 (0.36) before and after application of ASIR, respectively (p=0.12). Subjective scores for image sharpness decreased after application of ASIR from 4.94 (SD 0.24) to 4.77 (SD 0.47) (p=0.04) Conclusion: Compared to conventional FBP reconstruction, combination of ASIR with FBP reconstruction results in significant reduction in total radiation dose without affecting the overall image quality in non-contrast head CT.