Specific Dose Estimates Research Articles

HeadCTDosi: A python-based automated calculation of head water equivalent diameter and size specific dose estimate based on AAPM 220 report

The aim of the current study is to propose an algorithm for the automated calculation of water-equivalent diameter (Dw) and size-specific dose estimate (SSDE) from clinical computed tomography (CT) images in head protocol context, a python-based algorithm was developed in order to execute an interface to read DICOM images and compute the mentioned metrics. All CT datasets were retrospectively acquired by the Siemens emotion 16 C T scanner. The algorithm developed in this study presents a novel approach for preprocessing and analyzing DICOM images obtained from head CT scans. Exploiting a custom Python script, the preprocessing pipeline begins with the conversion of pixel values to Hounsfield Units (HU) to ensure quantitative analysis accuracy. Subsequently, Gaussian filtering reduced noise while preserving essential features, followed by thresholding using Otsu's method for head region segmentation. Morphological operations refined the binary mask, which enhanced the method for contour detection via active contours. The outcome of this procedure is an accurate measurement of the head size metrics, including lateral (LAT) and anteroposterior (AP) dimensions, effective diameter (Deff), and water equivalent diameter (Dw). Statistical analyses are performed to derive mean statistics and compute SSDE using a conversion factor derived from Dw. Validation of the proposed algorithm used images of patients who had undergone head examination in a major pediatric university hospital. The proposed algorithm was compared to IndoseCT v20 b for Dw and SSDE calculations. The Dw values from HeadCTDosi were strongly correlated to those of IndoseCT by R2 = 0.97 and the SSDE values also presented high correlation of R2 = 0.93. This study presents an improved algorithm for calculating Dw and SSDE in the context of head CT, which notably can outperform the manual, subjective, and time-consuming process of contouring the head region, positioning it as a potentially essential tool for routine clinical dose monitoring.

Radiation dose assessment of pediatric computed tomography of the chest: the need to consider patient size.

To evaluate the radiation dose of chest computed tomography (CT) examinations of pediatric patients and the extent to which volume CT dose index (CTDIvol) underestimates radiation dose in comparison to size specific dose estimates (SSDE). Single-center, retrospective study of consecutive unenhanced pediatric (age<18years) chest CTs between October 2015 and October 2016. Radiation dose as well as demographic and clinical data were recorded from 133 chest CTs. Patients were grouped into 4 categories based on mean effective diameter of the chest. SSDE was generated for each patient according to the water equivalent and effective diameter and compared to CTDIvol. Factors associated with higher radiation doses were assessed. CTDIvol underestimated radiation dose by 54.7%, 47.6%, 40.2%, and 31.2% (P<.001) for effective diameter groups 1 to 4, respectively, when compared to SSDE (calculated according to the water equivalent). When calculated according to the effective diameter, CTDIvol underestimated radiation dose by 47.6%, 39.4%, 27%, and 12.3% (P<.001) for effective diameter groups 1 to 4, respectively, when compared to SSDE. CT dose parameters, age, weight, Dw, and mean effective diameter were variables associated with higher radiation doses. CTDIvol systematically underestimated radiation dose in comparison to SSDE in pediatric patients submitted to chest CT and should not be used as the primary parameter to monitor CT protocols in these patients. SSDE calculated according to effective diameter also underestimates the radiation dose compared to SSDE calculated based on water equivalent.

ESTIMATION OF PATIENT RADIATION DOSE WITH SIZE SPECIFIC DOSE ESTIMATE (SSDE) METHOD IN ABDOMEN CT-SCAN EXAMINATION AT SEMEN GRESIK HOSPITAL

CT-Scan abdomen is an examination to see the anatomy and pathology of the abdominal organs, and the scanning image results are in the form of three-dimensional axial images of the body. The radiation dose released from the CT-Scan examination is more significant than other radiology modalities. Therefore, it is very important to estimate the patient's dose accurately. Computed Tomography Dose Index (CTDIvol) and Dose Length Product (DLP) are dose parameters used in CT-Scan to describe the dose value received by the patient. However, these parameters are the output of the CT-Scan, not as the dose received by the patient. The Size Specific Dose Estimate (SSDE) method based on AAPM Report No. 204 is used to determine the estimated dose received by the CT-Scan Abdomen patient. Calculations are done manually and with IndoseCT software. The data used are secondary data of 60 patients, namely 21 females and 39 males, who were on the CT-Scan Abdomen examination without contrast from the Instalasi Radiologi Rumah Sakit Semen Gresik. The SSDE value is obtained from the multiplication between the conversion factor and CTDIvol, where the conversion factor is an effective diameter function. The analysis examined the error value in manual calculations and IndoseCT software in men and women, the relationship between effective diameter and scanning radiation output (CTDIvol), and dose estimation estimates (SSDE). The difference in SSDE values between manual calculations and IndoseCT software was insignificant. The highest error value in women was 3% and 3.2% in men. Meanwhile, the relationship between effective diameter (Deff) and scanning radiation output (CTDIvol) and dose estimation estimates (SSDE) showed that the correlation between effective diameter (Deff) and CTDIvol showed a stronger correlation, namely with R2 around 0.7 in women and men, compared to the correlation between effective diameter (Deff) and SSDE with R2 around 0.03 in women and 0.2 in men. Keywords: CT-Scan, Abdomen, Size Specific Dose Estimate (SSDE).

Size specific dose estimation in pediatric CT: preliminary study and conversion factors.

The objective of this paper is to compare the differences between volumetric CT dose index (CTDIVOL) and size-specific dose estimate (SSDEWED) based on water equivalent diameter (WED) in radiation dose measurement, and explore a new method for fast calculation of SSDEWED. The imaging data of 1238 cases of head, 1152 cases of chest and 976 cases of abdominopelvic were analyzed retrospectively, and they were divided into five age groups: ≤ 0.5, 0.5~≤ 1, 1~≤ 5, 5~≤ 10 and 10~≤ 15years according to age. The area of interest (AR), CT value (CTR), lateral diameter (LAT) and anteroposterior diameter (AP) of the median cross-sectional image of the standard scanning range and the SSDEWED were manually calculated, and a t-test was used to compare the differences between CTDIVOL and SSDEWED in different age groups. Pearson analyzed the correlations between DE and age, DE and WED, f and age, and counted the means of conversion factors in each age group, and analyze the error ratios between SSDE calculated based on the mean age group conversion factors and actual measured SSDE. The CTDIVOL in head was (9.41±1.42) mGy and the SSDEWED was (8.25±0.70) mGy: the difference was statistically significant (t=55.04, P<0.001); the CTDIVOL of chest was (2.68±0.91) mGy and the SSDEWED was (5.16±1.16) mGy, with a statistically significant difference (t=-218.78, P<0.001); the CTDIVOL of abdominopelvic was (3.09±1.58) mGy and the SSDEWED was (5.89±2.19) mGy: the difference was also statistically significant (t=-112.28, P<0.001). The CTDIVOL was larger than the SSDEWED in the head except for the ≤ 0.5year subgroup, and CTDIVOL was smaller than SSDEWED within each subgroup in chest and abdominopelvic. There were strong negative correlations between f and age (head: r=-0.81; chest: r=-0.89; abdominopelvic: r=-0.86; P<0.001). The mean values of f at each examination region were 0.81~1.01 for head, 1.65~2.34 for chest and 1.71~2.35 for abdominopelvic region. The SSDEWED could be accurately estimated using the mean f of each age subgroup. SSDEWED can more accurately measure the radiation dose of children. For children of different ages and examination regions, the SSDEWED conversion factors based on age subgroup can be quickly adjusted and improve the accuracy of radiation dose estimation.

Advancing pediatric head CT dose prediction: correlating patient size metrics with AP and LAT dimensions in Moroccan population

This study aims to establish comprehensive relationships between patient size, focusing on effective diameter (Deff) and water-equivalent diameter (Dw), in conjunction with anterior-posterior (AP) and lateral (LAT) dimensions. The primary goal is to refine precise patient dose estimations in pediatric head computed tomography (CT) examinations. Our examination involved a dataset of 105 pediatric head CT images sourced from a Moroccan pediatric university hospital. These images, selected from the central scanning range, underwent quantification for LAT, AP, Deff, and Dw, with measurements carried out using RadiAnt Dicom Viewer for lateral and anteroposterior dimensions. Our analytical approach encompassed modeling Deff and Dw as functions of LAT, AP, and combined AP + LAT dimensions. Additionally, Dw was modeled as a function of Deff and calculated Size Specific Dose Estimates (SSDE) based on Dw was compared to SSDE computed from one single dimension. The outcomes revealed strong correlations among Deff, Dw, and fundamental geometric dimensions (LAT, AP, and AP + LAT), as indicated by consistently high coefficients of determination (R² > 0.8). SSDE calculated from Dw shows impressive correlation with SSDE computed from a single dimension (R² > 0.9). This study offers insights into the relationships between patient size and critical dimensions, identifying high correlations that can represent a significant advancement in predicting doses for pediatric head CT examinations. This introduces the potential for streamlining the determination of head diameter and dose by relying on a single dimension, thereby enhancing the efficiency of dose predictions by facilitating the monitoring of radiation exposure of this population in clinical routine.

Paediatric cancer risks associated with chest computed tomography (CT) scans: comparison of routine chest and COVID-19 diagnosis CT protocols

The aim of this study is to compare the radiation dose and cancer incidence risk associated with two chest Computed Tomography (CT) protocols: routine chest CT (RC-CT) and COVID-19 Diagnosis CT protocol (CD-CT). The study included 254 pediatric patients divided into three age groups: G1 (&lt;5), G2 (5–&lt;10), and G3 (10–15). The effective diameter, volumetric CT dose index (CTDIvol), dose length product (DLP), size specific dose estimate (SSDE), organ doses, and cancer incidence risk were calculated for the two protocols. Organ doses (mSv) and effective dose (mSv) were estimated using the National Cancer Institute dosimetry system for CT (NCICT) software. Estimation of cancer incidence risks were conducted according to the Biological Effects of Ionizing Radiation (BEIR) VII report. The oldest group (G3) in two protocols exhibited the greatest values for CTDIvol, DLP, effective dose and SSDE. The results showed that CD-CT protocol resulted in statistically significant (p &lt; 0.05) lower organ doses and cancer incidence risk. The cancer incidence risk for both protocols did not exceed the reference levels reported in literature surveys on pediatric CT chest radiation dose for all age groups. It can be concluded that the choice of CT protocol can significantly impact the radiation dose received by pediatric patients during CT imaging, highlighting the importance of carefully selecting the appropriate protocol to minimize radiation exposure.

Comparative Study of Image Quality and Radiation Dose between 120kVp Filtered Back Projection and 80kVp Iterative Reconstructed Computed Tomography Images

Background: Iterative Reconstruction techniques have been shown to produce diagnostically acceptable images at low doses to the patient. This study aimed to compare the image quality and radiation dose between 120kVp Filtered Back Projection and 80kVp Iterative Reconstructed (SAFIRE) CT images.Methods: This cross-sectional study was performed on patients referred for CT Urography examinations for various clinical indications to the Department of Radiology and Imaging, Tribhuvan University Teaching Hospital. Data were collected for a period of four months (From August to November 2019) after approval from the Institutional Review Committee of the Institute of Medicine. Convenience sampling was employed and a total of 96 examinations were included. Among them 48 were male and 48 were female. Data were obtained from the 128-slice MDCT Siemens Somaton Definition AS+ CT scanner. Venous phase scans were obtained with Protocol A (120kVp and Filtered Back Projection) and non-contrast scans were obtained with Protocol B (80kVp and SAFIRE). The mAs (tube current-time product) was fixed at 200 for both protocols.Results: There was a 72.5% reduction in Size Specific Dose Estimate (SSDE) in Protocol B compared to Protocol A. However, there was a 13.17% increase in noise in Protocol B compared to Protocol A. Image quality evaluation showed a 98.95% acceptability for the low dose i.e. Protocol B images.Conclusion: CT using low kVp (80kVp) and low current (200mAs) along with an iterative reconstruction algorithm (SAFIRE) can provide diagnostically acceptable images at very low doses for examinations of the Urinary tract

Feasibility study for the evaluation of doses received by organs during medical exposure for pediatric patient undergoing CT scan and estimation of the potential risk of radiation-induced cancers

Computed Tomography (CT) continues to contribute a significant portion of the total collective dose delivered to the public from medical procedures involving ionizing radiation. Children are considered to be at higher risk of developing radiation induced cancer due to the young age of exposure and increased tissue radio sensitivity. Organ dose estimation is essential for pediatric patient cancer risk assessment. The aim of this study was to evaluate the excess risk of radiation induced cancer following exposure to low-dose ionizing radiation from pediatric CT scans.We collected information from Radiation Dose Structured Report (RDSR) in 2 radiology department for 3 protocols and three (3) different age group in pediatric CT scan.We estimated the excess of cancer risk by using the Radiation Risk Assessment Tool RadRAT). For that, we calculate first the organ doses with National Cancer Institute for CT (NCICT). Effective dose and Size Specific Dose Estimate were also estimated, CTDI and DLP recorded from the RDSR were compared by the ones given by the software. The doses received by 30 organs including both inside and outside the scanning range were calculated and compared for the different age groups and protocols.The excess risk observed here range between 0.6 and 10.1‰ for respectively the thorax and Abdomen protocol in boy's cohort. This can be due to the significant dose variability observed among radiological protocols defined for the same CT scan and patient of the same age. For a head examination, a ratio of 2–4, depending on the age of the child, is estimated between the maximum and minimum doses delivered to the brain. For the other types of examination, this ratio is even greater: around 9 for chest examinations, 16 for abdominopelvic explorations.Careful justification of pediatric CT scans and dose optimization should be available in hospitals to minimize risks.

Circadian epidemiology: Structuring circadian causes of disease and practical implications

ABSTRACT That disruptions of the body’s internal clockwork can lead to negative health consequences, including cancer, is a plausible hypothesis. Yet, despite strong mechanistic and animal support, the International Agency for Research on Cancer (IARC) experts considered epidemiological evidence as limited regarding the carcinogenicity of “shift-work involving circadian disruption” (2007) and “night shift work” (2019). We use directed acyclic graphs (DAGs) to outline a concept of circadian causes that discloses challenges when choosing appropriate exposure variables. On this basis, we propose to move beyond shift-work alone as a direct cause of disease. Instead, quantifying chronodisruption as individual doses can lead to interpretable circadian epidemiology. The hypothesis is that doses of chronodisruption cause disrupted circadian organisation by leading to desynchronization of circadian rhythms. Chronodisruption can be conceptualized as the split physiological nexus of internal and external times. Biological (or internal) night – an individual’s intrinsically favoured sleep time window – could be the backbone of circadian epidemiology. In practice, individual doses that cause disrupted circadian organisation are derived from the intersection of time intervals of being awake and an individual’s biological night. After numerous studies counted work shifts, chronobiology may now advance circadian epidemiology with more specific dose estimation – albeit with greater challenges in measurement (time-dependent individual data) and analysis (time-dependent confounding).

Size Specific Dose Estimate in Abdominal Computed Tomography by AAPM TG Report-204 and AAPM TG Report-220

Purpose: The AAPM Task Group (TG) reports 204 and 220 presented methods for evaluation of patient dose by announcing the SSDE. The TG reports provide the Size Specific Conversion factors that can be multiplied to CTDIvol to calculate the patient dose in terms of SSDE constructed from Deff (AAPM TG-204) and Dw (AAPM TG-220). Our study presents a comparison of the two TG reports on SSDE for the routine Abdominal Computed Tomography. Materials and Methods: The scan lengths of abdomen were measured from computed tomography (CT) topographic images and cross-section at the mid-slice of the abdomen were measured from tomographic images of 61 adults who had undergone abdominal CT using the GE Advance Workstation (AWS) software. The Deff and Dw was computed according to TG- 204 and TG-220 reports, respectively. Further, we performed the correlation analysis between Deff and BMI, Dw and BMI and SSDE and BMI for both the TG- reports. The Student’s paired t-test was performed to compare the two of SSDE calculation methods. Results: The results confirm that the mean value of SSDE is 13.04 (𝑚𝐺𝑦) and 13.60 (𝑚𝐺𝑦) for AAPM TG-220 and AAPM TG-204, respectively. And a good positive correlation was observed between Deff and BMI, Dw and BMI with r = 0.67 and r = 0.68 respectively. Also, the weak correlation was observed between SSDE and BMI for both the TG - reports. The Student’s paired t-test shows that the two means of SSDE calculation methods are significantly different (𝑝&lt; 0.01) in abdominal computed tomography. Conclusion: We confirm the AAPM TG reports 204/220 using clinical data for SSDE calculation that the mean SSDE values computed from Deff and Dw in abdomenal computed tomography are significantly different and we conclude that the SSDE calculated by Dw method gives a more accurate evaluation of SSDE for the patients undergoing abdominal computed tomography scan then the SSDE calculated by Deff method.

Low dose CTPA using a low kV technique combined with high IR: A clinical study

IntroductionTo investigate optimising a computerised tomography pulmonary angiogram (CTPA) scan protocol in terms of radiation dose and image quality using a low kV technique combined with high iterative reconstruction (IR) parameters (>50%) and apply the optimised protocol in clinical practice on patients irrespective of their body weight. MethodsCTPA examinations were performed on 64 patients equally divided into control and experimental groups. Patients in the control group were scanned using the current protocol (100 kV with 50% IR) while patients in the experimental group were scanned using an optimised protocol (80 kV with 60%IR). The radiation dose indices volume computerised tomography dose index (CTDIvol), dose length product (DLP), size specific dose estimates (SSDE) and effective dose (ED) were recorded. Subjective image quality was evaluated by 3 radiologists through absolute visual grading analysis (VGA) using an image quality scoring tool. The resultant image quality scores were analysed using Visual Grading Characteristics (VGC). Objective image quality was recorded in terms of contrast-to-noise-ratio (CNR) and signal-to-noise-ratio (SNR). ResultsThe application of the optimised protocol resulted in a statistically significant (p < 0.05) reduction in mean CTDIvol (−49%), DLP (−48%), SSDE (−52%) and ED (−49%). Objective image quality was significantly (p < 0.05) improved both in CNR (32%) and SNR (13%). Subjective image quality scores were higher for the current protocol but variation between the two protocols was not significant (p = 0.650). ConclusionsWhen applying the low kV technique combined with high IR parameters, a significant dose reduction may be achieved while still maintaining diagnostic image quality. Implications for practiceThe low kV technique combined with high IR parameters is an effective optimisation technique which can be easily implemented for the CTPA protocol.

Estimating size specific dose estimate from computed tomography radiograph localizer with radiation risk assessment

Quantifying radiation burden is necessary for optimizing imaging protocols. The normalized dose coefficient (NDC) is determined from the water-equivalent diameter (WED) and is used to scale the CTDIvol based on body habitus to determine the size specific dose estimate (SSDE). In this study we determine the SSDE prior to the CT scan and how sensitive the SSDE from WED is to the lifetime attributable risk (LAR) from BEIR VII. For calibration, phantom images are used to relate the mean pixel values along a profile ( ) of the CT localizer to the water-equivalent area (AW ) of the CT axial scan at the same z-location. Images of the CTDIvol phantoms (32cm, 16cm, and ∼1cm) and ACR phantom (Gammex 464) were acquired on four scanners. The relationship between the AW and was used to calculate the WED from the CT localizer for patient scans. A total of 790 CT examinations of the chest and abdominopelvic regions were used in this study. The effective diameter (ED) was calculated from the CT localizer. The LAR was calculated based on the patient chest and abdomen using the National Cancer Institute Dosimetry System for Computed Tomography (NCICT). The radiation sensitivity index (RSI) and risk differentiability index (RDI) were calculated for SSDE and CTDIvol. The WED from CT localizers and CT axials scans show good correlation (R2 =0.96) with the maximum percentage difference being 13.45%. The NDC from WED correlates poorly with LAR for lungs (R2 =0.18) and stomach (R2 =0.19), however that is the best correlation. The SSDE can be determined within 20% as recommended by the report of AAPM TG 220. The CTDIvol and SSDE are not good surrogates for radiation risk, however the sensitivity for SSDE improves when using WED instead of ED.

Cancer risk in healthy patients who underwent chest tomography comparing three different technologies

This research aimed to estimate the risk of cancer associated with patients without previous disease undergoing chest tomography. Siemens CT scanners have 6, 64, and 128 detectors. The Biologic Effects of Ionizing Radiation Reports - BEIR VII methodology was used. The study presented a sample of 64 patients aged between 18 and 80 years, in the city of Belo Horizonte, Minas Gerais - Brazil. The IMPACT CT software and CalDose X CT Online were used to calculate the absorbed and equivalent dose from the Volumetric Computed Tomography Dose Index - CTDIvol (mGy) and Dose Length Product - DLP values provided by the equipment. CT-Expo Software was also used to estimate Specific Dose Estimates (SSDEs) values. The CTDvol results for the MG1, MG,2 and MG3 Diagnostic Centers in mGy were respectively 4.369 ± 1.352, 6.99 4 ± 1.53,3 and 9.984 ± 2.282 and the SSDE values were 3.800, 6.40,0 and 9,.500. The values for the equivalent dose, at the MG2 Diagnostic Center, by IMPACT CT, in (mSv) for the breasts, esophagus, heart, thyroid, lung and thymus were respectively 3.9, 5.7, 4.7, 1.0, 4.8 and 5.7. The CalDose Software, for the same equipment and the same organs, in mSv, estimated the values 7.4, 9.4, 11.1, 5.3, 10.8 and 11.3 for women and 7.1, 9.3, 11.0, 5.3, 10.2 and 10.9 for men. The estimated risk of cancer decreased according to the patient's age, but with a higher incidence for females. The use of each software must be carefully analyzed to avoid undue values due to the particularities of each one. The results also showed that the risk of developing cancer due to radiation decreases with patient age and is higher in females.

Size specific dose estimates for Computed Tomography cancer patients at an Oncology hospital.

Size specific dose estimates for Computed Tomography cancer patients at an Oncology hospital.

Truncation Effects on Effective Diameter Measurement for Size-specific Dose Estimation in Computed Tomography (CT) Imaging

The determination of size specific dose estimation (SSDE) has been proposed for accurate CT dose assessment. The SSDE introduction has prompted numerous manufacturers and researchers to develop various methodologies that have progressed from manual to automated methods in SSDE determination. Few studies reported on truncation effects with respect to specific size and SSDE determination and CT manufacturers are yet to incorporate truncation correction in their system [1,2].&#x0D; This study aimed to evaluate the effects of truncation artifacts on the measurement of effective diameter (Deff) and SSDE in CT imaging. A phantom study was performed using CTDI phantom of different diameters, 22 and 32 cm with Siemens SOMATOM Definition AS+ CT scanner. Phantom images of different truncation percentage (TP) of 5%, 10%, 15%, and 20% were simulated and acquired. The Deff and SSDE were determined based on the displayed CTDIvol, and the AAPM correction factor table was used to calculate the SSDE accurately [3]. The percentage error for each TP in comparison with non-truncated image (TP 0%) was computed.&#x0D; Results showed the percentage error (PE) for both Deff and SSDE increased as the TP increased. The PE was determined by comparing the Deff and SSDE of each TP with non-truncated (TP 0%) image. Table 1 shows the values of PE of truncated images of different TP (5%, 10%, 15%, and 20%) for both Deff and SSDE in phantom sizes of 22 and 32 cm. However, it can be observed that PE values for SSDE of 5% and 10% truncation were similar for both phantom sizes. This is because the correction factors for 5% and 10% were similar and had resulted in similar calculated SSDE. The highest recorded PE was observed in 20% truncation that determined the largest difference in Deff and SSDE with non-truncated image.&#x0D; This study demonstrates that there is a linear relationship between truncation percentage with measured Deff and SSDE computation. It can be concluded that the percentage error in Deff measurement and calculated SSDE will increase as TP increased. Therefore, the effects of truncation artefacts should be carefully considered in SSDE calculation for accurate estimation especially in development of automated calculation.

Size-specific dose estimates for pediatric head CT protocols based on the AAPM report TG-293

PurposeTo establish the Size Specific Dose Estimate (SSDE) typical values for pediatric head CT examinations based on the AAPM report TG-293; to provide a new stratification based on the water-equivalent diameter (Dw), given that SSDE is related to the head size. Methods296 Head CT scans of pediatric patients collected using a dose monitoring software were retrospectively analysed. Typical values were derived stratifying data by age in three methods: the first proposed by the European Guidelines on Diagnostic Reference Levels for Pediatric Imaging (RP185), the second by the National Istisan Report 20/22 and a local one related to the clinical protocols (LStrata). For each scan, a self-developed Matlab routine calculated the water-equivalent diameter (Dw) and related SSDE values with the conversion factors fH16and fB16provided by the AAPM reports TG-293 and TG-204, respectively. Eventually, a Dwstratification was introduced starting from a measure of the lateral dimension of the head. ResultsSSDE based on TG-204 overestimatesthe dose up to 12%. Four Dwgroups were identified thanks to the good correlation between the head lateral dimension andDw: Dw < 14 cm, 14 ≤ Dw < 16 cm, 16 ≤ Dw< 17 cm, Dw≥ 17 cm. The Dw-stratified dosimetric indices presentgreater variability than those grouped by age because of the large variability of the size of the infant's head. ConclusionsThe variability of the SSDE metric underlines that age-optimized protocols are not when size is considered.

Size Specific Dose Estimate Based on Water-Equivalent Diameter for Common Head Ct Examinations: A Monte Carlo Study

Size Specific Dose Estimate Based on Water-Equivalent Diameter for Common Head Ct Examinations: A Monte Carlo Study

Prospective Study of Low- and Standard-dose Chest CT for Pulmonary Nodule Detection: A Comparison of Image Quality, Size Measurements and Radiation Exposure.

To comprehensively and accurately analyze the out-performance of low-dose chest CT (LDCT) vs. standard-dose CT (SDCT). The image quality, size measurements and radiation exposure for LDCT and SDCT protocols were evaluated. A total of 117 patients with extra-thoracic malignancies were prospectively enrolled for non-enhanced CT scanning using LDCT and SDCT protocols. Three experienced radiologists evaluated subjective image quality independently using a 5-point score system. Nodule detection efficiency was compared between LDCT and SDCT based on nodule characteristics (size and volume). Radiation metrics and organ doses were analyzed using Radimetrics. The images acquired with the LDCT protocol yielded comparable quality to those acquired with the SDCT protocol. The sensitivity of LDCT for the detection of pulmonary nodules (n=650) was lower than that of SDCT (n=660). There was no significant difference in the diameter and volume of pulmonary nodules between LDCT and SDCT (for BMI <22 kg/m2, 4.37 vs. 4.46 mm, and 43.66 vs. 46.36 mm3; for BMI ≥22 kg/m2, 4.3 vs. 4.41 mm, and 41.66 vs. 44.86 mm3) (P>0.05). The individualized volume CT dose index (CTDIvol), the size specific dose estimate and effective dose were significantly reduced in the LDCT group compared with the SDCT group (all P<0.0001). This was especially true for dose-sensitive organs such as the lung (for BMI <22 kg/m2, 2.62 vs. 12.54 mSV, and for BMI ≥22 kg/m2, 1.62 vs. 9.79 mSV) and the breast (for BMI <22 kg/m2, 2.52 vs. 10.93 mSV, and for BMI ≥22 kg/m2, 1.53 vs. 9.01 mSV) (P<0.0001). These results suggest that with the increases in image noise, LDCT and SDCT exhibited a comparable image quality and sensitivity. The LDCT protocol for chest scans may reduce radiation exposure by about 80% compared to the SDCT protocol.

Conversion factor for size specific dose estimation of head CT scans based on age, for individuals from 0 up to 18 years old

Assessing the radiation doses received by patients in computed tomography is still challenging. To overcome this, the American Association of Physicists in Medicine has introduced the concept of the size specific dose estimate (SSDE). However, the calculation of SSDE for head CT scans requires the knowledge of attenuation characteristics of the volume scanned, making its implementation in the daily clinical workflow cumbersome. In this study, we defined conversion coefficients from CTDIvol,16cm to SSDE for head CT scans based solely on the age of the patient. Using the head circumference-for-age from the child growth standards of the World Health Organization (WHO), the effective diameter-for-age was calculated for male and female individuals from 0 to 60 months-old. The effective diameter was converted into a water equivalent diameter-for-age, using a correlation established from the measurements of both quantities in 295 exams of male and female patients, from 0 to 18 years-old. WHO-estimated water equivalent diameter-for-age was validated against the measured water equivalent diameter-for-age. The head circumference-for-age from WHO was extrapolated for male and females individuals up to 18 years-old and their respective water equivalent diameter were estimated. Finally, the SSDE was calculated for all the CT head scans performed in a 9-years period in patients aged from 0 to 18 years old. Typical values of CTDIvol,16cm and DLP were also defined. SSDE varied from 0.80 up to 1.16 of the CTDIvol,16cm, depending on sex and age of the patient. WHO-estimated water equivalent diameter-for-age differed less than 20% from the measured water equivalent diameter-for-age. Typical values of SSDE varied from 28.5 up to 38.9 mGy, while typical values ranged from 30.9 up to 47.6 mGy for the CTDIvol,16cm and from 417.6 up to 861.1 mGy*cm for the DLP. SSDE can be directly calculated for head CT scans once the age of the patient is known.

Radiation dose reduction, improved isocenter accuracy and CT scan time savings with automatic patient positioning by a 3D camera

PurposeTo compare CT isocenter accuracy, patient dose, and scan time in adults imaged with and without use of a 3D camera. Method571 CT examinations utilizing a 3D camera for initial patient positioning (optional radiographer isocenter adjustment) and 504 examinations scanned without the camera between 10/1/2018 and 3/19/2019 were retrospectively identified. All exams were chest or abdominopelvic CTs. The isocenters of these exams were compared with the true isocenters defined as the manually delineated centroid of the body in the CT volume. The size specific dose estimate (SSDE) (mGy) of radiation dose obtained from departmental software for the 4 most common protocols on one CT scanner was compared before and after implementation of the 3D camera. The times required for the entire scan and just the topogram “scout” were compared with and without the 3D camera for noncontrast chest and abdominopelvic CT enterography protocols. 2-tailed t-tests and Mann-Whitney U tests were used (P < 0.05 indicated statistical significance). ResultsThe deviation from true isocenter was 6.8 ± 6.1 mm (P = 0.043) and 16.3 ± 14.0 mm (P < 0.01) with and without the 3D camera, respectively (P < 0.01). CT radiographers accepted isocenter location without alteration in 93 % of examinations. Average SSDE savings with the 3D camera ranged 1.0–2.4 mGy (21–31 %) for the 4 most commonly performed protocols (p < 0.01). Median scout time savings was 32 s (Camera vs. No-Camera cohorts) (P < 0.01). Average noncontrast chest CT and CT enterography scan time savings were 19 s and 17 s with the 3D camera, respectively (P < 0.01). ConclusionsThe 3D camera improved accuracy of patient positioning while reducing radiation dose and examination time. Implementation of a 3D camera helps standardize workflow in a busy clinical practice.