CT dosimetry at the Australian Synchrotron for 25–100 keV photons and 35–160 mm-diameter biological specimens

2019 ◽  
Vol 26 (2) ◽  
pp. 517-527
Author(s):  
Stewart Midgley ◽  
Nanette Schleich ◽  
Alex Merchant ◽  
Andrew Stevenson
Keyword(s):  
Effective Dose ◽  
Beam Quality ◽  
Absorbed Dose ◽  
Body Region ◽  
Average Dose ◽  
Dose Length Product ◽  
Organ Doses ◽  
Ct Dose ◽  
Radiation Output ◽  
Ct Dosimetry

The dose length product (DLP) method for medical computed tomography (CT) dosimetry is applied on the Australian Synchrotron Imaging and Medical Beamline (IMBL). Beam quality is assessed from copper transmission measurements using image receptors, finding near 100% (20 keV), 3.3% (25 keV) and 0.5% (30–40 keV) relative contributions from third-harmonic radiation. The flat-panel-array medical image receptor is found to have a non-linear dose response curve. The amount of radiation delivered during an axial CT scan is measured as the dose in air alone, and inside cylindrical PMMA phantoms with diameters 35–160 mm for mono-energetic radiation 25–100 keV. The radiation output rate for the IMBL is comparable with that used for medical CT. Results are presented as the ratios of CT dose indices (CTDI) inside phantoms to in air with no phantom. Ratios are compared for the IMBL against medical CT where bow-tie filters shape the beam profile to reduce the absorbed dose to surface organs. CTDI ratios scale measurements in air to estimate the volumetric CTDI representing the average dose per unit length, and the dose length product representing the absorbed dose to the scanned volume. Medical CT dose calculators use the DLP, beam quality, axial collimation and helical pitch to estimate organ doses and the effective dose. The effective dose per unit DLP for medical CT is presented as a function of body region, beam energy and sample sizes from neonate to adult.

scholarly journals Whole Body Low Dose Computed Tomography Using Third-Generation Dual-Source Multidetector With Spectral Shaping: Protocol Optimization and Literature Review

Dose-Response ◽  
2020 ◽  
Vol 18 (4) ◽  
pp. 155932582097313
Author(s):  
Dario Baldi ◽  
Liberatore Tramontano ◽  
Vincenzo Alfano ◽  
Bruna Punzo ◽  
Carlo Cavaliere ◽  
...  
Keyword(s):  
Effective Dose ◽  
Low Dose ◽  
Whole Body ◽  
Dose Length Product ◽  
Osteolytic Lesions ◽  
Subjective Image Quality ◽  
Ct Dose ◽  
Dual Source ◽  
Ct Dose Index ◽  
Low Dose Computed Tomography

For decades, the main imaging tool for multiple myeloma (MM) patient’s management has been the conventional skeleton survey. In 2014 international myeloma working group defined the advantages of the whole-body low dose computed tomography (WBLDCT) as a gold standard, among imaging modalities, for bone disease assessment and subsequently implemented this technique in the MM diagnostic workflow. The aim of this study is to investigate, in a group of 30 patients with a new diagnosis of MM, the radiation dose (CT dose index, dose-length product, effective dose), the subjective image quality score and osseous/extra-osseous findings rate with a modified WBLDCT protocol. Spectral shaping and third-generation dual-source multidetector CT scanner was used for the assessment of osteolytic lesions due to MM, and the dose exposure was compared with the literature findings reported until 2020. Mean radiation dose parameters were reported as follows: CT dose index 0.3 ± 0.1 mGy, Dose-Length Product 52.0 ± 22.5 mGy*cm, effective dose 0.44 ± 0.19 mSv. Subjective image quality was good/excellent in all subjects. 11/30 patients showed osteolytic lesions, with a percentage of extra-osseous findings detected in 9/30 patients. Our data confirmed the advantages of WBLDCT in the diagnosis of patients with MM, reporting an effective dose for our protocol as the lowest among previous literature findings.

Radiation Dose to Patients and Personnel during Fluoroscopy at Percutaneous Renal Stone Extraction

1989 ◽  
Vol 30 (2) ◽  
pp. 201-206 ◽  
Author(s):  
K. Geterud ◽  
A. Larsson ◽  
S. Mattsson
Keyword(s):  
Radiation Dose ◽  
Effective Dose ◽  
Renal Stone ◽  
Absorbed Dose ◽  
Effective Dose Equivalent ◽  
Dose Equivalent ◽  
Organ Doses ◽  
The Mean ◽  
Total Effective Dose Equivalent ◽  
Total Effective Dose

The radiation dose to patients and personnel was estimated during 11 percutaneous renal stone extractions. For the patients the energy imparted, the mean absorbed dose to various organs, and the effective dose equivalent were estimated. For different personnel categories some organ doses and the effective dose equivalent were also estimated. Large differences in the radiation dose between patients were observed. The mean effective dose equivalent to the patient was 4.2 (range 0.6–8.3) mSv, and the energy imparted 285 (range 50–500) mJ. These figures are comparable to those reported for routine colon examination and urography. For the personnel there were also large differences between individuals and categories. The highest radiation dose was received by the radiologist. It was estimated that a radiologist who performs 150 percutaneous renal stone extractions per year will receive a yearly contribution to his/her effective dose equivalent of 2.4 mSv. Even when the contribution from other diagnostic and interventional radiologic procedures is added, the total effective dose equivalent hardly exceeds 5 mSv or 1/10 of the present dose limit for persons engaged in radiologic work. For the hands of the radiologist there is a risk of doses closer to the present limit for single organs or tissues of 500 mSv/year.

scholarly journals Assessment of Organ and Effective Doses Received by Paediatric Patients Undergoing Computed Tomography Examinations in Three Hospitals in Brazzaville, Congo Republic: An Urgent Necessity for Regulatory Control

2021 ◽  
pp. 527-550
Author(s):  
J. Bazoma ◽  
G. B. Dallou ◽  
P. Ondo Meye ◽  
C. Bouka Biona ◽  
Saïdou ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Effective Dose ◽  
Absorbed Dose ◽  
Regulatory Control ◽  
Ct Scans ◽  
Radiological Protection ◽  
Age Group ◽  
Organ Doses ◽  
Paediatric Patients ◽  
Effective Doses

The present study aimed at estimating organ and effective doses from computed tomography (CT) scans of paediatric patients in three hospitals in Brazzaville, Congo Republic. A total of 136 data on paediatric patients, from 0.25 (3 months) to 15 years old, who underwent head, chest, abdomen – pelvis (AP) and chest – abdomen – pelvis (CAP) CT scans was considered. The approach followed in the present study to compute organ doses was to use pre-calculated volume CT dose index (CTDIvol) – and 100 milliampere-second (mAs) – normalized organ doses determined by Monte Carlo (MC) simulation. Effective dose were then derived using the international commission on radiological protection (ICRP) publications 60 and 103 formalism. For comparison purposes, effective dose were also computed using dose-length product (DLP) – to – effective dose conversion factors. A relatively high variation in organ and effective doses was observed in each age group due to the dependence of patient dose on the practice of technicians who perform the CT scan within the same facility or from one facility to another, patient size and lack of adequate training of technicians. In the particular case of head scan, the brain and the eye lens were delivered maximum absorbed doses of 991.81 mGy and 1176.51 mGy, respectively (age group 10-15 y). The maximum absorbed dose determined for the red bone marrow was 246.08 mGy (age group 1-5 y). This is of concern as leukaemia and brain tumours are the most common childhood cancers and as the ICRP recommended absorbed dose threshold for induction of cataract is largely exceeded. Effective doses derived from MC calculations and ICRP publications 60 and 103 tissues weighting factors showed a 0.40-17.61 % difference while the difference between effective doses derived by the use of k- factors and those obtained by MC calculations ranges from 0.06 to 224.87 %. The study has shown that urgent steps should be taken in order to significantly reduce doses to paediatric patients to levels observed in countries where dose reduction techniques are successfully applied.

Spatial Distribution of Dose in Computed Tomography with Special Reference to Thin-Slice Techniques

1987 ◽  
Vol 28 (6) ◽  
pp. 771-777 ◽  
Author(s):  
U. Moström ◽  
C. Ytterbergh
Keyword(s):  
Computed Tomography ◽  
Spatial Distribution ◽  
Dose Distribution ◽  
Absorbed Dose ◽  
Average Dose ◽  
Ct Dose ◽  
Multiple Scan ◽  
Ct Dose Index ◽  
The Difference ◽  
Dose Index

The spatial dose distribution in a cylindrical polystyrene phantom with a diameter of 200 mm was measured for seven computed tomography (CT) scanners. The measurements were performed in the head mode and mainly for narrow slices in the range 1.5 to 4 mm. Both radial and axial dose profiles were measured and the dose distribution for multiple-scan procedures was calculated. The ratio between the surface and centre doses for a single scan varied between the extremes of 1.8 and 4.3 and was generally higher for narrow than for wide slices. With multiple nominally contiguous scans the difference in absorbed dose between surface and centre locations in the object decreased, on account of scattered radiation. The CT dose index for centre locations varied considerably between the tested scanners, with a range from 5.6 to 27.2 mGy per nominal 100 mAs. For a simulated multiple-scan procedure, comparable to a CT examination of the orbits, the multiple-scan average dose varied between 4.3 and 16.4 mGy per nominal 100 mAs.

scholarly journals Reference phantom selection in pediatric computed tomography using data from a large, multicenter registry

2021 ◽  
Author(s):  
Philip W. Chu ◽  
Sophronia Yu ◽  
Yifei Wang ◽  
J. Anthony Seibert ◽  
Luisa F. Cervantes ◽  
...  
Keyword(s):  
Computed Tomography ◽  
San Francisco ◽  
Body Region ◽  
Dose Length Product ◽  
Actual Usage ◽  
Ct Dose ◽  
Reference Phantom ◽  
Usage Patterns ◽  
Dose Metrics ◽  
Using Data

Abstract Background Radiation dose metrics vary by the calibration reference phantom used to report doses. By convention, 16-cm diameter cylindrical polymethyl-methacyrlate phantoms are used for head imaging and 32-cm diameter phantoms are used for body imaging in adults. Actual usage patterns in children remain under-documented. Objective This study uses the University of California San Francisco International CT Dose Registry to describe phantom selection in children by patient age, body region and scanner manufacturer, and the consequent impact on radiation doses. Materials and methods For 106,837 pediatric computed tomography (CT) exams collected between Jan. 1, 2015, and Nov. 2, 2020, in children up to 17 years of age from 118 hospitals and imaging facilities, we describe reference phantom use patterns by body region, age and manufacturer, and median and 75th-percentile dose–length product (DLP) and volume CT dose index (CTDIvol) doses when using 16-cm vs. 32-cm phantoms. Results There was relatively consistent phantom selection by body region. Overall, 98.0% of brain and skull examinations referenced 16-cm phantoms, and 95.7% of chest, 94.4% of abdomen and 100% of cervical-spine examinations referenced 32-cm phantoms. Only GE deviated from this practice, reporting chest and abdomen scans using 16-cm phantoms with some frequency in children up to 10 years of age. DLP and CTDIvol values from 16-cm phantom-referenced scans were 2–3 times higher than 32-cm phantom-referenced scans. Conclusion Reference phantom selection is highly consistent, with a small but significant number of abdomen and chest scans (~5%) using 16-cm phantoms in younger children, which produces DLP values approximately twice as high as exams referenced to 32-cm phantoms

scholarly journals Development of CT Effective Dose Conversion Factors from Clinical CT Examinations in the Republic of Korea

Diagnostics ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 727
Author(s):  
Sang-Kyung Lee ◽  
Jung Su Kim ◽  
Sang-Wook Yoon ◽  
Jung Min Kim
Keyword(s):  
Effective Dose ◽  
Nationwide Survey ◽  
Adult Brain ◽  
Radiological Protection ◽  
Dose Length Product ◽  
Conversion Factors ◽  
Ct Dose ◽  
Ct Protocol ◽  
Ct Data ◽  
The Republic

The aim of this study was to determine the conversion factors for the effective dose (ED) per dose length product (DLP) for various computed tomography (CT) protocols based on the 2007 recommendations of the International Commission on Radiological Protection (ICRP). CT dose data from 369 CT scanners and 13,625 patients were collected through a nationwide survey. Data from 3793 patients with a difference in height within 5% of computational human phantoms were selected to calculate ED and DLP. The anatomical CT scan ranges for 11 scan protocols (adult-10, pediatric-1) were determined by experts, and scan lengths were obtained by matching scan ranges to computational phantoms. ED and DLP were calculated using the NCICT program. For each CT protocol, ED/DLP conversion factors were calculated from ED and DLP. Estimated ED conversion factors were 0.00172, 0.00751, 0.00858, 0.01843, 0.01103, 0.02532, 0.01794, 0.02811, 0.02815, 0.02175, 0.00626, 0.00458, 0.00308, and 0.00233 mSv∙mGy−1∙cm−1 for the adult brain, intra-cranial angiography, C-spine, L-spine, neck, chest, abdomen and pelvis, coronary angiography, calcium scoring, aortography, and CT examinations of pediatric brain of <2 years, 4–6 years, 9–11 years, and 13–15 years, respectively. We determined ED conversion factors for 11 CT protocols using CT data obtained from a nationwide survey in Korea and Monte Carlo-based dose calculations.

scholarly journals Radiation Dose and Lifetime Risk of Cancer Incidence and Mortality in Patients Undergoing 16 Slice CT Emergency Examinations

2019 ◽  
Vol 8 (4) ◽  
pp. 5821-5825
Keyword(s):  
Radiation Dose ◽  
Cancer Incidence ◽  
Lifetime Risk ◽  
Dose Length Product ◽  
Organ Doses ◽  
Emergency Procedures ◽  
Ct Dose ◽  
European Guidelines ◽  
Incidence And Mortality ◽  
Risk Of Cancer

In this paper, we evaluate the patients effective and organ radiation dose in different CT emergency procedures and the associated lifetime risk of cancer incidence and mortality. The data were collected from 150 CT examinations. For each examination, we have collected CT exposure parameters including the number of series, tube voltage, various tube current values, patient age, gender, scan rotation time, slice width, number of slices, pitch, scan length, CT dose index (CTDIvol) and the Dose Length Product (DLP). Effective and organ doses were evaluated using DLP and k Coefficients from the European Guidelines and CT-Expo Software. Lifetime risk of cancer incidence and mortality were estimated using BEIR VII report conversion factors.

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