The role of effective dose in medicine now and into the future.

Effective dose was created as a radiological protection dose quantity linked to risk to enable planning of radiological protection for the control of exposure. Its application and use has evolved from occupational and public exposure during work with radiation sources to medicine and applications in patient dosimetry. Effective dose is the sum of doses to organs and tissues within the body weighted according to their sensitivity to radiation for induction of stochastic effects determined from epidemiological studies of exposed populations.

Estimation of organ and effective doses of CBCT scans of radiotherapy using size-specific field of view (FOV): a Monte Carlo study.

The kV cone beam computed tomography (CBCT) is one of the most common imaging modalities used for image-guided radiation therapy (IGRT) procedures. Additional doses are delivered to patients, thus assessment and optimization of the imaging doses should be taken into consideration. This study aimed to investigate the influence of using fixed and patient-specific FOVs on the patient dose.

Estimation of size-specific dose estimate (SSDE) of CT scans using an effective diameter electron density.

Objective: An assessment of the effective diameter of a patient's body using electron densities of tissues inside the scan area (D) was proposed to overcome challenges associated with the estimation of water-equivalent diameter (D), which is used for size-specific dose estimate (SSDE). The aims of this study were to (1) investigate the D method in two different forms using a wide range of patient sizes and scanning protocols, and (2) compare between four methods used to estimate the patient size for SSDE.

Materials And Methods: Under IRB approval, a total of 350 patients of varying sizes have been collected retrospectively from the Hospital.

Dose quantities for measurement and comparison of doses to individual patients in computed tomography (CT).

The dose quantities displayed routinely on CT scanners, the volume averaged CT dose index (CTDI) and dose length product, provide measures of doses calculated for standard phantoms. The American Association of Medical Physics has published conversion factors for the adjustment of CTDIto take account of variations in patient size, the results being termed size-specific dose estimate (SSDE). However, CTDIand SSDE, while useful in comparing and optimising doses from a set procedure, do not provide risk-related information that takes account of the organs and tissues irradiated and associated cancer risks.

Estimation of size-specific dose estimates (SSDE) for paediatric and adults patients based on a single slice.

Volume averaged CT dose index (CTDI) is an important dose index utilized for CT dosimetry. Measurements of CTDI are performed in reference cylindrical phantoms of specified diameters. A size-specific dose estimate (SSDE) has been recommended for assessment of doses delivered to individual patients.

A Monte Carlo investigation of dose length product of cone beam computed tomography scans.

The dose length product (DLP) provides a measurement related to energy imparted from a computed tomography (CT) scan. The DLP is based on the volume-averaged CT dose index (CTDI ), which is designed for fan beams. The aims of this study were to investigate the use of DLP for scans with wide beams used in cone beam CT (DLP ) in radiotherapy that would be analogous to the DLP of fan beam scans (DLP ), and to compare the efficiencies of DLP and DLP in reporting the total energy imparted in patients.

Influence of cone beam CT (CBCT) scan parameters on size specific dose estimate (SSDE): a Monte Carlo study.

The CT dose index (CTDI) is the dosimetric quantity used for multi-slice CT (MSCT) with beams  ⩽4 cm. Conversion factors (f ) based on patient size are applied to CTDI to adjust for differences in patient size and derive size-specific dose estimates (SSDE) relating to patient dose. The aim of this study is to: (1) investigate use of a similar technique to provide SSDE values for cone beam CT (CBCT) scans, (2) determine whether factors derived for narrow beam MSCT are suitable for CBCT, and (3) investigate the influence of CBCT parameters on f  values.

Evaluation of coefficients to derive organ and effective doses from cone-beam CT (CBCT) scans: a Monte Carlo study.

Regular imaging is used throughout image guided radiation therapy to improve treatment delivery. In order for treatment procedures to be optimized, the doses delivered by imaging exposures should be taken into account. CT dosimetry methods based on the CT dose index (CTDI), measured with a 100 mm long pencil ionization chamber (CTDI) in standard phantoms, are not designed for cone-beam CT (CBCT) imaging systems used in radiotherapy, therefore a modified version has been proposed for CBCT by the International Electrotechnical Commission (CTDI).

A Monte Carlo study of organ and effective doses of cone beam computed tomography (CBCT) scans in radiotherapy.

Cone-beam CT (CBCT) scans utilised for image guided radiation therapy (IGRT) procedures have become an essential part of radiotherapy. The aim of this study was to assess organ and effective doses resulting from new CBCT scan protocols (head, thorax, and pelvis) released with a software upgrade of the kV on-board-imager (OBI) system. Organ and effective doses for protocols of the new software (V2.

Organ doses can be estimated from the computed tomography (CT) dose index for cone-beam CT on radiotherapy equipment.

Cone beam computed tomography (CBCT) systems are fitted to radiotherapy linear accelerators and used for patient positioning prior to treatment by image guided radiotherapy (IGRT). Radiotherapists' and radiographers' knowledge of doses to organs from CBCT imaging is limited. The weighted CT dose index for a reference beam of width 20 mm (CTDIw,ref) is displayed on Varian CBCT imaging equipment known as an On-Board Imager (OBI) linked to the Truebeam linear accelerator.

Evaluation of cumulative dose for cone-beam computed tomography (CBCT) scans within phantoms made from different compositions using Monte Carlo simulations.

Measurement of cumulative dose ƒ(0,150) with a small ionization chamber within standard polymethyl methacrylate (PMMA) CT head and body phantoms, 150 mm in length, is a possible practical method for cone-beam computed tomography (CBCT) dosimetry. This differs from evaluating cumulative dose under scatter equilibrium conditions within an infinitely long phantom ƒ(0,∞), which is proposed by AAPM TG-111 for CBCT dosimetry. The aim of this study was to investigate the feasibility of using ƒ(0,150) to estimate values for ƒ(0,∞) in long head and body phantoms made of PMMA, polyethylene (PE), and water, using beam qualities for tube potentials of 80-140 kV.

Investigation of practical approaches to evaluating cumulative dose for cone beam computed tomography (CBCT) from standard CT dosimetry measurements: a Monte Carlo study.

A function called Gx(L) was introduced by the International Commission on Radiation Units and Measurements (ICRU) Report-87 to facilitate measurement of cumulative dose for CT scans within long phantoms as recommended by the American Association of Physicists in Medicine (AAPM) TG-111. The Gx(L) function is equal to the ratio of the cumulative dose at the middle of a CT scan to the volume weighted CTDI (CTDIvol), and was investigated for conventional multi-slice CT scanners operating with a moving table. As the stationary table mode, which is the basis for cone beam CT (CBCT) scans, differs from that used for conventional CT scans, the aim of this study was to investigate the extension of the Gx(L) function to CBCT scans.

A Monte Carlo investigation of cumulative dose measurements for cone beam computed tomography (CBCT) dosimetry.

Many studies have shown that the computed tomography dose index (CTDI100) which is considered as a main dose descriptor for CT dosimetry fails to provide a realistic reflection of the dose involved in cone beam computed tomography (CBCT) scans. Several practical approaches have been proposed to overcome drawbacks of the CTDI100. One of these is the cumulative dose concept.

An assessment of the efficiency of methods for measurement of the computed tomography dose index (CTDI) for cone beam (CBCT) dosimetry by Monte Carlo simulation.

The IEC has introduced a practical approach to overcome shortcomings of the CTDI100 for measurements on wide beams employed for cone beam (CBCT) scans. This study evaluated the efficiency of this approach (CTDIIEC) for different arrangements using Monte Carlo simulation techniques, and compared CTDIIEC to the efficiency of CTDI100 for CBCT. Monte Carlo EGSnrc/BEAMnrc and EGSnrc/DOSXYZnrc codes were used to simulate the kV imaging system mounted on a Varian TrueBeam linear accelerator.