Computed tomography phantom for radiochromic film dosimetry

Gotanda, Rumi; Katsuda, Toshizo; Gotanda, Tatsuhiro; Eguchi, M; Takewa, S; Tabuchi, Akihiko; Yatake, Hidetoshi

doi:10.1007/bf03178426

Cited by 27 publications

(27 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Gafchromic films are also applicable to X‐ray dose measurements in computed tomography (CT) 6 , 7 , 8 , 9 , 10 , 11 , 12 …”

Section: Introductionmentioning

confidence: 99%

“…In the CT dose measurements, a Gafchromic film is rolled up with a certain thickness of flexible acrylic sheet, (7) enabling three‐dimensional X‐ray dose measurements in CT 7 , 8 . Several pieces of Gafchromic films are placed between the flexible acrylic sheets, whose thickness determines the spatial resolution of the dose measurement.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Correction of nonuniformity error of Gafchromic EBT2 and EBT3

Katsuda

Gotanda

et al. 2016

J Applied Clin Med Phys

View full text Add to dashboard Cite

This study investigates an X‐ray dose measurement method for computed tomography using Gafchromic films. Nonuniformity of the active layer is a major problem in Gafchromic films. In radiotherapy, nonuniformity error is reduced by applying the double‐exposure technique, but this is impractical in diagnostic radiology because of the heel effect. Therefore, we propose replacing the X‐rays in the double‐exposure technique with ultraviolet (UV)‐A irradiation of Gafchromic EBT2 and EBT3. To improve the reproducibility of the scan position, Gafchromic EBT2 and EBT3 films were attached to a 3‐mm‐thick acrylic plate. The samples were then irradiated with a 10 W UV‐A fluorescent lamp placed at a distance of 72 cm for 30, 60, and 90 minutes. The profile curves were evaluated along the long and short axes of the film center, and the standard deviations of the pixel values were calculated over large areas of the films. Paired t‐test was performed. UV‐A irradiation exerted a significant effect on Gafchromic EBT2 (paired t‐test; p=0.0275) but not on EBT3 (paired t‐test; p=0.2785). Similarly, the homogeneity was improved in Gafchromic EBT2 but not in EBT3. Therefore, the double‐exposure technique under UV‐A irradiation is suitable only for EBT2 films.PACS number(s): 87.53 Bn

show abstract

“…Gafchromic films are also applicable to X‐ray dose measurements in computed tomography (CT) 6 , 7 , 8 , 9 , 10 , 11 , 12 …”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Correction of nonuniformity error of Gafchromic EBT2 and EBT3

Katsuda

Gotanda

et al. 2016

J Applied Clin Med Phys

View full text Add to dashboard Cite

show abstract

“…To measure the detailed dose distribution, a sheet roll CT dosimetry phantom (SRCT-P) with Radiochromic film (RF) was developed [4,5]. RFs have been developed for measurement of the absorbed dose of low-energy photons IFMBE Proceedings Vol.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, SRCT-P was flexible in terms of the phantom size and shape, and the depth of the measurement position in the phantom was determined according to where the RFs were inserted between the sheets. In addition, identification of the maximum dose position in the SRCT-P, evaluation of the absorbed dose in a local area, and the detailed dose distribution in the phantom were facilitated [4,5].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Dose Distribution According to Patient Setup Errors in Pediatric Head CT Examination: A Phantom Study

et al. 2015

View full text Add to dashboard Cite

Abstract-Radiation doses during computed tomography (CT) examinations are generally evaluated by CT dose index (CTDI). The CTDI is measured by means of a CTDI phantom, which is placed in the center of the CT gantry aperture. However, patients are not always positioned in the centered in clinical settings. In this study, dose distributions associated with patient setup errors and head size were evaluated using phantoms developed for pediatric patients. The phantoms were made using flexible acrylic sheets in a cylindrical shape [diameters of 6 (premature baby), 8 (neonate), 10 (infant), and 12 cm (child)] and placed on the end of the CT bed. The bed position was lowered from the center by up to a radius length for each phantom size. Dose distributions in the phantoms were measured using radiochromic film. By lowering the bed position, the surface doses at 0° increased and those at 180° and the center doses decreased. However, the other measurement positions exhibited complex changes depending on the phantom size. In addition, the shapes of the dose profile curves varied according to the distance from the X-ray tube (i.e. location in the gantry aperture). In this study, the surface doses became smaller with decreasing distance from the X-ray tube. Therefore, decreasing the distance from the lens to the X-ray tube would be an effective way to reduce the absorbed dose of the lens. However, the dose distributions in the phantoms varied in a complex manner depending on patient setup errors and phantom size. In addition, beam slice width and pitch were important factors in determining the amount of the CT dose. To keep radiation doses during CT examination as low as reasonably achievable, it is important to clarify the influence of CT scanning settings on CT dose.

show abstract

“…For CT dose measurements, three‐dimensional dosimetry methods have been developed, such as a sheet‐roll phantom (1) or a half cylindrical phantom with Gafchromic films (2) . Gafchromic film uniformity is an important consideration for these high‐resolution measurements.…”

Section: Introductionmentioning

confidence: 99%

Comparing three UV wavelengths for pre‐exposing Gafchromic EBT2 and EBT3 films

Katsuda

Gotanda

et al. 2015

J Applied Clin Med Phys

View full text Add to dashboard Cite

Gafchromic films are used for X‐ray dose measurements during diagnostic examinations and have begun to be used for three‐dimensional X‐ray dose measurements using the high‐resolution characteristics of Gafchromic films for computed tomography. However, the problem of unevenness in Gafchromic film active layers needs to be resolved. Double exposures using X‐rays are performed during therapeutic radiology, although this is difficult for a diagnostic examination because of a heel effect. Thus, it has been suggested that ultraviolet (UV) radiation be used as a substitute for X‐rays. However, the appropriate UV wavelength has not been determined. Thus, we conducted this study to decide an appropriate UV wavelength. UV peak wavelengths of 245 nm (UV‐A), 310 nm (UV‐B), and 365 nm (UV‐C) were used to irradiate EBT2 and EBT3 films. Each UV wavelength was irradiated for 5, 15, 30, and 60 min, and irradiation was then repeated every 60 min up to 360 min. Gafchromic films were scanned after every irradiation using a flatbed scanner. Images were split into RGB images, and red images were analyzed using ImageJ, version 1.44, image analysis software. A region of interest (ROI) one‐half inch in diameter was placed in the center of subtracted Gafchromic film images, and UV irradiation times were plotted against mean pixel values. There were reactions in the front and back of Gafchromic EBT3 and the back of Gafchromic EBT2 with UV‐A and UV‐B. However, UV‐C resulted in some reactions in both sides of Gafchromic EBT2 and EBT3. The UV‐A and UV‐B wavelengths should be used.PACS number(s): 87.53 Bn

show abstract

Computed tomography phantom for radiochromic film dosimetry

Cited by 27 publications

References 14 publications

Correction of nonuniformity error of Gafchromic EBT2 and EBT3

Correction of nonuniformity error of Gafchromic EBT2 and EBT3

Evaluation of Dose Distribution According to Patient Setup Errors in Pediatric Head CT Examination: A Phantom Study

Comparing three UV wavelengths for pre‐exposing Gafchromic EBT2 and EBT3 films

Contact Info

Product

Resources

About