Comparative dose evaluations between XVI and OBI cone beam CT systems using Gafchromic XRQA2 film and nanoDot optical stimulated luminescence dosimeters

Giaddui, T; Cui, Yunfeng; Galvin, James M.; Yan, Yu; Xiao, Ying

doi:10.1118/1.4803466

Cited by 36 publications

(37 citation statements)

References 33 publications

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“…Other studies 23,24 have noted the decrease in imaging dose for a given scan protocol with each new version of the system. Our measurements with XRQA2 film agree with the previous study using Rando phantom for imaging dose measurements for the OBI and XVI systems.…”

Section: Discussionmentioning

confidence: 99%

“…Measurements were acquired to convert the pixel value of the film to dose and a calibration curve was generated. The previous study utilizing GafChromic XRQA2 film 23 found minimal differences between the half-fan and full-fan calibration curves for 125 kVp setting on the Varian OBI system, so only one calibration curve was generated for this kVp setting. Otherwise, calibration curves were generated for each unique tube voltage and filtration setting.…”

Section: F Imaging Dose Studymentioning

confidence: 99%

“…Previous studies have shown that the uncertainty of the XRQA2 film reaches a stable minimum of about 3%-5% for doses above approximately 3 cGy. 23,24 To take advantage of this characteristic of the film, multiple scans were acquired for each scan type to deliver more than 3 cGy to the film when possible, thus reducing the uncertainty in dose measurement as much as possible. To simulate changing patient thickness, Superflab bolus and solid water slabs were used to increase the phantom diameter by 4 cm.…”

Section: G Imaging Dose Studymentioning

confidence: 99%

“…[23][24][25] The film was scanned using an Epson XL10000 flatbed scanner. The use of this scanner for dosimetric measurements in the diagnostic imaging energy range has been thoroughly investigated.…”

Section: G Imaging Dose Studymentioning

confidence: 99%

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Investigation into image quality and dose for different patient geometries with multiple cone‐beam CT systems

et al. 2014

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Purpose:To provide quantitative and qualitative image quality metrics and imaging dose for modern Varian On-board Imager (OBI) (ver. 1.5) and Elekta X-ray Volume Imager (XVI) (ver. 4.5R) conebeam computed tomography (CBCT) systems in a clinical adaptive radiation therapy environment by accounting for varying patient thickness. Methods: Image quality measurements were acquired with Catphan 504 phantom (nominal diameter and with additional 10 cm thickness) for OBI and XVI systems and compared to planning CT (pCT) (GE LightSpeed). Various clinical protocols were analyzed for the OBI and XVI systems and analyzed using image quality metrics, including spatial resolution, low contrast detectability, uniformity, and HU sensitivity. Imaging dose measurements were acquired in Wellhofer Scanditronix i'mRT phantom at nominal phantom diameter and with additional 4 cm phantom diameter using GafChromic XRQA2 film. Calibration curves were generated using previously published in-air Air Kerma calibration method. Results: The OBI system full trajectory scans exhibited very little dependence on phantom thickness for accurate HU calculation, while half-trajectory scans with full-fan filter exhibited dependence of HU calculation on phantom thickness. The contrast-to-noise ratio (CNR) for the OBI scans decreased with additional phantom thickness. The uniformity of Head protocol scan was most significantly affected with additional phantom thickness. The spatial resolution and CNR compared favorably with pCT, while the uniformity of the OBI system was slightly inferior to pCT. The OBI scan protocol dose levels for nominal phantom thickness at the central portion of the phantom were 2.61, 0.72, and 1.88 cGy, and for additional phantom thickness were 1.95, 0.48, and 1.52 cGy, for the Pelvis, Thorax, and Spotlight protocols, respectively. The XVI system scans exhibited dependence on phantom thickness for accurate HU calculation regardless of trajectory. The CNR for the XVI scans decreased with additional phantom thickness. The uniformity of the XVI scans was significantly dependent on the selection of the proper FOV setting for all phantom geometries. The spatial resolution, CNR, and uniformity for XVI were lower than values measured for pCT. The XVI scan protocol dose levels at the central portion of the phantom for nominal phantom thickness were 2.14, 2.15, and 0.33 cGy, and for additional phantom thickness were 1.56, 1.68, and 0.21 cGy, for the Pelvis M20, Chest M20, and Prostate Seed S10 scan protocols, respectively. Conclusions: The OBI system offered comparable spatial resolution and CNR results to the results for pCT. Full trajectory scans with the OBI system need little-to-no correction for HU calculation based on HU stability with changing phantom thickness. The XVI system offered lower spatial resolution and CNR results than pCT. In addition, the HU calculation for all scan protocols was dependent on the phantom thickness. The uniformity for each CBCT system was inferior to that of pCT for each phantom geometry. The dose for ea...

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Section: Discussionmentioning

confidence: 99%

Section: F Imaging Dose Studymentioning

confidence: 99%

Section: G Imaging Dose Studymentioning

confidence: 99%

Section: G Imaging Dose Studymentioning

confidence: 99%

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Investigation into image quality and dose for different patient geometries with multiple cone‐beam CT systems

et al. 2014

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“…The RT 4D CBCT and conven-tional 4D CBCT simulations are 'synthetic' as they select projections according to the input respiratory signal from the static projections collected in section 2.4.1. All conventional 4D CBCT simulations are based on the acquisition parameters used from a commercially available 4D CBCT system as listed by Giaddui et al (2013):…”

Section: 42mentioning

confidence: 99%

Quantifying the image quality and dose reduction of respiratory triggered 4D cone-beam computed tomography with patient-measured breathing

et al. 2015

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Respiratory triggered four dimensional cone-beam computed tomography (RT 4D CBCT) is a novel technique that uses a patient's respiratory signal to drive the image acquisition with the goal of imaging dose reduction without degrading image quality. This work investigates image quality and dose using patient-measured respiratory signals for RT 4D CBCT simulations. Studies were performed that simulate a 4D CBCT image acquisition using both the novel RT 4D CBCT technique and a conventional 4D CBCT technique. A set containing 111 free breathing lung cancer patient respiratory signal files was used to create 111 pairs of RT 4D CBCT and conventional 4D CBCT image sets from realistic simulations of a 4D CBCT system using a Rando phantom and the digital phantom, XCAT. Each of these image sets were compared to a ground truth dataset from which a mean absolute pixel difference (MAPD) metric was calculated to quantify the degradation of image quality. The number of projections used in each simulation was counted and was assumed as a surrogate for imaging dose. Based on 111 breathing traces, when comparing RT 4D CBCT with conventional 4D CBCT, the average image quality was reduced by 7.6% (Rando study) and 11.1% (XCAT study). However, the average imaging dose reduction was 53% based on needing fewer projections (617 on average) than conventional 4D CBCT (1320 projections). The simulation studies have demonstrated that the RT 4D CBCT method can potentially offer a 53% saving in imaging dose on average compared to conventional 4D CBCT in simulation studies using a wide range of patient-measured breathing traces with a minimal impact on image qualit1.

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Investigation of the radiation dose from cone‐beam CT for image‐guided radiotherapy: A comparison of methodologies

Buckley

Wilkinson

Malaroda

et al. 2017

J Applied Clin Med Phys

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Four methodologies were evaluated for quantifying kilovoltage cone‐beam computed tomography (CBCT) dose: the Cone‐Beam Dose Index (CBDI), IAEA Report 5 recommended methodology (IAEA), the AAPM Task Group 111 methodology (TG111), and the current dose metric; the Computed Tomography Dose Index (CTDI) on two commercial Varian cone‐beam CT imaging systems; the Clinac iX On‐Board Imager (OBI); and the TrueBeam X‐ray Imaging system (XI). The TG111 methodology measured the highest overall dose (21.199 ± 0.035 mGy OBI and 22.420 ± 0.002 XI for pelvis imaging) due to the full scatter of the TG111 phantom and was within 5% of CTDI measurements taken using a full scatter TG111 phantom and 30‐cm film strips. CBDI measured the second highest overall dose, within 10% of the TG111, with IAEA measuring the third highest dose. For head CBCT protocols, CBDI measured the highest dose, followed by IAEA. The CTDI method measured lowest across all scan modes highlighting its limitations for CBCT dosimetry. The XI imaging system delivered lower doses for head and thorax scan modes and similar doses to the OBI system for pelvis scan modes due to additional beam hardening filtration in the XI system. The TG111 method measured the highest dose in the center of a CBCT scan during image guidance procedures; however, CBDI provided a good approximation to TG111 with existing CTDI equipment and may be more applicable clinically.

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Comparative dose evaluations between XVI and OBI cone beam CT systems using Gafchromic XRQA2 film and nanoDot optical stimulated luminescence dosimeters

Cited by 36 publications

References 33 publications

Investigation into image quality and dose for different patient geometries with multiple cone‐beam CT systems

Investigation into image quality and dose for different patient geometries with multiple cone‐beam CT systems

Quantifying the image quality and dose reduction of respiratory triggered 4D cone-beam computed tomography with patient-measured breathing

Investigation of the radiation dose from cone‐beam CT for image‐guided radiotherapy: A comparison of methodologies

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