An in‐phantom dosimetry system using pin silicon photodiode radiation sensors for measuring organ doses in x‐ray CT and other diagnostic radiology

Aoyama, T.; Koyama, Shuji; Kawaura, Chiyo

doi:10.1118/1.1489042

Cited by 56 publications

(35 citation statements)

References 15 publications

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“…X-ray energy dependence of dosimeter sensitivity (i.e. reciprocal of the conversion factor) and its derivation is described in our previous papers [6,9].…”

Section: Evaluation Of Organ and Effective Dosesmentioning

confidence: 99%

“…The minimum detectable dose was estimated to be 0.02 mGy with 25% uncertainty [9]. Overall uncertainty, including both random and systematic errors that arose in the conversion from measured output voltage of the photodiode dosimeter to the absorbed dose, was estimated to be 7% at 95% confidence level.…”

Section: Evaluation Of Organ and Effective Dosesmentioning

confidence: 99%

“…Dose measurement for the trunk region was carried out using 32 photodiode dosimeters composed of Hamamatsu S2506-04 photodiodes (Hamamatsu Photonics, Hamamatsu, Japan), the same type used for the head region but with a larger sensitive area of 2.8 6 2.8 mm 2 . The construction detail and characteristics of the dosimeters were fully described in our previous paper [9]. The anthropomorphic phantom used for the dosimetry is the Kyoto Kagaku THRA1 (Kyoto Kagaku, Kyoto, Japan), which imitated the standard Japanese adult male, 60 kg in weight and 170 cm tall.…”

Section: Methodsmentioning

confidence: 99%

“…Since the sensitivity of the photodiode to diagnostic X-rays differed with the incident direction of X-rays between front and back, two photodiodes were glued together back to back with epoxy cement. This was used as a single dosimeter with a parallel connection to obtain isotropic sensitivity to incident X-rays [9]. These photodiode dosimeters were implanted in 16 sites of the head and neck region of the phantom.…”

Section: Methodsmentioning

confidence: 99%

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Radiation dose evaluation in multidetector-row CT imaging for acute stroke with an anthropomorphic phantom

Yamauchi-Kawara

Fujii²,

Aoyama³

et al. 2010

BJR

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ABSTRACT. This study evaluated radiation dose and dose reduction in CT imaging for acute stroke. Radiation doses in three types of CT imaging (i.e. non-contrast-enhanced CT, CT perfusion (CTP) and CT angiography (CTA)) were measured with an in-phantom dosimetry system for 4-, 16-and 64-detector CT scanners in 5 hospitals. To examine the relationship between image quality and radiation dose in CTA, image contrast-to-noise ratio was evaluated. Doses to the brain, lens, salivary glands and local skin obtained with scan protocols in routine use were: 42-71 mGy, 30-88 mGy, 3.9-7.3 mGy and 40-97 mGy in non-contrast-enhanced CT; 41-75 mGy, 9.9-10 mGy, 1.5-2.1 mGy and 107-143 mGy in CTP; and 8.2-55 mGy, 26-69 mGy, 2.0-73 mGy and 32-72 mGy in CTA. For the combination of these CT examinations, on average a patient would receive 236 mGy for the maximum local skin dose and 4.2 mSv for the effective dose evaluated by the International Commission on Radiological Protection (ICRP) 103. Effective doses in CTP in this study were less than those obtained with representative protocols of Western countries. Average effective doses in each CT examination were not more than 1.5 mSv. The use of reduced kV and a narrow scan range would be effective in dose reduction of CTA and CTP, and intermittent scanning would be essential in CTP. Although lens and maximum local skin doses were far less than the thresholds for deterministic effects, since radiation risks would be increased in repeated CT examinations, efforts should be devoted to dose reduction in stroke CT examinations. Most patients with suspected stroke undergo either CT or MRI as the initial diagnostic examination [1,2]. MRI has some advantages over CT in depicting stroke lesions; however, the provision of MR scanners in general hospitals is still low, an examination takes more time and patients with pacemakers cannot undergo MRI examinations. While CT techniques carry the risk of radiation exposure, CT scanners are nearly always available [3] and scans can be done quickly. Schramm et al [4] have reported that CT images obtained by the combination of various CT examinations allow diagnostic assessment of acute stroke with a quality comparable with that of stroke MRI. So CT examination has some advantages for the diagnosis of acute stroke patients who have no time to lose.The diagnostic CT examination for acute stroke generally requires three imaging techniques: non-contrast-enhanced CT of the head; CT perfusion (CTP); and CT angiography (CTA) of intracranial vessels. In these CT examinations the local skin dose in CTP might be considerably high. In a previous study we reported that the maximum skin dose was as high as 712 mGy, 13 times higher than that in non-contrast-enhanced CT of the head [5]. Although the latest multidetector-row CT (MDCT) scanners have a dose reduction function of intermittent scanning or shuttle scanning, detailed patient doses using the function have not been reported.The CTA technique has been developing with great potential owing to high scan speed and ...

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“…X-ray energy dependence of dosimeter sensitivity (i.e. reciprocal of the conversion factor) and its derivation is described in our previous papers [6,9].…”

Section: Evaluation Of Organ and Effective Dosesmentioning

confidence: 99%

Section: Evaluation Of Organ and Effective Dosesmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Radiation dose evaluation in multidetector-row CT imaging for acute stroke with an anthropomorphic phantom

Yamauchi-Kawara

Fujii²,

Aoyama³

et al. 2010

BJR

View full text Add to dashboard Cite

show abstract

“…Radiation dose to the anthropomorphic phantom was evaluated using a dosimetry system with pin photodiode sensors, which was developed in a previous study [9]. Commercially available planar silicon pin photodiodes (Hamamatsu TM S8385-04; Hamamatsu Photonics, Hamamatsu, Japan) possessing a sensitive area of 2.062.0 mm 2 were used as the dosemeters.…”

Section: Dose Measurement On Head Phantommentioning

confidence: 99%

Dose reduction and image quality in CT angiography for cerebral aneurysm with various tube potentials and current settings

Imai¹,

Ikeda²,

Kawaura³

et al. 2012

BJR

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Objectives: The purpose of this study is to investigate the image quality on both axial and three-dimensional CT angiograms of the brain at various tube potentials and currents, and to propose the use of descriptors for evaluating the image quality of three-dimensional CT angiograms using entropy analysis. Methods: A head phantom was used as a target object. Axial CT and threedimensional CT angiograms were obtained at various effective milliampere-second values (49-350 mAs) and tube potentials (80-140 kVp) with a 64-row detector CT scanner. Lens doses were measured using a planar silicon pin-photodiode system. The signal-to-noise ratio (SNR) and streak artefacts on the axial CT angiograms were evaluated and the image quality of the three-dimensional CT angiograms was assessed using entropy analysis. Results: Lens doses increased with tube potential and effective milliampere-seconds. From the evaluation of SNR and streak artefacts on axial CT angiograms, we found that the image quality was improved by setting the tube potential at 100 kVp. However, there was little visual difference in the image quality for 100 kVp between 252 (effective value recommended by the manufacturer) and 350 mAs (maximum effective value). In the entropy analysis of the image quality of three-dimensional CT angiograms, the mutual information (information gain) per lens dose was largest at 80 kVp and 252 mAs. Conclusion: Our results suggested that the suitable tube potentials for axial CT and three-dimensional CT angiograms were 100 and 80 kVp, respectively, and the effective milliampere-second value recommended by the manufacturer was appropriate.

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Evaluation of exposure dose to patients undergoing catheter ablation procedures—a phantom study

et al. 2008

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The aim of this study was to evaluate entrance skin dose (ESD), organ dose and effective dose to patients undergoing catheter ablation for cardiac arrhythmias, based on the dosimetry in an anthropomorphic phantom. ESD values associated with mean fluoroscopy time and digital cine frames were in a range of 0.12-0.30 Gy in right anterior oblique (RAO) and 0.05-0.40 Gy in left anterior oblique (LAO) projection, the values which were less than a threshold dose of 2 Gy for the onset of skin injury. Organs that received high doses in ablation procedures were lung, followed by bone surface, esophagus, liver and red bone marrow. Doses for lung were 24.8-122.7 mGy, and effective doses were 7.9-34.8 mSv for mean fluoroscopy time of 23.4-92.3 min and digital cine frames of 263-511. Conversion coefficients of dose-area product (DAP) to ESD were 8.7 mGy/(Gy cm(2)) in RAO and 7.4 mGy/(Gy cm(2)) in LAO projection. The coefficients of DAP to the effective dose were 0.37 mSv/(Gy cm(2)) in RAO, and 0.41 mSv/(Gy cm(2)) in LAO projection. These coefficients enabled us to estimate patient exposure in real time by using monitored values of DAP.

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An in‐phantom dosimetry system using pin silicon photodiode radiation sensors for measuring organ doses in x‐ray CT and other diagnostic radiology

Cited by 56 publications

References 15 publications

Radiation dose evaluation in multidetector-row CT imaging for acute stroke with an anthropomorphic phantom

Radiation dose evaluation in multidetector-row CT imaging for acute stroke with an anthropomorphic phantom

Dose reduction and image quality in CT angiography for cerebral aneurysm with various tube potentials and current settings

Evaluation of exposure dose to patients undergoing catheter ablation procedures—a phantom study

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