The direct use of CT numbers in radiotherapy dosage calculations for inhomogeneous media

Parker, R. P.; Hobday, Pauline; Cassell, K. J.

doi:10.1088/0031-9155/24/4/011

Cited by 94 publications

(30 citation statements)

References 11 publications

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“…The CT numbers can be used to calculate the radiotherapy dose distribution within human body, which is composed with inhomogeneous tissue. The generation of dose volume histograms and exportation of verification are also possible (7,8). In addition, simulation CT images can serve as medical images of the thorax.…”

Section: Introductionmentioning

confidence: 99%

Incidental Findings on Simulation CT Images for Adjuvant Radiotherapy in Breast Cancer Patients

Park

Choi

Huh

et al. 2015

Technol Cancer Res Treat

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We designed this study to evaluate the incidence of incidental findings on computed tomography (CT) scan implemented as simulation for adjuvant radiotherapy in breast cancer patients and to emphasize the need for careful review of simulation CT images before planning radiotherapy. A Resident and attending radiation oncologists retrospectively reviewed the medical records and simulation CT images of 776 patients treated with adjuvant radiotherapy at Samsung Medical Center during 2008. Previously undetected abnormal findings on simulation CT images were defined as incidental findings and interpreted by diagnostic radiologist. If the incidental findings required further evaluation or follow-up, they were defined as indeterminate findings. If subsequent cancers were diagnosed according incidental findings, they were defined as malignancy-related findings. There were 81 indeterminate findings (10.8%) including thyroid nodule, solitary pulmonary nodule, mediastinal lymph node, supraclavicular or axillary lymph node. Among them, there were nine malignancy-related findings (1.3%), including four thyroid cancers, three lung metastases, one primary lung cancer, and one axillary lymph node recurrence. The incidence of incidental findings in this study was low, but some of the findings were related to malignancy.Radiation oncologists should be alert to incidental findings on simulation CT, and incidental findings should be evaluated by diagnostic radiologists.

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Section: Introductionmentioning

confidence: 99%

Incidental Findings on Simulation CT Images for Adjuvant Radiotherapy in Breast Cancer Patients

Park

Choi

Huh

et al. 2015

Technol Cancer Res Treat

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“…1 The HU-ρ e conversion is usually performed using tissue substitutes with known electron densities in a calibration phantom. 2 However, the elemental composition of those tissue substitutes differs from that of real tissues; consequently, different calibration curves are used for the HU-ρ e conversion.…”

Section: Introductionmentioning

confidence: 99%

Technical Note: Exploring the limit for the conversion of energy-subtracted CT number to electron density for high-atomic-number materials

Saito

Tsukihara

2014

Med. Phys.

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“…[1][2][3][4][5][6][7] These quantities are typically derived from the computed tomography ͑CT͒ number ͑Hounsfield unit ͓HU͔͒ after an electron-density calibration is performed based on measurement of tissue-equivalent materials of known electron densities in a phantom. 8,9 Because CT scans are usually acquired at conventional kilovoltage x-ray energies ͑typically in the range of 70-140 kVp͒, CT numbers are converted into energy-independent radiological properties of human tissues ͑such as mass densities, electron densities, or stopping power ratios͒ before they are used to calculate doses with high-energy x rays or particletherapy beams ͑such as protons or carbon ions͒.…”

Section: Introductionmentioning

confidence: 99%

Improving accuracy of electron density measurement in the presence of metallic implants using orthovoltage computed tomography

et al. 2008

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The goal of this study was to evaluate the improvement in electron density measurement and metal artifact reduction using orthovoltage computed tomography (OVCT) imaging compared with conventional kilovoltage CT (KVCT). For this study, a bench-top system was constructed with adjustable x-ray tube voltage up to 320 kVp. A commercial tissue-characterization phantom loaded with inserts of various human tissue substitutes was imaged using 125 kVp (KVCT) and 320 kVp (OVCT) x rays. Stoichiometric calibration was performed for both KVCT and OVCT imaging using the Schneider method. The metal inserts-titanium rods and aluminum rods-were used to study the impact of metal artifacts on the electron-density measurements both inside and outside the metal inserts. It was found that the relationships between Hounsfield units and relative electron densities (to water) were more predictable for OVCT than KVCT. Unlike KVCT, the stoichiometric calibration for OVCT was insensitive to the use of tissue substitutes for direct electron density calibration. OVCT was found to significantly reduce metal streak artifacts. Errors in electron-density measurements within uniform tissue substitutes were reduced from 42% (maximum) and 18% (root-mean-square) in KVCT to 12% and 2% in OVCT, respectively. Improvements were also observed inside the metal implants. For the detectors optimized for KVCT, the imaging dose is almost doubled for OVCT for the image quality comparable to KVCT. OVCT may be a good option for high-precision radiotherapy treatment planning, especially for patients with metal implants and especially for charged particle therapy, such as proton therapy.

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The direct use of CT numbers in radiotherapy dosage calculations for inhomogeneous media

Cited by 94 publications

References 11 publications

Incidental Findings on Simulation CT Images for Adjuvant Radiotherapy in Breast Cancer Patients

Incidental Findings on Simulation CT Images for Adjuvant Radiotherapy in Breast Cancer Patients

Technical Note: Exploring the limit for the conversion of energy-subtracted CT number to electron density for high-atomic-number materials

Improving accuracy of electron density measurement in the presence of metallic implants using orthovoltage computed tomography

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