A Novel Method to Extend a Partial-Body CT for the Reconstruction of Dose to Organs beyond the Scan Range

Kuzmin, G.; Mille, Marie-Laure; Jung, Jae Won; Lee, Choonik; Pelletier, C; Akabani, Gamal; Lee, Choonsik

doi:10.1667/rr14999.1

Cited by 12 publications

(14 citation statements)

References 14 publications

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“…whole body CT image, as normal tissues of interest may be located outside the CT coverage. As also described byKuzmin et al (2018), to extend the partial patient anatomy to the whole body, the head CT scan of each patient was merged with a computational phantom in DICOM format with corresponding age, size and gender, summarized in table 2, developed by the University of Florida (UF) and the US National Cancer Institute (US-NCI)(Lee et al 2010). These phantoms belong to the UFH family of hybrid phantoms of different ages, sizes and both genders and represent the ICRP reference phantoms including the reference organ masses from ICRP Publication 89(ICRP 2002), the reference tissue densities and elemental compositions from both ICRP Publication 89 and Report 46 by the International Commission on Radiation Units and Measurements (1992).…”

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confidence: 89%

Secondary neutron dose contribution from pencil beam scanning, scattered and spatially fractionated proton therapy

Leite¹,

Ronga²,

Giorgi³

et al. 2021

Phys. Med. Biol.

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The Orsay Proton therapy Center (ICPO) has a long history of intracranial radiotherapy using both double scattering (DS) and pencil beam scanning (PBS) techniques, and is actively investigating a promising modality of spatially fractionated radiotherapy using proton minibeams (pMBRT). This work provides a comprehensive comparison of the organ-specific secondary neutron dose due to each of these treatment modalities, assessed using Monte Carlo (MC) algorithms and measurements. A MC model of a universal nozzle was benchmarked by comparing the neutron ambient dose equivalent, H*(10), in the gantry room with measurements obtained using a WENDI-II counter. The secondary neutron dose was evaluated for clinically relevant intracranial treatments of patients of different ages, in which secondary neutron doses were scored in anthropomorphic phantoms merged with the patients’ images. The MC calculated H*(10) values showed a reasonable agreement with the measurements and followed the expected tendency, in which PBS yields the lowest dose, followed by pMBRT and DS. Our results for intracranial treatments show that pMBRT yielded a higher secondary neutron dose for organs closer to the target volume, while organs situated furthest from the target volume received a greater quantity of neutrons from the passive scattering beam line. To the best of our knowledge, this is the first study to compare MC secondary neutron dose estimates in clinical treatments between these various proton therapy modalities and to realistically quantify the secondary neutron dose contribution of clinical pMBRT treatments. The method established in this study will enable epidemiological studies of the long-term effects of intracranial treatments at ICPO, notably radiation-induced second malignancies.

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mentioning

confidence: 89%

Secondary neutron dose contribution from pencil beam scanning, scattered and spatially fractionated proton therapy

Leite¹,

Ronga²,

Giorgi³

et al. 2021

Phys. Med. Biol.

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“…The use of computational phantoms can help model more of this anatomy. Recent work has shown methods to extend a partial-body CT by incorporating the CT image set into a matched computational phantom (Kuzmin et al 2018). Regardless of how the anatomy is extended, it should be noted that a well-performed extension of the patient's anatomy does not mean that out-of-field organ dosimetry is accurate.…”

Section: Future Applications and Limitationsmentioning

confidence: 99%

Conversion of computational human phantoms into DICOM-RT for normal tissue dose assessment in radiotherapy patients

et al. 2019

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Radiotherapy treatment planning systems are designed for the fast calculation of dose to the tumor bed and nearby organs at risk using x-ray computed tomography (CT) images. However, CT images for a patient are typically available for only a small portion of the body, and in some cases, such as for retrospective epidemiological studies, no images may be available at all. When dose to organs that lie out-of-scan must be estimated, a convenient alternative for the unknown patient anatomy is to use a matching whole-body computational phantom as a surrogate. The purpose of the current work is to connect such computational phantoms to commercial radiotherapy treatment planning systems for retrospective organ dose estimation. A custom software with graphical user interface, called the DICOM-RT Generator, was developed in MATLAB to convert voxel computational phantoms into the Digital Imaging and Communications in Medicine radiotherapy (DICOM-RT) format, compatible with commercial treatment planning systems. DICOM CT image sets for the phantoms are created via a density-to-Hounsfield unit conversion curve. Accompanying structure sets containing the organ contours are automatically generated by tracing binary masks of user-specified organs on each phantom CT slice. The software was tested on a library of body size-dependent phantoms, the International Commission on Radiological Protection reference phantoms, and a canine voxel phantom, taking only a few minutes per conversion. The resulting DICOM-RT files were tested on several commercial treatment planning systems. As an example application, a library of converted phantoms was used to estimate organ doses for members of the National Wilms Tumor Study cohort. The converted phantom library, in DICOM format, and a standalone MATLAB-compiled executable of the DICOM-RT Generator are available for others to use for research purposes (http://ncidose.cancer.gov).

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“…To map the scanning location of the patient CTs on the computational human phantoms, we adopted an algorithm we previously developed to extend partial body CT images to whole body [25]. The algorithm generated a two-dimensional (2D) skeletal mask by using ray-tracing from the front to back of a patient from a given patient CT set by applying a threshold of Hounsfield unit (285-3500) to CT pixels.…”

Section: Ct-to-phantom Mapping Algorithmmentioning

confidence: 99%

Automatic Mapping of CT Scan Locations on Computational Human Phantoms for Organ Dose Estimation

et al. 2018

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To develop an algorithm to automatically map CT scan locations of patients onto computational human phantoms to provide with patient-specific organ doses. We developed an algorithm that compares a two-dimensional skeletal mask generated from patient CTs with that of a whole body computational human phantom. The algorithm selected the scan locations showing the highest Dice Similarity Coefficient (DSC) calculated between the skeletal masks of a patient and a phantom. To test the performance of the algorithm, we randomly selected five sets of neck, chest, and abdominal CT images from the National Institutes of Health Clinical Center. We first automatically mapped scan locations of the CT images on a computational human phantom using our algorithm. We had several radiologists to manually map the same CT images on the phantom and compared the results with the automated mapping. Finally, organ doses for automated and manual mapping locations were calculated by an in-house CT dose calculator and compared to each other. The visual comparison showed excellent agreement between manual and automatic mapping locations for neck, chest, and abdomen-pelvis CTs. The difference in mapping locations averaged over the start and end in the five patients was less than 1 cm for all neck, chest, and AP scans: 0.9, 0.7, and 0.9 cm for neck, chest, and AP scans, respectively. Five cases out of ten in the neck scans show zero difference between the average manual and automatic mappings. Average of absolute dose differences between manual and automatic mappings was 2.3, 2.7, and 4.0% for neck, chest, and AP scans, respectively. The automatic mapping algorithm provided accurate scan locations and organ doses compared to manual mapping. The algorithm will be useful in cases requiring patient-specific organ dose for a large number of patients such as patient dose monitoring, clinical trials, and epidemiologic studies.

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A Novel Method to Extend a Partial-Body CT for the Reconstruction of Dose to Organs beyond the Scan Range

Cited by 12 publications

References 14 publications

Secondary neutron dose contribution from pencil beam scanning, scattered and spatially fractionated proton therapy

Secondary neutron dose contribution from pencil beam scanning, scattered and spatially fractionated proton therapy

Conversion of computational human phantoms into DICOM-RT for normal tissue dose assessment in radiotherapy patients

Automatic Mapping of CT Scan Locations on Computational Human Phantoms for Organ Dose Estimation

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