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Laidlaw J, Earl N, Shavdia N, Davis R, Mayer S, Karaman D, Richtsmeier D, Rodesch PA, Bazalova-Carter M. Design and CT imaging of casper, an anthropomorphic breathing thorax phantom. Biomed Phys Eng Express 2023; 9. [PMID: 36724499 DOI: 10.1088/2057-1976/acb7f7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Accepted: 02/01/2023] [Indexed: 02/03/2023]
Abstract
The goal of this work was to build an anthropomorphic thorax phantom capable of breathing motion with materials mimicking human tissues in x-ray imaging applications. The thorax phantom, named Casper, was composed of resin (body), foam (lungs), glow polyactic acid (bones) and natural polyactic acid (tumours placed in the lungs). X-ray attenuation properties of all materials prior to manufacturing were evaluated by means of photon-counting computed tomography (CT) imaging on a table-top system. Breathing motion was achieved by a scotch-yoke mechanism with diaphragm motion frequencies of 10-20 rpm and displacements of 1 to 2 cm. Casper was manufactured by means of 3D printing of moulds and ribs and assembled in a complex process. The final phantom was then scanned using a clinical CT scanner to evaluate material CT numbers and the extent of tumour motion. Casper CT numbers were close to human CT numbers for soft tissue (46 HU), ribs (125 HU), lungs (-840 HU) and tumours (-45 HU). For a 2 cm diaphragm displacement the largest tumour displacement was 0.7 cm. The five tumour volumes were accurately assessed in the static CT images with a mean absolute error of 4.3%. Tumour sizes were either underestimated for smaller tumours or overestimated for larger tumours in dynamic CT images due to motion blurring with a mean absolute difference from true volumes of 10.3%. More Casper information including a motion movie and manufacturing data can be downloaded from http://web.uvic.ca/~bazalova/Casper/.
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Affiliation(s)
- Josie Laidlaw
- Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Nicolas Earl
- Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Nihal Shavdia
- Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Rayna Davis
- Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Sarah Mayer
- Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Dmitri Karaman
- Axolotl Bioscience, Victoria, British Columbia V8W 2Y2, Canada
| | - Devon Richtsmeier
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Pierre-Antoine Rodesch
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Magdalena Bazalova-Carter
- Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
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Doi Y, Shimohigashi Y, Kai Y, Maruyama M, Toya R. Validation of four-dimensional computed tomography without external reference respiratory signals for radiation treatment planning of lung tumors. Biomed Phys Eng Express 2022; 8. [PMID: 35905637 DOI: 10.1088/2057-1976/ac8555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 07/28/2022] [Indexed: 11/12/2022]
Abstract
Deviceless four-dimensional (4D) computed tomography (CT) allows the acquisition of respiratory signals from six features without requiring an external device for cine CT processing. This method has been recently introduced in radiation treatment planning of lung tumors. To validate deviceless 4D CT, it must be compared with conventional 4D CT, which requires an external monitoring device. We compared the two methods using a multicell 4D phantom that simulates patient's movement during respiration regarding the target volume (TV), target position (TP), and internal TV for lung tumor radiation therapy. We retrospectively obtained images of 10 patients who underwent radiation treatment planning of lung tumors and compared the two methods, as in the phantom study. For the phantom study, the mean TV, root mean square errors of the TP, and mean internal TV differences between the two methods ranged from -4.5% to 1.2%, 0.7 to 2.6 mm, and -1.1% to 3.4%, respectively. The corresponding results of the clinical study ranged from -1.5% to 14.9%, 0.1 to 5.9 mm, and -9.7% to 10.1%, respectively. The results of deviceless 4D CT for the clinical study were consistent with those of conventional 4D CT, except for target movements with high excursions. Therefore, deviceless 4D CT can be an alternative to conventional 4D CT for radiation treatment planning of lung tumors.
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Affiliation(s)
- Yasuhiro Doi
- Department of Radiological Technology, Kumamoto University Hospital, 1-1-1 Honjo, Chuo-ku, Kumamoto, Japan, Kumamoto, 860-8556, JAPAN
| | - Yoshinobu Shimohigashi
- Department of Radiological Technology, Kumamoto University Hospital, 1-1-1 Honjo, Chuo-ku, Kumamoto, Japan, Kumamoto, 860-8556, JAPAN
| | - Yudai Kai
- Kumamoto University Hospital, Hospital, 1-1-1 Honjo, Chuo-ku, Kumamoto, Japan, Kumamoto, 860-8556, JAPAN
| | - Masato Maruyama
- Kumamoto University Hospital, Hospital, 1-1-1 Honjo, Chuo-ku, Kumamoto, Japan, Kumamoto, 860-8556, JAPAN
| | - Ryo Toya
- Department of Radiation Oncology, Kumamoto University Hospital, 1-1-1 Honjo, Chuo-ku, Kumamoto, Japan, Kumamoto, 860-8556, JAPAN
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