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Karger CP, Elter A, Dorsch S, Mann P, Pappas E, Oldham M. Validation of complex radiotherapy techniques using polymer gel dosimetry. Phys Med Biol 2024; 69:06TR01. [PMID: 38330494 DOI: 10.1088/1361-6560/ad278f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 02/08/2024] [Indexed: 02/10/2024]
Abstract
Modern radiotherapy delivers highly conformal dose distributions to irregularly shaped target volumes while sparing the surrounding normal tissue. Due to the complex planning and delivery techniques, dose verification and validation of the whole treatment workflow by end-to-end tests became much more important and polymer gel dosimeters are one of the few possibilities to capture the delivered dose distribution in 3D. The basic principles and formulations of gel dosimetry and its evaluation methods are described and the available studies validating device-specific geometrical parameters as well as the dose delivery by advanced radiotherapy techniques, such as 3D-CRT/IMRT and stereotactic radiosurgery treatments, the treatment of moving targets, online-adaptive magnetic resonance-guided radiotherapy as well as proton and ion beam treatments, are reviewed. The present status and limitations as well as future challenges of polymer gel dosimetry for the validation of complex radiotherapy techniques are discussed.
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Affiliation(s)
- Christian P Karger
- Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
- National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany
| | - Alina Elter
- Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
- National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany
- Department of Radiation Oncology, University Hospital Heidelberg, Im Neuenheimer Feld 400, D-69120 Heidelberg, Germany
| | - Stefan Dorsch
- Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
- National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany
| | - Philipp Mann
- Department of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
- National Center for Radiation Research in Oncology (NCRO), Heidelberg Institute for Radiation Oncology (HIRO), Heidelberg, Germany
| | - Evangelos Pappas
- Radiology & Radiotherapy Sector, Department of Biomedical Sciences, University of West Attica, Athens, Greece
| | - Mark Oldham
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, United States of America
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Magugliani G, Marranconi M, Liosi GM, Locatelli F, Gambirasio A, Trombetta L, Hertsyk V, Torri V, Galluccio F, Macerata E, Mossini E, Santi A, Mariani M, Bombardieri E, Vavassori V, Salmoiraghi P. Pilot scale validation campaign of gel dosimetry for pre-treatment quality assurance in stereotactic radiotherapy. Phys Med 2023; 114:103158. [PMID: 37806152 DOI: 10.1016/j.ejmp.2023.103158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 09/25/2023] [Accepted: 09/28/2023] [Indexed: 10/10/2023] Open
Abstract
PURPOSE Complex stereotactic radiotherapy treatment plans require prior verification. A gel dosimetry system was developed and tested to serve as a high-resolution 3D dosimeter for Quality Assurance (QA) purposes. MATERIALS AND METHODS A modified version of a polyacrylamide polymer gel dosimeter based on chemical response inhibition was employed. Different sample geometries (cuvettes and phantoms) were manufactured for calibration and QA acquisitions. Irradiations were performed with a Varian Trilogy linac, and analyses of irradiated gel dosimeters were performed via MRI with a 1.5 T Philips Achieva at 1 mm3 or 2 mm3 isotropic spatial resolution. To assess reliability of polymer gel data, 54 stereotactic clinical treatment plans were delivered both on dosimetric gel phantoms and on the Delta4 dosimeter. Results from the two devices were evaluated through a global gamma index over a range of acceptance criteria and compared with each other. RESULTS A quantitative and tunable control of dosimetric gel response sensitivity was achieved through chemical inhibition. An optimized MRI analysis protocol allowed to acquire high resolution phantom dose data in timeframes of ≈ 1 h. Conversion of gel dosimeter data into absorbed dose was achieved through internal calibration. Polymer gel dosimeters (2 mm3 resolution) and Delta4 presented an agreement within 4.8 % and 2.7 % at the 3 %/1 mm and 2 %/2 mm gamma criteria, respectively. CONCLUSIONS Gel dosimeters appear as promising tools for high resolution 3D QA. Added complexity of the gel dosimetry protocol may be justifiable in case of small target volumes and steep dose gradients.
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Affiliation(s)
- G Magugliani
- Department of Energy, Nuclear Engineering Division, Politecnico di Milano, Milano, Italy.
| | - M Marranconi
- U. O. Medical Physics, Humanitas Gavazzeni, Bergamo, Italy
| | - G M Liosi
- Department of Energy, Nuclear Engineering Division, Politecnico di Milano, Milano, Italy
| | - F Locatelli
- U. O. Medical Physics, Humanitas Gavazzeni, Bergamo, Italy
| | - A Gambirasio
- U. O. Medical Physics, Humanitas Gavazzeni, Bergamo, Italy
| | - L Trombetta
- U. O. Medical Physics, Humanitas Gavazzeni, Bergamo, Italy
| | - V Hertsyk
- Fondazione Humanitas per la Ricerca, Milano, Italy
| | - V Torri
- Department of Oncologic Research, Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Milano, Italy
| | - F Galluccio
- Department of Energy, Nuclear Engineering Division, Politecnico di Milano, Milano, Italy
| | - E Macerata
- Department of Energy, Nuclear Engineering Division, Politecnico di Milano, Milano, Italy
| | - E Mossini
- Department of Energy, Nuclear Engineering Division, Politecnico di Milano, Milano, Italy
| | - A Santi
- Department of Energy, Nuclear Engineering Division, Politecnico di Milano, Milano, Italy
| | - M Mariani
- Department of Energy, Nuclear Engineering Division, Politecnico di Milano, Milano, Italy
| | - E Bombardieri
- Scientific Direction, Humanitas Gavazzeni, Bergamo, Italy
| | - V Vavassori
- U. O. Radiotherapy, Humanitas Gavazzeni, Bergamo, Italy
| | - P Salmoiraghi
- U. O. Medical Physics, Humanitas Gavazzeni, Bergamo, Italy
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Ogilvy A, Collins S, Hilts M, Hare W, Jirasek A. Commissioning of a solid tank design for fan-beam optical CT based 3D radiation dosimetry. Phys Med Biol 2023; 68:175034. [PMID: 37451252 DOI: 10.1088/1361-6560/ace7aa] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Accepted: 07/10/2023] [Indexed: 07/18/2023]
Abstract
Objective.Optical computed tomography (CT) is one of the leading modalities for imaging gel dosimeters used in the verification of complex radiotherapy treatments. In previous work, a novel fan-beam optical CT scanner design was proposed that could significantly reduce the volume of the refractive index baths that are commonly found in optical CT systems. Here, the proposed scanner has been manufactured and commissioned.Approach.Image reconstruction is performed through algebraic reconstruction technique and iterated using the fast iterative shrinkage-thresholding algorithm (FISTA) algorithm. Ray tracing for algebraic reconstruction was performed using an in-house developed ray tracing simulator. A set of Sylgard® 184 phantoms were created to commission spatial resolution, geometric deformity, contrast-to-noise ratio (CNR), and scan settings.Main Results.The scanner is capable of a 0.929 mm-1spatial resolution, observed at 200 iterations, although the spatial resolution is highly dependent on the number of iterations. The geometric distortion, measured by scanning a needle phantom with the prototype scanner as well as a conventional x-ray CT was found to be within <0.25 mm. The CNR was found to peak between 65 and 190 occurring between 50 and 100 iterations and was highly dependent on the region chosen for background noise calculation. The proposed scanner is capable of scanning and reading out slices in less than 1 min per slice.Significance.This work displays the viability of a fan-beam optical CT scanner with minimal index matching using ray-traced algebraic reconstruction.
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Affiliation(s)
- A Ogilvy
- Department of Physics, University of British Columbia-Okanagan campus, Kelowna BC V1V 1V7, Canada
| | - S Collins
- Department of Physics, University of British Columbia-Okanagan campus, Kelowna BC V1V 1V7, Canada
| | - M Hilts
- Department of Physics, University of British Columbia-Okanagan campus, Kelowna BC V1V 1V7, Canada
- Medical Physics, BC Cancer-Kelowna, Kelowna BC V1Y 5L3, Canada
| | - W Hare
- Department of Mathematics, University of British Columbia-Okanagan campus, Kelowna BC V1V 1V7, Canada
| | - A Jirasek
- Department of Physics, University of British Columbia-Okanagan campus, Kelowna BC V1V 1V7, Canada
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De Deene Y. Radiation Dosimetry by Use of Radiosensitive Hydrogels and Polymers: Mechanisms, State-of-the-Art and Perspective from 3D to 4D. Gels 2022; 8:gels8090599. [PMID: 36135311 PMCID: PMC9498652 DOI: 10.3390/gels8090599] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 09/07/2022] [Accepted: 09/10/2022] [Indexed: 12/22/2022] Open
Abstract
Gel dosimetry was developed in the 1990s in response to a growing need for methods to validate the radiation dose distribution delivered to cancer patients receiving high-precision radiotherapy. Three different classes of gel dosimeters were developed and extensively studied. The first class of gel dosimeters is the Fricke gel dosimeters, which consist of a hydrogel with dissolved ferrous ions that oxidize upon exposure to ionizing radiation. The oxidation results in a change in the nuclear magnetic resonance (NMR) relaxation, which makes it possible to read out Fricke gel dosimeters by use of quantitative magnetic resonance imaging (MRI). The radiation-induced oxidation in Fricke gel dosimeters can also be visualized by adding an indicator such as xylenol orange. The second class of gel dosimeters is the radiochromic gel dosimeters, which also exhibit a color change upon irradiation but do not use a metal ion. These radiochromic gel dosimeters do not demonstrate a significant radiation-induced change in NMR properties. The third class is the polymer gel dosimeters, which contain vinyl monomers that polymerize upon irradiation. Polymer gel dosimeters are predominantly read out by quantitative MRI or X-ray CT. The accuracy of the dosimeters depends on both the physico-chemical properties of the gel dosimeters and on the readout technique. Many different gel formulations have been proposed and discussed in the scientific literature in the last three decades, and scanning methods have been optimized to achieve an acceptable accuracy for clinical dosimetry. More recently, with the introduction of the MR-Linac, which combines an MRI-scanner and a clinical linear accelerator in one, it was shown possible to acquire dose maps during radiation, but new challenges arise.
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Affiliation(s)
- Yves De Deene
- Liverpool & Macarthur Cancer Therapy Centres, Liverpool, NSW 1871, Australia; or
- Ingham Institute, Liverpool, NSW 2170, Australia
- School of Science, Western Sydney University, Penrith, NSW 2751, Australia
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Mohyedin MZ, Zin HM, Hashim S, Bradley DA, Aldawood S, Alkhorayef M, Sulieman A, Abdul Rahman AT. 2D and 3D dose analysis of PRESAGE® dosimeter using a prototype 3DmicroHD-OCT imaging system. Radiat Phys Chem Oxf Engl 1993 2022. [DOI: 10.1016/j.radphyschem.2022.110312] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Bleuse O, Gschwind R, Bailly Y, Laurent K, Bártová H, Pilařová K, Spěváček V, Makovicka L. 3D Dosimetry based on a new optical approach for dosimetry gels: Use of the polarisation ratio of the scattering light. ACTA ACUST UNITED AC 2017. [DOI: 10.1088/1742-6596/847/1/012010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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7
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Dose verification of volumetric modulation arc therapy by using a NIPAM gel dosimeter combined with a parallel-beam optical computed tomography scanner. J Radioanal Nucl Chem 2017. [DOI: 10.1007/s10967-016-5161-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Du Y, Wang X, Xiang X, Wei Z. Evaluation of hybrid SART + OS + TV iterative reconstruction algorithm for optical-CT gel dosimeter imaging. Phys Med Biol 2016; 61:8425-8439. [PMID: 27845916 DOI: 10.1088/0031-9155/61/24/8425] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Optical computed tomography (optical-CT) is a high-resolution, fast, and easily accessible readout modality for gel dosimeters. This paper evaluates a hybrid iterative image reconstruction algorithm for optical-CT gel dosimeter imaging, namely, the simultaneous algebraic reconstruction technique (SART) integrated with ordered subsets (OS) iteration and total variation (TV) minimization regularization. The mathematical theory and implementation workflow of the algorithm are detailed. Experiments on two different optical-CT scanners were performed for cross-platform validation. For algorithm evaluation, the iterative convergence is first shown, and peak-to-noise-ratio (PNR) and contrast-to-noise ratio (CNR) results are given with the cone-beam filtered backprojection (FDK) algorithm and the FDK results followed by median filtering (mFDK) as reference. The effect on spatial gradients and reconstruction artefacts is also investigated. The PNR curve illustrates that the results of SART + OS + TV finally converges to that of FDK but with less noise, which implies that the dose-OD calibration method for FDK is also applicable to the proposed algorithm. The CNR in selected regions-of-interest (ROIs) of SART + OS + TV results is almost double that of FDK and 50% higher than that of mFDK. The artefacts in SART + OS + TV results are still visible, but have been much suppressed with little spatial gradient loss. Based on the assessment, we can conclude that this hybrid SART + OS + TV algorithm outperforms both FDK and mFDK in denoising, preserving spatial dose gradients and reducing artefacts, and its effectiveness and efficiency are platform independent.
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Affiliation(s)
- Yi Du
- Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, People's Republic of China
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9
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Development of a 3D optical scanner for evaluating patient-specific dose distributions. Phys Med 2015; 31:553-9. [DOI: 10.1016/j.ejmp.2015.05.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 05/11/2015] [Accepted: 05/13/2015] [Indexed: 11/17/2022] Open
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10
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Role of gel dosimeters in boron neutron capture therapy. Appl Radiat Isot 2015; 103:72-81. [PMID: 26070173 DOI: 10.1016/j.apradiso.2015.05.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 02/10/2015] [Accepted: 05/26/2015] [Indexed: 12/27/2022]
Abstract
Gel dosimeters have acquired a unique status in radiotherapy, especially with the advent of the new techniques in which there is a need for three-dimensional dose measurement with high spatial resolution. One of the techniques in which the use of gel dosimeters has drawn the attention of the researchers is the boron neutron capture therapy. Exploring the history of gel dosimeters, this paper sets out to study their role in the boron neutron capture therapy dosimetric process.
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11
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Doran S, Gorjiara T, Kacperek A, Adamovics J, Kuncic Z, Baldock C. Issues involved in the quantitative 3D imaging of proton doses using optical CT and chemical dosimeters. Phys Med Biol 2015; 60:709-26. [PMID: 25555069 PMCID: PMC5390951 DOI: 10.1088/0031-9155/60/2/709] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Revised: 10/17/2014] [Accepted: 10/29/2014] [Indexed: 11/12/2022]
Abstract
Dosimetry of proton beams using 3D imaging of chemical dosimeters is complicated by a variation with proton linear energy transfer (LET) of the dose-response (the so-called 'quenching effect'). Simple theoretical arguments lead to the conclusion that the total absorbed dose from multiple irradiations with different LETs cannot be uniquely determined from post-irradiation imaging measurements on the dosimeter. Thus, a direct inversion of the imaging data is not possible and the proposition is made to use a forward model based on appropriate output from a planning system to predict the 3D response of the dosimeter. In addition to the quenching effect, it is well known that chemical dosimeters have a non-linear response at high doses. To the best of our knowledge it has not yet been determined how this phenomenon is affected by LET. The implications for dosimetry of a number of potential scenarios are examined.Dosimeter response as a function of depth (and hence LET) was measured for four samples of the radiochromic plastic PRESAGE(®), using an optical computed tomography readout and entrance doses of 2.0 Gy, 4.0 Gy, 7.8 Gy and 14.7 Gy, respectively. The dosimeter response was separated into two components, a single-exponential low-LET response and a LET-dependent quenching. For the particular formulation of PRESAGE(®) used, deviations from linearity of the dosimeter response became significant for doses above approximately 16 Gy. In a second experiment, three samples were each irradiated with two separate beams of 4 Gy in various different configurations. On the basis of the previous characterizations, two different models were tested for the calculation of the combined quenching effect from two contributions with different LETs. It was concluded that a linear superposition model with separate calculation of the quenching for each irradiation did not match the measured result where two beams overlapped. A second model, which used the concept of an 'effective dose' matched the experimental results more closely. An attempt was made to measure directly the quench function for two proton beams as a function of all four variables of interest (two physical doses and two LET values). However, this approach was not successful because of limitations in the response of the scanner.
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Affiliation(s)
- Simon Doran
- CRUK Cancer Imaging Centre, Institute of Cancer Research, London, UK
- Department of Physics, University of Surrey, Guildford, Surrey, UK
| | - Tina Gorjiara
- Royal Prince Alfred Hospital, Camperdown, NSW 2050, Australia
| | | | - John Adamovics
- Department of Chemistry and Biology, Rider University, Lawrenceville, NJ 08648, USA
| | - Zdenka Kuncic
- Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006, Australia
| | - Clive Baldock
- Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006, Australia
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13
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Chen L, Kumar S, Kelly D, Andrews N, Dallman MJ, French PMW, McGinty J. Remote focal scanning optical projection tomography with an electrically tunable lens. BIOMEDICAL OPTICS EXPRESS 2014; 5:3367-75. [PMID: 25360356 PMCID: PMC4206308 DOI: 10.1364/boe.5.003367] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Revised: 07/08/2014] [Accepted: 07/23/2014] [Indexed: 05/04/2023]
Abstract
We describe a remote focal scanning technique for optical projection tomography (OPT) implemented with an electrically tunable lens (ETL) that removes the need to scan the specimen or objective lens. Using a 4× objective lens the average spatial resolution is improved by ∼46% and the light collection efficiency by a factor of ∼6.76, thereby enabling increased acquisition speed and reduced light dose. This convenient implementation is particularly appropriate for lower magnifications and larger sample diameters where axial objective scanning would encounter problems with speed and stability.
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Affiliation(s)
- Lingling Chen
- Photonics Group, Department of Physics, Imperial College London, SW7 2AZ,
UK
| | - Sunil Kumar
- Photonics Group, Department of Physics, Imperial College London, SW7 2AZ,
UK
| | - Douglas Kelly
- Institute for Chemical Biology, Department of Chemistry, Imperial College London, SW7 2AZ,
UK
| | - Natalie Andrews
- Institute for Chemical Biology, Department of Chemistry, Imperial College London, SW7 2AZ,
UK
| | - Margaret J. Dallman
- Division of Cell and Molecular Biology, Department of Life Sciences, Imperial College London, SW7 2AZ,
UK
- Centre for Integrative Systems Biology, Department of Life Sciences, Imperial College London, SW7 2AZ,
UK
| | - Paul M. W. French
- Photonics Group, Department of Physics, Imperial College London, SW7 2AZ,
UK
| | - James McGinty
- Photonics Group, Department of Physics, Imperial College London, SW7 2AZ,
UK
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14
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Qian X, Adamovics J, Wuu CS. Performance of an improved first generation optical CT scanner for 3D dosimetry. Phys Med Biol 2013; 58:N321-31. [PMID: 24262134 DOI: 10.1088/0031-9155/58/24/n321] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Performance analysis of a modified 3D dosimetry optical scanner based on the first generation optical CT scanner OCTOPUS is presented. The system consists of PRESAGE dosimeters, the modified 3D scanner, and a new developed in-house user control panel written in Labview program which provides more flexibility to optimize mechanical control and data acquisition technique. The total scanning time has been significantly reduced from initial 8 h to ∼2 h by using the modified scanner. The functional performance of the modified scanner has been evaluated in terms of the mechanical integrity uncertainty of the data acquisition process. Optical density distribution comparison between the modified scanner, OCTOPUS and the treatment plan system has been studied. It has been demonstrated that the agreement between the modified scanner and treatment plans is comparable with that between the OCTOPUS and treatment plans.
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Affiliation(s)
- Xin Qian
- Department of Radiation Oncology, Columbia University, New York, NY, USA
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15
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Palmer AL, Di Pietro P, Alobaidli S, Issa F, Doran S, Bradley D, Nisbet A. Comparison of methods for the measurement of radiation dose distributions in high dose rate (HDR) brachytherapy: Ge-doped optical fiber, EBT3 Gafchromic film, and PRESAGE® radiochromic plastic. Med Phys 2013; 40:061707. [PMID: 23718586 DOI: 10.1118/1.4805100] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
PURPOSE Dose distribution measurement in clinical high dose rate (HDR) brachytherapy is challenging, because of the high dose gradients, large dose variations, and small scale, but it is essential to verify accurate treatment planning and treatment equipment performance. The authors compare and evaluate three dosimetry systems for potential use in brachytherapy dose distribution measurement: Ge-doped optical fibers, EBT3 Gafchromic film with multichannel analysis, and the radiochromic material PRESAGE(®) with optical-CT readout. METHODS Ge-doped SiO2 fibers with 6 μm active core and 5.0 mm length were sensitivity-batched and their thermoluminescent properties used via conventional heating and annealing cycles. EBT3 Gafchromic film of 30 μm active thickness was calibrated in three color channels using a nominal 6 MV linear accelerator. A 48-bit transmission scanner and advanced multichannel analysis method were utilized to derive dose measurements. Samples of the solid radiochromic polymer PRESAGE(®), 60 mm diameter and 100 mm height, were analyzed with a parallel beam optical CT scanner. Each dosimetry system was used to measure the dose as a function of radial distance from a Co-60 HDR source, with results compared to Monte Carlo TG-43 model data. Each system was then used to measure the dose distribution along one or more lines through typical clinical dose distributions for cervix brachytherapy, with results compared to treatment planning system (TPS) calculations. Purpose-designed test objects constructed of Solid Water and held within a full-scatter water tank were utilized. RESULTS All three dosimetry systems reproduced the general shape of the isolated source radial dose function and the TPS dose distribution. However, the dynamic range of EBT3 exceeded those of doped optical fibers and PRESAGE(®), and the latter two suffered from unacceptable noise and artifact. For the experimental conditions used in this study, the useful range from an isolated HDR source was 5-40 mm for fibers, 3-50 mm for EBT3, and 4-21 mm for PRESAGE(®). Fibers demonstrated some over-response at very low dose levels, suffered from volume averaging effects in the dose distribution measurement, and exhibited up to 9% repeatability variation over three repeated measurements. EBT3 demonstrated excellent agreement with Monte Carlo and TPS dose distributions, with up to 3% repeatability over three measurements. PRESAGE(®) gave promising results, being the only true 3D dosimeter, but artifacts and noise were apparent. CONCLUSIONS The comparative response of three emerging dosimetry systems for clinical brachytherapy dose distribution measurement has been investigated. Ge-doped optical fibers have excellent spatial resolution for single-direction measurement but are currently too large for complex dose distribution assessment. The use of PRESAGE(®) with optical-CT readout gave promising results in the measurement of true 3D dose distributions but further development work is required to reduce noise and improve dynamic range for brachytherapy dose distribution measurements. EBT3 Gafchromic film with multichannel analysis demonstrated accurate and reproducible measurement of dose distributions in HDR brachytherapy. Calibrated dose measurements were possible with agreement within 1.5% of TPS dose calculations. The suitability of EBT3 as a dosimeter for 2D quality control or commissioning work has been demonstrated.
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Affiliation(s)
- A L Palmer
- Department of Physics, Faculty of Engineering and Physical Science, University of Surrey, Surrey GU2 7JP, United Kingdom.
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16
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Chen L, Andrews N, Kumar S, Frankel P, McGinty J, French PMW. Simultaneous angular multiplexing optical projection tomography at shifted focal planes. OPTICS LETTERS 2013; 38:851-3. [PMID: 23503237 DOI: 10.1364/ol.38.000851] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
We describe an angular multiplexing technique for optical projection tomography that improves resolution, signal-to-noise ratio, and imaging speed by ameliorating the trade-off between spatial resolution and depth of field and improving the light collection efficiency. Here we demonstrate that imaging at two orthogonal angular projections simultaneously, focused on shifted planes in the sample, improves the average spatial resolution by ~20% and the light collection efficiency by a factor of ~4, thereby enabling increased acquisition speed and reduced light dose.
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Affiliation(s)
- Lingling Chen
- Photonics Group, Department of Physics, Imperial College London, London, UK.
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17
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Chang YJ, Hsieh BT. Effect of composition interactions on the dose response of an N-isopropylacrylamide gel dosimeter. PLoS One 2012; 7:e44905. [PMID: 23077487 PMCID: PMC3470576 DOI: 10.1371/journal.pone.0044905] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Accepted: 08/09/2012] [Indexed: 11/19/2022] Open
Abstract
In this study, a two-level full factorial design was used to identify the effects of the interactions between compositions in an N-isopropylacrylamide (NIPAM) gel dosimeter involving the following variables: (A) gelatin, (B) NIPAM, (C) the crosslinker N, N′-methylene-bis-acrylamide (Bis), and (D) the antioxidant tetrakis (hydroxymethyl) phosphonium chloride (THPC). The dose range was from 0 Gy to 5 Gy. Optical computed tomography was used to scan the polymer gel dosimeter. Each component was set to two levels for all four variables, including (A) 4% and 6%, (B) 4% and 6%, (C) 2% and 4%, as well as (D) 5 and 15 mM. Response surface methodology and a central composite design were adopted for the quantitative investigation of the respective interaction effects on the dose response curve of the gel. The results showed that the contributions of the interaction effects, i.e., AB (6.22%), AC (8.38%), AD (7.74%), BC (9.44%), ABC (18.24%), BCD (12.66%), and ABCD (13.4%), were greater than those of the four main effects, accounting for over 76.08% of the total variability. These results also indicated that the NIPAM gel recipe with the highest sensitivity was at 40%C (mass fraction of Bis).
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Affiliation(s)
- Yuan-Jen Chang
- Department of Management Information Systems, Central Taiwan University of Science and Technology, Taichung, Taiwan, Republic of China.
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Cheng HW, Ho CJ, Lee CC, Tu SJ, Shih BY, Chao TC. Development of a novel optical CT employing a laser to create a collimated line-source with a flat-top intensity distribution. RADIAT MEAS 2011. [DOI: 10.1016/j.radmeas.2011.05.032] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Olding T, Holmes O, Dejean P, McAuley KB, Nkongchu K, Santyr G, Schreiner LJ. Small field dose delivery evaluations using cone beam optical computed tomography-based polymer gel dosimetry. J Med Phys 2011; 36:3-14. [PMID: 21430853 PMCID: PMC3048952 DOI: 10.4103/0971-6203.75466] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2010] [Revised: 08/07/2010] [Accepted: 11/05/2010] [Indexed: 01/05/2023] Open
Abstract
This paper explores the combination of cone beam optical computed tomography with an N-isopropylacrylamide (NIPAM)-based polymer gel dosimeter for three-dimensional dose imaging of small field deliveries. Initial investigations indicate that cone beam optical imaging of polymer gels is complicated by scattered stray light perturbation. This can lead to significant dosimetry failures in comparison to dose readout by magnetic resonance imaging (MRI). For example, only 60% of the voxels from an optical CT dose readout of a 1 l dosimeter passed a two-dimensional Low's gamma test (at a 3%, 3 mm criteria, relative to a treatment plan for a well-characterized pencil beam delivery). When the same dosimeter was probed by MRI, a 93% pass rate was observed. The optical dose measurement was improved after modifications to the dosimeter preparation, matching its performance with the imaging capabilities of the scanner. With the new dosimeter preparation, 99.7% of the optical CT voxels passed a Low's gamma test at the 3%, 3 mm criteria and 92.7% at a 2%, 2 mm criteria. The fitted interjar dose responses of a small sample set of modified dosimeters prepared (a) from the same gel batch and (b) from different gel batches prepared on the same day were found to be in agreement to within 3.6% and 3.8%, respectively, over the full dose range. Without drawing any statistical conclusions, this experiment gives a preliminary indication that intrabatch or interbatch NIPAM dosimeters prepared on the same day should be suitable for dose sensitivity calibration.
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Affiliation(s)
- Timothy Olding
- Department of Physics, Queen's University, Kingston, Ontario, Canada
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Thomas A, Newton J, Oldham M. A method to correct for stray light in telecentric optical-CT imaging of radiochromic dosimeters. Phys Med Biol 2011; 56:4433-51. [PMID: 21719946 DOI: 10.1088/0031-9155/56/14/013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Radiochromic plastic and gel materials have recently emerged which can yield 3D dose information over clinical volumes in high resolution. These dosimeters can provide a much more comprehensive verification of complex radiation therapy treatments than can be achieved by conventional planar and point dosimeters. To achieve full clinical potential, these dosimeters require a fast and accurate read-out technology. Broad-beam optical-computed tomography (optical-CT) systems have shown promise, but can be sensitive to stray light artifacts originating in the imaging chain. In this work we present and evaluate a method to correct for stray light artifacts by deconvolving a measured, spatially invariant, point spread function (PSF). The correction was developed for the DLOS (Duke large field-of-view optical-CT scanner) in conjunction with radiochromic PRESAGE® dosimeters. The PSF was constructed from a series of acquisitions of projection images of various sized apertures placed in the optical imaging chain. Images were acquired with a range of exposure times, and for a range of aperture sizes (0.2-11 mm). The PSF is investigated under a variety of conditions, and found to be robust and spatially invariant, key factors enabling the viability of the deconvolution approach. The spatial invariance and robustness of the PSF are facilitated by telecentric imaging, which produces a collimated light beam and removes stray light originating upstream of the imaging lens. The telecentric capability of the DLOS therefore represents a significant advantage, both in keeping stray light levels to a minimum and enabling viability of an accurate PSF deconvolution method to correct for the residual. The performance of the correction method was evaluated on projection images containing known optical-density variations, and also on known 3D dose distributions. The method is shown to accurately account for stray light on small field dosimetry with corrections up to 3% in magnitude shown here although corrections of >10% have been observed in extreme cases. The dominant source of stray light was found to be within the imaging lens. Correcting for stray light extended the dynamic range of the system from ∼30 to ∼60 dB. The correction should be used when measurements need to be accurate within 3%.
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Abdul Rahman AT, Bräuer-Krisch E, Brochard T, Adamovics J, Clowes SK, Bradley D, Doran SJ. Sophisticated test objects for the quality assurance of optical computed tomography scanners. Phys Med Biol 2011; 56:4177-99. [DOI: 10.1088/0031-9155/56/14/001] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Thomas A, Pierquet M, Jordan K, Oldham M. A method to correct for spectral artifacts in optical-CT dosimetry. Phys Med Biol 2011; 56:3403-16. [PMID: 21572184 DOI: 10.1088/0031-9155/56/11/014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The recent emergence of radiochromic dosimeters with low inherent light-scattering presents the possibility of fast 3D dosimetry using broad-beam optical computed tomography (optical-CT). Current broad beam scanners typically employ either a single or a planar array of light-emitting diodes (LED) for the light source. The spectrum of light from LED sources is polychromatic and this, in combination with the non-uniform spectral absorption of the dosimeter, can introduce spectral artifacts arising from preferential absorption of photons at the peak absorption wavelengths in the dosimeter. Spectral artifacts can lead to large errors in the reconstructed attenuation coefficients, and hence dose measurement. This work presents an analytic method for correcting for spectral artifacts which can be applied if the spectral characteristics of the light source, absorbing dosimeter, and imaging detector are known or can be measured. The method is implemented here for a PRESAGE® dosimeter scanned with the DLOS telecentric scanner (Duke Large field-of-view Optical-CT Scanner). Emission and absorption profiles were measured with a commercial spectrometer and spectrophotometer, respectively. Simulations are presented that show spectral changes can introduce errors of 8% for moderately attenuating samples where spectral artifacts are less pronounced. The correction is evaluated by application to a 16 cm diameter PRESAGE® cylindrical dosimeter irradiated along the axis with two partially overlapping 6 × 6 cm fields of different doses. The resulting stepped dose distribution facilitates evaluation of the correction as each step had different spectral contributions. The spectral artifact correction was found to accurately correct the reconstructed coefficients to within ∼1.5%, improved from ∼7.5%, for normalized dose distributions. In conclusion, for situations where spectral artifacts cannot be removed by physical filters, the method shown here is an effective correction. Physical filters may be less viable if they introduce strong sensitivity to Schlieren bands in the dosimeters.
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Olding T, Schreiner LJ. Cone-beam optical computed tomography for gel dosimetry II: imaging protocols. Phys Med Biol 2011; 56:1259-79. [DOI: 10.1088/0031-9155/56/5/003] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Papadakis AE, Maris TG, Zacharakis G, Papoutsaki V, Varveris C, Ripoll J, Damilakis J. Technical Note: A fast laser-based optical-CT scanner for three-dimensional radiation dosimetry. Med Phys 2011; 38:830-5. [DOI: 10.1118/1.3538924] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Newton JR, Thomas A, Appleby A, Marsden C, Christman EA, Wolodzko JG, Oldham M. Preliminary Investigation of the Dosimetric Properties of 'RadGel'. ACTA ACUST UNITED AC 2010; 250:49-53. [PMID: 21617743 DOI: 10.1088/1742-6596/250/1/012011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A preliminary investigation into the efficacy of a new 3D dosimetry material, RadGel™, for verification of radiation therapy dose distributions is presented. Small volumes of RadGel™ were found to exhibit a linear, reproducible response to dose. A gradual increase in optical-density (OD) with time was observed, suggesting scanning should be completed within 18 hours to keep a linear correlation of R(2) > 0.99. A larger 10 cm diameter volume of RadGel™ was irradiated with a rotationally symmetric "spoke" plan designed to rigorously evaluate scanner/dosimeter combined performance. The dosimeter was imaged with the Duke Mid-sized Optical-CT Scanner (DMOS). Promising OD and corresponding dose maps were obtained. Edge artefacts were observed and are suspected to be exacerbated by the particular container used in this early study. Further studies will evaluate new containers and methods for refractive matching at the gel-container-fluid interface.
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Newton J, Thomas A, Ibbott G, Oldham M. Preliminary commissioning investigations with the DMOS-RPC optical-CT Scanner. ACTA ACUST UNITED AC 2010; 250:12078. [PMID: 21218171 DOI: 10.1088/1742-6596/250/1/012078] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
A midsized broad beam Optical-CT scanner is being developed for collaborative research between Duke and the Radiological Physics Center (RPC). The Duke Midsized Optical-CT Scanner (DMOS-RPC) is designed to be compatible with several of the RPC phantoms, including the head and neck, stereotactic SRS, and lung phantoms. Preliminary data investigating the basic performance of the scanner is described. Two 10 cm PRESAGE cylinders were irradiated with simple test plans. Projections of ~80 μm resolution of each dosimeter were collected at 1 degree intervals over a full 360 degrees both before and after irradiation. 3 dimensional reconstructions of attenuation coefficients throughout the dosimeter were computed with 1 mm(3) resolution. Scans were normalized to the calculated dose distribution and a 3D comparison was made with a commissioned treatment planning system. Initial results indicate DMOS-RPC can produce accurate relative dose distributions with high spatial resolution (up to 1 mm(3) in 3D) in less than 30 minutes (acquisition and reconstruction). A maximum dose of ~3.6Gy was delivered in these tests, and observed noise was ~2% for 1 mm(3) reconstructions. Good agreement is observed with the planning system in these simple distributions, indicating promising potential for this scanner.
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Affiliation(s)
- J Newton
- Dept. of Radiation Oncology, Duke University Medical Center, Durham, NC, USA
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Papadakis AE, Zacharakis G, Maris TG, Ripoll J, Damilakis J. A new optical-CT apparatus for 3-D radiotherapy dosimetry: is free space scanning feasible? IEEE TRANSACTIONS ON MEDICAL IMAGING 2010; 29:1204-1212. [PMID: 20304723 DOI: 10.1109/tmi.2010.2044800] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
In this paper, we present a new optical computed tomography (Optical-CT) scanner for the verification of the radiation dose schemes delivered in modern radiotherapy applications. The optical-CT scanner is capable of providing rapid relative 3-D dosimetry with high spatial resolution with the use of normoxic N-Vinylpyrrolidone based polymer gel dosimeter. The scanner employs a diffuse uncollimated light illumination beam, a computer controlled motorized rotation stage and a charge-coupled device (CCD) camera. Various test experiments were performed to determine the performance characteristics of the optical-CT apparatus. Attenuation coefficient (micro) versus dose calibration data were generated from two calibration experiments using gel containers of two different diameters. All irradiations were performed using a 6 MV linear accelerator. A comparison of the reconstructed images between optical-CT scans using refractive index (RI) matching fluid and corresponding scans performed in free space was demonstrated. The dose readout of a test irradiation model was found to be in good agreement with independent readout performed by MR imaging. The findings presented in this study suggest that polymer dosimeters combined with the new optical-CT scanner constitute a potentially feasible method capable of measuring complex 3-D dose distributions with high resolution and in a wide dose range.
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MESH Headings
- Algorithms
- Gels
- Image Processing, Computer-Assisted/instrumentation
- Imaging, Three-Dimensional/instrumentation
- Imaging, Three-Dimensional/methods
- Phantoms, Imaging
- Radiometry/instrumentation
- Radiometry/methods
- Radiotherapy Dosage
- Radiotherapy Planning, Computer-Assisted/instrumentation
- Radiotherapy Planning, Computer-Assisted/methods
- Tomography, Optical/instrumentation
- Tomography, Optical/methods
- Tomography, X-Ray Computed/instrumentation
- Tomography, X-Ray Computed/methods
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Affiliation(s)
- Antonios E Papadakis
- Department of Medical Physics, University Hospital of Heraklion, 71110 Crete, Greece.
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29
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Olding T, Holmes O, Schreiner LJ. Cone beam optical computed tomography for gel dosimetry I: scanner characterization. Phys Med Biol 2010; 55:2819-40. [DOI: 10.1088/0031-9155/55/10/003] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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30
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Brady SL, Brown WE, Clift CG, Yoo S, Oldham M. Investigation into the feasibility of using PRESAGE/optical-CT dosimetry for the verification of gating treatments. Phys Med Biol 2010; 55:2187-201. [PMID: 20348606 PMCID: PMC3018756 DOI: 10.1088/0031-9155/55/8/005] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
This work presents an investigation into the use of PRESAGE dosimeters with an optical-CT scanner as a 3D dosimetry system for quantitative verification of respiratory-gated treatments. The CIRS dynamic thorax phantom was modified to incorporate a moving PRESAGE dosimeter-simulating respiration motion in the lungs. A simple AP/PA lung treatment plan was delivered three times to the phantom containing a different but geometrically identical PRESAGE insert each time. Each delivery represented a treatment scenario: static, motion (free-breathing) and gated. The dose distributions, in the three dosimeters, were digitized by the optical-CT scanner. Improved optical-CT readout yielded an increased signal-to-noise ratio by a factor of 3 and decreased reconstruction artifacts compared with prior work. Independent measurements of dose distributions were obtained in the central plane using EBT film. Dose distributions were normalized to a point corresponding to the 100% isodose region prior to the measurement of dose profiles and gamma maps. These measurements were used to quantify the agreement between measured and ECLIPSE(R) dose distributions. Average gamma pass rates between PRESAGE and EBT were >99% (criteria 3% dose difference and 1.2 mm distance-to-agreement) for all three treatments. Gamma pass rates between PRESAGE and ECLIPSE(R) 3D dose distributions showed excellent agreement for the gated treatment (100% pass rate), but poor for the motion scenario (85% pass rate). This work demonstrates the feasibility of using PRESAGE/optical-CT 3D dosimetry to verify gating-enabled radiation treatments. The capability of the Varian gating system to compensate for motion in this treatment scenario was demonstrated.
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Affiliation(s)
- Samuel L Brady
- Medical Physics Graduate Program, Duke University, Durham, NC 27710, USA
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31
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Baldock C, De Deene Y, Doran S, Ibbott G, Jirasek A, Lepage M, McAuley KB, Oldham M, Schreiner LJ. Polymer gel dosimetry. Phys Med Biol 2010. [PMID: 20150687 DOI: 10.1088/0031‐9155/55/5/r01] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented.
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Affiliation(s)
- C Baldock
- Institute of Medical Physics, School of Physics, University of Sydney, Australia.
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32
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Doran SJ, Brochard T, Adamovics J, Krstajic N, Bräuer-Krisch E. An investigation of the potential of optical computed tomography for imaging of synchrotron-generated x-rays at high spatial resolution. Phys Med Biol 2010; 55:1531-47. [PMID: 20157228 DOI: 10.1088/0031-9155/55/5/018] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
X-ray microbeam radiation therapy (MRT) is a novel form of treatment, currently in its preclinical stage, which uses microplanar x-ray beams from a synchrotron radiation source. It is important to perform accurate dosimetry on these microbeams, but, to date, there has been no accurate enough method available for making 3D dose measurements with isotropic, high spatial resolution to verify the results of Monte Carlo dose simulations. Here, we investigate the potential of optical computed tomography for satisfying these requirements. The construction of a simple optical CT microscopy (optical projection tomography) system from standard commercially available hardware is described. The measurement of optical densities in projection data is shown to be highly linear (r2=0.999). The depth-of-field (DOF) of the imaging system is calculated based on the previous literature and measured experimentally using a commercial DOF target. It is shown that high quality images can be acquired despite the evident lack of telecentricity and despite DOF of the system being much lower than the sample diameter. Possible reasons for this are discussed. Results are presented for a complex irradiation of a 22 mm diameter cylinder of the radiochromic polymer PRESAGE, demonstrating the exquisite 'dose-painting' abilities available in the MRT hutch of beamline ID-17 at the European Synchrotron Radiation Facility. Dose distributions in this initial experiment are equally well resolved on both an optical CT scan and a corresponding transmission image of radiochromic film, down to a line width of 83 microm (6 lp mm(-1)) with an MTF value of 0.40. A group of 33 microm wide lines was poorly resolved on both the optical CT and film images, and this is attributed to an incorrect exposure time calculation, leading to under-delivery of dose. Image artefacts in the optical CT scan are discussed. PRESAGE irradiated using the microbeam facility is proposed as a suitable material for producing phantom samples for quantitative characterization of optical CT microscopy systems.
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Affiliation(s)
- Simon J Doran
- Department of Physics, University of Surrey, Guildford, UK.
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Baldock C, De Deene Y, Doran S, Ibbott G, Jirasek A, Lepage M, McAuley KB, Oldham M, Schreiner LJ. Polymer gel dosimetry. Phys Med Biol 2010; 55:R1-63. [PMID: 20150687 DOI: 10.1088/0031-9155/55/5/r01] [Citation(s) in RCA: 443] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented.
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Affiliation(s)
- C Baldock
- Institute of Medical Physics, School of Physics, University of Sydney, Australia.
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Doran SJ, Stanley SJ, Jenneson PM, Prott E, Adamovics J. RadBall™: A new departure for 3-D dosimetry. ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/164/1/012042] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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36
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Doran SJ. The history and principles of optical computed tomography for scanning 3-D radiation dosimeters: 2008 update. ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/164/1/012020] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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37
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Doran SJ. The history and principles of chemical dosimetry for 3-D radiation fields: Gels, polymers and plastics. Appl Radiat Isot 2009; 67:393-8. [DOI: 10.1016/j.apradiso.2008.06.026] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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38
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Kim E, Bowsher J, Thomas AS, Sakhalkar H, Dewhirst M, Oldham M. Improving the quantitative accuracy of optical-emission computed tomography by incorporating an attenuation correction: application to HIF1 imaging. Phys Med Biol 2008; 53:5371-83. [PMID: 18765891 DOI: 10.1088/0031-9155/53/19/007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Optical computed tomography (optical-CT) and optical-emission computed tomography (optical-ECT) are new techniques for imaging the 3D structure and function (including gene expression) of whole unsectioned tissue samples. This work presents a method of improving the quantitative accuracy of optical-ECT by correcting for the 'self'-attenuation of photons emitted within the sample. The correction is analogous to a method commonly applied in single-photon-emission computed tomography reconstruction. The performance of the correction method was investigated by application to a transparent cylindrical gelatin phantom, containing a known distribution of attenuation (a central ink-doped gelatine core) and a known distribution of fluorescing fibres. Attenuation corrected and uncorrected optical-ECT images were reconstructed on the phantom to enable an evaluation of the effectiveness of the correction. Significant attenuation artefacts were observed in the uncorrected images where the central fibre appeared approximately 24% less intense due to greater attenuation from the surrounding ink-doped gelatin. This artefact was almost completely removed in the attenuation-corrected image, where the central fibre was within approximately 4% of the others. The successful phantom test enabled application of attenuation correction to optical-ECT images of an unsectioned human breast xenograft tumour grown subcutaneously on the hind leg of a nude mouse. This tumour cell line had been genetically labelled (pre-implantation) with fluorescent reporter genes such that all viable tumour cells expressed constitutive red fluorescent protein and hypoxia-inducible factor 1 transcription-produced green fluorescent protein. In addition to the fluorescent reporter labelling of gene expression, the tumour microvasculature was labelled by a light-absorbing vasculature contrast agent delivered in vivo by tail-vein injection. Optical-CT transmission images yielded high-resolution 3D images of the absorbing contrast agent, and revealed highly inhomogeneous vasculature perfusion within the tumour. Optical-ECT emission images yielded high-resolution 3D images of the fluorescent protein distribution in the tumour. Attenuation-uncorrected optical-ECT images showed clear loss of signal in regions of high attenuation, including regions of high perfusion, where attenuation is increased by increased vascular ink stain. Application of attenuation correction showed significant changes in an apparent expression of fluorescent proteins, confirming the importance of the attenuation correction. In conclusion, this work presents the first development and application of an attenuation correction for optical-ECT imaging. The results suggest that successful attenuation correction for optical-ECT is feasible and is essential for quantitatively accurate optical-ECT imaging.
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Affiliation(s)
- E Kim
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC, USA
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39
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Oldham M, Sakhalkar H, Guo P, Adamovics J. An investigation of the accuracy of an IMRT dose distribution using two- and three-dimensional dosimetry techniques. Med Phys 2008; 35:2072-80. [PMID: 18561683 DOI: 10.1118/1.2899995] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Complex dose delivery techniques like intensity-modulated radiation therapy (IMRT) require dose measurement in three dimensions for comprehensive validation. Previously, we demonstrated the feasibility of the "PRESAGE/optical-computed tomography (CT)" system for the three-dimensional verification of simple open beam dose distributions where the planning system was known to be accurate. The present work extends this effort and presents the first application of the PRESAGE/optical-CT system for the verification of a complex IMRT distribution. A highly modulated 11 field IMRT plan was delivered to a cylindrical PRESAGE dosimeter (16 cm in diameter and 11 cm in height), and the dose distribution was readout using a commercial scanning-laser optical-CT scanner. Comparisons were made with independent GAFCHROMIC EBT film measurements, and the calculated dose distribution from a commissioned treatment planning system (ECLIPSE). Isodose plots, dose profiles, gamma maps, and dose-volume histograms were used to evaluate the agreement. The isodose plots and dose profiles from the PRESAGE/optical-CT system were in excellent agreement with both the EBT measurements and the ECLIPSE calculation at all points except within 3 mm of the outer edge of the dosimeter where an edge artifact occurred. Excluding this 3 mm rim, gamma map comparisons show that all three distributions mutually agreed to within a 3% (dose difference) and 3 mm (distance-to-agreement) criteria. A 96% gamma pass ratio was obtained between the PRESAGE and ECLIPSE distributions over the entire volume excluding this rim. In conclusion, for the complex IMRT plan studied, and in the absence of inhomogeneities, the ECLIPSE dose calculation was found to agree with both independent measurements, to within 3%, 3 mm gamma criteria.
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Affiliation(s)
- Mark Oldham
- Radiation Oncology Physics, Duke University Medical Center, Durham, North Carolina 27710, USA.
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40
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Wai P, Adamovics J, Krstajic N, Ismail A, Nisbet A, Doran S. Dosimetry of the microSelectron-HDR Ir-192 source using PRESAGE and optical CT. Appl Radiat Isot 2008; 67:419-22. [PMID: 18684629 DOI: 10.1016/j.apradiso.2008.06.038] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Optical CT, using a solid polyurethane (PRESAGE) radiochromic dosimeter, has been used to evaluate dose distributions produced by the microSelectron-HDR Ir-192 source. The anisotropy functions obtained through optical CT are in good agreement with Monte Carlo and previously published results especially at polar angle above 20 degrees. The results indicated an evident potential for using solid polymer dosimetry as an accurate method for 3-D dosimetry, although refinements to the existing methods are necessary before the technique can be used clinically.
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Affiliation(s)
- P Wai
- Department of Physics, School of Electronics & Physical Sciences, University of Surrey, Guildford, Surrey, UK.
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Al-Nowais S, Doran S, Kacperek A, Krstajic N, Adamovics J, Bradley D. A preliminary analysis of LET effects in the dosimetry of proton beams using PRESAGE and optical CT. Appl Radiat Isot 2008; 67:415-8. [PMID: 18691895 DOI: 10.1016/j.apradiso.2008.06.032] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
PRESAGE is a solid dosimeter based on a clear polyurethane matrix doped with radiochromic components (leuco dyes). On exposure to ionizing radiation a colour change is generated in the dosimeter, and hence an optical absorption or optical density change that can be read out by optical CT. The main focus of present investigations has been to investigate the possible LET dependence of PRESAGE to the dose deposited at the Bragg maxima using proton beam absorbed dose measurements, and the linearity of response of the dosimeter. Proton irradiations were performed using the proton beam facility at the Douglas Cyclotron, Clatterbridge Centre for Oncology (CCO) using a configuration that approximates the one routinely used in treatment of patients with ocular tumours. The samples were irradiated with both monoenergetic and modulated proton beams. Optical tomography measurements were carried out with our in-house CCD-based optical-CT system. Initial results for monoenergetic beams show that in PRESAGE the measured ratio of the Bragg peak dose to entrance dose is approximately 2:1 whereas the true value measured at CCO is approximately 5:1. For range-modulated proton beams, the absorbed dose close to the end of the proton range, i.e. at the Bragg peak, is underestimated by approximately 20% compared to the corresponding diode measurement. Further investigations are necessary to understand and quantify the effect of LET on PRESAGE, and to measure the uncertainties related to our optical CT.
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Affiliation(s)
- S Al-Nowais
- Department of Physics, Faculty of Electronics & Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, UK.
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Sakhalkar HS, Oldham M. Fast, high-resolution 3D dosimetry utilizing a novel optical-CT scanner incorporating tertiary telecentric collimation. Med Phys 2008; 35:101-11. [PMID: 18293567 DOI: 10.1118/1.2804616] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
This study introduces a charge coupled device (CCD) area detector based optical-computed tomography (optical-CT) scanner for comprehensive verification of radiation dose distributions recorded in nonscattering radiochromic dosimeters. Defining characteristics include: (i) a very fast scanning time of approximately 5 min to acquire a complete three-dimensional (3D) dataset, (ii) improved image formation through the use of custom telecentric optics, which ensures accurate projection images and minimizes artifacts from scattered and stray-light sources, and (iii) high resolution (potentially 50 microm) isotropic 3D dose readout. The performance of the CCD scanner for 3D dose readout was evaluated by comparison with independent 3D readout from the single laser beam OCTOPUS-scanner for the same PRESAGE dosimeters. The OCTOPUS scanner was considered the "gold standard" technique in light of prior studies demonstrating its accuracy. Additional comparisons were made against calculated dose distributions from the ECLIPSE treatment-planning system. Dose readout for the following treatments were investigated: (i) a single rectangular beam irradiation to investigate small field and very steep dose gradient dosimetry away from edge effects, (ii) a 2-field open beam parallel-opposed irradiation to investigate dosimetry along steep dose gradients, and (iii) a 7-field intensity modulated radiation therapy (IMRT) irradiation to investigate dosimetry for complex treatment delivery involving modulation of fluence and for dosimetry along moderate dose gradients. Dose profiles, dose-difference plots, and gamma maps were employed to evaluate quantitative estimates of agreement between independently measured and calculated dose distributions. Results indicated that dose readout from the CCD scanner was in agreement with independent gold-standard readout from the OCTOPUS-scanner as well as the calculated ECLIPSE dose distribution for all treatments, except in regions within a few millimeters of the edge of the dosimeter, where edge artifact is predominant. Agreement of line profiles was observed, even along steep dose gradients. Dose difference plots indicated that the CCD scanner dose readout differed from the OCTOPUS scanner readout and ECLIPSE calculations by approximately 10% along steep dose gradients and by approximately 5% along moderate dose gradients. Gamma maps (3% dose-difference and 3 mm distance-to-agreement acceptance criteria) revealed agreement, except for regions within 5 mm of the edge of the dosimeter where the edge artifact occurs. In summary, the data demonstrate feasibility of using the fast, high-resolution CCD scanner for comprehensive 3D dosimetry in all applications, except where dose readout is required close to the edges of the dosimeter. Further work is ongoing to reduce this artifact.
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Affiliation(s)
- H S Sakhalkar
- Department of Radiation Oncology, Duke University Medical Center, Durham, NC 27710, USA.
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Krstajić N, Doran SJ. Characterization of a parallel-beam CCD optical-CT apparatus for 3D radiation dosimetry. Phys Med Biol 2007; 52:3693-713. [PMID: 17664571 DOI: 10.1088/0031-9155/52/13/003] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
3D measurement of optical attenuation is of interest in a variety of fields of biomedical importance, including spectrophotometry, optical projection tomography (OPT) and analysis of 3D radiation dosimeters. Accurate, precise and economical 3D measurements of optical density (OD) are a crucial step in enabling 3D radiation dosimeters to enter wider use in clinics. Polymer gels and Fricke gels, as well as dosimeters not based around gels, have been characterized for 3D dosimetry over the last two decades. A separate problem is the verification of the best readout method. A number of different imaging modalities (magnetic resonance imaging (MRI), optical CT, x-ray CT and ultrasound) have been suggested for the readout of information from 3D dosimeters. To date only MRI and laser-based optical CT have been characterized in detail. This paper describes some initial steps we have taken in establishing charge coupled device (CCD)-based optical CT as a viable alternative to MRI for readout of 3D radiation dosimeters. The main advantage of CCD-based optical CT over traditional laser-based optical CT is a speed increase of at least an order of magnitude, while the simplicity of its architecture would lend itself to cheaper implementation than both MRI and laser-based optical CT if the camera itself were inexpensive enough. Specifically, we study the following aspects of optical metrology, using high quality test targets: (i) calibration and quality of absorbance measurements and the camera requirements for 3D dosimetry; (ii) the modulation transfer function (MTF) of individual projections; (iii) signal-to-noise ratio (SNR) in the projection and reconstruction domains; (iv) distortion in the projection domain, depth-of-field (DOF) and telecentricity. The principal results for our current apparatus are as follows: (i) SNR of optical absorbance in projections is better than 120:1 for uniform phantoms in absorbance range 0.3 to 1.6 (and better than 200:1 for absorbances 1.0 to 3.5 with the test target and a novel absorbance range extension method), (ii) the spatial resolution is shown to be at worst 0.5 mm (and often better than this) with an associated DOF of 8 cm, (iii) the SNR of uniform phantoms in reconstruction domain is above 80:1 (one standard deviation) over an absorbance dynamic range of 0.3 to 1.6, (iv) the apparatus is telecentric and without distortion. Finally, a sample scan and reconstruction of a scan of a PRESAGE dosimeter are shown, demonstrating the capabilities of the apparatus.
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Affiliation(s)
- Nikola Krstajić
- Department of Physics, University of Surrey, Guildford, Surrey, GU2 7XH, UK.
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Abstract
Optical computed tomography (optical-CT) of 3D radiation dosimeters is a promising avenue for delivering an economic and reliable quality control of radiotherapy treatments such as intensity modulated radiotherapy, brachytherapy and stereotactic radiosurgery. The main problems in transferring 3D dosimeters to clinical setting have been in (1) the complexity of manufacture and behaviour of 3D dosimeters and (2) time-consuming readout and analysis of 3D dosimeters. This paper addresses the readout problem by showing that fast (20 min tomography scan), precise (projection absorbance signal-to-noise ratio is greater than 100:1 across the absorbance range 0.2 to 1.5) and accurate (good linearity in the calibration curve) measurements are possible using a novel method of optically scanning a laser beam across the 3D dosimeter.
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Affiliation(s)
- Nikola Krstajić
- Department of Physics, University of Surrey, Guildford, Surrey, GU2 7XH, UK.
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Walls JR, Sled JG, Sharpe J, Henkelman RM. Resolution improvement in emission optical projection tomography. Phys Med Biol 2007; 52:2775-90. [PMID: 17473351 DOI: 10.1088/0031-9155/52/10/010] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A new imaging technique called emission optical projection tomography (eOPT), essentially an optical version of single-photon emission computed tomography (SPECT), provides molecular specificity, resolution on the order of microns to tens of microns, and large specimen coverage ( approximately 1 cubic centimetre). It is ideally suited to gene expression studies in embryos. Reconstructed eOPT images suffer from blurring that worsens as the distance from the axis of rotation increases. This blur is caused in part by the defocusing of the lens' point-spread function, which increases with object distance from the focal plane. In this paper, we describe a frequency space filter based on the frequency-distance relationship of sinograms to deconvolve the distance-dependent point-spread function and exclude highly defocused data from the eOPT sinograms prior to reconstruction. The method is shown to reduce the volume at half-maximum of the reconstructed point-spread function to approximately 20% the original, and the volume at 10% maximum to approximately 6% the original. As an illustration, the visibility of fine details in the vasculature of a 9.5 day old mouse embryo is dramatically improved.
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Affiliation(s)
- Johnathon R Walls
- Mouse Imaging Centre, Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON M5G 1X8, Canada.
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Abstract
The need for an accurate, practical, low-cost 3D dosimetry system is becoming ever more critical as modern dose delivery techniques increase in complexity and sophistication. A recent report from the Radiological Physics Center (RPC) (1), revealed that 38% of institutions failed the head-and-neck IMRT phantom credentialing test at the first attempt. This was despite generous passing criteria (within 7% dose-difference or 4mm distance-to-agreement) evaluated at a half-dozen points and a single axial plane. The question that arises from this disturbing finding is - what percentage of institutions would have failed if a comprehensive 3D measurement had been feasible, rather than measurements restricted to the central film-plane and TLD points? This question can only be adequately answered by a comprehensive 3D-dosimetry system, which presents a compelling argument for its development as a clinically viable low cost dosimetry solution. Optical-CT dosimetry is perhaps the closest system to providing such a comprehensive solution. In this article, we review the origins and recent developments of optical-CT dosimetry systems. The principle focus is on first generation systems known to have highest accuracy but longer scan times.
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Affiliation(s)
- Mark Oldham
- Radiation Oncology Physics, Duke University Medical Center, Duke University, NC USA
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Doran SJ, Krstajić N. The history and principles of optical computed tomography for scanning 3-D radiation dosimeters. ACTA ACUST UNITED AC 2007. [DOI: 10.1088/1742-6596/56/1/005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Doran S, Al-Nowais S, Krstajić N, Adamovics J, Kacperek A, Brunt J. True-3D scans using PRESAGETMand Optical-CT: A case study in proton therapy. ACTA ACUST UNITED AC 2007. [DOI: 10.1088/1742-6596/56/1/036] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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49
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Krstajić N, Doran SJ. Characterization of a parallel beam CCD optical-CT apparatus for 3D radiation dosimetry. ACTA ACUST UNITED AC 2007. [DOI: 10.1088/1742-6596/56/1/026] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Oldham M, Sakhalkar H, Wang YM, Guo P, Oliver T, Bentley R, Vujaskovic Z, Dewhirst M. Three-dimensional imaging of whole rodent organs using optical computed and emission tomography. JOURNAL OF BIOMEDICAL OPTICS 2007; 12:014009. [PMID: 17343484 DOI: 10.1117/1.2709858] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
We explore the potential of optical computed tomography (optical-CT) and optical emission computed tomography (optical-ECT) in a new area-whole organ imaging. The techniques are implemented on an in-house prototype benchtop system with improved image quality and the capacity to image larger samples (up to 3 cm) than previous systems based on stereo microscopes. Imaging performance tests confirm high geometrical accuracy, accurate relative measurement of linear attenuation coefficients, and the ability to image features at the 50-microm level. Optical labeling of organ microvasculature was achieved using two stains deposited via natural in vivo circulatory processes: a passive absorbing ink-based stain and an active fluorescin FITC-lectin conjugate. The lectin protein binds to the endothelial lining, and FITC fluorescense enables optical-ECT imaging. Three-dimensional (3-D) optical-CT images have been acquired of a normal rat heart and left lung and a mouse right lung showing exquisite detail of the functional vasculature and relative perfusion distribution. Coregistered optical-ECT images were also acquired of the mouse lung and kidney. Histological sections confirmed effective labeling of microvasculature throughout the organs. The advantages of optical-CT and optical-ECT include the potential for a unique combination of high resolution and high contrast and compatibility with a wide variety of optical probes, including gene expression labeling fluorescent reporter proteins.
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Affiliation(s)
- Mark Oldham
- Duke University Medical Center, Department of Radiation Oncology and Biomedical Engineering, Durham, North Carolina 27710, USA.
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