1
|
Huck SM, Fung GSK, Parodi K, Stierstorfer K. On the potential of ROI imaging in x-ray CT - A comparison of novel dynamic beam attenuators with current technology. Med Phys 2021; 48:3479-3499. [PMID: 33838055 DOI: 10.1002/mp.14879] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 03/24/2021] [Accepted: 03/29/2021] [Indexed: 12/30/2022] Open
Abstract
PURPOSE In this work, we explore the potential of region-of-interest (ROI) imaging in x-ray computed tomography (CT). Using two dynamic beam attenuator (DBA) concepts for fluence field modulation (FFM) previously developed, we investigate and evaluate the potential dose savings in comparison with current FFM technology. METHODS ROI imaging is a special application of FFM where the bulk of x-ray radiation is propagated toward a certain anatomical target (ROI), specified by the imaging task, while the surrounding tissue is spared from radiation. We introduce a criterion suitable to quantitatively describe the balance between image quality inside an ROI and total radiation dose with respect to a given ROI imaging task. It accounts for the mean image variance at the ROI and the effective patient dose calculated from Monte Carlo simulations. The criterion is further used to compile task-specific DBA trajectories determining the primary x-ray fluence, and eventually used for comparing different FFM techniques, namely the sheet-based dynamic beam attenuator (sbDBA), the z-aligned sbDBA (z-sbDBA), and an adjustable static operation mode of the z-sbDBA. Furthermore, two static bowtie filters and the influence of tube current modulation (TCM) are included in the comparison. RESULTS Our findings demonstrate by simulations that the presented trajectory optimization method determines reasonable DBA trajectories. The influence of TCM is strongly depending on the imaging task. The narrow bowtie filter allows for dose reductions of about 10% compared to the regular bowtie filter in the considered ROI imaging tasks. The DBAs are shown to realize substantially larger dose reductions. In our cardiac imaging scenario, the DBAs can reduce the effective dose by about 30% (z-sbDBA) or 60% (sbDBA). We can further verify that the noise characteristics are not adversely affected by the DBAs. CONCLUSION Our research demonstrates that ROI imaging using the presented DBA concepts is a promising technique toward a more patient- and task-specific CT imaging requiring lower radiation dose. Both the sbDBA and the z-sbDBA are potential technical solutions for realizing ROI imaging in x-ray CT.
Collapse
Affiliation(s)
- Sascha Manuel Huck
- Siemens Healthcare GmbH, Forchheim, Germany.,Department of Medical Physics, Faculty of Physics, Ludwig-Maximilians-Universität München, Garching, Germany
| | | | - Katia Parodi
- Department of Medical Physics, Faculty of Physics, Ludwig-Maximilians-Universität München, Garching, Germany
| | | |
Collapse
|
2
|
Dickmann J, Rit S, Pankuch M, Johnson RP, Schulte RW, Parodi K, Dedes G, Landry G. An optimization algorithm for dose reduction with fluence‐modulated proton CT. Med Phys 2020; 47:1895-1906. [DOI: 10.1002/mp.14084] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 01/30/2020] [Accepted: 02/05/2020] [Indexed: 01/12/2023] Open
Affiliation(s)
- J. Dickmann
- Department of Medical Physics Faculty of Physics Ludwig‐Maximilians‐Universität München Am Coulombwall 1 85748 Garching b. München Germany
| | - S. Rit
- Univ Lyon INSA‐Lyon Université Claude Bernard Lyon 1 UJM‐Saint Étienne CNRS, Inserm CREATIS UMR 5220 U1206 F‐69373 Lyon France
| | - M. Pankuch
- Northwestern Medicine Chicago Proton Center Warrenville IL 60555 USA
| | - R. P. Johnson
- Department of Physics University of California Santa Cruz Santa Cruz CA 95064 USA
| | - R. W. Schulte
- Division of Biomedical Engineering Sciences Loma Linda University Loma Linda CA 92354 USA
| | - K. Parodi
- Department of Medical Physics Faculty of Physics Ludwig‐Maximilians‐Universität München Am Coulombwall 1 85748 Garching b. München Germany
| | - G. Dedes
- Department of Medical Physics Faculty of Physics Ludwig‐Maximilians‐Universität München Am Coulombwall 1 85748 Garching b. München Germany
| | - G. Landry
- Department of Medical Physics Faculty of Physics Ludwig‐Maximilians‐Universität München Am Coulombwall 1 85748 Garching b. München Germany
- Department of Radiation Oncology University Hospital, LMU Munich 81377 Munich Germany
- German Cancer Consortium (DKTK) 81377 Munich Germany
| |
Collapse
|
3
|
Shen C, Lou Y, Chen L, Zeng T, Ng MK, Zhu L, Jia X. Comparison of three undersampling approaches in computed tomography reconstruction. Quant Imaging Med Surg 2019; 9:1229-1241. [PMID: 31448209 DOI: 10.21037/qims.2019.07.07] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Background Projection data undersampling is an effective approach to reduce X-ray radiation dose in computed tomography (CT). In modern CT technologies, undersampling is also a favorable method to reduce projection data size to facilitate rapid CT scan and imaging. It is an intriguing question that given an undersampling ratio, what is the optimal undersampling approach that enables the best CT image reconstruction. While this is in general a challenging mathematical question, it is the motivation of this paper to compare three types of undersampling operations, which we hope to shed some light to this question. Methods We considered regular view undersampling that acquires X-ray projections at equiangular projection angles, regular ray undersampling that acquires projections at all angles but with X-ray lines blocked within each projection under a periodic pattern, and random ray undersampling that acquires each X-ray line with a certain probability. By representing the undersampling projection operators under the basis of singular vectors of full projection operator, we generated matrix representations of these undersampling operators and numerically perform singular value decomposition (SVD). Singular value spectra and singular vectors were compared. Results For a given undersampling ratio, the random ray undersampling approach preserves the properties of the full projection operator better than the other two approaches. This translates to advantages of reconstructing a CT image at a lower error, which has also been demonstrated in the numerical experiments. Conclusions We compared three undersampling strategies and found that random undersampling preserves the most information and outperforms the other two in terms of reconstruction quality.
Collapse
Affiliation(s)
- Chenyang Shen
- Innovative Technology of Radiotherapy Computations and Hardware (iTORCH) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Yifei Lou
- Department of Mathematical Sciences, University of Texas Dallas, Richardson, TX, USA
| | - Liyuan Chen
- Innovative Technology of Radiotherapy Computations and Hardware (iTORCH) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Tieyong Zeng
- Department of Mathematics, Chinese University of Hong Kong, Hong Kong, China
| | - Michael K Ng
- Department of Mathematics, Hong Kong Baptist University, Hong Kong, China
| | - Lei Zhu
- Department of Modern Physics, School of Physical Sciences, University of Science and Technology of China, Hefei 230026,China
| | - Xun Jia
- Innovative Technology of Radiotherapy Computations and Hardware (iTORCH) Laboratory, Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| |
Collapse
|
4
|
Dickmann J, Wesp P, Rädler M, Rit S, Pankuch M, Johnson RP, Bashkirov V, Schulte RW, Parodi K, Landry G, Dedes G. Prediction of image noise contributions in proton computed tomography and comparison to measurements. ACTA ACUST UNITED AC 2019; 64:145016. [DOI: 10.1088/1361-6560/ab2474] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
5
|
Shunhavanich P, Bennett NR, Hsieh SS, Pelc NJ. Implementation of a piecewise-linear dynamic attenuator. J Med Imaging (Bellingham) 2019. [DOI: 10.1117/1.jmi.6.2.023502] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
| | | | - Scott S. Hsieh
- University of California, Los Angeles, Department of Radiological Sciences, Los Angeles, California
| | - Norbert J. Pelc
- Stanford University, Department of Bioengineering, Stanford, California
| |
Collapse
|
6
|
Rädler M, Landry G, Rit S, Schulte RW, Parodi K, Dedes G. Two-dimensional noise reconstruction in proton computed tomography using distance-driven filtered back-projection of simulated projections. Phys Med Biol 2018; 63:215009. [PMID: 30277469 DOI: 10.1088/1361-6560/aae5c9] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We present a formalism for two-dimensional (2D) noise reconstruction in proton computed tomography (pCT). This is necessary for the application of fluence modulated pCT (FMpCT) since it permits image noise prescription and the corresponding proton fuence optimization. We aimed at extending previously published formalisms to account for the impact of multiple Coulomb scattering (MCS) on projection noise, and the use of filtered back projection (FBP) reconstruction along curved paths with distance driven binning (DDB). 2D noise reconstruction for a beam of protons with parallel initial momentum vectors, and for projections binned both at the rear tracker and with DDB, was established. Monte Carlo (MC) simulations of pCT scans of a water cylinder were employed to generate pCT projections and to calculate their noise for use in 2D noise reconstruction. These were compared to results from an analytical model accounting for MCS for rear tracker binning as well as against the previously published central pixel model which ignores MCS. Image noise reconstructed with the formalism for rear tracker binning and DDB were compared to MC results using annular regions of interest (ROIs). Agreement better than 8% was obtained between the noise of projections calculated with MC simulation and our model. Noise from annular ROIs agreed with our noise reconstructions for rear tracker binning and DDB. The central pixel model ignoring MCS underestimated projection and thus image noise by up to 40% towards the object's edge. The use of DDB decreased the image noise towards the object's edge when compared to rear tracker binning and yielded more uniform noise throughout the image. MCS should not be neglected when predicting image noise for pixels away from the center of an object in a pCT scan due to the increasing influence of the gradient of the object's hull closer to the edges.
Collapse
Affiliation(s)
- Martin Rädler
- Department of Medical Physics, Ludwig-Maximilians-Universität München, 85748 Garching b. München, Germany. Authors contributed equally
| | | | | | | | | | | |
Collapse
|
7
|
Dedes G, Johnson RP, Pankuch M, Detrich N, Pols WMA, Rit S, Schulte RW, Parodi K, Landry G. Experimental fluence‐modulated proton computed tomography by pencil beam scanning. Med Phys 2018; 45:3287-3296. [DOI: 10.1002/mp.12989] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 05/14/2018] [Accepted: 05/14/2018] [Indexed: 01/22/2023] Open
Affiliation(s)
- George Dedes
- Department of Medical Physics Faculty of Physics Ludwig‐Maximilians‐Universität München (LMU Munich) 85748 Garching b. München Germany
| | | | - Mark Pankuch
- Northwestern Medicine Chicago Proton Center Warrenville IL 60555 USA
| | - Nick Detrich
- IBA and Northwestern Medicine Chicago Proton Center Warrenville IL 60555 USA
| | - Willemijn M. A. Pols
- Department of Medical Physics Faculty of Physics Ludwig‐Maximilians‐Universität München (LMU Munich) 85748 Garching b. München Germany
| | - Simon Rit
- Université de Lyon CREATIS CNRS UMR5220 Inserm U1044 INSA‐Lyon Université Lyon 1 F69373 Lyon France
| | - Reinhard W. Schulte
- Division of Radiation Research Loma Linda University Loma Linda CA 92354 USA
| | - Katia Parodi
- Department of Medical Physics Faculty of Physics Ludwig‐Maximilians‐Universität München (LMU Munich) 85748 Garching b. München Germany
| | - Guillaume Landry
- Department of Medical Physics Faculty of Physics Ludwig‐Maximilians‐Universität München (LMU Munich) 85748 Garching b. München Germany
| |
Collapse
|
8
|
Larsen TC, Gopalakrishnan V, Yao J, Nguyen CP, Chen MY, Moss J, Wen H. Optimization of a secondary VOI protocol for lung imaging in a clinical CT scanner. J Appl Clin Med Phys 2018; 19:271-280. [PMID: 29785839 PMCID: PMC6036356 DOI: 10.1002/acm2.12354] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 04/02/2018] [Accepted: 04/10/2018] [Indexed: 11/10/2022] Open
Abstract
We present a solution to meet an unmet clinical need of an in-situ "close look" at a pulmonary nodule or at the margins of a pulmonary cyst revealed by a primary (screening) chest CT while the patient is still in the scanner. We first evaluated options available on current whole-body CT scanners for high resolution screening scans, including ROI reconstruction of the primary scan data and HRCT, but found them to have insufficient SNR in lung tissue or discontinuous slice coverage. Within the capabilities of current clinical CT systems, we opted for the solution of a secondary, volume-of-interest (VOI) protocol where the radiation dose is focused into a short-beam axial scan at the z position of interest, combined with a small-FOV reconstruction at the xy position of interest. The objective of this work was to design a VOI protocol that is optimized for targeted lung imaging in a clinical whole-body CT system. Using a chest phantom containing a lung-mimicking foam insert with a simulated cyst, we identified the appropriate scan mode and optimized both the scan and recon parameters. The VOI protocol yielded 3.2 times the texture amplitude-to-noise ratio in the lung-mimicking foam when compared to the standard chest CT, and 8.4 times the texture difference between the lung mimicking and reference foams. It improved details of the wall of the simulated cyst and better resolution in a line-pair insert. The Effective Dose of the secondary VOI protocol was 42% on average and up to 100% in the worst-case scenario of VOI positioning relative to the standard chest CT. The optimized protocol will be used to obtain detailed CT textures of pulmonary lesions, which are biomarkers for the type and stage of lung diseases.
Collapse
Affiliation(s)
- Thomas C Larsen
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Vissagan Gopalakrishnan
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA.,Rush Medical College, Chicago, IL, USA
| | - Jianhua Yao
- Department of Radiology, Hatfield Clinical Center, National Institutes of Health, Bethesda, MD, USA
| | - Catherine P Nguyen
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Marcus Y Chen
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Joel Moss
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Han Wen
- National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| |
Collapse
|
9
|
Dedes G, De Angelis L, Rit S, Hansen D, Belka C, Bashkirov V, Johnson RP, Coutrakon G, Schubert KE, Schulte RW, Parodi K, Landry G. Application of fluence field modulation to proton computed tomography for proton therapy imaging. ACTA ACUST UNITED AC 2017; 62:6026-6043. [DOI: 10.1088/1361-6560/aa7734] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
10
|
Parsons D, Robar JL. Volume of interest CBCT and tube current modulation for image guidance using dynamic kV collimation. Med Phys 2016; 43:1808. [DOI: 10.1118/1.4943799] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
|