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Werner R, Szkitsak J, Sentker T, Madesta F, Schwarz A, Fernolendt S, Vornehm M, Gauer T, Bert C, Hofmann C. Comparison of intelligent 4D CT sequence scanning and conventional spiral 4D CT: a first comprehensive phantom study. Phys Med Biol 2021; 66. [PMID: 33171441 DOI: 10.1088/1361-6560/abc93a] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 11/10/2020] [Indexed: 11/11/2022]
Abstract
4D CT imaging is a cornerstone of 4D radiotherapy treatment. Clinical 4D CT data are, however, often affected by severe artifacts. The artifacts are mainly caused by breathing irregularity and retrospective correlation of breathing phase information and acquired projection data, which leads to insufficient projection data coverage to allow for proper reconstruction of 4D CT phase images. The recently introduced 4D CT approach i4DCT (intelligent 4D CT sequence scanning) aims to overcome this problem by breathing signal-driven tube control. The present motion phantom study describes the first in-depth evaluation of i4DCT in a real-world scenario. Twenty-eight 4D CT breathing curves of lung and liver tumor patients with pronounced breathing irregularity were selected to program the motion phantom. For every motion pattern, 4D CT imaging was performed with i4DCT and a conventional spiral 4D CT mode. For qualitative evaluation, the reconstructed 4D CT images were presented to clinical experts, who scored image quality. Further quantitative evaluation was based on established image intensity-based artifact metrics to measure (dis)similarity of neighboring image slices. In addition, beam-on and scan times of the scan modes were analyzed. The expert rating revealed a significantly higher image quality for the i4DCT data. The quantitative evaluation further supported the qualitative: While 20% of the slices of the conventional spiral 4D CT images were found to be artifact-affected, the corresponding fraction was only 4% for i4DCT. The beam-on time (surrogate of imaging dose) did not significantly differ between i4DCT and spiral 4D CT. Overall i4DCT scan times (time between first beam-on and last beam-on event, including scan breaks to compensate for breathing irregularity) were, on average, 53% longer compared to spiral CT. Thus, the results underline that i4DCT significantly improves 4D CT image quality compared to standard spiral CT scanning in the case of breathing irregularity during scanning.
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Affiliation(s)
- René Werner
- University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
| | - Juliane Szkitsak
- Department of Radiation Oncology, Universitätsklinikum Erlangen, Friederich-Alexander-Universität Erlangen-Nürnberg, 91504 Erlangen, Germany
| | - Thilo Sentker
- University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
| | - Frederic Madesta
- University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
| | - Annette Schwarz
- Friederich-Alexander-Universität Erlangen-Nürnberg, 91504 Erlangen, Germany.,Siemens Healthcare GmbH, Siemensstr. 3, 91301 Forchheim, Germany
| | - Susanne Fernolendt
- Friederich-Alexander-Universität Erlangen-Nürnberg, 91504 Erlangen, Germany.,Siemens Healthcare GmbH, Siemensstr. 3, 91301 Forchheim, Germany
| | - Marc Vornehm
- Friederich-Alexander-Universität Erlangen-Nürnberg, 91504 Erlangen, Germany.,Siemens Healthcare GmbH, Siemensstr. 3, 91301 Forchheim, Germany
| | - Tobias Gauer
- University Medical Center Hamburg-Eppendorf, Martinistr. 52, 20246 Hamburg, Germany
| | - Christoph Bert
- Department of Radiation Oncology, Universitätsklinikum Erlangen, Friederich-Alexander-Universität Erlangen-Nürnberg, 91504 Erlangen, Germany
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Hamill JJ, Meier JG, Betancourt Cuellar SL, Sabloff B, Erasmus JJ, Mawlawi O. Improved Alignment of PET and CT Images in Whole-Body PET/CT in Cases of Respiratory Motion During CT. J Nucl Med 2020; 61:1376-1380. [PMID: 32005768 DOI: 10.2967/jnumed.119.235804] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 01/10/2020] [Indexed: 11/16/2022] Open
Abstract
Respiratory motion during the CT and PET parts of a PET/CT scan leads to imperfect alignment of anatomic features seen by the 2 modalities. In this work, we concentrate on the effects of motion during CT. We propose a novel approach for improving the alignment. Methods: Respiratory waveform data were gathered during the CT and PET parts of 28 PET/CT scans of cancer patients with 40 lesions up to 3 cm in size in the lung or upper abdomen. PET list-mode data were reconstructed by 3 reconstruction methods: PET/static (the standard method with no motion correction); PET/ex (a method that calculates a range of expiratory amplitudes from the lowest one to the highest one); and PET/matched (a novel method that uses both waveforms). The 3 methods were compared. The distance between tumor positions in PET and CT were characterized in visual interpretation by physicians as well as quantitatively. Tumor SUVs (SUVmax and SUVpeak) were determined relative to SUV based on the static method. Image noise was evaluated in the liver and compared with PET/static. Results: In visual interpretation, the rate of good alignment was 13 of 21, 13 of 23, and 18 of 21 for the PET/static, PET/ex, and PET/matched methods, respectively, and the mean PET/CT distances were 3.5, 5.1, and 2.8 mm. In visual comparison with PET/ex, the rate of good alignment was increased in 1 of 10 and 7 of 10 cases for PET/static and PET/matched, respectively. SUVmax was on average 21% higher than PET/static when either PET/ex or PET/matched was used. SUVpeak was 12% higher. Image noise in the liver was 15% higher than PET/static for the PET/ex method, and 40% higher for PET/matched; that is, noise was much lower than in gated PET. Conclusion: Acquiring respiratory waveforms both in PET (as in the current state of the art) and in CT (an unusual key step in this approach) has the potential to improve the alignment of PET and CT images. A proposed method for using this information was tested. Improved alignment was demonstrated.
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Affiliation(s)
- James J Hamill
- Siemens Medical Solutions USA, Inc., Knoxville, Tennessee
| | - Joseph G Meier
- Department of Imaging Physics, M.D. Anderson Cancer Center, Houston Texas.,M.D. Anderson Cancer Center UTHealth Science Center at Houston Graduate School of Biomedical Sciences, Houston, Texas; and
| | | | - Bradley Sabloff
- Department of Diagnostic Radiology, M.D. Anderson Cancer Center, Houston Texas
| | - Jeremy J Erasmus
- Department of Diagnostic Radiology, M.D. Anderson Cancer Center, Houston Texas
| | - Osama Mawlawi
- Department of Imaging Physics, M.D. Anderson Cancer Center, Houston Texas.,M.D. Anderson Cancer Center UTHealth Science Center at Houston Graduate School of Biomedical Sciences, Houston, Texas; and
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