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  • IOP Publishing  (7)
  • Biodiversity Research  (7)
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  • IOP Publishing  (7)
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  • Biodiversity Research  (7)
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  • 1
    Online Resource
    Online Resource
    Synthetic CT generation from CBCT images via unsupervised deep learning
    IOP Publishing ; 2021
    In:  Physics in Medicine & Biology Vol. 66, No. 11 ( 2021-06-07), p. 115019-
    Details
    In: Physics in Medicine & Biology, IOP Publishing, Vol. 66, No. 11 ( 2021-06-07), p. 115019-
    Abstract: Adaptive-radiation-therapy (ART) is applied to account for anatomical variations observed over the treatment course. Daily or weekly cone-beam computed tomography (CBCT) is commonly used in clinic for patient positioning, but CBCT’s inaccuracy in Hounsfield units (HU) prevents its application to dose calculation and treatment planning. Adaptive re-planning can be performed by deformably registering planning CT (pCT) to CBCT. However, scattering artifacts and noise in CBCT decrease the accuracy of deformable registration and induce uncertainty in treatment plan. Hence, generating from CBCT a synthetic CT (sCT) that has the same anatomical structure as CBCT but accurate HU values is desirable for ART. We proposed an unsupervised style-transfer-based approach to generate sCT based on CBCT and pCT. Unsupervised learning was desired because exactly matched CBCT and CT are rarely available, even when they are taken a few minutes apart. In the proposed model, CBCT and pCT are two inputs that provide anatomical structure and accurate HU information, respectively. The training objective function is designed to simultaneously minimize (1) contextual loss between sCT and CBCT to maintain the content and structure of CBCT in sCT and (2) style loss between sCT and pCT to achieve pCT-like image quality in sCT. We used CBCT and pCT images of 114 patients to train and validate the designed model, and another 29 independent patient cases to test the model’s effectiveness. We quantitatively compared the resulting sCT with the original CBCT using the deformed same-day pCT as reference. Structure-similarity-index, peak-signal-to-noise-ratio, and mean-absolute-error in HU of sCT were 0.9723, 33.68, and 28.52, respectively, while those of CBCT were 0.9182, 29.67, and 49.90, respectively. We have demonstrated the effectiveness of the proposed model in using CBCT and pCT to synthesize CT-quality images. This model may permit using CBCT for advanced applications such as adaptive treatment planning.
    Type of Medium: Online Resource
    ISSN: 0031-9155 , 1361-6560
    URL: Article
    DOI: 10.1088/1361-6560/ac01b6
    RVK:
    WA 15000
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 1473501-5
    SSG: 12
    Location Call Number Limitation Availability
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    Online Resource
  • 2
    Online Resource
    Online Resource
    An iterative image-based inter-frame motion compensation method for dynamic brain PET imaging
    IOP Publishing ; 2022
    In:  Physics in Medicine & Biology Vol. 67, No. 3 ( 2022-02-07), p. 035012-
    Details
    In: Physics in Medicine & Biology, IOP Publishing, Vol. 67, No. 3 ( 2022-02-07), p. 035012-
    Abstract: As a non-invasive imaging tool, positron emission tomography (PET) plays an important role in brain science and disease research. Dynamic acquisition is one way of brain PET imaging. Its wide application in clinical research has often been hindered by practical challenges, such as patient involuntary movement, which could degrade both image quality and the accuracy of the quantification. This is even more obvious in scans of patients with neurodegeneration or mental disorders. Conventional motion compensation methods were either based on images or raw measured data, were shown to be able to reduce the effect of motion on the image quality. As for a dynamic PET scan, motion compensation can be challenging as tracer kinetics and relatively high noise can be present in dynamic frames. In this work, we propose an image-based inter-frame motion compensation approach specifically designed for dynamic brain PET imaging. Our method has an iterative implementation that only requires reconstructed images, based on which the inter-frame subject movement can be estimated and compensated. The method utilized tracer-specific kinetic modelling and can deal with simple and complex movement patterns. The synthesized phantom study showed that the proposed method can compensate for the simulated motion in scans with 18 F-FDG, 18 F-Fallypride and 18 F-AV45. Fifteen dynamic 18 F-FDG patient scans with motion artifacts were also processed. The quality of the recovered image was superior to the one of the non-corrected images and the corrected images with other image-based methods. The proposed method enables retrospective image quality control for dynamic brain PET imaging, hence facilitating the applications of dynamic PET in clinics and research.
    Type of Medium: Online Resource
    ISSN: 0031-9155 , 1361-6560
    URL: Article
    DOI: 10.1088/1361-6560/ac4a8f
    RVK:
    WA 15000
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 1473501-5
    SSG: 12
    Location Call Number Limitation Availability
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Investigation of scan path optimization in improving proton pencil beam scanning continuous delivery
    IOP Publishing ; 2023
    In:  Physics in Medicine & Biology Vol. 68, No. 19 ( 2023-10-07), p. 195023-
    Details
    In: Physics in Medicine & Biology, IOP Publishing, Vol. 68, No. 19 ( 2023-10-07), p. 195023-
    Abstract: Objective . To investigate the impact of scan path optimization on the dose accuracy and beam delivery time (BDT) of proton pencil beam scanning in the dose-driven continuous scanning (DDCS). Approach . A diverse set of six clinical plans, representing various spot patterns and treatment sites, was used to evaluate the effectiveness of scan time optimization and scan length optimization. The DDCS dose discrepancy and BDT with optimized scan paths was compared to the default serpentine scan path. Main results . Both scan time optimization and scan path optimization were able to reduce the DDCS dose discrepancy compared to the default serpentine scan path. All plans, except for the layer repainting lung plan, achieved a 2%/2 mm gamma pass rate of over 99% and less than 1% PTV DVH root mean square error (RMSE) through scan path optimization. In the case of the layer repainting lung plan, when compared to the default serpentine scan path, the 2%/2 mm gamma pass rate showed improvements from 91.3% to 93.1% and 95.8%, while the PTV DVH RMSE decreased from 2.1% to 1.7% and 1.1% for scan time optimization and scan length optimization, respectively. Although scan time optimization resulted in shorter total scan times for all plans compared to the default scan path and scan length optimization tended to have longer total scan times. However, due to the short total scan times and their minimal contribution to the total BDT, the impact of scan path optimization on the total BDT was practically negligible. Significance . Both scan time optimization and scan length optimization proved to be effective in minimizing DDCS dose discrepancy. No definitive winner can be determined between these two optimization approaches. Both scan time and scan length optimization had minimal effect on the total BDT.
    Type of Medium: Online Resource
    ISSN: 0031-9155 , 1361-6560
    URL: Article
    DOI: 10.1088/1361-6560/acf98e
    RVK:
    WA 15000
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2023
    detail.hit.zdb_id: 1473501-5
    SSG: 12
    Location Call Number Limitation Availability
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    Online Resource
  • 4
    Online Resource
    Online Resource
    Investigation of beam delivery time for synchrotron-based proton pencil beam scanning system with novel scanning mode
    IOP Publishing ; 2022
    In:  Physics in Medicine & Biology Vol. 67, No. 17 ( 2022-09-07), p. 175001-
    Details
    In: Physics in Medicine & Biology, IOP Publishing, Vol. 67, No. 17 ( 2022-09-07), p. 175001-
    Abstract: Objective. To investigate synchrotron-based proton pencil beam scanning (PBS) beam delivery time (BDT) using novel continuous scanning mode. Approach. A BDT calculation model was developed for the Hitachi particle therapy system. The model was validated against the measured BDT of 36 representative clinical proton PBS plans with discrete spot scanning (DSS) in the current Hitachi proton therapy system. BDTs were calculated with the next generation using Mayo Clinic Florida system operating parameters for conventional DSS, and novel dose driven continuous scanning (DDCS). BDTs of DDCS with and without Break Spots were investigated. Main results. For DDCS without Break Spots, the use of Stop Ratio to control the transit dose largely reduced the beam intensity and consequently, severely prolonged the BDT. DDCS with Break Spots was able to maintain a sufficiently high beam intensity while controlling transit dose. In DDCS with Break Spots, tradeoffs were made between beam intensity and number of Break Spots. Therefore, BDT decreased with increased beam intensity but reached a plateau for beam intensity larger than 10 MU s −1 . Averaging over all clinical plans, BDT was reduced by 10% for DDCS with Break Spots compared to DSS. Significance. DDCS with Break Spots reduced BDT. DDCS has the potential to further reduce BDT under the ideal scenario which requests both stable beam intensity extraction and accurately modelling the transit dose. Further investigation is warranted.
    Type of Medium: Online Resource
    ISSN: 0031-9155 , 1361-6560
    URL: Article
    DOI: 10.1088/1361-6560/ac8410
    RVK:
    WA 15000
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 1473501-5
    SSG: 12
    Location Call Number Limitation Availability
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    Online Resource
  • 5
    Online Resource
    Online Resource
    Staging of cervical cancer based on tumor heterogeneity characterized by texture features on 18 F-FDG PET images
    IOP Publishing ; 2015
    In:  Physics in Medicine and Biology Vol. 60, No. 13 ( 2015-07-07), p. 5123-5139
    Details
    In: Physics in Medicine and Biology, IOP Publishing, Vol. 60, No. 13 ( 2015-07-07), p. 5123-5139
    Type of Medium: Online Resource
    ISSN: 0031-9155 , 1361-6560
    URL: Article
    DOI: 10.1088/0031-9155/60/13/5123
    RVK:
    WA 15000
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2015
    detail.hit.zdb_id: 1473501-5
    SSG: 12
    Location Call Number Limitation Availability
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    Online Resource
  • 6
    Online Resource
    Online Resource
    Imaging depth adaptive resolution enhancement for optical coherence tomography via deep neural network with external attention
    IOP Publishing ; 2021
    In:  Physics in Medicine & Biology Vol. 66, No. 19 ( 2021-10-07), p. 195006-
    Details
    In: Physics in Medicine & Biology, IOP Publishing, Vol. 66, No. 19 ( 2021-10-07), p. 195006-
    Abstract: Optical coherence tomography (OCT) is a promising non-invasive imaging technique that owns many biomedical applications. In this paper, a deep neural network is proposed for enhancing the spatial resolution of OCT en face images. Different from the previous reports, the proposed can recover high-resolution en face images from low-resolution en face images at arbitrary imaging depth. This kind of imaging depth adaptive resolution enhancement is achieved through an external attention mechanism, which takes advantage of morphological similarity between the arbitrary-depth and full-depth en face images. Firstly, the deep feature maps are extracted by a feature extraction network from the arbitrary-depth and full-depth en face images. Secondly, the morphological similarity between the deep feature maps is extracted and utilized to emphasize the features strongly correlated to the vessel structures by using the external attention network. Finally, the SR image is recovered from the enhanced feature map through an up-sampling network. The proposed network is tested on a clinical skin OCT data set and an open-access retinal OCT dataset. The results show that the proposed external attention mechanism can suppress invalid features and enhance significant features in our tasks. For all tests, the proposed SR network outperformed the traditional image interpolation method, e.g. bi-cubic method, and the state-of-the-art image super-resolution networks, e.g. enhanced deep super-resolution network, residual channel attention network, and second-order attention network. The proposed method may increase the quantitative clinical assessment of micro-vascular diseases which is limited by OCT imaging device resolution.
    Type of Medium: Online Resource
    ISSN: 0031-9155 , 1361-6560
    URL: Article
    DOI: 10.1088/1361-6560/ac2267
    RVK:
    WA 15000
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 1473501-5
    SSG: 12
    Location Call Number Limitation Availability
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    Online Resource
  • 7
    Online Resource
    Online Resource
    Theoretical investigation of the signal performance of HgI 2 x-ray converters incorporating a Frisch grid structure at mammographic energies
    IOP Publishing ; 2021
    In:  Physics in Medicine & Biology Vol. 66, No. 15 ( 2021-08-07), p. 155019-
    Details
    In: Physics in Medicine & Biology, IOP Publishing, Vol. 66, No. 15 ( 2021-08-07), p. 155019-
    Type of Medium: Online Resource
    ISSN: 0031-9155 , 1361-6560
    URL: Article
    DOI: 10.1088/1361-6560/ac1365
    RVK:
    WA 15000
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2021
    detail.hit.zdb_id: 1473501-5
    SSG: 12
    Location Call Number Limitation Availability
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    Online Resource
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