WITHDRAWN: Techniques for Building Internal Target Volumes (ITV) in CT Imaging Through Calibration, Artifact Management, Image Registration, and 4DCT Incorporating Motion-Encompassing Methods

doi:10.21203/rs.3.rs-4926919/v1

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WITHDRAWN: Techniques for Building Internal Target Volumes (ITV) in CT Imaging Through Calibration, Artifact Management, Image Registration, and 4DCT Incorporating Motion-Encompassing Methods

https://doi.org/10.21203/rs.3.rs-4926919/v1

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This study aimed to enhance the accuracy and efficiency of ITV construction in CT imaging. It utilized a combination of calibration techniques to ensure precise imaging measurements, artifact management strategies to reduce image distortion, advanced image registration methods for spatial alignment, and 4DCT technology to capture dynamic motion information. By incorporating motion-encompassing methods into the process, the study sought to improve the delineation of internal target volumes for more effective treatment planning and delivery in medical settings.

Through a systematic evaluation of the proposed techniques, this study work generated promising results in optimizing ITV construction in CT imaging. The findings highlighted the impact of calibration, artifact management, image registration, and 4DCT integration on enhancing the quality and accuracy of internal target volume delineation. The study demonstrated the potential benefits of utilizing motion-encompassing methods to account for patient motion during imaging procedures, leading to more precise and reliable ITV generation for radiation therapy and other medical applications.

Overall, the study shed light on the importance of incorporating advanced techniques in CT imaging for building internal target volumes. By addressing key challenges such as motion artifacts and inaccuracies in volume delineation, the study provided valuable insights into improving the quality of medical imaging processes. The results underscored the potential of motion-encompassing methods to revolutionize ITV construction practices, paving the way for enhanced treatment planning and delivery strategies in the field of medical physics and radiation oncology.

Medical Physics

CT Imaging

4DCT

Motion-Encompassing Methods

Radiation Therapy

Internal Target Volumes (ITV)

In the context of radiation therapy, imaging exercises typically involve practical training or educational activities focused on using imaging techniques for treatment planning and delivery. These exercises aim to enhance the skills and knowledge of radiation therapy professionals, including radiation oncologists, medical physicists, dosimetrists, and radiation therapists, in utilizing various imaging modalities for accurate and effective treatment. In the current exercise, we were able to understand the impact of incorrect CT calibration on treatment planning (TPS), which was verified with the calibration of HU-ρ_e (or ρ_m). Changes in Hounsfield Units (HU) and mass density can lead to dosimetric inaccuracies, affecting parameters such as Monitor Units (MU) and patient dose. A treatment plan was developed on CT images with motion artifacts following the calculation of the MU [1].

When dealing with CT images that have motion artifacts, it is essential to correct these artifacts to ensure accurate treatment planning. Additionally, wedges are commonly used in radiation therapy to shape the radiation beam and deliver a more uniform dose to irregularly shaped tumors or target volumes. In this exercise, we utilized the variant-enhanced dynamic wedge at an angle of 60 degrees. [2].

Image registration refers to the process of aligning and overlaying multiple images or datasets to compare or combine different sources of information. In the context of medical imaging, two common types of image registration techniques are rigid and global registration. Rigid registration is suitable for aligning images of the same modality and anatomy but acquired at different orientations or positions, while global registration is useful for aligning images of different modalities, time points, or anatomical variations that require more extensive transformations for accurate alignment [3].

By utilizing 4DCT to construct an Internal Target Volume (ITV) using a motion-encompassing technique, radiation oncologists can effectively address tumor motion and ensure precise targeting during radiation therapy, ultimately enhancing treatment outcomes for patients with tumors affected by respiratory or other types of motion [4].

The experimental work took place at the Adriatic Guest House (ICTP), Riva Massimiliano and Carlotta, Grignano TS, Italy. It was held in the Eklund lecture room for the entire day on Tuesday to the entire day on Wednesday, June 26, 2024.

2.1. Material

The imaging work in radiotherapy was performed using the Ray Station software installed on the desktop, under the guidance of our teacher.

The materials used in a simulation would typically include specific equipment, software, phantoms, imaging datasets, and any other tools or resources utilized in the classroom exercise. These materials are crucial for conducting the simulation and testing the proposed techniques for building Internal Target Volumes (ITV) in CT imaging.

2.2. Methods

In the study work a systematic approach was adopted to enhance the accuracy and precision of ITV construction. The methods utilized in the study included the calibration of CT imaging equipment to ensure consistent and accurate measurements.

Artifact management techniques were employed to address image distortions and artifacts that could affect the quality of the imaging data. Advanced image registration algorithms were applied to align and merge multiple images for improved spatial accuracy. Additionally, 4DCT technology was utilized to capture dynamic motion information and incorporate it into the ITV construction process, enabling a more comprehensive representation of internal target volumes [5].

Furthermore, motion encompassing methods were integrated to account for patient motion during imaging procedures. These methods aimed to capture and incorporate motion information into the ITV construction process, allowing for more accurate and reliable target volume delineation. By combining calibration, artifact management, image registration, and 4DCT with motion-encompassing techniques, the study sought to address key challenges in ITV construction in CT imaging and optimize the process for improved treatment planning and delivery in medical settings [6].

In this exercise, three imaging activities have been performed as presented below. The first activity is to demonstrate the impact of incorrect CT calibration on treatment planning (TP).

3.1. The impact of wrong CT calibration on treatment planning (TP)

The impact of the incorrect CT calibration was verified using the calibration of HU-ρe (or ρm). Based on the data from the CT scan of the calibration phantom in Table 1 below, we conducted a preliminary check of image quality, revealing defects in quality.

Based on the data provided in Table 1, we can understand how variations in Hounsfield units (HU) and mass density impact the calibration of different CT scanners. The figure below illustrates how changes in HU and mass density lead to alterations in the monitor units (MU) and the patient dose. To accomplish this, we accessed the CT commissioning tab and configured a machine where we adjusted the HU and mass density curve, as depicted in the Fig. 1, below.

Table 1

Realistic vs Miscalibration
Realistic		Miscalibration
HU	Mass Density (g/cm³)	HU	Mass Density (g/cm³)
-1000	0.00121	-1000	0.00121
-992	0.00121	-992	0.00121
-976	0.00121	-976	0.00121
-480	0.5	-550	0.5
0	1.0	-100	1.0
128	1.1	0	1.1
540	1.35	300	1.35
1000	1.7	700	1.7
1500	1.85	1200	1.85
1824	2.1	1424	2.1
2200	2.4	1800	2.4
2830	2.83	2400	2.83
2831	7.87	2401	7.87
3096	7.87	3096	7.87

In addition, we created a plan using the same gantry angle for both based on CT1 and CT2 commissioned data, which resulted in changes in the MU values as shown in the figure below.

3.2. Planning on CT Images with Artifacts:

Following the calculation of the monitor units (MU), we created a treatment plan for the CT image with artifacts. The treatment plan was adjusted using the variant-enhanced dynamic wedge at an angle of 60 degrees, as illustrated in the figure below.

As we planned the CT image with artifacts, we performed rigid and global image registration.

3.3. Image Registration – Rigid and Global

The process of image registration in radiotherapy involves aligning and overlaying different imaging datasets or images from various modalities or time points. This alignment is crucial for accurate treatment planning and delivery in radiotherapy. In this class room work, we utilized an automatic tool for image registration and focused on a specific region to accurately overlay the two images. We defined and selected a region of interest for the image registration and utilized fusion tools to visualize the accuracy of the image alignment, as depicted in Fig. 4. The primary advantage of employing automatic tools for image registration is their capability to deliver precise, efficient, and consistent alignment of images, enabling a broad spectrum of applications in research, diagnostics, treatment planning, and beyond. While manual tools for image registration provide control, insight, and customization, they are labor-intensive, subjective, and demand expertise. Despite offering flexibility and quality assurance, manual methods can be time-consuming, error-prone, and less scalable compared to automatic tools. It is essential to thoroughly weigh the advantages and disadvantages when selecting between manual and automatic tools for image registration based on specific needs and priorities.

4DCT is essential for capturing dynamic anatomical changes and motion in radiation therapy.

3.4. Use of 4DCT To Build ITV in a Motion-Encompassing Technique

4D CT represents the next advancement in imaging technology, significantly enhancing the speed and accuracy of CT scans. This innovative method allows for the capture of both the location and movement of tumors, as well as the movement of body organs over time. It is particularly beneficial for precisely treating tumors located on or near organs that are in motion, such as those in the chest and abdomen. In our case, we utilized this technique to identify maximum expiration and inspiration with nine-phase gating in the lung nodule and drew nine contours to represent the Gross Tumor Volume (GTV) as shown below.

We have also drawn contours in the other seven intermediate phases and constructed the Internal Target Volume (ITV) from the nine phases, as shown below.

We measured the volume of the ITV as shown below.

The maximum CT reconstruction and ITV delineation are shown below.

Finally, we compared the volumes between the two groups and calculated an average volume to use for planning.

4.1. Summary

The introduction background of the study would typically provide an overview of the importance and relevance of internal target volumes (ITV) in the context of CT imaging. It would likely discuss the challenges and limitations associated with traditional ITV construction methods and introduce the need for incorporating calibration, artifact management, image registration, and 4DCT techniques to enhance the accuracy and effectiveness of ITV generation. The background section would set the stage for the study by highlighting the gaps in current practices and explaining how the proposed motion-encompassing methods aim to address these issues in CT imaging.

The materials and methods of the study would typically outline the equipment, tools, procedures, and techniques used in the research. This section would detail how CT calibration was performed, how artifact management was addressed, how image registration was carried out, and how 4DCT was utilized to build ITV using motion-encompassing methods. It would provide a comprehensive description of the setup, data collection processes, and analytical methods employed in the class room exercise.

The results of the study would typically present the outcomes of the research based on the application of the described techniques. It would include findings related to the effectiveness of CT calibration, artifact management strategies, image registration accuracy, and the utilization of 4DCT for building ITV using motion-encompassing methods. The results would likely include quantitative data, measurements, images, and any statistical analysis conducted to evaluate the performance and outcomes of the proposed techniques in enhancing ITV construction in CT imaging.

In conclusion, the study would typically summarize the key findings and implications of the research. It would discuss the significance of the results obtained from applying the described techniques and how they contribute to the field of CT imaging and ITV construction. The conclusion may also highlight any limitations of the class room exercise, suggest areas for future research, and provide recommendations for clinical practice or further development of motion-encompassing methods in CT imaging for building ITV.

4.2. Conclusion

The purpose of the study was to examine the effects of incorrect CT calibration on treatment planning, CT planning with motion artifacts, image registration, and the use of 4DCT to create ITV in motion-encompassing techniques. Throughout the exercise, we made the following key observations:

We verified that incorrect CT calibration can lead to dosimetric inaccuracies, impacting metrics such as MU and patient dose. It is crucial to ensure accurate CT calibration to optimize treatment planning accuracy and patient outcomes in radiation therapy.
When planning on CT images with motion artifacts, we developed a treatment plan and utilized a variant-enhanced dynamic wedge at a 60-degree angle to shape the radiation beam.
During image registration, we used an automatic tool to align specific regions accurately.
Using 4DCT to create an ITV in a motion-encompassing technique, we compared the volume of combined phases and obtained a volume of 95.10 cm³.

4.3. Recommendations

In this context of the study some recommendations could include:

Further validation and refinement of the proposed techniques to enhance their accuracy and efficiency in ITV construction.
Exploration of real-world clinical applications and studies to assess the practical utility of the motion-encompassing methods in improving patient outcomes.
Collaboration with medical physicists, radiologists, and other healthcare professionals to integrate the developed techniques into routine clinical practice.
Continued research and development to address any identified limitations or challenges in implementing the motion-encompassing methods for ITV building in CT imaging.

Conflict of Interests

The Authors have no conflict of interest.

Financial Support

This study received no specific grant from any funding agency in the public or commercial sectors

Acknowledgments

The authors of this study would like to express their gratitude to University of Trieste specifically to the Abdus Salam International Center for Theoretical Physics (ICTP), Medical Physics Programme, Trieste Italy.

Shikha Goyal, and Tejinder Kataria (2014) Image Guidance in Radiation Therapy: Techniques and Applications, Image and Vision Computing, 21(2003):977–1000. https://doi.org/10.1155/2014/705604
Julia F, Barrett NK (2004) Artifacts in CT: Recognition and Avoidance. Radiographics 24(6):1679–1691. https://doi.org/10.1148/rg.246045065
Barbara Zitova and Jan Flusser (2003) Image Registration Methods: A Survey, Image and Vision Computing 21 (2003):977–1000
Dumas M, Laugeman E, Sevak P et al (2020) Technical Note: Comparison of the internal target volume (ITV) contours and dose calculations on 4DCT, average CBCT, and 4DCBCT imaging for lung stereotactic body radiation therapy (SBRT). J Appl Clin Med Phys 21(11). https://doi.org/10.1002/acm2.13041
Triche BL, Nelson JT Jr, McGill NS, Kristin K, Porter R, Sanyal FN, Tessler JE, McConathy DM, Gauntt MV, Yester, Satinder P, Singh (2019) Recognizing and Minimizing Artifacts at CT, MRI, US, and Molecular Imaging. Radio Graphics Fundamentals. https://doi.org/10.1148/rg.2019180022
Dhont J, Harden SV, Chee LYS, Aitken K, Hanna GG, Bertholet J (2020) Image-guided Radiotherapy to Manage Respiratory Motion: Lung and Liver. Clin Oncol 32. https://doi.org/10.1016/j.clon.2020.09.008

The authors declare no competing interests.

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WITHDRAWN: Techniques for Building Internal Target Volumes (ITV) in CT Imaging Through Calibration, Artifact Management, Image Registration, and 4DCT Incorporating Motion-Encompassing Methods

Status:

Version 1

Editorial Note

Abstract

Figures

1. Introduction

2. Material and Methods

2.1. Material

2.2. Methods

3. Results and Discussion

3.1. The impact of wrong CT calibration on treatment planning (TP)

3.2. Planning on CT Images with Artifacts:

3.3. Image Registration – Rigid and Global

3.4. Use of 4DCT To Build ITV in a Motion-Encompassing Technique

4. Summary, conclusion, and recommendations

4.1. Summary

4.2. Conclusion

4.3. Recommendations

Declarations

Conflict of Interests

Financial Support

Acknowledgments

References

Additional Declarations

Supplementary Files

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