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Artificial Intelligence in Adaptive Radiation Therapy
[98] Haskins G, Kruger U and Yan P 2020 Deep learning in medical image registration: a
survey Mach. Vis. Appl.
[99] Balakrishnan G, Zhao A, Sabuncu M R, Guttag J and Dalca A V 2019 VoxelMorph: a
learning framework for deformable medical image registration IEEE Trans. Med. Imaging
38 1788–800
[100] Jaderberg M, Simonyan K and Zisserman A 2015 Spatial transformer networks arXiv:
1506.02025
[101] McKenzie E M, Santhanam A, Ruan D, OConnor D, Cao M and Sheng K 2020
Multimodality image registration in the head-and-neck using a deep learning-derived synthetic CT as a bridge Med. Phys.
[102] Zhao Y, Chen X, McDonald B, Yu C, Mohamed A S, Fuller C D, Court L E, Pan T, Wang H
and Wang X 2023 A transformer-based hierarchical registration framework for multimodality deformable image registration Comput. Med. Imaging Graph.
[103] Chen J, Frey E C, He Y, Segars W P, Li Y and Du Y 2022 Transmorph: transformer for
unsupervised medical image registration Med. Image Anal.
[104] Lim S Y, Tran A, Tran A N K, Sobremonte A, Fuller C D, Simmons L and Yang J 2022
Dose accumulation of daily adaptive plans to decide optimal plan adaptation strategy for head-and-neck patients treated with MR-linac Med. Dosim.
[105] Boman E, Kapanen M, Pickup L and Lahtela S-L 2017 Importance of deformable image
registration and biological dose summation in planning of radiotherapy retreatments
Med. Dosim.
[106] Wang M, Zhang Q, Lam S, Cai J and Yang R 2020 A review on application of deep
learning algorithms in external beam radiotherapy automated treatment planning Front.
Oncol.
[107] Shen C, Nguyen D, Chen L, Gonzalez Y, McBeth R, Qin N, Jiang S B and Jia X 2020
Operating a treatment planning system using a deep-reinforcement learning-based virtual treatment planner for prostate cancer intensity-modulated radiation therapy treatment planning Med. Phys.
[108] Paganelli C, Whelan B, Peroni M, Summers P, Fast M, van de Lindt T, McClelland J,
Eiben B, Keall P and Lomax T 2018 MRI-guidance for motion management in external beam radiotherapy: current status and future challenges Phys. Med. Biol.
[109] Chen X, Ahunbay E, Paulson E S, Chen G and Li X A 2020 A daily end-to-end quality
assurance workow for MR-guided online adaptive radiation therapy on MR-linac J. Appl.
Clin. Med. Phys.
42 296–303
10 580919
31 8
47 1094–104
108 102286
82 102615
47 103–9
47 2329–36
63 22TR03
21 205–12
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IOP Publishing
Artificial Intelligence in Adaptive Radiation Therapy
Yi Wang and X. Sharon Qi
Chapter 17
Functional imaging-guided adaptive
radiation therapy
Bin Han and Yu Gao
Conventional adaptive radiation therapy (ART) mainly adjusts treatment plans based on daily anatomical changes, such as the shape and position variations of organs at risk (OARs). However, different tumors and patients can exhibit diverse responses to treatment, which can impact the effectiveness of radiation treatment. Functional imaging techniques, such as positron emission tomography (PET) and functional magnetic resonance imaging (MRI), provide crucial insights into the tumors metabolism, physiology, and molecular characteristics, offering a more comprehensive understanding than anatomy-based imaging alone. By integrating functional imaging into radiation therapy, we can more precisely tailor treatment plans to individual response. This holds great promise for enhancing treatment effectiveness and improving patient outcomes. This chapter delves deeply into the crucial role of functional imaging in rening ART, with a spotlight on PET and MRIs signicant contributions and breakthroughs. Our analysis will showcase how PET and MRI not only form the cornerstone for creating individualized treatment protocols but also pave the way for groundbreaking oncological research and innovation. We aim to illuminate the signicant strides in functional imaging, marking a new era in the precision, efcacy, and patient outcomes within radiation therapys rapidly advancing domain. Sections 17.1 and 17.2 will specically focus on PET and MRI applications in ART, respectively.

17.1 Functional PET-guided ART

PET imaging has become a pivotal tool in the realm of adaptive radiation therapy [1, 2], primarily due to its unmatched capability in visualizing the metabolic activities of tumors. This functional imaging technique allows for a highly detailed assessment of a tumors response to radiation therapy, making it possible to tailor treatment plans with unparalleled precision. By highlighting areas of increased
doi:10.1088/978-0-7503-6119-4ch17 17-1 ª IOP Publishing Ltd 2025. All rights,
including for text and data mining (TDM), artificial intelligence (AI) training, and similar technologies, are reserved.
Artificial Intelligence in Adaptive Radiation Therapy
metabolic activity, positron emission tomography (PET) imaging aids in the accurate delineation of tumors, ensuring that radiation doses are optimally targeted to cancerous tissues while sparing adjacent healthy structures.
The application of PET imaging in adaptive radiation therapy (ART) extends to monitoring the effectiveness of treatment over time. Clinicians utilize PET scans to evaluate changes in a tumors size and metabolic activity during the course of therapy, providing critical insights that can prompt adjustments to the treatment plan [3]. This dynamic approach enables the adaptation of radiation doses, optimizing therapy based on the tumors real-time response. Furthermore, PET imaging facilitates dose painting [4], where varying radiation doses are applied to different tumor regions based on their metabolic activity, thereby enhancing the efcacy of treatment and minimizing damage to healthy tissues.
Moreover, PET imaging plays a crucial role in the post-treatment phase, serving as a sensitive tool for early detection of cancer recurrence [5]. Its ability to identify metabolic changes offers a signicant advantage in monitoring patients for signs of tumor regrowth, ensuring prompt intervention when necessary. Through these applications, PET imaging in adaptive radiation therapy represents a signicant stride toward personalized cancer care, offering hope for improved treatment outcomes and reduced side effects for patients undergoing radiation therapy.
17.1.1 PET-based functional imaging overview
PET-based functional imaging leverages PET to visualize the metabolic activities within the body, offering crucial insights beyond what is possible with traditional anatomical imaging techniques. By injecting radiotracers, which are substances designed to target specic biochemical processes, PET can illuminate areas of increased metabolic activity, such as tumors with high glucose consumption. This allows for the precise detection and monitoring of various diseases, particularly in oncology, by providing detailed images of how tissues and organs function at a molecular level. As a result, PET imaging has become an indispensable tool in diagnosis, treatment planning, and the evaluation of therapeutic responses, paving the way for personalized medicine through its ability to reveal the unique functional characteristics of diseases within the body.
17.1.1.1 Principles of PET imaging
The process of generating PET images is a fascinating intersection of physics, chemistry, and medical science, providing a window into the bodys functional processes. This journey begins with the careful administration of a radiotracer, a specially designed molecule tagged with a radioactive isotope. These radiotracers are ingeniously crafted to seek out specic biological activities or cell types, with uorodeoxyglucose (FDG), a glucose analog, being among the most commonly used. Once injected, this compound circulates through the bloodstream, distributing itself across various tissues but preferentially accumulating in areas with high metabolic demand, such as rapidly growing tumors.
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Artificial Intelligence in Adaptive Radiation Therapy
Upon reaching its target, the radiotracer undergoes radioactive decay, emitting positrons. These subatomic particles travel a short distance within the tissue before encountering electrons, their negatively charged counterparts. This meet­ing results in a phenomenon known as annihilation, where the mass of the positron and electron is converted into energy in t he form of two gamma rays, ejected in nearly opposite directions. This release of energy is a critical moment, marking the point where invisible biological activities start to translate into visible signals.
The PET scanner plays a crucial role in capturing these signals. Encircling the patient, its ring of detectors is nely tuned to detect the high-energy gamma rays emerging from the annihilation events. By registering the precise timing and location of these rays, the scanner reconstructs a detailed 3D-map of where the radiotracer has accumulated. Advanced algorithms then process these raw data, piecing together a comprehensive three-dimensional image. This image not only reveals the physical structure of the scanned area but, more importantly, highlights the variations in biological activities across different tissues. Bright spots in the image indicate regions of high radiotracer concentration, often correlating with areas of disease, such as cancerous growths. Through this detailed visual representation, PET imaging offers an unparalleled view into the bodys inner workings, providing crucial information for the diagnosis, treatment planning, and monitoring of various diseases, thereby embodying a remarkable blend of scientic innovation and clinical utility.
17.1.1.2 Radiotracers used in PET
Common radiotracers used in PET imaging play a crucial role in visualizing different physiological and biochemical processes within the body. Each radiotracer is designed to target specic functions or tissues, enabling the detailed study of various diseases and conditions. The following describes some of the most frequently used radiotracers in PET.
18F-uorodeoxyglucose (FDG) [6] is the most widely used radiotracer in PET imaging. FDG is a glucose analog that is taken up by cells with high glucose metabolism, making it particularly useful for identifying cancerous tumors, as cancer cells often have higher rates of glucose uptake than normal cells. FDG-PET is also used in the evaluation of brain disorders such as Alzheimers disease [7] and in cardiology to assess myocardial viability [8].
11C-choline is used primarily for imaging prostate cancer [9] and brain tumors [10]. Choline is a nutrient that is involved in building cell membranes, and prostate cancer cells tend to take up more choline than normal cells due to their increased need for membrane synthesis as they grow and multiply. By labeling choline with carbon-11, doctors can use PET scans to detect areas of increased choline uptake in the body, which may indicate the presence of tumors.
Prostate-specic membrane antigen (PSMA) tracers are used in PET imaging for prostate cancer [11]. They target the PSMA, a protein abundantly expressed on prostate cancer cells. 68Ga-PSMA-11 and 18F-DCFPyL are common examples. 68Ga-DOTATATE (or DOTATOC/DOTANOC) targets somatostatin receptors, which are often overexpressed in neuroendocrine tumors. The use of 68Ga-labeled
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Artificial Intelligence in Adaptive Radiation Therapy
peptides allows for the precise detection and localization of neuroendocrine tumors. 18F-DCFPyL is marked with the radioactive isotope uorine-18, which allows for detection of prostate cancer cells due to their expression of PSMA. This tracer has been particularly useful for identifying prostate cancer metastases and is valuable in both initial staging and the detection of recurrence. The high afnity of 18F­DCFPyL for PSMA-expressing cells leads to more accurate imaging results, which can signicantly impact the treatment decisions and management of prostate cancer. PSMA tracers have signicantly improved the detection of prostate cancer meta­stases and recurrence, offering high sensitivity and specicity. This advancement aids in accurate staging and treatment planning, enhancing personalized therapy approaches for prostate cancer patients.
18F-sodium uoride (NaF) is used for bone scanning [12]. When injected into the body, 18F-sodium uoride binds to areas of bone remodeling, which is indicative of bone growth or repair. Due to its high afnity for areas of calci cation, it is particularly effective for detecting bone metastases in cancer patients. 18F-NaF PET scans offer higher sensitivity and resolution compared to traditional bone scintig­raphy, providing valuable information for the diagnosis and management of skeletal diseases.
18F-uciclovine (FACBC) is an amino acid analog used primarily for imaging prostate cancer [13]. It is useful for detecting recurrent prostate cancer, particularly in cases where standard imaging has been inconclusive.
These radiotracers, each with their specic targeting mechanisms, underscore the versatility of PET imaging in diagnosing and monitoring a wide range of conditions. The development and application of new radiotracers continue to expand the capabilities of PET, offering more detailed insights into disease processes and enhancing personalized treatment strategies.
17.1.1.3 Advantages of PET as a functional imaging modality
PET offers unparalleled insight into cellular activity and metabolic processes. Its ability to differentiate between active and dormant cells enhances radiation therapys precision and effectiveness. PET distinguishes itself in the landscape of functional imaging by its exceptional sensitivity to minute changes in metabolic processes, a trait not as pronounced in other functional imaging techniques such as SPECT [14], which, while functional, cannot match the resolution or quanti­tative precision of PET. Unlike fMRI, which tracks blood ow as a surrogate for neural activity, PET measures cellular metabolism directly, offering insights into a broader spectrum of diseases, including cancer, beyond the scope of fMRI’s primarily neurological applications. MR spectroscopy [15], which o ffers chemical composition data of tissue, provides a localized spectrum but lacks the whole­body metabolic mapping that PET delivers. Thus, in the functional imaging sphere, PET stands out for its comprehensive metabolic proling, which, when integrated with anatomical imaging from CT or MRI, provides a holistic view of a patients condition, crucial for personalized medicine and targeted treatment strategies.
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17.1.2 From anatomy to function: the power of PET in radiation therapy
17.1.2.1 Differentiating between anatomical and functional imaging
Anatomical imaging, such as regular MRI and CT scans, excels in providing detailed visualizations of the bodys structures, showcasing the physical form, size, shape, and position of organs and tissues. These modalities are particularly adept at detecting structural abnormalities, such as tumors, fractures, or anatomical malfor­mations, by producing high-resolution images that delineate the intricate details of the bodys anatomy.
In contrast, functional imaging techniques, such as PET, delve into the bio­chemical and physiological processes occurring within tissues and organs. PET scans, for instance, track the distribution of radiotracers to reveal metabolic activity, offering insights into cellular function that can indicate the presence of disease even before structural changes become apparent. This differentiation between anatomical and functional imaging underscores their complementary roles in medical diagnosis and treatment planning. While anatomical imaging offers a static picture of what is present, functional imaging provides a dynamic view of how the body operates, enabling early detection of diseases based on metabolic changes and aiding in the assessment of treatment efcacy. Together, these imaging modalities furnish a comprehensive understanding of both the form and function of the human body, facilitating precise diagnoses and tailored therapeutic approaches.
17.1.2.2 Role of PET imaging in detecting and targeting tumor heterogeneity and
treatment response
Tumors are not uniform; they possess areas of varied metabolic activity. PET imaging can identify these active zones [16], enabling precise targeting during radiation treatment. PET imaging signicantly inuences the planning and execu­tion of radiation therapy by illuminating the metabolic heterogeneity within tumors. This advanced imaging technique identies areas within the tumor that exhibit higher metabolic activity, indicative of aggressive cancer cells. By precisely targeting these hotspots with tailored radiation doses, clinicians can optimize treatment efcacy, sparing surrounding healthy tissues. Furthermore, PETs capability to monitor the tumors metabolic response to treatment over time provides invaluable feedback, allowing for the dynamic adjustment of radiation plans [17]. This adaptability ensures that therapy remains aligned with the evolving nature of the tumor, enhancing the potential for personalized treatment strategies that directly address the unique characteristics of the cancer. Such a focused approach not only aims to improve therapeutic outcomes but also minimizes the risk of side effects, contributing to an overall enhancement in patient care and prognosis in the battle against cancer.
Regular PET scans during treatment allow clinicians to monitor tumor response, adjusting radiation plans as necessary. This adaptive approach ensures optimal radiation delivery while preserving healthy tissues. PET imaging is pivotal in monitoring the evolution of tumors over the course of treatment by meticulously assessing the metabolic activity within the tumor at various stages prior to the
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Artificial Intelligence in Adaptive Radiation Therapy
initiation of therapy, during the treatment period, and following the conclusion of therapy. This is achieved through the measurement of uctuations in the uptake of specic radiotracers, such as FDG, which are indicative of the tumors metabolic rate. A discernible reduction in the uptake of these radiotracers over successive scans generally signals a favorable response to the treatment, manifesting the therapys effectiveness in curtailing the tumors metabolic activity. Conversely, a consistent or escalating uptake could denote the tumors resistance to the current treatment regimen or the advancement of the disease. This capability of PET imaging to non­invasively track these metabolic changes offers a dynamic insight into the tumors response, enabling clinicians to tailor treatment plans more accurately and make informed decisions regarding the patients therapeutic strategy, thereby signicantly impacting the overall management and prognosis of the disease.
17.1.3 Practicalities and clinical implications of PET-guided adaptive radiation
therapy
17.1.3.1 Treatment planning: incorporating PET information
In the treatment planning phase, PET data can be invaluable. It aids in delineating tumor boundaries, understanding metabolic hotspots, and designing precise radia­tion beams. Incorporating PET information into daily radiation treatments signi­cantly enhances the personalization and precision of therapy strategies. By utilizing the detailed metabolic activity and tumor extent data provided by PET scans, clinicians can more accurately dene the target areas for radiation, differentiating between cancerous and healthy tissues with greater precision than conventional imaging allows. This detailed insight enables the meticulous adjustment of radiation dose distributions, focusing on eradicating cancer cells while minimizing exposure to surrounding healthy tissues. Furthermore, the concept of ART comes into play, wherein PET imaging is repeatedly used to monitor the tumors response to treatment over time. Adjustments to the radiation plan are made dynamically, based on these sequential PET scans, to address changes in tumor size, shape, or metabolic activity. Such an adaptive approach not only aims to improve the accuracy of radiation delivery but also holds the promise of enhancing patient outcomes by reducing treatment-related side effects. Through this integration of PET data, radiation therapy is tailored to the unique characteristics of each patients tumor, ensuring a highly individualized treatment process that adapts to the evolving nature of the disease.
17.1.3.2 PET-based biology-guided adaptive radiation therapy
The SCINTIX
®
biology-guided radiotherapy (BgRT) represents a cutting-edge advancement that merges real-time PET imaging with radiotherapy, enhancing the precision of tumor targeting and the efcacy of treatments. The ReeXion X1 system (ReeXion Medical, Inc., Hayward, CA) is a novel PET-guided radiation therapy machine [18, 19] featuring an 85 cm O-ring gantry linear accelerator (linac) capable of rotating at 60 revolutions per minute (rpm). It incorporates fan-beam kilovoltage computed tomography (kVCT) for precise image guidance in intensity-modulated
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Artificial Intelligence in Adaptive Radiation Therapy
radiation therapy (IMRT) and stereotactic body radiation therapy (SBRT). Additionally, it utilizes PET imaging for real-time tumor tracking in BgRT. The design of the X1 system is highlighted by its two symmetrically opposing 90-degree arcs of PET detectors seamlessly integrated into the ring gantry’s architecture, to direct therapeutic radiation beams in real time, utilizing the tumor as a natural marker to guide and adapt the radiation dose dynamically during treatment. For real-time guidance, the system performs high-speed computations to generate limited time­sample PET images at 100-millisecond intervals, drawing on 500 milliseconds worth of accumulated line of response data.
This sophisticated system is specially tailored for providing comprehensive, real­time, BgRT for the treatment of bone and lung tumors, ensuring precise targeting and treatment delivery. The BIOGUIDE-X study [20] conducted sequential cohorts of participants to ascertain the optimal FDG dosage for SCINTIX therapy application, and to validate that the emulated radiation dose distribution corre­sponds with the physician-endorsed radiotherapy scheme. This forward-looking study enrolled individuals who presented with at least one FDG-avid tumor that was primary or metastatic, targetable, and measured between 2 and 5 cm, located in the lung or bone. Cohort I employed a modied 3 + 3 scheme to identify the FDG dose necessary for SCINTIX therapy to produce an adequate signal. In cohort II, PET imaging was utilized on the X1 system to acquire data before the commencement and after the conclusion of the initial and nal sessions of conventional stereotactic body radiotherapy. The SCINTIX therapy dose distributions were emulated using patient-specic CT anatomy and the acquired PET data for each treatment fraction. These were then compared against the physician-sanctioned plan.
The ndings from cohort I showing sufcient FDG activity in all six evaluable participants following the administration of an initial dose level of 15 mCi FDG. In cohort II, the study saw the enrollment of four patients with lung tumors and ve with bone tumors, from which data points for 17 treatment fractions were collected and evaluated. Out of these, 16 emulated deliveries yielded SCINTIX dose distributions that aligned accurately with the authorized SCINTIX therapy plan. Notably, all emulated uences were found to be feasible for delivery. Furthermore, no adverse effects were ascribed to the repeated administrations of FDG. In essence, SCINTIX therapy presents a pioneering approach in radiotherapy where the radiolabeled tumor inherently serves as a ducial marker for targeting.
As it stands, FDG is the sole radionuclide that has received FDA approval for use in BgRT. However, the scope of BgRT is set to broaden with the exploration of additional promising radionuclides such as PSMA and
89
Zr-labeled Panitumumab [21]. The incorporation of these new radionuclides into BgRT practices aims to enhance the specicity with which radiation targets tumor biology. This advance­ment has the potential to extend BgRT applicability across a wider spectrum of diseases and clinical contexts, particularly in improving the targeting of challenging tumors with more precise radionuclide-tumor binding. The SCINTIX radiotherapy system stands out due to its consistent accuracy and replicability in dose delivery. Such reliability, particularly under static conditions, marks SCINTIX as a
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signicant technological development poised to push the boundaries of current radiotherapy modalities.
17.1.4 Articial intelligence in PET-guided adaptive radiation therapy
17.1.4.1 Role of AI in enhancing image interpretation
Articial intelligence can signicantly enhance the analysis and interpretation of PET images [22, 23]. Machine learning algorithms can detect patterns or anomalies that might be overlooked by human observers, ensuring a more accurate diagnosis and treatment planning. AI algorithms can analyse complex imaging data with high precision and speed, identifying patterns and anomalies that may be subtle or invisible to the human eye. This capability signicantly improves diagnostic accuracy and efciency, enabling earlier and more accurate detection of diseases. AI can also learn from vast datasets to continuously improve its diagnostic capabilities, supporting radiologists in making more informed decisions. By reduc­ing the potential for human error and increasing the consistency of image interpretations, AI ultimately contributes to better patient outcomes and stream­lined workows in healthcare settings.
17.1.4.2 Predictive modeling for treatment outcomes
AI, combined with PET imaging, can predict patient-specic responses to radiation therapy. These predictive models utilize vast amounts of data to estimate how a tumor might react, allowing for more personalized treatments [24]. It enhances the ability to predict patient-specic responses to radiation therapy by analysing metabolic and physiological data from PET scans. AI algorithms can identify patterns in the data that correlate with treatment outcomes, enabling personalized treatment plans that are more likely to be effective for individual patients. This predictive capability allows for the optimization of radiation doses, minimizing exposure to healthy tissues while targeting tumors more precisely. AI-driven analysis of PET imaging data can lead to better treatment decisions, reduced side effects, and potentially improved survival rates for patients undergoing radiation therapy.
17.1.4.3 AI-driven real-time treatment adjustments
With the assistance of AI, real-time adjustments during radiation sessions become feasible [25]. By analysing the ongoing PET data, AI systems can suggest immediate modications to the treatment plan if deviations or unexpected responses are detected. It is a pivotal advancement in adaptive radiation therapy by enabling highly personalized and dynamic treatment protocols. By continuously analysing data from diagnostic images, patient responses, and other relevant clinical informa­tion, AI algorithms can detect subtle changes in tumor size, shape, and metabolic activity. This capability allows for the immediate adjustment of radiation doses and targeting strategies to reect the tumors current state and the patients unique response to treatment. Consequently, treatments can be optimized on-the-y, enhancing efcacy while minimizing damage to surrounding healthy tissues. This approach not only improves the precision and adaptability of radiation therapy but
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also opens up new possibilities for individualized patient care, potentially leading to better outcomes and reduced side effects.
17.1.5 Conclusions and future prospects
After exploring PETs role in adaptive radiation therapy and AIs promising potential, it is evident that these technologies are revolutionizing oncology treat­ments. Their convergence offers better patient outcomes with increased precision. The use of PET in oncology treatments is revolutionizing the eld due to its ability to provide detailed metabolic insights into tumors, beyond what conventional imaging offers. PETs capacity to visualize the biological activity of tumors allows for earlier detection, precise staging, and monitoring of treatment responses, leading to more personalized and effective therapy strategies. This improved diagnostic accuracy and treatment monitoring enhance patient outcomes, making PET a cornerstone in the advancement of oncology care.
The synergistic combination of PET and adaptive radiation therapy can lead to innovations such as time-of-ight PET. Using PET functional images in radiation therapy offers potential benets such as precise tumor targeting, enhanced treatment personalization, and the ability to adapt therapy based on real-time tumor responses. Innovations include more accurate dose distribution, minimizing expo­sure to healthy tissues, and improved detection of treatment-resistant tumor areas. These advancements lead to better patient outcomes and reduced side effects, marking a signicant leap forward in the precision and effectiveness of cancer treatment. Such advancements, along with integration possibilities with other modalities, promise even more accurate and effective treatments in the future.
As technology evolves, so will the landscape of adaptive radiation therapy. Future research should delve into rening techniques, improving patient comfort, and reducing costs while maximizing outcomes. The use of PET in adaptive radiation therapy is poised for signicant growth, with future research focusing on enhancing tumor characterization, treatment personalization, and real-time mon­itoring of therapy effectiveness. Advancements in PET technology and AI integra­tion are expected to improve the precision of radiation dose delivery, reduce side effects, and facilitate the development of novel therapeutic strategies. These trends underscore PETs pivotal role in evolving adaptive radiation therapy towards more targeted, efcient, and patient-specic approaches, promising substantial improve­ments in cancer care and outcomes.

17.2 Functional MRI-guided ART

MRI has been routinely used in the clinic to facilitate target and OAR delineation owing to its superior soft-tissue contrast. Recent advancements in engineering have led to the successful integration of MR scanners with linear accelerators (linacs) for radiation treatment [2628]. This integration opens up exciting possibilities for online MRI-based treatment adaptation to account for inter-fraction anatomy variations as well as real-time MRI-based gating to minimize the effect of intra-fraction motion on
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