|Year : 2015 | Volume
| Issue : 4 | Page : 181-182
Expanding horizons in medical physics: Standardization to visualization and quantitative assessment based personalized treatments
Bhudatt R Paliwal
Department of Human Oncology and Medical Physics, University of Wisconsin, School of Medicine and Public Health, Madison, Wisconsin, USA
|Date of Web Publication||1-Dec-2015|
Prof. Bhudatt R Paliwal
Department of Human Oncology and Medical Physics, University of Wisconsin, School of Medicine and Public Health, K4/B47 CSC, 600 Highland Ave, Madison, Wisconsin 53792
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Paliwal BR. Expanding horizons in medical physics: Standardization to visualization and quantitative assessment based personalized treatments. J Med Phys 2015;40:181-2
|How to cite this URL:|
Paliwal BR. Expanding horizons in medical physics: Standardization to visualization and quantitative assessment based personalized treatments. J Med Phys [serial online] 2015 [cited 2021 Jun 19];40:181-2. Available from: https://www.jmp.org.in/text.asp?2015/40/4/181/170795
The role of a medical physicist has advanced considerably in the recent decades through the development of advanced radiation treatment modalities, technological hardware and software tools. Several of our early colleagues made their mark through the innovation in the design and standardization of radiation sources. As a result of decades of these efforts, it is possible to achieve radiation source calibration within one-tenth of one percent accuracy from a sharply defined pencil beam of radiation of high-dose rate delivery systems. It is truly remarkable that a radiation dose of 85 Gy in one fraction can be delivered to a sub-millimeter diameter ninth cranial nerve with multiple beams without any toxicity to normal brain tissue around it. Protons and other high linear energy transfer particles have gained significant acceptance due to their ability to deliver highly conformal and normal tissue sparing properties.
To claim sub-millimeter accuracy, one actually needs to know where the target is in real-time. High-field magnetic resonance imaging (MRI)-guided radiation therapy (RT) gives us this knowledge. A new paradigm is emerging within the field of RT with a promise of a superior approach to treat cancer. It is anticipated that the high-field MRI-guided RT will be the standard of care within the next 10 years. The high-field MRI-guided linear accelerator is expected to bring to clinics and cancer patients a gentler treatment, fewer side effects with potential for better outcomes, and lower costs.
Several technical breakthroughs have already demonstrated the ability of real-time targeting. The first generation MRI-guided RT systems for nonclinical and clinical treatment are in testing phase, which include the performance evaluation of MRI pulse sequences, testing of different adaptive delivery methods, establishing quality assurance techniques, and defining workflow. Several of the sites are now undertaking treatment planning evaluation using the Monte Carlo based MRI-corrected algorithms.
A high level of confidence has promoted myriads of other beneficial applications in radiation oncology and medical imaging and in the cancer field, providing outstanding disease control with the extension of life span and reduction in human suffering. Furthermore, these applications are beginning to increasingly cross-link the imaging methods to more widely plan, guide, monitor, and assess the treatments. The technologies used are so complex and so computer-driven that it is difficult for nonmedical physics personnel to know exactly what is happening at the point of care without the aid of medical physicists. Scientists/investigators in the field of medical physics are assuming greater responsibilities in the clinical arena to ensure that what is intended for the patient is actually delivered in a safe and effective manner.
New techniques such as intensity modulated RT, volumetric modulated arc therapy, and stereotactic body RT are now routinely used. Radiation intensity in these treatments is modulated dynamically to achieve customized dose painting. Interestingly, new treatment advances such as "four-dimensional" delivery, in which target motion is quantified and its impact is assessed and compensated through adaptive RT. In this approach, a patient's treatment may be modified during the course of treatment using the new information gained, often through real-time imaging. New imaging information could involve a wide range of molecular, cellular functions, and physical characteristics of organs in the human body. It is acquired through multimodality imaging techniques. These developments have expanded the role and responsibility of a conventional RT medical physicist.
We are on the threshold of a new era of "Integrated Precision Imaging" (IPI). It is defined as the use of multimodality imaging derived data tailored to optimize medical treatments to the individual characteristics of each patient. It can be used to combine data about a patient's clinical phenotype (imaging studies leading to grading, scoring, and classification systems linked to their findings) and genotype (gene expression).
The IPI data comes from several fields of noninvasive, in vivo medical imaging, including MRI optical imaging, computed tomography (CT), positron emission tomography, single photon emission CT, and ultrasound. Relevant techniques that have been developed report on, for example, tumor cellularity, vessel perfusion and permeability, hypoxic fractions, as well as cellular and molecular signatures. It is a reasonable hypothesis that characterization of tissue status can offer increased sensitivity and specificity when diagnosing and grading tumors. Furthermore, as many current anticancer drugs are designed to alter these specific tumor characteristics, imaging metrics is designed to report on those phenomena that promise to offer improved methods of planning the treatment as well as assessing the response of tumors to treatment.
Yet for all the progress that has taken place in biomedical imaging science, many of these techniques are yet to be used clinically. For example, the assessment of treatment response in the clinical setting is still dominated by Response Evaluation Criteria in Solid Tumors (RECIST) criteria. The RECIST is based entirely on changes in the sum of the longest dimension of target lesions. In other words, the current standard of care in assessing treatment response is based on one-dimensional morphological and anatomical changes. Again, it is reasonable to expect that some subset of the emerging imaging metrics described above will provide more specific information on treatment response and the physiological and cellular status of the tumor. Furthermore, since anatomical and morphological changes often occur temporally downstream from the underlying physiological, cellular, and molecular changes, the emerging imaging metrics may be applied early in the course of treatment to determine if a given treatment is efficacious.
MRI is currently one of the more powerful techniques available in medical imaging; in the same imaging session, MRI can acquire high-resolution anatomical data with excellent soft tissue contrast, as well as data reporting on physiological and even cellular information, all of which is accomplished without ionizing radiation. Quantitative MRI techniques are poised to move rapidly from bench to bedside. It is anticipated that some subset of the MRI techniques will make a significant contribution to IPI and to personalized medicine in the next decade.
The rapid pace of these developments and the significant increase in the associated complexities have introduced considerable new challenges to the radiation treatment team. This is particularly true for the clinical medical physicist, whose role it is to ensure the correct delivery of the radiation dose distribution prescribed and approved for a patient's treatment by the oncologist through IPI guidance of a patient. It is unquestionable that the burden presented by modern radiation delivery validation is significant. It requires accessing, managing, analyzing, and integrating datasets of varied data types that are ever growing in size and complexity. Medical physicists today are uniquely positioned to harness the power of this data and make an even greater contribution to the treatment planning and delivery of each patient based upon a customized approach. This approach needs considerable development to establish robust process of treatment planning, quality assurance, and safety considerations. It is a challenge and an opportunity for medical physicists to make big gains, both professionally and for the cancer patients undergoing treatments in clinics around the world. This work is the new horizon for medical physics.
Since these developments are providing the potential to expand the role and responsibilities of conventional RT medical physicists, we should broaden the scope of our teaching and training syllabi, incorporating efficient and cost-effective methods of Web-based eLearning using blended (elements consisting of didactic, interactive, and applied hands-on learning) courses. In particular, our educational programs should provide electives in the following areas:
- Imaging-based data collection and management
- Statistical methods to identify patterns and interdependencies
- Learning the language of quantitative data
- Extraction of data from record and verify systems such as Aria and Mosaiq
- Skills to analyze radiogenomic and pathologic/genetic information
- Development of skills to optimize outcome data within radiation oncology and integrate it with patient data from other disciplines.
It behooves us to build the bridges necessary for us to link and establish collaboration with other multidisciplinary professionals in the field. We should promote teaming efforts with information technologists, biomedical engineers, imaging specialists, biologists, and medical professionals. These are all exciting opportunities, and I sincerely hope the medical physics community is prepared to explore these new horizons.