Advancing Nuclear Medicine Through Innovation (2007) / Chapter Skim
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2 Nuclear Medicine
2 Nuclear Medicine
Pages 17-42
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From page 17... ...
In a nuclear medicine scan, a radiopharmaceutical is administered to the patient, and an imaging instrument that detects radiation is used to show biochemical changes in the body. Nuclear medicine imaging (Sidebar 2.2)
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From page 18... ...
. They have collaborated to develop: • nuclear reactors and particle accelerators that produce radionuclides; • chemical processes to synthesize radiopharmaceuticals that can be used for imaging and treatment; and • instruments that can detect radiation emitted from the radionuclides that accumulate in the human body.
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From page 19... ...
Single photon emission computed tomography (SPECT) is another com mon nuclear medicine imaging device.
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From page 20... ...
It is this modular nature, where the two components can be varied like Lego® pieces to match characteristics specific to the tumor that makes targeted radionuclide therapy an attractive approach to cancer treatment (Zalutsky 2003)
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From page 21... ...
. More importantly, the use of nuclear medicine procedures has improved patient care in many ways.
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From page 22... ...
2000 2005 All 3.83 4.99 5 100 100 CT 0.35 0.57 11 9 10 MRI 0.10 0.19 13 3 3 Nuclear Medicine Non-PET 0.21 0.33 9 5 6 PET and PET/CT 0.00 0.01 80 0.02 0.05 Ultrasound 0.84 1.14 6 22 22 Interventional 0.17 0.26 8 5 5 Mammography 0.21 0.33 9 6 6 X-ray, excluding mammography 1.94 2.14 2 51 49 Other 0.01 0.03 37 0.2 0.2 SOURCE: Data from American College of Radiology Research Department. procedure, which has been in use for over 25 years, is also used to diagnose and stage esophageal cancer and non-small-cell lung cancer; to stage melanoma and colorectal cancers; and to monitor treatment response in lymphoma and locally advanced and metastatic breast cancer.
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From page 23... ...
This information will allow one to predict an individual's risk for disease, detect diseases earlier, predict disease outcome, and identify more effective treatments that will further personalize health care. Disease Detection and Treatment Response Omic3 analyses are revealing differences in DNA, RNA, and protein expression between patients with cancer or heart disease and healthy subjects that can be detected in their blood, urine, feces, and sputum.
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Today, technetium-99m is used in over 70 percent of nuclear medicine procedures worldwide (Nuclear Energy Agency 2000)
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From page 25... ...
Michael Welch of Washington University and John Katzenellenbogen of the University of Illinois develop the first PET radiotracer used to image tumors ex pressing the estrogen receptor. Scientists at Harvard Medical School and MIT develop technetium-99m-me thoxyisobutylnitrile, an agent to measure blood flow to the heart muscle (used in myocardial perfusion scans)
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From page 26... ...
Example 1: Trastuzumab (Herceptin®) as Treatment for Breast Cancer Breast cancer is the most common form of cancer in women, after non-mela noma skin cancer and lung cancer, and approximately 180,000 new cases are diagnosed each year (CDC 2006)
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From page 27... ...
In contrast, the image taken after treatment shows a marked decrease in FDG up take, indicating a favorable response to therapy. FDG-PET has the potential to im prove patient care by allowing treatments with approved medicines to be selected to maximize individual patient response (Kelloff et al.
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From page 28... ...
Other current as well as next-generation nuclear medicine procedures will similarly accelerate the delivery of personalized care to the patient. Physiological Assessment Nuclear medicine imaging will enable functional investigations of numerous aspects of normal and abnormal physiologies.
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From page 29... ...
. The time and expense required to bring a drug to market may be reduced by using nuclear medicine imaging technologies to identify which drugs should advance from animal to human studies, reveal mechanisms of drug action, evaluate drug distribution to target tissue; establish the drug occupancy of receptor sites; assess the actions of new agents on specific molecular targets or pathways; and determine appropriate dose range and regimen (Eckelman 2003)
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Treatment trials are the most common, and clinical trials are conducted in phases, where each phase has a different purpose. Phase I trials: An experimental drug or treatment is given to a small group of patient volunteers (usually between 20 and 80)
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From page 31... ...
In this way, the optimal biologic dosage may be used without running the risk of binding to collateral receptor targets in the brain and producing undesirable toxicity. Targeted Radiotherapeutics Therapeutic nuclear medicine procedures are now used to treat thyroid cancer and other thyroid disorders, relieve pain from bone metastases, or
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From page 32... ...
treat blood disorders such as lymphoma and polycythemia vera.5 Research programs and clinical trials are currently underway to address the utility of molecularly targeted radionuclide therapies in treating rheumatoid arthritis, degenerative joint diseases, heart disease, non-small-cell lung cancer, colon cancer, prostate cancer, pancreatic cancer, ovarian cancer, meningitis, and AIDS. However, this is only the beginning.
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From page 33... ...
Compact Devices to Generate Radionuclides with Short Half-Lives One of the principal obstacles to realizing the full potential of nuclear medicine in advancing medical science and patient care is the limited accessibility of radionuclides with short half-lives (i.e., less than 30 minutes)
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From page 34... ...
The initial investment for such a cyclotron is $2 million, with an additional $0.5 million needed for renovation and installation. At a minimum, another $0.8 million is needed to cover annual operating costs,7 assuming no major repairs are needed (personal communication, Thomas Budinger, Lawrence Berkeley National Laboratory, July 2, 2007)
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From page 35... ...
CT, MRI, and PET all provide complementary "views" of normal and diseased tissues, with PET offering quantitative functional information and MRI and CT scans providing high-resolution anatomical information. The power of combined-modality imaging will increase dramatically as molecularly targeted radiotracers with high specific activity are developed and as the sensitivity and resolution of PET increase to allow for high-resolution, temporal imaging.
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From page 36... ...
. FIGURE 1 Positron emission and annihilation.
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From page 37... ...
Since the closer photon will arrive at the detector first, calculat ing the difference in arrival time helps determine the location of the annihilation event between the two detectors. Theoretically, perfect time-of-flight information would eliminate the need to reconstruct images.
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From page 38... ...
However, for the field to flourish, there are scientific, regulatory, and financial obstacles that need to be addressed. Section 2.3.1 describes the basic science research challenges; Section 2.3.2 summarizes clinical research challenges; Section 2.3.3 summarizes the regulatory hurdles and explores the costs and economics of the field; and Section 2.3.4 discusses radiation exposure from nuclear medicine procedures and its relative safety.
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From page 39... ...
In the field of targeted radionuclide therapy, for example, there are currently too many individual clinical trials enrolling too few patients and treating them in widely varying ways. Similarly, clinical trials for diagnostic imaging suffer from different clinical centers using different imaging platforms.
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For example, obtaining an IND to permit clinical evaluation of a promising targeted radiotherapeutic agent requires toxicology data and information on pharmacokinetics and dosimetry of the radiopharmaceutical (FDA 2005)
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From page 41... ...
to examine the feasibility of monitoring and quantifying the cumulative radiation exposure sustained by individual patients in medical settings; and (b) to discuss methods to educate physicians and the public on the appropriate use and risks of low linear energy transfer radiation in order to reduce unnecessary exposure in the medical setting." The increasing use of FDG-PET scanning, which provides approximately the same absorbed dose to patients as cardiac studies, deserves similar considerations as well as raises some additional concerns given the higher energy of annihilation (positron-producing)
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From page 42... ...
Although there are challenges ahead, by investing in the infrastructure of radionuclide production; committing to train and nurture the next generation of nuclear medicine researchers, technicians, and clinicians; and developing a program that will sustain nuclear medicine research, we will all reap the benefits of better health care.
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