Nuclear Medicine and PET. D. J. McMahon rev cewood

Transcription

1 Nuclear Medicine and PET D. J. McMahon rev cewood

2 Key Points Nuclear Medicine and PET: Imaging: Understand how Nuc Med & PET differ from Radiography & CT by the source of radiation. Be aware of As Low As Reasonably Practicable, ALARP Understand the difference between the scintillation camera and the PET scanner Be aware of the chemical 18 F FDG (fluorodeoxyglucose) & the element Tc (Technetium) Understand what the color spectrum means in a PET visualization: Brighter, hotter colors indicate high glucose uptake; brain, liver, cancer Therapy: Be aware of interventional nuclear medicine therapy and radiosurgery techniques; Radiopharmaceuticals, Brachytherapy, Radiosurgery, Gamma Knife, Linac.

3 Nuclear Medicine Imaging - The application of radioactive substances in the diagnosis of disease. - Nuclear medicine, in a sense, is "radiology done inside out" or "endoradiology" because it records radiation emitting from within the body rather than radiation that is generated by external sources like X-rays. - Nuclear medicine scans differ from radiology as the emphasis is not on imaging anatomy but imaging the function instead. It is called a physiological imaging modality. - In nuclear medicine imaging, radiopharmaceuticals are taken internally, intravenously or orally. Then, external detectors (gamma cameras) capture and form images from the radiation emitted by the radiopharmaceuticals. - All human radiation exposures should be kept As Low As Reasonably Practicable, ALARP (replaces ALARA).

4 John Lawrence Anger scintillation camera Hal Anger

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6 Gamma Imaging Camera ( gic ) or γ-camera

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11 GE Maxicamera 400 Gamma Camera PET Scanner

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13 Patient with infection: Patient with joint disease: Nuclear medicine scans can be superimposed, using software or hybrid cameras, on images from modalities such as CT or MRI to highlight the part of the body in which the radiopharmaceutical is concentrated. Often referred to as image fusion or co-registration.

14 Before-&-after isotope studies of two patients treated with a study medication for Non-Hodgkins Lymphomas:

15 PET: Positron Emission Tomography PET is both a medical and research tool. It is used heavily in clinical oncology. A tomographic technique that uses isotopes which emit two gamma rays rather than one, enabling images with a high signal-to-noise ratio and good spatial resolution. PET is used for physiology and function rather than anatomy. PET scans are more expensive than "conventional" imaging using computed tomography (CT) and magnetic resonance imaging (MRI) Oncology scans using 18 F FDG (fluorodeoxyglucose) tracer make up over 90% of all PET scans in current practice This tracer is a glucose analog that is taken up by glucose-using cells. This results in intense radiolabeling of tissues with high glucose uptake, such as the brain, the liver, and most cancers. Brighter, hotter colors indicate high glucose uptake

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17 47 y/o female, pre- & post chemotherapy for leukemia:

18 MRI and PET scans of brain, normal and with Alzheimer s Disease:

19 (animation) Maximum Intensity Projection (MIP) of a wholebody positron emission tomography (PET) acquisition of a 79 kg (174 lb) weighting female after intravenous injection of 371 MBq of 18 F-FDG (one hour prior measurement). The investigation has been performed as part of a tumor diagnosis prior to applying a radiotherapy (tumor staging step) Besides normal accumulation of the tracer in the heart, bladder, kidneys and brain, liver metastases of a colorectal tumor are clearly visible within the abdominal region of the image. MIPS-anim.gif

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21 Interventional Nuclear Medicine Therapy... Radiopharmaceuticals typically consist of a radioactive atom (also known as a radionuclide) combined with a cell-targeting molecule that seeks and destroys cancer cells. Some radionuclides have the ability to target specific cells on their own. Some Conditions include: hyperthyroidism and thyroid cancer refractory lymphoma neuroendocrine tumors palliative bone pain treatment Brachytherapy (from Greek word for "short"), or internal radiation therapy for prostate cancer. A doctor or clinician implants radioactive seeds into the prostate gland using an ultrasound for guidance. Anywhere from 40 to 100 seeds are commonly implanted.

22 Interventional Nuclear Medicine Therapy... Radiosurgery Radiosurgery is the destruction of precisely selected areas of tissue using ionizing radiation rather than excision with a blade. Like other forms of radiation therapy (also called radiotherapy), it is usually used to treat cancer. The principle of this instrument is to hit the intra-cranial target with narrow beams of radiation from multiple directions. The beam paths converge in the target volume, delivering a lethal cumulative dose of radiation there, while limiting the dose to the adjacent healthy tissue. In stereotactic radiosurgery (SRS), the word "stereotactic" refers to a threedimensional coordinate system that enables accurate correlation of a virtual target seen in the patient's diagnostic images.

23 Interventional Nuclear Medicine Therapy Gamma Knife The Gamma Knife is used to treat brain tumors. It consists of several radioactive sources placed in a kind of helmet with central channels for irradiation with gamma rays. This produces slit-like radiation lesions for functional neurosurgical procedures to treat pain, movement disorders, or behavioral disorders that do not respond to conventional treatment. Linac A similar approach uses a linear particle accelerator or Linac which emits high energy X-rays, called Cyberknife therapy. Radiosurgery does not remove the tumor but inactivates it biologically. Lack of growth of the lesion is normally considered to be treatment success. In the U.S. the Food and Drug Administration (FDA) regulates radiosurgery devices, whereas the Gamma Knife is regulated by the Nuclear Regulatory Commission.

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25 PET videos: iphone app for PET visualization: Scans of brain injury for a lawsuit: Major players in Nuc Med > ADAC/Philips > GE > Hitachi/Vision > IS 2 > Siemens > SMV > Sopha > Toshiba > NuQuest Workstations > Segami Workstations