Positive medical aspects of radiation

Transcription

1 Positive medical aspects of radiation Diagnosis and treatment of disease Michael Joiner Wayne State University Detroit, Michigan Therapeutic Radiological Physics The therapeutic applications of X-ray, gamma ray, neutron, electron, and charged-particle beams, and radiation from sealed radionuclide sources The equipment associated with their production, use, measurement, and evaluation The quality of images resulting from their production and use Medical health physics associated with this subfield Effects of Radiological Agents 1

2 Cell killing by ionizing radiation Diagnostic Radiological Physics The diagnostic applications of X-rays, gamma rays from sealed sources, ultrasonic radiation, and radio frequency radiation and magnetic fields The equipment association with their production, use, measurement and evaluation The quality of images resulting from their production and use Medical health physics associated with this subfield Effects of Radiological Agents 2

3 Discovery of X-rays On 8 Nov 1895, Wilhelm Conrad Röntgen (accidentally) discovered an image cast from his cathode ray generator Medical Nuclear Physics The therapeutic and diagnostic applications of radionuclides in unsealed sources The equipment association with their production, use, measurement, and evaluation The quality of images resulting from their production and use Medical health physics associated with this subfield Effects of Radiological Agents 3

4 Gamma Camera Scan Liver metastasis from prostate carcinoma IV administration of Tc99m Accumulates in areas of increased blood flow due to active bone metabolism, oedema of inflammation or the angiogenesis associated with tumors Therapeutic Radiological Physics An Introduction Effects of Radiological Agents 4

5 Modern radiation therapy using high energy X-rays and electrons Radiation Therapy: Isocentric patient Effects of Radiological Agents 5

6 100 Therapeutic Gain A compromise between tumor cure and normal tissue complications Complication (%) 50 Normal Tissue Damage Tumor Cell Killing Tumor Control (%) Dose (Gy) External beam radiation therapy 25 Gy 45 Gy 65 Gy 70 Gy 78 Gy 76 Gy 3D Conformal Technique for Treating Prostate Cancer Effects of Radiological Agents 6

7 9-field Head & Neck IMRT case Diagnostic Radiological Physics An Introduction Effects of Radiological Agents 7

8 Diagnostic use of X-rays Angiography: Subtraction Imaging Effects of Radiological Agents 8

9 Computed Radiography AC-3 ADC / EDR PACS Soft-Copy Read Hard Copy QCW Network Computed Tomography principle X-rays intensity angle Effects of Radiological Agents 9

10 Example of a CT image of abdomen Axial image looking up from the feet Liver metastasis from colon carcinoma Medical Nuclear Physics An Introduction Effects of Radiological Agents 10

11 Medical Nuclear Physics Functional and morphological imaging Radionuclide therapies Nuclear Medicine Radioactive material attached to agent Physical Half-life of radioactive material Biological Half-life of radioactive material A t = A 0 e -λt Radiopharmaceutical administered to patient Wait for distribution Radioactivity yields images of function Effects of Radiological Agents 11

12 Image fusion: MRI and NMI MRI (anatomy) NMI (functional) Positron Emission Tomography (PET) β + Decay Proton-rich radioisotopes e.g. 15 O, 11 C, 18 F Produced by proton bombardment in a particle accelerator called a CYCLOTRON Decay by: p n e + ν e + = positron. This is ANTI-MATTER 18 F ½ life ~ 110 minutes. 11 C ½ life ~ 20 minutes. 15 O ½ life ~ 2 minutes!! Get that cyclotron near the scanner!! Effects of Radiological Agents 12

13 Positron Emission Tomography (PET) Rings of dense & segmented scintillation crystals (BGO) coupled to PMT s surround patient. ~ 1mm 2 x 511 kev photons emitted back-to-back at annihilation. Image of human brain - Stroke Glucose molecule labelled with Fluorine-18 Dead areas of brain No glucose metabolism Intravenous administration Effects of Radiological Agents 13

14 Radiation is GOOD for mankind Modern medicine depends on radiation! Specific uses are in: Therapeutic radiology e.g. curing cancer with high precision X-ray delivery Diagnostic radiology e.g. angiography, and high resolution computerized tomography Medical nuclear physics e.g. positron emission tomography to measure organ function Effects of Radiological Agents 14