Brain tumors are often treated with radiation consisting of high energy photons, like gamma rays, that kill cancer cells through apoptosis, autophagy, DNA damage, etc.  Local drug delivery provides a high concentration of drug in the tumor while decreasing systemic toxicity.Researchers study a new drug that emits gamma rays at 50 × 1018 Hz and is injected into tumors using a vascular catheter and x-ray imaging guidance.  The x-rays have a lower frequency, 100 × 1015 Hz, compared to gamma rays.  The catheter also collects tumor samples for optical analysis using lenses, as shown in Figure 1.Figure 1  A tissue sample placed 2.5 cm from the center of a convex lens forms an image 10 cm from the lensAn x-ray tube propels high energy electrons at a tungsten target to produce x-rays but also heats the target.  To avoid overheating, tube current I is applied only to collect one x-ray image, followed by a cooling period (Figure 2).  The tungsten target is 1000 °C and 2 cm long after cooling, but it heats to 2000 °C and increases in length by 0.1 mm when generating x-rays.Figure 2  X-ray tube current over timeThe drug is injected into a blood vessel feeding the tumor with the injection syringe and catheter at the same level to eliminate gravitational effects.  In one experiment, two drug doses were compared and the higher drug dose had a greater therapeutic response.  In another experiment, the drug injection velocity was varied and the lowest injection velocity had the greatest therapeutic response. Question 44The advantage of using gamma rays for tumor therapy over x-rays is that gamma rays:A.are not electromagnetic radiation.B.are photons.C.have higher energy.D.have a longer wavelength.

Recall which radioisotope is often used in radiotherapy machines as a source of gamma rays.

Which of the following statements about gamma rays is incorrect?Gamma rays are used in both medical imaging and radiotherapyGamma rays are produced when there are changes to the nuclei of atomsGamma rays can penetrate the body and can damage, mutate or kill cellsWhen a gamma ray is emitted, the amount of nuclear energy stored within a nucleus increases2Which of the following statements about x-rays is incorrect?X-rays are the second shortest-wavelength type of wave on the electromagnetic spectrum (only gamma rays have shorter wavelengths than x-rays)X-rays are used in both medical imaging and medical treatmentX-rays are produced by the rapid deceleration of free electrons and by changes in the organisation of the electrons that orbit the nuclei of atomsX-rays are absorbed effectively by soft body tissue but pass easily through bone3Which of the following types of electromagnetic radiation has the lowest frequency?Radio wavesMicrowavesUltravioletVisible light4In the visible spectrum, which colour lies between blue and violet?LilacPinkUltravioletIndigo5Which of the following does NOT involve the use of infrared waves?RadiotherapyRemote controlsCookersFibre-optic communications6What a control variable?The variable which is measured in an investigationThe variable which is changed in an investigationA variable which is more important than (at least some of) the other variables in an investigationA variable that is kept constant in an investigation

The scientific unit of measurement used to measure the dose received from radiations, such as X-rays or background radiation, is the millisievert (mSv). The table shows the X-ray dose resulting from CT scans of various parts of the body. The table also frequencywavelengthfrequency = wave speed / 1500(3.0*10^8)/1500 = 2*10^5Hz2*10^5can cause burnscan cause skin cancerradiographythe ability to penetrate the skin and tissue but not the bone allowing for an imageof the bones to be createdPage 18 shows the time it would take to get the same dose from background radiation. Part of the body X-ray dose in mSv Time it would take to get the same dose from background radiation Abdomen 9.0 3 years Sinuses 0.5 2 months Spine 4.0 16 months A student suggests that the X-ray dose and the time it would take to get the same dose from background radiation are directly proportional. Use calculations to test this suggestion and state your conclusion.

X-ray imaging requires the use of harmful ionizing radiation to image structures inside the body.  An x-ray image intensifier, shown in Figure 1, allows high-quality imaging with very low radiation exposure to the patient.Figure 1  Schematic of an x-ray image intensifierThe x-ray image intensifier amplifies the imaging signal by approximately 300,000 times.  The intensifier converts the image data from x-ray photons to visible light, then to electrons, and back to visible light.  At each conversion stage, the signal is amplified up to 1,000 times.The x-ray image intensifier consists of a vacuum chamber that contains an input phosphor, a photocathode, focusing electrodes (not shown in Figure 1), an anode, and an output phosphor.  The anode voltage is 25 kV higher than the photocathode, generating a strong electric field in the vacuum.  The input phosphor converts x-ray photons into visible light, which then ejects electrons from the photocathode.  Even with an anode voltage of 25 kV, no current will flow through the vacuum unless electrons are ejected from the photocathode.  Ejected electrons are accelerated toward the anode and focused onto the output phosphor.  At the output phosphor, the electrons are converted back into visible light, allowing image data to be recorded with a camera or video system.  (Note:  Use c = 3 × 108 m/s in a vacuum, if needed.)Question 30Is the vacuum chamber in an x-ray image intensifier an electrical insulator?A.Yes, because only electrons ejected from the photocathode can travel through the vacuum chamberB.Yes, because no electrons can travel through the vacuum chamberC.No, because electrons can travel through the vacuum chamber even without x-rays at the input phosphorD.No, because electrons in the vacuum chamber are not exposed to a voltage difference

Cancer Treatment Options: Treating Xerostomia Following Radiation