Cataracts are formed when cells are damaged or die in the lens of the eye. The dose level which leads to cataract induction depends on the dose fractionization, ie. how many weeks/months was the dose delivered. The radiation dose which has been shown to cause cataract is between 2mGy (single fraction) -5.5 mGy (dose distributed […]
Cataract Induction from X-ray Radiation (Illustrations, Dose levels) Read More »
The Contrast to Noise Ratio (CNR) in a medical image is a measure of the contrast between the tissue of interest and the background (i.e. the neighboring tissue). The Signal to Noise Ratio (SNR) is a measure of the image signal in a given region to the background. The ability to visualize objects in a
The spatial resolution of an x-ray or CT system is a measure of how the ability of a system to differentiate small structures. If you imagine imaging a very small point like object an image of that object is called the Point Spread Function (PSF). When this function is radially averaged the Line Spread Function
X- ray Resolution (PSF, MTF, NPS, DQE) for radiologic technologists Read More »
In x-ray imaging (radiography and CT) the contrast between the tissues in the image is generated by the difference between the x-ray attenuation (influenced by density and atomic number). In this post we demonstrate the material dependence for x-ray attenuation. For all radiographers, radiologic technologists and students understanding the basic principles of x-ray interactions, which
X-ray attenuation of tissues [thickness, atomic number] for Radiologic Technologists Read More »
An interactive calculator for answering the question: what is the thickness of material A that we would need to match the x-ray transmission through a given thickness of material B. For instance how much water is equivalent to 1mm of lead in stopping an 50 keV x-rays? If you have been loosing sleep over such
A review of radiation dose measurements in CT and a calculator for changing multiple technical parameters (kVp, mA, pitch, s) and observing the effect on the mA needed to keep the dose relatively constant. We also provide a couple use cases that would motivate changing the technical parameters of a protocol at the time of
Here is a simple calculator to compute the Effective Dose (mSv) from the Dose Length Product (mGy cm) for a CT exam of a single organ. In this article we review how dose measurements are made and how the Effective Dose is related to the Absorbed dose, and the approximation that is used in CT
This is a calculator the transmission, (fraction of the x-ray beam), that will penetrate different thickness of materials such as water, bone, air and lead. This calculator is useful to get a sense of what fraction of the x-ray beam will pass through different objects. The calculator has the option for a few energies of
In this post we present a brief history of Radiology equipment focusing on the major developments which lead to x-ray Radiography, CT, SPECT, PET and Ultrasound imaging. 1880 Piezo-electric effect discovered Ultrasound Predecessor French physict brothers Piere and Paul-Jacques Curie discovered that when pressure is put on certain crystals that electricity comes out. This effect
Illustrated History of Radiology (X-Ray, CT, PET, MRI, Ultrasound) Read More »
Highlights of X-ray radiology from the discovery of x-rays through its multiple uses including: radiography, fluoroscopy, mammography, cardiac catherization, digital subtraction angiography, and bone densitometry. 1875 Crookes Cathode Ray Tube Invented Modern X-ray Tube Predecessor The cathode ray tube was invented by English physicist William Crookes before scientists had discovered x-rays or electrons. After later
