Physics • How Radiology Works

What is Computed Radiography? (Illustrated guide for Rad Techs)

Computed Radiography (CR) is a method to generate digital images in x-ray radiography that uses photo-stimulated luminescence to store the x-ray exposure into a latent image, that is then digitized. Computed Radiography is rapidly replacing film screen radiography, and at the same time a newer technology termed Digital Radiography (DR) is beginning to displace CR …

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Digital Radiography (Direct vs Indirect Flat panels)

X-Ray, Physics

Digital radiography detectors are used to directly acquire x-ray images in place of film or computed radiography (CR) systems and are separated into direct and indirect detectors. Direct detectors convert from the x-rays electrons (that are measured), whereas indirect detector convert from x-rays to visible light first and then to electrons (that are measured). Digital …

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Should previous CT dose influence prescribing an exam? [guide for radiologic technologists, also for x-ray and nuc med]

Dose, Physics

Is the risk of developing cancer from radiation dependent on previous radiation dose? In order to answer the question, “Should previous CT dose influence a given exam?” we need to understand if there are cumulative effects of being exposed to radiation that will change the relative risk for subsequent exams. For each patient that is …

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Filtered BackProjection (FBP) Illustrated Guide for Radiologic Technologists

CT, Physics

The Filtered BackProjection (FBP) algorithm is the basis for image reconstruction (converting from the measured data to the image) on modern CT scanners. FBP is a fast and direct method to generate CT images. As the name suggests it is composed of two main steps filtering the data (along the row direction in the detector) …

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X-ray physics intro for starting x-ray school, a step by step guide for new radiologic technologists (radiographers).

Physics, X-Ray

If you are a student in training or totally new to x-ray physics are you feeling: overwhelmed or confused with the all the terminology and physics concepts pressured or embarrassed that you don’t know the answers to questions from senior technologists during your clinicals unsure of radiation effects and nervous about mass media coverage you …

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X-Ray Tech Exposure Calculator, 5 Simple relationships that guide Technical Parameters In X-Ray Imaging

Calculators, Physics

An interactive calculator for changing multiple technical parameters (kVp, SID, s, Bucky Factor) in and observing the effect on the mA needed to keep the exposure on the image receptor constant. Great for studying for your ARRT boards or brushing up to sharpening your technical parameter skills for Radiography exams. X-Ray Exposure Calculator Overview of …

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Slip Ring CT pictorial guide [helical, cardiac, perfusion, 4DCT]

Physics, CT

After the invention of CT itself and moving from first generation CT to third generation CT the incorporation of slip rings into modern CT is the most import enabler of improved scanning. It has enabled a number of clinical applications which were hypothesized when the Nobel Prize was granted for CT, but not possible until …

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Illustrated comparison of CT Scan Modes [axial, helical, wide-cone axial, low pitch, high pitch] for Radiologic Technologists

CT, Physics

CT (Computed Tomography) scanning can be accomplished with multiple different scan modes which have different characteristics. Axial non-volumetric scanning is how CT began where one (or just a few) slices are acquired during each gantry rotation. Traditional helical scanning (some call spiral) has the advantage of being faster than non volumetric axial scanning and also …

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LET, RBE and OER (Oh My!). Radiologic Technologists Guide to 3 Radiation Biology Terms.

Physics, Dose, Uncategorized

LET (Linear Energy Transfer), RBE (Relative Biological Effectiveness) and OER (Oxygen Enhancement Ratio) are important terms in radiation biology and relate to the relative damage that will occur with radiation under different circumstances. As LET increases there are more energetic electrons deposited closely together and thus damage to DNA is more likely. Therefore, even with …

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Acute vs Chronic, tissue sensitivities to radiation and [4 cell damage pathways] for Radiologic Technologists

Dose, Physics

Radiation damage can be either acute or chronic depending on the conditions. Acute radiation effects are due to short exposures to radiation at a relatively high dose rates and the impact is observed within days or weeks (examples include acute radiation syndromes). Whereas chronic radiation effects are typically associated with lower doses and the effects …

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