# Physics and Instrumentation

 The flashcards below were created by user randy794 on FreezingBlue Flashcards. Partial volume averaging on the CT image may be decreased by A. decreasing matrix size B. increasing slice thickness C. increasing matrix size D. decreasing slice thickness D. decreasing slice thickness(this multiple choice question has been scrambled) The loss of anatomic information between contiguous sections due to inconsistent patient breathing is called A. overshoot artifact B. out of field artifact C. misregistration D. cupping artifact C. misregistration(this multiple choice question has been scrambled) A CT image is formed in part by projecting back all of the attenuation values recorded during data acquisition onto a A. voxel B. pixel C. reformat D. matrix D. matrix(this multiple choice question has been scrambled) What is the dimension of each pixel in an image with a 512x512mm matrix and a DFOV equaling 25.6cm? A. 0.5mm B. both a and c C. 0.5cm D. 0.05cm B. both a and c the dimension of a pixel may be calculated by dividing the FOV by the matrix size(this multiple choice question has been scrambled) The following formula is used to calculate the linear attenauation coefficient: I= Ioe The reduction in intensity of an xray beam as it interacts with matter is termed A. transmission B. attenuation C. luminescence D. scatter B. attenuation(this multiple choice question has been scrambled) The major disadvantage of the fan-shaped xray beams used in modern CT units when compared with the pencil-thin beams is A. excess tube wear B. increased patient dose C. decreased transmission dose D. increased transmission measurements B. increased patient dose(this multiple choice question has been scrambled) Which of the following is the most common type of noise found in the CT image? A. filter noise B. artifactual noise C. statistical noise D. electronic noise C. statistical noise(this multiple choice question has been scrambled) Scintillation crystals are used exclusively as detectors in _______CT scanners A. electron beam B. fourth-generation C. third-generation D. spiral B. fourth-generation(this multiple choice question has been scrambled) A first generation CT scanner consists of an xray tube and two detectors that translate across the patient's head while rotating in 1 degree increments for a total of A. 360 B. 180 C. 90 D. 45 B. 180(this multiple choice question has been scrambled) Which of the following factors does not affect the dimensions of a voxel? A. slice thickness B. DFOV C. matrix-size D. kernel D. kernel the dimension of a voxel is determined by mutiplying the pixel dimension by the slice thickness(this multiple choice question has been scrambled) Areas of a CT image that contain abrupt changes in tissue density are electronically represented by which of the following? A. postitive CT numbers B. low spatial frequencies C. negative CT numbers D. high spatial frequencies D. high spatial frequencies(this multiple choice question has been scrambled) Which of the following is an analytic form of image reconstruction? 1. iterative technique 2. Fourier reconstruction 3. filtered back-projection A. 1,2, and 3 B. 1 only C. 2 and 3 only D. 1 and 2 only C. 2 and 3 only(this multiple choice question has been scrambled) The term used to describe the relation between the linear attenuation coefficients of an object and the calculated CT numbers is A. linearity B. mottle C. quantum noise D. spatial resolution A. linearity(this multiple choice question has been scrambled) The component of the CT scanner responsible for the mathematical calculations of the image reconstruction process is the A. analog-to-digital converter B. digital-to-analog converter C. Data acquisition system (DAS) D. array processor D. array processor(this multiple choice question has been scrambled) Which of the folowing statements regarding retrospective image reconstruction is false? A. the algorithm, matrix sixe, and DFOV may all be changed B. the slice thickness and the SFOV may be changed C. retrospective image reconstruction may be used to adjust the center of the displayed image D. scan (raw) data must be available B. the slice thickness and the SFOV may be changed(this multiple choice question has been scrambled) Which of the following decreases the noise of a CT image? A. increase in matrix size B. decrease in dose C. decrease in slice thickness D. decrease in matrix size D. decrease in matrix size(this multiple choice question has been scrambled) Increasing the pitch during a spiral CT examination adversely affects the spatial resolution along with which of the following? A. y axis B. axial plane C. x axis D. z axis D. z axis(this multiple choice question has been scrambled) When an operator reduces the SFOV for a particular body part, which of the following technical changes occurs? A. the displayed image appears smaller B. a smaller number of detectors are activated C. the displayed image appears larger D. spatial resolution increases B. a smaller number of detectors are activated(this multiple choice question has been scrambled) The mathematical manipulations required during the reconstruction of a CT image are accomplished using a(n) 1. algorithm 2. kernel 3. mathematical filter function A. 1, 2, and 3 B. 1 and 3 only C. 1 only D. 1 and 2 only A. 1, 2, and 3(this multiple choice question has been scrambled) Which of the following technical parameters would greatly improve the quality of CT studies requiring multiplanar reformats? A. overlapping scans with narrow section thickness B. wide section thickness C. contiguous scans with wide section thickness D. noncontiguous scans A. overlapping scans with narrow section thickness(this multiple choice question has been scrambled) Which of the following mathematical techniques is used exclusively for image reconstruction with spiral CT scanners? a. back-projection c. convolution c. interpolation d. iterative techniques c. interpolation Which of the following reduces scatter radiation reaching the detectors? A. postpatient collimation B. both a and c C. prepatient collimation D. predetector collimation B. both a and c(this multiple choice question has been scrambled) A voxel may be defined as which of the following? A. an arrangement of pixels B. the portion of the CRT displaying the image C. a volume element D. a miniature image C. a volume element(this multiple choice question has been scrambled) Which of the following would increase spatial resolution of a CT examination using the following parameters: large focal spot size, 10mm sections, 512 X 512mm matrix? 1. change to small focal spot size 2. perform 5mm sections 3. reconstruct images in a 320 X 320mm matrix A. 1 and 2 only B. 1 and 3 only C. 1 only D. 1, 2, and 3 A. 1 and 2 only(this multiple choice question has been scrambled) A pixel may be defined as A. a picture element B. the portion of the CRT displaying the image C. a miniature image D. a volume element A. a picture element(this multiple choice question has been scrambled) The mathematical technique that involves the estimation of an unknown value from values on either side of it is known as A. interpolation B. filtering C. summation D. convolution A. interpolation(this multiple choice question has been scrambled) When compared with conventional radiography, CT produces diagnostic images with improved A. spatial resolution B. patient dose reduction C. minute detail D. low contrast resolution D. low contrast resolution(this multiple choice question has been scrambled) In 1917, the Austrian mathematician________ proved that it was possible tp reconstruct a three-dimensional object ftom the infinite set of all its projections A. Radon B. Tsien C. Bracewell D. Cormack A. Radon(this multiple choice question has been scrambled) Which of the following is not commonly used as a CT scintillation detector material? A. silver halide B. cadmium tungstate C. ceramic rare earth D. bismuth germinate A. silver halide(this multiple choice question has been scrambled) Authorrandy794 ID5970 Card SetPhysics and Instrumentation Descriptionct, registry, physics Updated2010-02-03T16:49:44Z Show Answers