Modalities and Data Acquisition

Abstract

Acquisition modalities are the image engines in a picture archiving and communications system (PACS). Of the modality mix, radiography comprises approximately 60–70% of all studies performed in a diagnostic radiology department. Since analog screen-film recording technology is still being used in many hospitals and clinics, the implementation of a PACS for electronic image acquisition, display, and archiving is associated with the conversion of analog to digital radiography technology. But the imaging modalities are much more than radiography. Real-time digital fluoroscopy, interventional angiography, and cardiology studies are producing hundreds to thousands of images per examination. Cross-sectional imaging acquisition systems such as computed tomography (CT), magnetic resonance imaging (MRI), ultrasound (US), single-photon emission computed tomography (SPECT), and positron-emission computed tomography (PET) are expanding rapidly and are in many cases becoming the examinations of choice over projection imaging.

Self-Assessment Questions

• 1. The image matrix size of a computed tomography image is?

  • a. 128 × 128 × 12 bits

  • b. 128 × 192 × 12 bits

  • c. 256 × 256 × 12 bits

  • d. 512 × 512 × 8 bits

  • e. 512 × 512 × 12 bits

  As a follow-up, consider the other distracters in the question and think about the modalities that produce those size images.

• 2. Which one of the following modalities uses nonionizing radiation from interactions with the body to generate the resultant image?

  • a. Pulsed fluoroscopy

  • b. Computed tomography

  • c. Positron emission tomography

  • d. Magnetic resonance

  • e. Single-photon emission computed tomography

• 3. Of the following, which modality has the largest data size for a single image?

  • a. MRI with an 8 channel phased array coil

  • b. CT with a 128 channel multidetector array

  • c. DR chest X-ray with 43 × 43 cm FOV, 200 μm detector element

  • d. Digital photospot camera with a 40 cm diameter intensifier

  • e. Mammography with 24 × 30 cm FOV, 50 μm detector element

• 4. A radiographic image has areas of saturation and no anatomical information, but is acquired using an appropriate technique (kV and mAs). This outcome is likely due to which one of the following?

  • a. histogram scaling error

  • b. overexposure

  • c. underexposure

  • d. antiscatter grid

  • e. exposure index miscalibration

• 5. Which procedure is used to transfer patient demographic information from the RIS to the image acquisition device?

  • a. Performed procedure step (PPS)

  • b. Presentation of grouped procedures (PGP)

  • c. Key image note (KIN)

  • d. Modality worklist (MWL)

  • e. Portable data for imaging (PDI)

• 6. Which image acquisition technique uses annihilation radiation to create tomographic images?

  • a. SPECT

  • b. PET

  • c. CT

  • d. Emission imaging

  • e. γ-ray absorptiometry

• 7. The largest drawback of radiography compared to computed tomography is ______.

  • a. higher radiation dose

  • b. lower spatial resolution

  • c. anatomical superimposition

  • d. time required for the examination

  • e. image storage requirements

• 8. Which of the following is the most important environmental patient safety aspect concerning MRI?

  • a. Tissue heating

  • b. RF noise

  • c. Ferromagnetic projectile

  • d. Gradient switching

  • e. Eddy currents

• 9. The window width and window level setting most appropriate for viewing a CT image when bones are being evaluated (e.g., wide contrast latitude) is closest to which setting? (WW is window width, WL is window level).

  • a. WW = 400 WL = 40

  • b. WW = 2000 WL = 300

  • c. WW = 80 WL = 35

  • d. WW = 200 WL = 50

  • e. WW = 1500 WL = –700

• 10. The CT number most likely to be encountered in the lung area of a CT image is which of the following?

  • a. –800

  • b. –20

  • c. 0

  • d. 500

  • e. 2000

• 11. Which of the following modalities has the highest spatial resolution?

  • a. MRI

  • b. Fluoroscopy

  • c. CT

  • d. Radiography

  • e. Ultrasound

• 12. Which one of the following parameters for an MR image acquisition is user defined, rather than a property of the patient’s tissues?

  • a. T1

  • b. T2

  • c. Proton density

  • d. TR

  • e. Blood flow

• 13. An attribute that a typical diagnostic PACS workstation used for ultrasound image review does not commonly provide is the ability to ______.

  • a. display acoustic grayscale images

  • b. simultaneously play multiple avi video clips

  • c. retrieve archived ultrasound images

  • d. show color images for Doppler studies

  • e. use measurement tools for evaluating distances

• 14. Besides providing high-resolution anatomy fused with low-resolution metabolic activity, the other chief reason for CT and PET system combination is to ________.

  • a. provide attenuation correction for the PET reconstruction

  • b. reduce the injected dose of the radionuclide

  • c. eliminate the need for a CT scan elsewhere

  • d. use the CT scan data for treatment planning

  • e. allow 3D rendering for improved diagnosis