Ch 15: Display and Image Processing Review Questions

7. What is the number of shades that can be represented by 10 bits?

1,024 different gray shades are stored using 10 bits. 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 1,024 Ch 15 Pg. 246

6. What is the number of shades that can be represented by 8 bits?

256 different gray shades are stored using 8 bits. 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 256 Ch 15 Pg. 246

8. What is the number of shades that can be represented by n bits?

2n different gray shades can be stored using n bits. Ch 15 Pg. 246

4. How many gray shades can be represented by a group of: 4 bits? 2 bits?

4 bits: represents 16 shades 2 bits: 4 shades (To determine the number of gray shades that a group of bits can represent, multiply 2 by itself as many times as there are bits) Ch 15 Pg. 245

467. Which of the following components typically has the lowest dynamic range? A. display B. pulser C. amplifier D. demodulator

A. Ch 15 Pg. 266

470. A signal with a 120 dB dynamic range was previously compressed by 40 dB. What is the dynamic range of the original uncompressed signal? A. 160 dB B. 120 dB C. 3 dB D. 80 dB

A. 120+40= 160 dB Ch 15 Pg. 266

468. Why is it necessary for the receiver to perform compression on the electrical signals that it processes? A. the dynamic range of the system's electronics is less than the dynamic range of the received sound reflection B. the display's range exceeds the transducer's dynamic range C. the dynamic range of the receiver is less than the dynamic range of the image processor D. the dynamic range of the display exceeds the dynamic range of all other components of the ultrasound system

A. Compression matches the dynamic range of the signal to the dynamic range of the system's electrical components. Ch 15 Pg. 266

445. What happens to a digital image when the pixel density increases? A. spatial detail improves B. temporal resolution increases C. the field of view expands D. there are more shades of gray

A. Greater pixel density improves spatial detail. Ch 15 Pg. 244

11. Are the following procedures usually pre- or post processing? A. Modifying a frozen image: B. Read zoom: C. Write zoom: D. Adjusting the brightness of a monitor: E. Increasing the receiver gain:

A. Postprocessing B. Postprocessing C. Preprocessing D. Postprocessing E. Preprocessing Ch 15 Pg. 249

462. All of the following are true of read zoom except: A. preprocessing function of a receiver B. same number of pixels are in the original ROI and the zoomed image C. on the screen, the pixels in the zoomed image are larger than those in the ROI D. the same number of ultrasound pulses are used to create the original ROI and the zoomed image

A. Read zoom is post processing. Ch 15 Pg. 249

444. Two digital scan converters are undergoing evaluation. Both produce images of the same size. System A has 1,000,000 pixels, with 10 bits assigned to each. System B has 250,000 pixels, with 12 bits assigned to each. Which system is more likely to have the capability to display very small image details in an image? A. System A B System B C. both are the same D. cannot be determined

A. The scan converter with the greatest number of pixels assigned to an image of fixed size will provide the viewer with the greatest spatial detail. Ch 15 Pg. 243

449. What is the smallest amount of digital storage called? A. bit B. byte C. pixel D. fractel

A. the bit is the smallest amount of digital storage or computer memory. Ch 15 Pg. 245

441. Which of the following is best described as an analog number? A. the weight of a person B. the number of people in a room C. the number of stars in the sky D. the number of tires on a car

A. the weight of a person because it is continuous and can achieve an unlimited number of values. Ch 15 Pg. 243

19. With frequency compounding, how many pulses are transmitted down each scan line? A: 1 B: 2 C: 4 D: can not be determined

A: 1 (With frequency compounding, one pulse is transmitted down each scan line) Ch 15 Pg. 255

18. Which of the following technologies uses long sound pulses to create an image? A: Coded Excitation B: Harmonics C: Pulse Inversion D: Rendering

A: Coded Excitation Ch 15 Pg. 253

3. Which of these statements regarding a bit of computer memory is false? A: It is the smallest element of an image. B: It is bistable. C: Eight bits combine to make a byte. D: It is a component of a digital scan converter

A: It is the smallest element of an image. A bit is not part of an image, it is the smallest element of computer memory. Ch 15 Pg. 245

458. What is the number of binary digits required to store 29 levels of gray? A. 4 B. 5 C. 6 D. 29

B. 5 Ch 15 Pg. 246

450. Which of these is a binary number? A. 12211221 B. 10000000 C. 98765432 D. 01010102

B. A binary number is a string of 0's and 1's only. Ch 15 Pg. 245

452. A byte is composed of _____ bits. A word is composed of _____ bytes. A. 2, 2 B. 8, 2 C. 16, 16 D. 8, 16

B. A string of eight bits of computer memory is a byte. Two bytes make a word. A byte is 8 bits so a word is 16 bits. Ch 15 Pg. 245

438. A video display that is limited to black and white only, with no shades of gray, is called... A. Binary B. Bistable C. Monochrome D. Inchworm

B. A video display with the ability to show black and white only, without any intermediate shades of gray, is called bistable. Ch 15 Pg. 239

451. Two digital scan converters are undergoing evaluation. System A has 1,000,000 pixels, with 4 bits assigned to each. System B has 250,000 pixels, with 12 bits assigned to each. Which system is more likely to display images with very subtle differences in grayscale? A. System A B System B C. both are the same D. cannot be determined

B. Gray scale levels are determined by the number of bits assigned to each pixel in an image. Since System B has 12 bits assigned to each pixel and System A has only 4, System B will display more gray shades and, thus, display subtle differences. Ch 15 Pg. 244

446. Two digital scan converters are undergoing evaluation. System A has 1,000,000 pixels and the picture size is 100 square inches. System B has an image size of 10 square inches composed of 250,000 pixels. Which image is more likely to display very small details? A. System A B System B C. both are the same D. cannot be determined

B. System B has greater pixel density which improves spatial resolution. Ch 15 Pg. 244

439. What is the approximate number of frames that must be presented each second for the human eye to perceive the display without flickering? A. 2 B. 30 C. 100 D. 500

B. The frame rate required to perceive smooth, flicker-free motion is in the range of 30 frames/sec. Ch 15 Pg. 239

463. All of the following are true of write zoom except: A. preprocessing function of the receiver B. the same number of pixels are in the original ROI and the zoomed image C. the pixel size in the zoomed image and the ROI are the same D. in comparison to the zoomed image, fewer ultrasound pulses are used to create the original ROI

B. Write zoom is preprocessing. all pixels in the image are now concentrated into the ROI, thereby increasing the pixel density and image quality of the zoomed portion. Ch 15 Pg. 249

17. What is the primary storage device on a PACS system? A: Magneto-optical storage B: Hard disc drives C: Solid state memory D: Compact discs

B: Hard disc drives Ch 15 Pg. 259

12. What is the primary disadvantage of video tape and computer disc methods of image archiving? A: These methods are very costly B: The information is vulnerable to erasure when exposed to strong magnetic fields C: Only low resolution images are stored. D: Only black and white images are stored.

B: The information is vulnerable to erasure when exposed to strong magnetic fields. Data stored on videotape and computer discs can be erased by strong magnetic fields Ch 15 Pg. 260

466. Which of these components typically has the greatest dynamic range? A. display B. pulser C. amplifier D. demodulator

C. Ch 15 Pg. 266

473. Which of the following terms is not associated with a wide dynamic range image? A. low contrast B. many shades of gray C. bistable

C. A bistable image contains only black and white. AN image described as wide dynamic range contains many shades of gray and my be called "low contrast". Ch 15 Pg. 239

471. Which display is limited to a single pair of brightness or display levels? A. CRT B. binary C. bistable D. grayscale

C. A display that presents data in one of only two colors is bistable. Each dot on the image is either white or black, bright or dark, on or off. Bistable images are considered high contrast. Ch 15 Pg. 239

472. All of the following are consistent with an image containing black and white only with no shades of gray except: A. bistable B. high contrast C. wide dynamic range

C. An image described as wide dynamic range contains many shades of gray. Wide dynamic range (also called high dynamic range) means "many choices". Ch 15 Pg. 239

465. The relationship between the largest and the smallest signal amplitudes processed by a component of an ultrasound system is called the______ and has units of ________. A. decibels, watts B. intensity, W/cm^2 C. dynamic range, dB D. proportionality, dB

C. Dynamic range is defined as the ratio of the largest to the smallest signal amplitude that a device can process. The units of dynamic range are decibels, dB. Ch 15 Pg. 266

447. What is the smallest part of a digital picture called? A. bit B. byte C. pixel D. fractel

C. The basic element of an image is a pixel. Ch 15 Pg. 244

456. With 6 bits, what is the largest number of different gray shades that can be stored? A. 8 B. 16 C. 64 D. 256

C. multiply 2 by itself the same number of times that there are bits Ch 15 Pg. 246

21. In modern elastography, how are the tissues deformed? A: By pressing the transducer into the skin B: With the use of a second probe C: Automatically D: As a result of respiration

C: Automatically Ch 15 Pg. 258

20. Which of the following techniques is used to create image data where none really exists? A: Edge Enhancement B: Temporal compounding C: Fill-in interpolation D: Spatial compounding

C: Fill-in Interpolation. (Fill-in interpolation is used when gaps exist between scan lines. The info is created by this technique is a prediction based on the actual data that surrounds the gaps) Ch 15 Pg. 257

13. Where does coded excitation take place? A: In the transducer B: In the receiver C: In the pulser D: In the PACS system

C: In the pulser Ch 15 Pg. 253

10. Which of the following statements regarding a pixel is false? A: It is the smallest part of a digital image B: A collection of bits, assigned to each pixel, stores the shade of gray C: It displays up to 3 gray shades simultaneously D: Image quality is improved when the number of pixels is high.

C: It displays up to 3 gray shades simultaneously. At any given moment, a pixel can display only a single shade of gray. Ch 15 Pg. 244

457. How many bits are required to display 10 different shades of gray? 14 shades? 15 shades? A. 4 bits, 5 bits, 6 bits B. 10 bits, 14 bits, 15 bits C. 4 bits, 4 bits, 2 bits D. 4 bits, 4 bits, 4 bits

D. Ch 15 Pg. 246

469. A signal with a 120 dB dynamic range is compressed by 40 dB. What is the dynamic range of the compressed signal? A. 40 dB B. 120 dB C. 3 dB D. 80 dB

D. 120-40= 80 dB Ch 15 Pg. 266

440. What was the original purpose for the ultrasound system's analog scan converter? A. to increase the dynamic range of the ultrasound systems B. to make real-time imaging possible C. to increase the sensitivity of the ultrasound system D. to allow for gray scale imaging

D. It allowed for the presentation of gray scale images. Ch 15 Pg. 240

454. What happens to an image when the number of bits allocated to each pixel increases? A. spatial detail improves B. frame rate increases C. field of view expands D. more shades of gray

D. as the number of bits assigned to each pixel increases, the number of different shades of gray increases. Ch 15 Pg. 245

455. What is the maximum number of shades of gray that are represented with 4 bits? A. 4 B. 8 C. 12 D. 16

D. multiply 2 by itself the number of times that there are bits. Ch 15 Pg. 246

2. Which of the following scan converters will provide the best spatial resolution? A: 256 x 256 pixels B: 512 x 512 pixels C: 128 x 128 pixels D: 1000 x 1000 pixels

D: 1000 x 1000 pixels The scan converter with the highest # of picture elements produces the best spatial resolution in an image, Ch 15 Pg. 244

14. Which of the following is not true about spatial compounding? A: Data is collected from different viewing angles B: Frame rates are reduced C: Shadowing artifact can be eliminated D: Can be performed with a mechanical transducer

D: Can be performed with a mechanical transducer. (Spatial compounding is performed only with phased array transducers that electronically steer sound beams in different directions) Ch 15 Pg. 254

15. All of the following are advantages of PACS systems except: A: Data will not deteriorate over time B: Images can be delivered to distant locations on the imaging network C: Older, archived studies and reports can be reviewed easily D: Images have higher resolution than what appears on the systems display

D: Images have higher resolution than what appears on the systems display. (Image resolution is not improved simply with the use of a PACS system) Ch 15 Pg. 259

16. What is DICOM? A: Standards for transducer design B: Standards for patient exposure C: Protocols for two-dimensional imaging D: Protocols for medical image data

D: Protocols for medical image data Ch 15 Pg. 259

1. Which electronic component is required for grayscale imaging. A: VCR B: Non-interlaced display C: Computer memory D: Scan converter

D: Scan converter technology is used to create grayscale displays. Ch 15 Pg. 239

5. What is the number of shades that can be represented by 3 bits?

Eight different gray shades are stored using 3 bits. 2 x 2 x 2 = 8 Ch 15 Pg. 246

443. True or False? Digital scan converters do not use computer technology to process electronic data into images.

False. Digital scan converters use computer technology to process data. Ch 15 Pg. 243

460. True or False? Preprocessing of image data occurs after the data has been stored in the scan converter.

False. Preprocessing occurs before storage. TGC and write magnification are preprocessing examples. Ch 15 Pg. 249

453. True or False? The greater the number of bits assigned to each pixel of a digital image, the greater the spatial resolution of the image is.

False. The number of bits assigned to each pixel of a digital image does not directly affect the spatial resolution of the image. Ch 15 Pg. 244

9. How many bits are needed to store: 10 shades of gray? 11 shades of gray? 15 shades of gray?

Four bits are required to store from 9 to 16 shades of gray. Ch 15 Pg. 246

464. True or False? The assignment of different shades of gray to the digital numbers stored in the scan converter acts to improve the diagnostic value of an ultrasound exam.

True. Ch 15 Pg. 249

459. True or False? For digital image information to be displayed on a conventional television screen, the data must be processed by a digital-to-analog converter.

True. Ch 15 Pg. 251

442. True or False? A digital representation of a number can achieve only specific fixed values.

True. A digital number is limited to discrete values. Ch 15 Pg. 243

461. True or False? Post processing of image data occurs after the data has been stored in the scan converter.

True. Processing of image data after the data is stored is called post processing. Read magnification is post processing. Manipulation of a frozen image is post processing. Ch 15 Pg. 249

448. True or False? The greater number of bits assigned to each pixel of a digital image, the greater the number of shades of gray the image has.

True. number of shades of gray increase with number of bits assigned to each pixel increases. Ch 15 Pg. 245