CH6: Digital Image Processing, Display, and Health Information Management

Comprehensive flashcards covering digital radiography image formation, histogram analysis, lookup tables, exposure indicators, image artifacts, monitor specifications, post-processing techniques, and health informatics (MIPS, DICOM, HL7, HIPAA).

In digital radiography, what is the "value of interest" (VOI)?

The range of histogram data that should be included in the displayed image for a specific anatomic examination.

What process is used to maintain consistent digital image brightness for over/underexposure?

Automatic Rescaling

In computed radiography (CR), what is the minimum number of collimated edges that must be identified on the imaging plate to avoid a histogram analysis error?

3 edges

On an exposure histogram, what is represented along the x-axis and the y-axis?

The x-axis represents the range of assigned pixel values (brightness levels), while the y-axis represents the number or frequency of pixels for each value.

What impacts the location and shape of a histogram?

Exposure technique, positioning & collocation

What digital process alters image brightness and grayscale to improve visibility of anatomic structures?

Lookup Table Application (LUT)

What is automatic rescaling in digital image processing?

It maintains consistent image brightness by mapping grayscales to the value of interest, regardless of whether the image receptor was overexposed or underexposed.

Which two exposure-related causes of image noise cannot be compensated for by automatic rescaling?

Underexposure (which produces quantum mottle/graininess) and scatter radiation (fog caused by Compton interactions).

How much tissue thickness does it typically take to reduce the quantity of X-ray photons by half?

$4\text{ to }5\,cm$ of tissue.

What is "dose creep" in digital radiography?

The tendency of radiographers to routinely use higher exposure techniques because automatic rescaling produces high-quality images without noise, inadvertently increasing patient radiation dose.

What is the primary function of a lookup table (LUT)?

It alters original raw pixel values to adjust the display brightness and grayscale/contrast of the digital image using computer algorithms.

How does the lookup table (LUT) graph differ between original raw data and processed image data?

Original raw image data is represented as a linear straight line, whereas processed image data is represented as an S-shaped curve.

What does an exposure indicator (EI) measure, and what does it NOT measure?

It provides a numerical value indicating the radiation exposure delivered to IR ; it is not a measurement of radiation dose to the patient.

What does a Deviation Index ($DI$) value of $0$ indicate?

It indicates that the image receptor exposure was ideal and exactly on target with the recommended exposure for that examination.

In the Deviation Index ($DI$) system, what do values of $+3.0$ and $-3.0$ signify?

A $DI$ of $+3.0$ represents excessive exposure by approximately a factor of $2$, while a $DI$ of $-3.0$ represents insufficient exposure by half ($50\%$).

What happens if DI value is > +3.0 SD?

Saturation & patient OVERexposure

What is the value that reflects the difference between the desired/target exposure to the IR and the actual exposure to IR?

Deviation Index (DI)

What is dual-energy subtraction used for in radiographic post-processing?

It removes either the skeletal structures or soft tissues (such as the lungs) to visualize one anatomical component without anatomical superimposition.

What trade-off occurs when applying the post-processing technique of smoothing (low-bandpass filtering)?

It reduces visible image noise but causes a loss of spatial resolution (image sharpness).

What aspects of image display are controlled by window level and window width, respectively?

Window level controls image brightness, while window width controls image contrast (grayscale).

How does selecting a wide window width versus a narrow window width alter image contrast?

A wide window width decreases contrast by providing a longer scale with more shades of gray ; narrow window width increases contrast by providing fewer shades of gray (predominantly black and white)

What causes radio frequency (RF) interference artifacts on a digital detector?

Proximity of the detector panel or data cables to active RF sources (such as cell phones, routers, or medical electronics) or damaged communication cables failing to shield electromagnetic noise.

What are the recommended resolution and luminance boundaries for a primary diagnostic display monitor?

A resolution of $5\text{ megapixels}$ ($2048 \times 2560\text{ pixels}$), a minimum luminance of $1.0\,cd/m^2$, and a maximum luminance of $350\,cd/m^2$.

What is pixel pitch, and what is the recommended value at a standard viewing distance of $24\,inches$?

Pixel pitch is the distance from the midpoint of one pixel to the midpoint of the next adjacent pixel; it should be $0.2\,mm$.

How many shades of gray are represented by a digital imaging system with a $14\text{-bit}$ pixel depth?

$2^{14} = 16{,}384$ shades of gray.

What are the AAPM and SMPTE test patterns used for in quality control?

They are standard test patterns used to evaluate display monitor performance, including spatial resolution, contrast, and brightness.

What newer term and acronym is designated to replace PACS? It is designed to store, archive and transmit digital images.

MIMPS (Medical Image Management and Processing System)

What is the distinction between ICD-10-CM codes and CPT-4 codes?

ICD-10-CM codes are established by the WHO to diagnose diseases, injuries, and clinical symptoms; CPT-4 codes are five-digit numeric codes maintained by the AMA that describe the medical, surgical, or diagnostic services performed.

What international standard is required to transmit , store, retrieve, and display medical images across healthcare systems?

DICOM

What is the communication standard for sharing info between MIMPS & imaging modalities?

DICOM

What is the primary difference between lossless and lossy image compression?

Lossless compression is REVERSIBLE with no loss of image data upon decompression; lossy compression is IRREVERSIBLE and causes data loss to achieve smaller file sizes and faster transmission.

Under HIPAA requirements discussed in the lecture, how long must medical images and patient data be stored?

$7\text{ years}$.

What is teleradiology?

The practice of off-site diagnostic image interpretation used for preliminary emergency diagnoses, after-hours coverage, subspecialty consults, and addressing radiologist shortages in rural facilities.