**8.1. Image quality**

Image quality, which is defined as the exactness of representation of patient anatomy, is affected by many factors including organ of interest, imaging modality, patient, and imaging modality characteristics. Images in clinical environment are evaluated subjectively by operators (radiography technologist or radiologists) or objectively (independently of an observer opinion) by measuring certain parameters. These parameters include brightness, contrast resolution, special resolution distortion, artifact, and noise, as illustrated in **Table 3**.

**Tables 4** and **5** show factors affecting patient doses during interventional procedures. Patient dose depends, among other factors, on X-ray unit technology, proper equipment design and utilization, proper set up of equipment parameters, and operator skills.

Optimization in diagnostic radiology signifies balancing diagnostic information (image quality) and patient dosage through identifying an image acquisition technique that maximizes the perceived information content and minimizes radiation risk or keeps it at a reasonably low level (ALARA).

The factors that affect patient dose and image quality and form the backbone of optimization in diagnostic radiology fall into three categories: facilities and equipment, operational conditions, and application factors.


**Table 3.** Image quality factors and their controlling/influencing factors in DR.

#### **8.2. Establishment of diagnostic reference levels**

To improve the optimization in diagnostic procedures, the ICRP recommends the use of diagnostic reference levels (DRLs) to ensure that the doses do not deviate significantly from internationally reported levels to those achieved at peer departments for that procedure unless there is a known, relevant, and acceptable reason for this deviation. Practitioners and referrers

**3.** comparison with DRLs shall be made using mean/median values of a sample of patient doses; **4.** the use of DRLs should be made in conjunction with the evaluation of the required image

should understand the following hits about DRLs for best practices [14]:

**1.** DRLs are not dose limits; they should be used as investigation levels;

**2.** DRLs are not applicable to individual patients;

**Table 5.** Operator related factors affecting patient radiation doses.

quality or diagnostic information;

**Parameter Control of** 

**Parameter Control of** 

Fluoroscopy time Partially

Type of procedure and pathology

Patient preparation and communication

Radiation dose monitoring

Use of specified protocol

**parameter**

**Table 4.** Patient related factors affecting patient radiation doses.

Experience Not controllable Increase the exposure parameters

**parameter**

controllable

Patient size Not controllable Increase the exposure parameters

**Management**

procedures

**Management**

procedures

Radiographic images Controllable The number of image is proportional to patient dose

Magnification Controllable Radiation dose in increasing by magnification

Patient setup Controllable Accurate patient positioning before the procedure reduces the need for patient positing using fluoroscopy

the possibility of image blurring

Dose reference levels Controllable DRL could be used to improve patient dose management in order to avoid unnecessary radiation exposure

the possibility of image blurring Collimation Controllable Proper collimation of radiation to the region of interest reduces patient and staff dose and improves image quality

Dose mode Controllable Low dose mode setting requires low tube current and less patient dose Image geometry Controllable Increasing the source-skin distance (SSD) and decreasing patient detector distance reduces patient doses

Fluoroscopy time is proportional to dose

Not controllable Therapeutic procedures require more fluoroscopic time than diagnostic

Controllable Good patient communication increases patient cooperation and reduces the

Not controllable Therapeutic procedures require more fluoroscopic time than diagnostic

Controllable Good patient communication increases patient cooperation and reduces the

possibility of patient movement during the exposure and hence minimizes

possibility of patient movement during the exposure and hence minimizes

Medical Imaging and Image-Guided Interventions http://dx.doi.org/10.5772/intechopen.76608 47


**Table 4.** Patient related factors affecting patient radiation doses.


**Table 5.** Operator related factors affecting patient radiation doses.

there is a known, relevant, and acceptable reason for this deviation. Practitioners and referrers should understand the following hits about DRLs for best practices [14]:


**8.2. Establishment of diagnostic reference levels**

**Image quality factor Definition/controlling factor(s)**

46 Medical Imaging and Image-Guided Interventions

brightness.

ing media

selection of optimal kVp

the contrast of the digital image Resolution • **Definition:** the recorded sharpness or detail of structures on the image

Noise • **Definition:** random disturbance that obscures or reduces clarity.

• Increasing input doses

resolution

**Table 3.** Image quality factors and their controlling/influencing factors in DR.

Brightness • **Definition:** the intensity of light representing image pixels on the monitor

Contrast • **Definition:** the difference in brightness between light and dark areas of an image

Distortion • **Definition:** the misrepresentation of an object size or shape as projected onto record-

Artifact • **Definition:** EI is a measure of the amount of exposure received by the image receptor

image receptor alignment, and central ray alignment (**Table 1**)

turers provide a recommended EI range for optimal image quality

nonuniformity of the image receptor, or power fluctuations.

• **Controlling factors:** the optimal digital image brightness is influenced by a wide range of exposure factors and controlled by processing software through digital processing algorithms. The operator can apply post processing algorithms to modify pixel values of the image. Windowing is used to manipulate and adjust the brightness of the digital image after exposure by altering the window level (WL) within a certain range. Smoothing and edge enhancement of the image can also be increased for better

• **Controlling factors:** control of scatter radiation is an important factor in obtaining the appropriate image contrast through correct use of grid, close collimation, and

• Radiographic contrast is affected by the digital processing computer through application of predetermined algorithms. Through post processing, the user can manipulate

• **Controlling factors:** traditional factors as for film screen imaging besides acquisition pixel size inherent to the digital imaging detector and display matrix. Perceived resolution of the image dependent on the display capabilities of the monitor

• **Controlling factors:** as for film screen imaging, the factors that affect distortion are the source image receptor distance (SID), object image receptor distance (OID), object

• **Controlling factors:** EI is dependent on mAs, total detector area irradiated, and beam attenuation. The exposure index is indicative of image quality. Equipment manufac-

• **Controlling factors:** technologists must ensure that exposure factors used for examination are not beyond those required for the projection by checking the exposure index to avoid needless overexposure of the patient. On the other hand, scattered radiation is a potential source of noise that can be controlled by the use of grids and correct collimation. Image noise may also be related to the electronic system,

• Frame averaging—smooth by adding successive images at the expense of temporal

To improve the optimization in diagnostic procedures, the ICRP recommends the use of diagnostic reference levels (DRLs) to ensure that the doses do not deviate significantly from internationally reported levels to those achieved at peer departments for that procedure unless


**5.** DRLs should be applied with flexibility, allowing tolerances for patient size, condition, etc.;

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