WhatsApp +91 9847 069 684

Blog

Ultrasound Quality Analysis & Quality Control – Niranjan Ultrasound India

Ultrasound Quality Analysis & Quality Control – Niranjan Ultrasound India

Preface(Most Commonly Asked Questions)

  • Why do we need quality control?
  • What is the Quality control schedule?
  • What does Baseline reference measurements mean?
  • Why Quality control procedures?
  • Physical and mechanical inspection is it required?
  • How necessary is Image screen monitor set up?
  • Why should there be a Image uniformity?
  • What is Dead zone?
  • What are the Aims on the vertical plane?
  • Why Penetration depth is so important?
  • How important is Beam profile / Lateral resolution / Focal zone?
  • What is the use of Vertical distance measurements?
  • What is the use of Horizontal distance measurements?
  • How Axial resolution will be useful?
  • Why is Lateral resolution so important?
  • What is Anechoic masses?
  • What is Hyperechoic masses?

In several technology application areas, various quality control procedures are utilized. Such procedures evaluate the general quality of the equipment used in many clinical procedures, for both diagnoses and treatments. Many diagnostic instruments in radiology and radiotherapy are routinely analyzed and tested by several quality control procedures, and maintenance reports are provided to ensure the quality of the instruments.

This guideline has the objective to help health and technical professionals to do the basics quality control procedures in diagnostic ultrasound equipment. Here, are available the main tests such as axial and lateral resolution, dead zone, focal zone, maximum depth, vertical and horizontal distances and others.

Why do we need quality control?

Basically, these questions could be answered by two main reasons: The extensive ultrasound equipment use creates a progressive degradation, where it interferes in the image quality and for the further diagnostic procedure. When you suspect a malfunctioning of the equipment that appears in an equipment piece Quality control schedule is required. The schedule could be split into two approaches: quick tests and a more deep evaluation. For the quick test, it could be applied in every tree months for portable ultrasound equipment, emergency facilities rooms and general diagnostic purposes ultrasound equipment. A more deep evaluation could be applied in every six months for all those ultrasound equipment cited before.

Baseline reference measurements

The baseline measures represent the maximum performance that the ultrasound equipment to make an effort for a specific quality test. Subtle changes are compared with the baselines values for thresholds of safety in order to have a level comparison with a ground truth. This measurement plays an essential role to all the quality control procedures because its guarantee a normal behavior that the ultrasound equipment must fit in.

The baseline should be determined preferably immediately after the installation of the ultrasound equipment or as soon as possible. If the testing values, for a specific quality control procedure, are less than or above than the baseline value, the system must be repaired.

The control settings related with the dynamic range, gray level map, the body slice, power, gain, the target gain control (TGC) should be adjusted using a phantom that simulates the liver parenchyma. A phantom or simulated object is the basic equipment that must be used to perform the quality control tests. These equipment adjustments are necessary to adequate the resultant image as the usual clinical environment, i.e the usual clinical ultrasound image appearance in contrast and brightness. Once you’ve done the settings, the final set up should be stored in a data sheet and should be used every time that the quality control tests are performed in the future.

In order to determine the baselines values to each quality control procedure:

 a) Examine the phantom using the control settings listed in the data sheet. Set the depth and the focal zone as necessary and stores these settings into the data sheet for future testing procedures.

 b) Perform the tests exactly as described in the quality control guideline section and store these values in the data sheet. These values are the baseline values.

The level of action, or simply the actual interference in the ultrasound maintenance, is indicated by the comparative value with the baseline measurement and it has a threshold for the corrective action that should be taken. The base threshold adopted is 75% of the baseline measurement. See Figure 1. For example, if the maximum acceptable error of a measure is \pm 2%, the acceptable value is 0.75 x 2 % = \pm1.5 %.

Figure 1

A simulator object (phantom) illustration for ultrasound quality control purposes. In particular, this phantom model is part of CIRS phantom models

Quality control procedures

Physical and mechanical inspection

Transducers: Check if the cables, plugs and surfaces transmission have damages or any other issues. The plugs insertions and the safety key closing must be easy to do. The transducer connections must be firms and not appear broken. Verify if exist air bubbles in the transducer head, and also if the transducer moves smoothly, without any noisy sound and vibrations.

Power cable: Check if exist any type of damage in the cable as well as in the plug.

Controls: Check if exist buttons or controls that are dirty and need some physical repairment. Also see if the lights are not broken.

Image screen: The image screen must be clean and free of any type of damage. The brightness and contrast controls must be in perfect functioning and must be set up on the appropriated levels.

Rotations buttons: Check if the rotations buttons operates perfectly well without any type of noise and are easy to handle.

Dust and air filters: Verify if the dust and air filters are cleans and free of any type of damage. Filters in bad physical conditions may cause an equipment overheating and could cause a future damage in other electronical devices. The cleaning procedures are the technical person responsibility.

Image screen monitor set up

Initial configurations to set up the baseline measures:

a) Show the default grayscale pattern on the screen

b) Decrease the brightness and contrast level until the lowest position (just until the screen been as darker as possible). Further, increase the brightness until the image on the screen be a little visible and the text letters becomes distorted (usually blurred and right shifted). When you get at this point, slow down the contrast level until the text not presents any distortion, which at this way the image monitor will be optimized to the default setup.

c) Get a clinical image to check if the image is adequate, otherwise repeat the previous process.

d) Show again the grayscale level and see how many different gray levels you can distinguish. This value will be your image screen baseline.

Procedure to quality control test:

 a) Check if the brightness and contrast buttons are on the default baseline positions.

 b) Show the grayscale levels pattern.

 c) Check the first and last levels and how many lines you can distinguish.

 d) Examine the text on the screen and verify if it is blurred.

Image uniformity

The image uniformity is defined as the equipment ability to give ultrasound echos with the same amplitude and deepness when the brightness is fixed. This quality test is also important to verify if the transducer crystals have a well functioning.

Figure 2

Damage examples that could be found on ultrasound equipments image screens.

Procedure to image uniformity test:

a) Apply the coupling gel on the ultrasound transducer or cover with water the surface in order to give an impedance coupling between the ultrasound transducer and the phantom.

b) Fit the ultrasound transducer position in a region that contains a minimum aims amount.

c) Adjust the ultrasound equipment configuration settings (gain, TGC, etc) as usual. Record these configuration settings to be used on futures tests.

d) Align the ultrasound transducer in order that the aims will be maximized.

e) Freeze the image and get a copy.

f) Observe the global phantom image appearance. Check if all the same depth regions have the same signal amplitude.

g) Record your observations.

Dead zone

This quality control test is done with the closest aims group’s presents in the phantom, which each dot have a different depth. The region where you cannot distinguish a couple of dots is the dead zone region. The dead zone appears where the ultrasound equipment does not able to split these two different dots in the image, and it is basically related with the ultrasound transducer instrumentation characteristics. When the pulse frequency increases, the dead zone automatically decreases. When a problem occurs in the dead zone test, it is an indicative issue in both ultrasound transducer and the electronic pulse system.

The aims are thin nylon rows with 0.1 mm of diameter and 6 mm gap between each of then. The Figure 3 shows an example of dead zone configuration.

Figure 3

Dead zone configuration usually adopt for ultrasound simulator objects

Procedure to dead zone test:

a) Apply the coupling gel on the ultrasound transducer or cover with water the surface in order to give an impedance coupling between the ultrasound transducer and the phantom.

b) Fit the ultrasound transducer position in a region that contain the dead zone aims dots group.

c) Adjust the ultrasound equipment configuration settings (gain, TGC, etc) as usual. Record these configuration settings to be used on futures tests.

d) Freeze the image and get a copy.

e) Observe where you cannot discriminate the gap between the dots.

f) Record your observations and compare then with the baseline measures.

Aims on the vertical plane

To do these quality control tests, it is very important not apply pression on the phantom surface because the vertical measure could be affected. The aims on the vertical plane are used for many other measurements. This group of aim dots is useful to perform depth penetration, beam profile, lateral pulse response, vertical distance calibration and dead zone tests. Usually exist 15 mono nylon rows with 0.1 mm diameter with a vertical distance fixed with 1 cm, where its get a total 16 cm of depth.

Penetration depth

The penetration depth, also called as de maximum sensitive penetration, is the maximum depth that the ultrasonic beam could reach until the signal is lost by the receiver system. This test is made using the vertical aim dots as cited on the previous vertical plane test. Further, the depth has a strict relationship with the pulse frequency.

Procedure to penetration depth:

a) Apply the coupling gel on the ultrasound transducer or cover with water the surface in order to give an impedance coupling between the ultrasound transducer and the phantom.

b) Fit the ultrasound transducer position in a region that contain the penetration depth aims dots group.

c) Adjust the ultrasound equipment configuration settings (gain, TGC, etc) as usual. Record these configuration settings to be used on futures tests.

d) Arrange the ultrasound transducer to a position that maximize the penetration depth aims in order to reach a good visibility.

e) Freeze the image and get a copy.

f) Use the ultrasound equipment distance tool to measure each vertical distance.

g) Record your observations and compare then with the baseline measures.

Beam profile / Lateral resolution / Focal zone

The ultrasonic beam profile, focal zone and the general ultrasonic beam behavior into the medium are defined as seen in the Figure 4

Figure 4

Focal zone and natural sound irradiation into the medium illustration

The region where the ultrasonic beam becomes thin is defined as the focal zone. This local beam focalization is related with the optimum image resolution, due to the strict ultrasonic beam. You can note this effect with the vertical aims, which in the focal zone the aims, has a better visualization.

Procedure to beam profile, lateral resolution and dead zone tests:

a) Apply the coupling gel on the ultrasound transducer or cover with water the surface in order to give an impedance coupling between the ultrasound transducer and the phantom.

b) Fit the ultrasound transducer position in a region that contain the penetration depth aims dots group.

c) Adjust the ultrasound equipment configuration settings (gain, TGC, etc) as usual. Record these configuration settings to be used on futures tests.

d) Arrange the ultrasound transducer to a position that maximize the penetration depth aims in order to reach a good visibility.

e) Freeze the image and get a copy.

f) Some aims will appear as little lines and other as dots.

g) Measure the length of each aim. The minimum length indicates the focal zone.

h) Watch each dot at the image and see the beam profile and the focal zone.

i) Repeat the above steps to different focal zones.

f) Record your observations and compare then with the baseline measures.

Vertical distance measurements

The vertical distance is defined as the distance along the ultrasonic beam axial direction. The distances are used to measure areas, volumes, depth and separations between objects.

Procedure to vertical distance measurements:

 a) Apply the coupling gel on the ultrasound transducer or cover with water the surface in order to give an impedance coupling between the ultrasound transducer and the phantom.

b) Fit the ultrasound transducer position in a region that contain the vertical aims dots group.

c) Adjust the ultrasound equipment configuration settings (gain, TGC, etc) as usual. Record these configuration settings to be used on futures tests.

d) Arrange the ultrasound transducer to a position that maximize the penetration depth aims in order to reach a good visibility.

e) Freeze the image and get a copy.

f) Using the default distance tool of the ultrasound equipment, measure the distance between each couple of aims in the image, for different depth.

g) Record the distances.

h) Record your observations and compare then with the baseline measures.

 Horizontal distance measurements

This group of aims is used to determine the measurements performed at the horizontal direction. In general, these are the same steps as made in vertical distance procedure. The phantom has two horizontal planes to perform this type of quality test. Usually exit one group at 3 cm of depth which contains 4 lines with 10 and 20 mm gap between them; another group at 9 cm of depth which contains 7 lines with 20 mm gap.

 Procedure to vertical distance measurements:

 a) Apply the coupling gel on the ultrasound transducer or cover with water the surface in order to give an impedance coupling between the ultrasound transducer and the phantom.

b) Fit the ultrasound transducer position in a region that contain the horizontal aims dots group.

c) Adjust the ultrasound equipment configuration settings (gain, TGC, etc) as usual. Record these configuration settings to be used on futures tests.

d) Arrange the ultrasound transducer to a position that maximize the penetration depth aims in order to reach a good visibility.

e) Freeze the image and get a copy.

f) Using the default distance tool of the ultrasound equipment, measure the distance between each couple of aims in the image, for different depth.

g) Record the distances.

h) Record your observations and compare them with the baseline measures.

 Axial resolution

The axial resolution is defined as the ultrasound equipment ability to distinguish objects that are too close at the transversal plane. This measurement is proportional to the ultrasonic pulse length.

In general, the axial resolution quality control test consists of 12 aims made by mono nylon filaments with 0.1 mm of diameter. The Figure 5 show how these aims may appear in a phantom. Also, the axial resolution test has 6 pairs of nylon filaments in parallel orientations which each of them has 0.1 mm of diameter. The distance between them is gradually shorter, which usually has 5, 4, 3, 2, 1, and 0.5 mm for each region.

Figure 5

Region where usually the axial aims are found in a phantom

Procedure to axial resolution test:

a) Apply the coupling gel on the ultrasound transducer or cover with water the surface in order to give an impedance coupling between the ultrasound transducer and the phantom.

b) Fit the ultrasound transducer position in a region that contains the axial resolution aims dots group.

c) Adjust the ultrasound equipment configuration settings (gain, TGC, etc) as usual. Record these configuration settings to be used on futures tests.

d) Arrange the ultrasound transducer to a position that maximizes the aims in order to reach a good visibility.

e) Freeze the image and get a copy.

f) Exam the image to determine where you can see that a pair of dots does not have a sufficient, visible, separation.

Lateral resolution

The lateral resolution is a similar procedure that was made with the axial resolution. The interest here is to define how much accurate is the image to distinguish aims that are in the longitudinal plane. The ultrasonic pulse bandwidth has a direct effect in the lateral resolution.

For this test, we usually found 3 groups of aims that contains 5 nylon filaments paralleling arranged with 1, 2, 3, 4 and 5 mm distance. One group is at 2.5 cm depth, another at 6 cm depth and the last is at 10 cm depth. The Figure 6 show how these groups are arranged in a phantom.

Figure 6

Region where usually the axial aims are found in a phantom

Procedure to lateral resolution test: 

a) Apply the coupling gel on the ultrasound transducer or cover with water the surface in order to give an impedance coupling between the ultrasound transducer and the phantom.

b) Fit the ultrasound transducer position in a region that contain the lateral resolution aims dots group.

c) Adjust the ultrasound equipment configuration settings (gain, TGC, etc) as usual. Record these configuration settings to be used on futures tests.

d) Arrange the ultrasound transducer to a position that maximizes the aims in order to reach a good visibility.

e) Freeze the image and get a copy.

f) Exam the image to determine where you can see that a pair of dots does not have a sufficient, visible, separation.

g) Record the distance and compare with the baseline measurement.

Anechoic masses

The ultrasound equipment tends to represent lower contrast for small structures and smooth irregular objects borders. The anechoic masses test has the object to preserve the natural contrast from small objects.

Procedure to anechoic masses test:

a) Apply the coupling gel on the ultrasound transducer or cover with water the surface in order to give an impedance coupling between the ultrasound transducer and the phantom.

b) Fit the ultrasound transducer position in a region that contain the cylindrical aims group, in order to be perpendicular.

c) Adjust the ultrasound equipment configuration settings (gain, TGC, etc) as usual. Record these configuration settings to be used on futures tests.

d) Arrange the ultrasound transducer to a position that maximize the aims in order to reach a good visibility.

e) Freeze the image and get a copy.

f) Observe the general cylindrical shape. Note if exist structural deformations such as holes in each cystic structure. Certify if you can see all the aims.

g) Record the height, width and area values from each cylindrical aim. Take care with the measurement units. Compare the results with the baseline measures.

Hyper echoic masses

This test has the possibility to check the ultrasound equipment ability to detect solid tumors in different depth and sizes.

Procedure to hyper echoic masses test:

a) Apply the coupling gel on the ultrasound transducer or cover with water the surface in order to give an impedance coupling between the ultrasound transducer and the phantom.

b) Fit the ultrasound transducer position in a region that contain the cylindrical aims group, in order to be perpendicular.

c) Adjust the ultrasound equipment configuration settings (gain, TGC, etc) as usual. Record these configuration settings to be used on futures tests.

d) Arrange the ultrasound transducer to a position that maximize the aims in order to reach a good visibility.

e) Freeze the image and get a copy.

f) Observe the general tumor shape. Check if you can see all the aims.

g) Record your observations and compare the results with the baseline measures.

Niranjan Ultrasound India’s reputation is who we are today.  We strive to provide quality services.  We want our customers not only to expect the best, but to receive the same from us.  We are committed to providing the following:

  • 100% working parts. Our parts are tested and quality checked by our Quality Control Cell before being put into inventory.
  • Adhering to a Quality Management System. Having a quality system in place ensures that every employee is trained and involved in our strict quality guidelines.
  • Dedicated Test Beds and our in-house large inventory of functioning and maintained Ultrasound machines guarantee that every part is “live” tested on an ultrasound machine and passes all system checks by the QC.

2 People have



» Snow said: { Jul 23, 2016 - 09:07:48 }

A rolling stone is worth two in the bush, thanks to this arltcie.

» Fukuda8@gmail.com said: { Sep 21, 2017 - 01:09:16 }

The best site I saw , Thank you for your troubles



OUR RELATED WEBSITES
© 2016-2019 Niranjan Ultrasound India Pvt. Ltd. All rights reserved.