Calculation resolution

1. Ignorance upstairs. There is difference between resolution and resolution in instrument range display

resolution refers to the ability of the instrument indicating device to distinguish two adjacent values of the indicated quantity

resolution refers to the ratio of the resolution of the instrument to the measured value of each level of the instrument It has been changed to relative resolution instead of resolution)

take the measurement of test force as an example:

the accuracy of test force refers to the maximum allowable error between the value and the true value of the measurement result indicated by the test force indicating device after the sample is tested on the testing machine

the resolution of test power refers to the minimum measured value that can be indicated on the test power indicating device

"relative resolution of test force" refers to the ratio of the minimum measured value that can be indicated on the test force indicating device to the measured value of each gear of the testing machine indicating device

the "resolution of test power" on the digital indicating device is the number value of the last digit displayed in each gear

2.

Clear answer: resolution calculation method:

extended data:

generally, the higher the resolution of an image, the more pixels it contains, the clearer the image, and the better the printing quality. At the same time, it also increases the storage space occupied by files. The units used to describe the resolution are: DPI points per inch, LPI lines per inch, and PPI pixels per inch. But only LPI is the scale of optical resolution. Although DPI and PPI also belong to resolution units, their meanings are different from LPI. Moreover, LPI and DPI can not be converted and can only be estimated by experience

3. Resolution means, for example, the screen of mobile phone, with higher resolution, looks clearer

4. Ha ha, I guess what you want to say is ad or Da, 8 bit or 12 bit. Is that it? The so-called 8-bit ad means that the intensive reading that can be achieved is one eighth power of 2, that is, 1 / 512, which means that the maximum voltage can be measured is 1.95mv. For example, if you want to measure 1.9mv, he can't identify it. This is his accuracy. Other reasons are the same

5.

1、 Difference

1, different resolution

(1) the density resolution represents the minimum density difference that can be displayed in the image

(2) the density resolution of CT is limited by the noise and the size of the display. The smaller the noise and the larger the display, the better the density resolution. The density resolution of CT image is much higher than that of X-ray

2. The degree of density difference that can be distinguished by density resolution is expressed in%. If the density resolution of CT is 0.5%, it means that the density difference between two substances is equal to or greater than 0.5%, which can be identified. When the density difference is less than 0.5%, it can not be identified e to the interference of noise

Spatial resolution is sometimes called geometric resolution or high contrast resolution in CT equipment. It refers to the ability to identify fine structures in the case of high contrast, that is, the ability to display the smallest volume of lesions or structures. When evaluating CT image quality, spatial resolution is often considered first

The spatial resolution of CT images is determined by the geometric size of the X-ray tube focus, but not by the X-ray dose, because the detector has a certain size and the sampling has a certain distance. When the X-ray dose is fixed, the spatial resolution and density resolution are restricted to some extent, so it is impossible to improve the spatial resolution and contrast resolution at the same time

expanded materials:

medical imaging: X-ray, CT, MRI & # 8194; Imaging technology and clinical application

Image archiving and transmission system (PACS) is a device and software system for saving and transmitting images. Its advantages are as follows:

1. It saves image information and is easy to be processed in the future

The doctors far away from the radiology department can read and diagnose the images at any time, which improves the work efficiency

It is convenient for image transmission and communication, and can carry out composite image diagnosis and multidisciplinary consultation

It can avoid the loss and error of film in the process of transmission, and become a modern management means of hospital

Save film expenses, management costs, rece storage space, so as to enter the era of no film&# 8194;

(2) digital subtraction angiography (DSA) &; Through the calculator processing digital image information, commonly used time subtraction method, eliminate bone and soft tissue image, make blood vessel clear development of imaging technology&# 8194;

cerebral angiography; It is a method of displaying cerebral vessels by introcing organic iodine contrast agent into cerebral vessels, including carotid arteriography and vertebral arteriography. DSA technique is commonly used to take images of cerebral artery phase, venous phase and venous sinus phase&# 8194;

X-ray imaging – electromagnetic wave, wavelength 0.0006 ~ 50nm & # 8194

(3) the principle of X-ray imaging is related to the penetrability, fluorescence effect and photosensitive effect, as well as the difference of density and thickness of human tissue structure. The higher the voltage, the stronger the penetration&# 8194;

2. X-ray excited ZnS, CDW, caw to emit fluorescence

3. Photosensitive effect; The foundation of X-ray photography. Silver ions in silver bromide are reced to metallic silver and precipitated in the film

4. Ionization effect; The basis of radiotherapy. X-ray into the human body, causing biological changes, that is, biological effects&# 8194;

Four, X-ray image characteristics:

1, gray scale image

2

3

There may be distortion&# 8194;

Gray scale images reflect the anatomical and pathological state of human tissue structure by optical density. In addition to the thickness, the white and black shadows on the image mainly reflect the density of the tissue (white shadows in high density and black shadows in low density)

Advantages: it can rotate the patient's position; Understand the dynamic changes of organs; In terms of operation, the cost is low

Disadvantages: poor contrast and definition; Lack of objective records&# 8194;

Advantages: good contrast and definition

There is no three-dimensional concept; Unable to observe the function&# 8194; (5) angiographic examination; The contrast agent is introced into the body to proce artificial contrast

Barium: Medical barium sulfate

Iodine agents: inorganic (Lipiodol, iodophenyl ester), organic (ionic type), such as meglumine diatrizoate; Non ionic type, such as iobil, youweixian)&# 8194;

ionic contrast media had high permeability and high toxicity; Non ionic hypotonic, low year, low toxicity

9. Low density contrast medium; Air, O2, CO2 & 8194

(1) indirect introction: IVP

Direct introction: oral administration, perfusion and puncture&# 8194; 5. Clinical application; The gastrointestinal tract, skeletal system and chest were selected&# 8194;

(11) CT imaging: X-ray beam is used to irradiate a certain layer of human body, and the amount of X-ray transmitted is measured. After digitization, the absorption coefficient of each unit volume of the layer tissue is obtained by computer, and then the image is reconstructed&# 8194;

(1) advantages: high density resolution, quantitative value (CT value) to explain the degree of density

(2) the spatial resolution is not as good as X-ray image

(3) multiple consecutive slice images are needed&# 8194;

(1) water: 0-8194; HU

(2) air: – 1000 & # 8194; HU

(3) fat: – 90 ~ – 70 & 8194; HU

(4) soft tissue; 20~50  HU

(5) bone + 1000 & # 8194; HU&# 8194;

(1) central nervous system diseases: intracranial tumor, abscess and granuloma, parasitic disease, traumatic hematoma and brain injury, ischemic cerebral infarction and cerebral hemorrhage

(2) space occupying lesions, sinus carcinoma, nasopharyngeal carcinoma, etc

(3) lung cancer and mediastinal tumor

(4) liver, gallbladder, pancreas, spleen, abdominal cavity and retroperitoneal space, adrenal gland and genitourinary system

(5) extraluminal invasion or distant metastasis of gastrointestinal lesions&# 8194;

12. MRI imaging: MRI signals have parameters such as T-1, T2, and proton density, which constitute MRI images&# 8194;

T-1- When the RF pulse is terminated, the longitudinal magnetization graally returns to its original state. This process is longitudinal relaxation, and the recovery time is longitudinal relaxation time, referred to as T-1. The images composed of T1 parameters were T1 weighted images (t-1-wi)&# 8194;

T2 The transverse magnetization also disappears quickly. This process is transverse relaxation, and the time required is transverse relaxation time (T-2). T2 weighted imaging (T2-WI) was used as the image composed of T2 parameters&# 8194;

1, MR signal generation; In the relaxation process, the proton absorbs the energy of RF pulse combination and releases the MR signal. By adjusting the imaging parameters TR and Te, MR signals mainly reflecting the contrast of T1, T2 and PDWI can be obtained respectively, and then t-1-wi, T2-WI or PDWI images can be generated

(1) high signal intensity on t-1-wi; Subacute hematoma, fat, high protein content, melanin&# 8194;

(2) low signal on t-2wi; Calcium, air, air, fat and protein content is less&# 8194;

(1) multi parameter gray scale images

(2) multidirectional tomographic images

(3) flow void effect: the flowing liquid can't collect the signal in the imaging process, but has no signal shadow

(4) MRI contrast enhancement effect: paramagnetic material as contrast agent can shorten the relaxation time of surrounding proton, which is called proton relaxation enhancement effect

(5) pseudo color function image&# 8194;

(1) sequence technique

(2) self cyclotron wave (SE) sequence

(3) gradient echo (GRE) sequence

(4) inversion recovery (IR) sequence

(5) plane echo imaging (EPI)&# 8194;

4. MR water imaging technology; Heavy T2-WI can be obtained with very long TR and very long TE, which can make the static or slow flowing liquid show high signal and other tissues in the background show low signal

after reconstruction, the liquid containing organs or spaces can show high signal, and the images like contrast effect can be obtained, that is, Mr hydrography, including MRCP, MRU, MRM, etc&# 8194;&# 8194;

(1) brain and spinal cord diseases

(2) hilar and mediastinal lymph nodes

(3) the lumen of heart and great vessels

(4) diagnosis of breast cancer

(5) cartilage and articular capsule were clearly displayed&# 8194;

6, the preferred instrument for each system examination was

(1) bone and bone; Plain film is the first choice, and CT is the next choice

(2) joint MRI&# 8194;

(3) respiratory system; Plain film is the first choice, and CT is the next choice

(4) acute abdomen; Plain film is the first choice, and CT is the next choice

(5) closed abdominal injury; Ultrasound, CT

(6) esophageal lesions; Barium meal examination&# 8194;

(7) stomach and odenum; Ultrasound and air barium double contrast were used

(8) liver; Ultrasound and C ﹥ 8194; T is the first choice, further MRI and hepatic arteriography can be used

(9) pancreas; Ultrasound, CT

6. According to the total score of all the tested objects, they are sorted; Then the 25% with the highest total score and the 25% with the lowest total score were taken out, and the average score of each statement of the two groups was calculated; The resolution coefficient of this statement is obtained by subtracting the two averages.

7. The "pixel" of human eye is 576 million. There are 5 million cone-shaped cells in the retina of ordinary people. These cone-shaped cells are used to sense visual color, and the human eye can be imagined as equal to 5 million pixels. However, there are 100 million rod cells in the eye, which are used to sense monochromatic contrast, light and shade, and play an important role in the sharpness of the picture shown by your eyes. Moreover, even if the eye pixels as 105 million, still underestimate them, because it is not a camera after all.

8. Resolution is the precision of the screen image, which refers to the number of points that can be displayed on the display. Because the points, lines and surfaces on the screen are all composed of points, the more points the display can display, the finer the picture will be, and the more information can be displayed in the same screen area, so the resolution is one of the most important performance indicators. We can think of the whole image as a large chessboard, and the resolution is expressed by the number of intersection points of all longitudes and latitudes
the resolution is 1024 × 768 screen, that is, each horizontal line contains 1024 pixels, a total of 768 lines, that is, the number of scanning columns is 1024, and the number of rows is 768. The resolution is not only related to the display size, but also affected by the distance between CRTs and video bandwidth. Among them, it is closely related to the refresh rate. Strictly speaking, only when the refresh rate is "flicker free refresh rate", can the display achieve the highest resolution. The resolution of measurement is an important concept related to image, which is a technical parameter to measure the expressiveness of image details. But there are many kinds of resolution, and their meanings are also different. It is an important step to understand the meaning of resolution in various situations and the relationship between different representation methods. Some users often confuse resolution with point distance. In fact, these two concepts are quite different. Point distance refers to the distance between pixels. The more pixels, the higher the resolution. Therefore, the resolution is usually measured by the number of pixels, such as 640 × 480, and its prime number is 307200
note: 640 is the number of horizontal pixels and 480 is the number of vertical pixels
in the graphic environment, high resolution can effectively shrink the screen image. Therefore, when the screen size remains unchanged, its resolution cannot exceed its maximum reasonable limit, otherwise, it will lose its significance
display size maximum resolution
14 inch 1024 × 768
15 inch 1024 × 768
17 inch 1280 × 1024
21 inch 1600 × 1280
the resolution of the touch screen refers to the number of contacts that divide the screen into recognizable parts. It is usually represented by the number of contacts in the horizontal and vertical directions, such as 32 × 32 Some people think that the higher the resolution of the touch screen, the better. In fact, this is not the case. When choosing the touch screen, it should be considered according to the specific purpose. The touch screen with analog technology has a high resolution of 1024 × 1024, can be competent for some similar screen painting and writing (handwriting recognition) work. In most cases, the application of touch technology only allows people to use their hands to select the "button" of software design, there is no need to use a very high resolution. For example, when using a touch screen on a 14 inch monitor, the actual size of the display area is usually 25cm × 5 cm, a resolution of 32 × 32 touch screen can be divided into 1024 0.78cm × 58cm (smaller than a cigarette). The touch screen that a person's finger presses on is much larger than the diameter of a cigarette, so such a touch is enough.

9.

Resolution, also known as resolution and resolution, can be classified from the two directions of display resolution and image resolution

display resolution (screen resolution) is the precision of the screen image, which refers to the number of pixels that the display can display. Because the points, lines and surfaces on the screen are all composed of pixels, the more pixels the display can display, the finer the picture will be, and the more information can be displayed in the same screen area, so the resolution is a very important performance index

imagine the whole image as a large chessboard, and the expression of resolution is the number of intersection points of all longitudes and latitudes. When the display resolution is fixed, the smaller the display screen is, the clearer the image is. On the contrary, when the display size is fixed, the higher the display resolution is, the clearer the image is

image resolution is the number of pixels contained in the unit inch, which is closer to the definition of resolution itself

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extended data

the meaning of pixel pitch is similar to dot pitch of CRT, which generally refers to the distance between two adjacent pixels on the display screen. The picture we see is formed by many points, and the delicacy of the picture quality is determined by the point distance, which is calculated by dividing the panel size by the resolution

take LCD as an example, the visual area of 14 inch LCD is generally 300 mm × 190mm, resolution 1280 × 800, so the dot distance of this LCD is calculated to be 300 / 1280 = 0.2344mm or 190 / 800 = 0.2375mm. The smaller the distance between dots, the more delicate the image

The best resolution of 22 (21.5) and 20 (20.1) inch wide screen LCD with

16:10 ratio is 1680 × 1050

The best resolution of 23 and 22 (21.5) inch wide screen LCD with

16:9 ratio is 1920 × 1080

for the refresh frequency of LCD, use the default 60Hz of the operating system, and do not change it (no matter how much the system defaults). LCD is not a CRT display, its interior is not a cathode ray tube, and it does not rely on the electron gun to bombard the phosphor powder on the picture tube to proce images

LCD displays are passive light-emitting, with the rear lamp illuminating the front LCD panel. There are only differences between on and off, light and dark. Therefore, LCD does not have the principle of electron gun scanning the screen line by line and interlaced, so there is no concept of refresh rate. It is the same whether it is changed or not. Refresh rate does not work for all LCDs

the display card has adaptive function to the display. When you plug in the LCD, the refresh frequency option of the display card will not work automatically, so as to protect the LCD. So under windows, you can't tune to 85Hz. This is the most basic common sense

10. Do you mean accuracy
for example, it can detect the zero point and zero point at least??