Introduction of myocardial perfusion imaging

Directory 1 Pinyin 2 English Reference 3 Overview 4 Operation Name 5 Indications for Myocardial Perfusion Imaging 6 Contraindications for Myocardial Perfusion Imaging 7 Preparations 8 Methods 9 Precautions 1 Pinyin X

English reference myocardial perfusion imaging

It is concluded that normal myocardial cells have the function of absorbing some imaging agents, and their uptake is directly proportional to myocardial blood flow. The uptake function of ischemic or necrotic myocardium is reduced or lost, which shows that the segmental radioactive distribution area of myocardium is reduced or defective. It is mainly used for the diagnosis of coronary heart disease, the choice of treatment scheme, the judgment of curative effect and the evaluation of prognosis.

4 name of operation myocardial perfusion imaging

5 myocardial perfusion imaging indications are applicable to:

1. Diagnosis of myocardial ischemia and evaluation of the location, scope and degree of myocardial ischemia.

2. Prepare coronary angiography.

(1) Chest pain, chest tightness or arrhythmia.

(2) No obvious symptoms but abnormal electrocardiogram.

(3) those with positive ECG exercise test.

3. Localization diagnosis of myocardial infarction, and judge the range and degree of infarction.

4. Diagnosis of ventricular aneurysm.

Contraindications As long as the patient can tolerate the examination, there is no absolute contraindication in myocardial perfusion imaging, except for exercise and drug load test.

7 prepare 1. Explain the purpose, method and matters needing attention of the examination to the patient, and fully obtain the cooperation of the patient.

2. Patient preparation

(1) During stress myocardial imaging, β -blockers and drugs for slowing heart rate were stopped for 48h, and nitrolipids 12 ~ 24h.

(2) 2) It is best to be on an empty stomach during 201TL myocardial imaging.

8 method 1. Imaging agent? There are three main types of myocardial perfusion imaging agents.

(1) chlorite 20 1 thallium [20 1TlCl].

(2)99mTc isocyanides, of which 99mTc methoxyisobutyl isocyanide 99mTcMIBI is the most widely used.

(3) Other compounds labeled with 99mTc, such as tetrofo *** in (p53) labeled with 99mtc.

2. Imaging instrument? Plane imaging adopts gamma camera imaging or SPECT, and tomographic imaging adopts single probe or multi-probe SPECT.

3. Imaging scheme? It varies according to the radioactive drugs used. At present, the commonly used SPECT myocardial perfusion imaging schemes are as follows:

(1)20 1Tl exercise redistribution imaging method: at the peak of exercise, 201TL 92.5 ~165438+74 mbq (2.5 ~ 3 MCI) was injected intravenously, and the early imaging was 5 minutes, and then the redistribution imaging was carried out after 3 ~ 4h hours if necessary.

(2) 99mTcMIBI exercise rest imaging every other day: 740 ~ 925mbq (20 ~ 25mci), 1.0 ~ 1.5h were injected at the peak of exercise, and 740 ~ 925mbq and1~/kloc-0 were injected every other day.

(3) One-day method 3)99mTcMIBI exercise resting imaging: 296 ~ 333 mbq (8 ~ 9 MCI) was injected at rest,1~1~ 4 hours for resting imaging,1~ 4 hours for exercise test, and then 81at rest.

(4) Dual-core imaging: at rest, intravenous injection of 201TL 74 ~11mbq (2 ~ 3mci), 15min imaging, 60min exercise test, and then injection of 99 MTC MIBI 925mbq (29 MTC). This scheme is mainly to overcome the shortcoming that two injections of 99mTcMIBI take a long time, and exercise and rest imaging can be completed within 2 hours.

4. Acquisition conditions

(1) plane imaging: generally, the front and rear positions are taken, the left front oblique position is 30 ~ 45, the left front oblique position is 70 * * * and the left and right front oblique positions are 30 if necessary. The probe is equipped with a low-energy universal collimator or a high-resolution collimator, and the peak energy of 20 1Tl is 80keV. If there are multiple devices, two groups of energy peaks, 167 and 135keV, can be added, with a window width of 25%, a 99mTc energy peak 140keV and a window width of 20%. Matrix 128× 128 or 256×256, each * * * acquires 10 minute or the preset count is 5× 105 ~ 6× 105. The probe should be as close to the body wall as possible to improve the resolution and sensitivity.

(2) Tomography: The examinee takes the supine position, holds the head with the upper arm and fixes it. The probe is close to the chest wall and the field of vision includes the whole heart. The probe rotates 1 80 or 360 degrees from the right front oblique position of 45 to the left rear oblique position, and collects1frame every 3 ~ 6 degrees, 30 ~ 40s/ frame, and * * * collects 30 ~ 60 frames. The energy windows of 20 1Tl and 99mTc are set in the same plane with a matrix of 64×64. The probe is equipped with low-energy universal or high-resolution collimator.

(3) gated myocardial imaging: 99mTcMIBI imaging is superior to 20 1Tl. The acquisition method of plane and fault is the same as above. With ECG as the gating signal, the plane image acquires 8 ~ 16 frames per cardiac cycle, with RR window width 15% and matrix 128× 128, and the tomographic image acquires 8 ~ 12 frames per cardiac cycle, with RR window value of 20% and matrix.

5. Image processing

(1) Image reconstruction: At present, the processing software of most instruments uses filtered back projection method to reconstruct tomographic images. The selection of filter function type and cut-off frequency should be determined according to factors such as counting. Various types of filters can be different, and images of short axis, horizontal long axis and vertical long axis sections can be reconstructed, and the thickness of each section is generally 6 ~ 9mm.

(2) Quantitative analysis of circumferential contour: This method is carried out on early imaging and delayed imaging respectively. After background subtraction, the image is smoothed by multi-point weighting. Taking the center of the left ventricular cavity as the midpoint, 60 sectors (6 in each sector) are generated, and the maximum count value of these sectors is 100%, and the relative percentage of the maximum count value of each sector is obtained. With this percentage as the ordinate and the 360 circle diameter of the heart as the abscissa, a circular plane curve is drawn to show the relative radioactivity distribution of each sector of the myocardium. Comparing the peripheral plane curve coupling of early imaging and delayed imaging, the elution rate of delayed imaging 20 1Tl was calculated. Each unit must determine its own normal reference value.

(3) Bull's-eye: After reconstructing the images of myocardial short-axis sections, the section curves of each short-axis myocardial section are formed, and the peripheral section curves of each section are arranged into concentric circles from the apex to the basal part, with the center of the circle as the apex and the outermost layer of the circle as the basal part, that is, the bull's-eye diagram. The percentage of each sector counted in the original bull's-eye chart is compared with the normal percentage in this area one by one. Where the deviation from the normal average is 2.5 or 3.0 standard deviation, the black bull's-eye chart is displayed in black, indicating that the myocardial perfusion in this area is abnormal. Using bull's-eye diagram to display myocardial radioactivity distribution can objectively and intuitively evaluate the range of normal, reversible and fixed perfusion defects, and can quantitatively determine the percentage of diseased myocardium in left ventricular myocardium.

6. Gated tomography? Reconstruction of short axis, horizontal long axis and vertical long axis images, each axial section can obtain 8 ~ 12 images in each cardiac cycle. In image reconstruction, 1 ~ 2 images of end-diastolic and end-systolic in each axial direction can be superimposed into end-diastolic and end-systolic images respectively, which is convenient for reading films.

7. Quantitative analysis of gated images? It is divided into global left ventricular function measurement and regional wall motion evaluation. Global functions, such as calculating left ventricular end-diastolic volume (EDV), end-systolic volume (ESV) and left ventricular ejection fraction (LVEF). Regional wall motion can be used to measure regional myocardial thickening rate and directly observe wall motion.

9 precautions 1. Before inspection, the daily quality control inspection of the instrument should be strictly carried out, and the appearance and quality control of radioactive drugs should be carried out. If the drug must have a formal factory test report, it can only be used after it is qualified.

2. The diagnosis of myocardial ischemia in coronary heart disease must be combined with stress (exercise or drug) test and resting myocardial perfusion imaging.

3. Before the examination, the patient must stop taking related drugs, such as antiarrhythmia or bradycardia and nitrate drugs, and obtain the patient's cooperation.

4.20 1Tl myocardial perfusion imaging can reduce the interference of 20 1Tl concentration in abdominal organs and lungs on myocardial imaging.

5. With 99mTcMIBI as imaging agent, the labeling rate should be above 95%. Eating fat meal 30 minutes after intravenous injection can eliminate the radioactive interference in gallbladder. If the radioactive clearance in liver area is slow, patients can be encouraged to exercise properly.

6. The patient should be kept still during the examination, and the patient should be instructed to keep breathing smoothly during the examination to reduce the influence of diaphragm movement on myocardial imaging. Uncooperative patients should be fixed.

7. Exercise load must be strictly controlled. Before this work, nuclear medicine doctors should be specially trained in cardiology, familiar with ECG diagnosis and possible emergency measures, and can independently carry out this examination after passing the examination, otherwise professional cardiologists are generally required to be present; ECG monitor, defibrillator, necessary first aid instruments, oxygen, drugs, etc. Should be equipped in the examination room.

8. During the exercise load test, the patient's condition, electrocardiogram and blood pressure changes should be closely observed. If there are serious situations such as blood pressure drop and the patient's condition is not good, the examination should be stopped immediately, and the changes of blood pressure, heart rate and electrocardiogram should be continuously observed. If necessary, please consult a cardiologist.

9. In any of the following cases, whether the predicted heart rate is reached or not, the trial should be terminated: the patient complains of dizziness and headache, pallor, excessive sweating, unsteady gait, blurred vision and paroxysmal cough, severe persistent angina pectoris, sudden increase or decrease of blood pressure, and if systolic blood pressure increases ≥200mmHg or blood pressure decreases ≥ 65,438+00 mmHg, the ST segment of ECG decreases ≥3mV, or the ST wave rises in an arched back for 3 m.

10. In early and delayed imaging, the conditions of patient * * *, data acquisition and image processing must be consistent for comparison and quantitative analysis. Technicians should strictly observe the patient's condition in the process of image acquisition, and must not leave their posts without permission. If there is any change in the condition, they should inform the doctor in time.

1 1. When the same patient performs stress and resting myocardial perfusion imaging, the alignment should be as consistent as possible, and the axial direction, color scale and pairing should be consistent in image processing, especially in tomographic processing, so as to better judge whether there is abnormality.

12. Understand the medical history in detail, and make a comprehensive analysis based on the examination results of the patient's age, gender and typical symptoms, so as to get a more comprehensive diagnosis result.