Correction of respiratory motion in gated SPECT imaging of the heart

Dissertation for Master's Degree (MS.c)

Tension: Nuclear

Dissertation abstract:

In this research, imaging of the heart muscle by SPECT method is a non-invasive method for diagnosing patients with suspected coronary artery disease. One of the most important movement artifacts in SPECT imaging is respiratory movement, which will reduce image quality. The purpose of this research is to investigate the effect of normal respiratory movement in the RCA region of the left ventricle.

However, by using NCAT software, phantoms with and without normal respiratory movement were made, defective and healthy, and were simulated using Gate and SIMIND simulation codes. In the next step, several processes were performed on the gated phantoms by the Matlab program: 1. In each of the studied groups, all the phantoms were gathered together. 2. Divide the breathing cycle into six parts and collect the phantoms of each part together. 3. In the breathing cycle, the phantoms were moved for 0.208 seconds in three stages and then gathered together. 4. Adjust them in the final processing with a correction program for the effect of respiratory movement. Then, for all the processed phantoms, a head corresponding to the language of the device was made and it was reconstructed by the backprojection filter method without applying attenuation and scattering correction in the Xeleris workstation. At the end, quantitative blood supply analysis was performed on the samples with 4D-MSPECT software in Xeleris workstation. The observations indicated that the counts and the ratio of the count of the lower regions and the lower interventricular wall to the lateral region were reduced in the presence of respiratory movement and the images of samples with respiratory movement resembled the images of a heart patient with a problem in the lower region of the heart. Performing the respiratory gate moderated the results and its presence in the imaging process was fruitful. The gated images of the second and fifth parts of the respiratory cycle were close to the images without respiratory movement.

The results of the present study showed that respiratory movement has the greatest effect on the lower region and the lower interventricular wall of the heart, and this effect can be moderated by respiratory gating and examining the images of several specific parts in a respiratory cycle. Using the proposed respiratory motion correction program, this effect can be corrected to a large extent after image simulation and before reconstruction.

Abstract

Introduction: Imaging of the heart muscle using SPECT method is a non-invasive method for diagnosing patients with suspected coronary artery disease. One of the most important movement artifacts in SPECT imaging is respiratory movement, which will reduce image quality. The purpose of this research is to investigate the effect of normal respiratory movement in the RCA region of the left ventricle. Materials and methods: Using NCAT software, phantoms with and without normal respiratory movement were made, defective and healthy (to perform respiratory gating, 24 phantoms were made in one breathing cycle for groups with respiratory movement and one gated phantom without respiratory movement was also made for each group) and using Gate and SIMIND simulation codes were simulated. In the next step, several processes were performed on the gated phantoms by the Matlab program: 1. In each of the studied groups, all the phantoms were gathered together. 2. Divide the breathing cycle into six parts and collect the phantoms of each part together. 3. In the breathing cycle, the phantoms were moved for 0.208 seconds in three stages and then gathered together. 4. In the final processing, with a correction program (in which the maximum counts are determined and the surrounding counts are transferred to those points and added with them, equivalents for the position of the diaphragm were proposed so that its effect in those positions can be removed) to adjust the effect of respiratory movement in them. Then, for all the processed phantoms, a head corresponding to the language of the device was made and it was reconstructed by the backprojection filter method without applying attenuation and scattering correction in the Xeleris workstation. At the end, quantitative blood supply analysis was performed on the samples with 4D-MSPECT software in the Xeleris workstation.

Results: The observations indicated that the counts and the ratio of the count of the lower regions[1] and the lower interventricular wall[2] to the lateral region[3] were reduced in the presence of respiratory movement, and the images of samples with respiratory movement resembled the images of heart patients with problems in the lower region of the heart. Performing the respiratory gate moderated the results and its presence in the imaging process was fruitful. The gated images of the second and fifth parts of the respiratory cycle were close to the images without respiratory movement.

Conclusion: The results of the present study showed that respiratory movement has the greatest effect on the lower region and the lower interventricular wall of the heart, and with respiratory gating and examining the images of several specific parts in a respiratory cycle, this effect can be moderated. By using the proposed respiratory movement correction program, this effect can be corrected to a great extent after image simulation and before reconstruction.    Chapter 1: Introduction and overview rtl;"> 

1- Introduction and generalities:

1-1. Medical imaging:

Diagnosis of disease by performing physical examinations and observing the signs of disease has been common among doctors since ancient times, and countless books have been written in this regard. But with the ever-increasing population growth in the world and the emergence of complex diseases, it became difficult to diagnose diseases, and diagnosis became particularly important. In this regard, many methods and devices were invented and used. Imaging of different parts of the human body is one of the best diagnostic methods that have been used so far. Imaging has made timely diagnosis of diseases possible and has led to the discovery of many diseases and rare and unknown phenomena. During the last hundred years, medical imaging has seen an upward growth. Today, different types of imaging are used to examine the vital organs of the body. There are different types of medical imaging that can be divided according to the eyes used for imaging. [1]

A- Source outside the body:

Emission

X-ray

[4] CT

Projection radiology

Reflection, refraction

Ultrasound

Endoscopy

Photography

Videography

B- Inside the body :

External excitation:

Nuclear magnetic resonance

Bioluminescence[5]

Internal tracking:

Single photon scinography[6]

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SPECT

Positron emission tomography

Natural source:

thermography

ECG map, EEG

1-1-1: Radiation beam computed tomography:

Radiation beam computed tomography makes it possible to take three-dimensional images of the distribution of radiopharmaceutical activity given to a patient in a living environment. Computed tomography can be divided into two main groups:

Computerized tomography with positron radiation ([7]PET)

Computerized tomography with single photon radiation ([8]SPECT)

1-1-1-1: PET:

The basis of tracking in this method is positron tracking and they usually use radioactive substances that emit positive beta rays. The positron is destroyed in the body.