Slide 1:The Principles of SPECT


What is SPECT? :What is SPECT? Single Photon Emission Computed Tomography is an imaging technique associated with single gamma-ray-emitting radiopharmaceuticals obtained using a scintillation camera that moves around the patient to obtain images from multiples angles for tomographic image reconstruction.


Slide 3:SPECT imaging is very demanding and expensive. It requires a lot of careful attention in order to acquire a great image. In that case it’s essential to understand the principle of SPECT to produce the highest quality scans.


Principles :Principles Reconstruction Image reconstruction is the process of transforming a set of 2D projections into a 3D image. The essence of the reconstruction is the smearing back projection into the reconstruction space of each projection, maintaining the correct angular offset.


Principles :Principles Filtering is a computer algorithm applied to projections obtained from an imaging system to eliminate noise and artifacts. Filters are mathematical functions that are multiplied into the frequency domain data sets to change the frequency distribution of the power spectrum. A filter is a magnitude – vs – frequency function.


Types of Filters :Types of Filters Three types of filters: Low Pass High Pass Band Pass


Low Pass Filters :Low Pass Filters Low pass filters are used to, allow low frequencies through the filter and to reduce (or attenuate) high frequencies. Used to get rid of high frequency noise (statistical count fluctuations). Example: Butterworth filter


High Pass Filter :High Pass Filter High pass filters are used to, allow high frequencies through the filter and to reduce or attenuate low frequencies. Used to enhance edges or small objects. Example: ramp filter


Band Pass Filters :Band Pass Filters Band Pass Filters are used to, allow a certain band or range of frequencies through the filter. Example: Combination filters like Ramp-Hamming Filter & Butterworth-Ramp Filter.


Slide 10:Unfiltered Myocardial Perfusion Filtered with Hanning Filter cutoff 0.822 1/cm Cutoff 0.6 1/cm Cutoff 0.4 1/cm; smoothes most of the details out of the image *The lower the cutoff the smoother the image after the filter is applied. Comparison of transverse slice through the liver reconstructed with filtered back production and Ordered subsets expectation maximization. *Notice the Streak artifact in the first image and on the last image the improved image with streak artifact and noise reduced, after being filtered.


Conclusion :Conclusion These Filters, help to eliminate noise and artifacts such as “star” artifact and blurred images in order to have the best quality scans. SPECT is a technique that is generally used to scan tomography images with NM Radiopharmaceuticals. NMT have principles that they must do in order to obtained the best visible scans of their patients, which includes reconstruction and filtering.


True or False :True or False Image reconstruction is the process of transforming a set of 2D projections into a 3D image. Filtering is a computer algorithm applied to projections obtained from an imaging system to increase noise and artifacts. Low Pass Filters are used to get rid of high frequency noise. An example of high pass filter is a ramp filter. Band Pass Filters are used to get rid of low frequency only.


Answers :Answers True False True True False