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Master's Proposal

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by

Lisa Russell

on 6 February 2013

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Transcript of Master's Proposal

To do:
"Blind study" of all reconstructed images
Have images assessed by radiologist
Include obese and normal patients throughout study
Rank images from 1 - 4,
1 = Excellent, diagnostic quality
2 = Good, still diagnostic quality
3 = Moderate, non-diagnostic
4 = Poor, non-diagnostic Background SPECT/CT Research
Objective Methodology Literature
Review Myocardial Perfusion SPECT/CT Image Optimisation for Patients of Varying BMI Obesity
in General Definition:
"A disease in which excess body fat has
accumulated to an extent that health is
adversely affected". Assessed by:
Body Mass Index (BMI)
Waist circumference Obesity
in Ireland Over the past decade, Ireland has observed a dramatic rise in obesity levels.
This obesity epidemic has brought with it a number of challenges in the field of Nuclear Medicine. "Hybrid Imaging Technique"
Combines:
SPECT
CT Benefits
of SPECT/CT Myocardial Perfusion Imaging SPECT imaging of the heart
Both gamma cameras detect decay of isotope from myocardium 2 sets of images are acquired:
The patient is stressed either physically or pharmacologically. The drug is injected at peak stress, then imaging is performed.
Tc-99m injected while the patient is at rest, then the myocardium is imaged. The resulting two sets of images are compared with each other to distinguish:
Ischemic
Infarcted
areas of the myocardium. Procedure Results Issues with
Obese Patients MPI imaging of obese patients has shown:
Increased noise
Increased scatter
Decreased contrast
Leading to images that are:
sub-optimal
non-diagnostic quality Phantom Study Retrospective/Prospective Patient Study Clinical Assessment of Images "How do we optimise cardiac SPECT/CT imaging for clinically obese patients?" Image Acquisition Optimisation Image Reconstruction Optimisation Current method:
32 views through 180 rotation
Each view = 25sec o Can we assess available reconstruction algorithms and variable parameters to optimise:
SNR
CNR
Spatial Resolution Can Image quality be improved by:
Extending time-per-view?
Acquiring "counts based"
views vs. time based? When scanning obese patients. To do:
Model chest wall thickness of obese patients
Model cardiac phantom to contain Tc-99m
Determine optimum reconstruction parameters/technique for "obese" phantom
Determine BMI cut-off for optimal reconstruction To do:
Identify obese demographic
Identify control group
Reconstruct retrospective images in various ways to come up with optimum reconstruction techniques
Acquire and reconstruct prospective images using a range of parameters to further optimise image quality Work has been done in areas surrounding this topic, but not on the topic itself: SPECT/CT of
Obese Patients Studies have shown SPECT imaging is feasible for the majority of morbidly obese patients (BMI>45) with the use of:
Dual-head camera
Attenuation correction
High stress Tc-99m tracer activity Mean Tc-99m stress activity of 35.6±5.4 mCi (=1.3±0.2 GBq) Duvall WL, Croft LB, Corriel JS, Einstein AJ, Fisher JE, Haynes PS, et al. SPECT myocardial perfusion imaging in morbidly obese patients: image quality, hemodynamic response to pharmacologic stress, and diagnostic and prognostic value. J Nucl Cardiol 2006;13(2):202–9 Center for Cardiovascular Health, Mount Sinai Medical Center, New York, NY, USA MPI SPECT/CT Reconstruction
Algorithms Phantom study
for MPI SPECT/CT Realistic silicone 3-D gated cardiac phantom with known:
Left ventricular (LV) volumes
Ejection fractions (EFs)
produced to evaluate quantitative measurements obtained from GSPECT. Eur J Nucl Med Mol Imaging. 2004 Feb;31(2):222-8.
A realistic 3-D gated cardiac phantom for quality control of gated myocardial perfusion SPET: the Amsterdam gated (AGATE) cardiac phantom.Visser JJ, Sokole EB, Verberne HJ, Habraken JB, et al. Department of Nuclear Medicine, Academic Medical Center, Amsterdam, The Netherlands. Studies to "rank" reconstruction algorithms have been undertaken prior to this study, but have only included patients of normal BMI (i.e <25 kg/m2). Evaluation of image reconstruction methods for 123I-MIBG-SPECT: a rank-order study.
Marcus Soderberg, Soren Mattsson, Jenny Oddstig, Helena Uusijarvi-Lizana, et al. Medical Radiation Physics, Department of Clinical Sciences, Lund University, Sweden. Optimisation of Cardiac SPECT/CT imaging of obese patients using:
Moderate tracer activity (400MBq)
Modified acquisition parameters
Modified reconstruction algorithms
Blind study to rank image quality Phantom study - to quantify:
Image quality degradation with increased thickness of fat layer surrounding chest cavity
BMI cut-off point, at which new reconstruction techniques are required Topics to
cover in Study: Provides:
Functional information from SPECT
Isotope activity/uptake
Detailed anatomical information from CT
Image fusion providing precision alignment of both sets of data
Eliminates inaccuracy caused by:
Variations in patient position/couch surfaces
Internal changes within patient from
During separate imaging sessions.

Allows Radiologist to potentially diagnose patients without further imaging required
Full transcript