Effect of misalignment between transmission and emission scans on attenuation-corrected SPECT

Matsunari, Ichiro; Böning, Guido; Ziegler, Sybille; Nekolla, SG; Kosa, J.I; Ficaro, Edward P.; Schwaiger, M

doi:10.1016/s1071-3581(97)91578-6

Cited by 16 publications

(25 citation statements)

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“…Changes in tracer uptake in the lateral wall and septum due to overlap with lung tissue have been previously reported using radionuclide transmission sources (13,14), but decreased uptake in the anterior wall for a caudal shift as found in the present study was not consistently demonstrated, potentially because of differences in the previously used phantom and the assessed patient population.…”

Section: Discussioncontrasting

confidence: 43%

“…The advent of routinely available software for reregistration raises, however, the question of which directions of misalignment between SPECT and CT most severely affect AC myocardial perfusion image quality. Changes in relative regional myocardial tracer uptake as a function of misalignment of AC performed with a radioactive line source (13,14) or coregistered from separately performed SPECT and CT (15) have been previously reported. There is, however, only a paucity of literature regarding frequency of misregistration, the potential relationship between its location and effect on image quality, and guidelines for reregistration of transmission-emission hybrid cardiac SPECT/CT.…”

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confidence: 84%

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Directions and Magnitudes of Misregistration of CT Attenuation-Corrected Myocardial Perfusion Studies: Incidence, Impact on Image Quality, and Guidance for Reregistration

Kennedy¹,

Israel²,

Frenkel³

2009

J Nucl Med

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CT-based attenuation-corrected (AC) myocardial perfusion imaging (MPI) studies may show significant artifacts caused by misregistration between SPECT and CT data. The present study aimed at identifying the directions and magnitudes of misregistration with greatest impact on AC myocardial perfusion image quality. Methods: The incidence, magnitude, and direction of misregistration were assessed in 248 consecutive stress-rest MPI studies in 124 patients. In addition, cardiac SPECT/CT registration was artificially modified in 40 studies, shifting CT data by 61, 62, and 63 pixels along the cephalad/caudal, dorsal/ventral, and left/right axes. Percentage of change in 5-wall AC-MPI polar map scoring was calculated for each region, and the direction of the shift along each axis was analyzed statistically (Student t test, P , 0.05) and compared to determine the region most significantly affected by each shift (Newman-Keuls test, P , 0.05). Changes in the normal and abnormal summed stress score (SSS) due to artificial misregistration were assessed (k-statistics, McNemar differences). Results: SPECT/CT misregistration of more than 1 pixel was found in 73% (181/248) of studies and more than 2 pixels in 23% of studies (57/248). A 3-pixel ventral shift most significantly affected polar map scoring (215.4% 6 6.1% change in lateral wall; 27.5% 6 5.5% change in inferior wall). A 3-pixel dorsal shift resulted in a 29.5% 6 5.3% apical and 28.8% 6 5.8% septal change. Polar map scoring was least affected by the cephalad/caudal shift (,5% average change in all regions except for the anterior wall; 29.9% 6 7.4% change for 3-pixel caudal shift). The most significant changes occurred in the lateral and anterior walls when the myocardium on SPECT overlapped lung tissue on CT, encountered in 16% of studies (40/248). Clinically significant changes (in SSS) occurred for the 3-pixel caudal, dorsal, and right shifts. Conclusion: A misregistration of significant magnitude occurred in 23% of studies and in the direction of the most severe artifacts in 16% of studies. Severe misregistration along the dorsal/ventral axis most significantly affected AC-MPI. Quality control of SPECT and CT registration and manual realignment should be performed routinely, with the highest priority in AC studies showing an overlay of the myocardium on SPECT with lung tissue on the CT component of AC-MPI. Cl inically significant artifacts on CT-based attenuationcorrected (AC) myocardial perfusion imaging (MPI) studies may be caused by misregistration of 1 pixel or more between the SPECT and CT data (1). The present study was performed to identify the directions and magnitudes of misregistration that have the greatest effect on AC myocardial perfusion image quality.Hybrid SPECT/CT scanners provide an efficient method of obtaining CT-based AC-MPI (2,3). Frequent artifacts seen on MPI studies include an apparent reduction in radiotracer uptake due to breast attenuation in women or to diaphragmatic attenuation, more often found in men (4). These findings are reduced or r...

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Section: Discussioncontrasting

confidence: 43%

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confidence: 84%

Directions and Magnitudes of Misregistration of CT Attenuation-Corrected Myocardial Perfusion Studies: Incidence, Impact on Image Quality, and Guidance for Reregistration

Kennedy¹,

Israel²,

Frenkel³

2009

J Nucl Med

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“…Possible sources of misregistration include improper patient positioning, respiratory motion, other voluntary patient movement, or mechanical misalignment of the SPECT/CT device. Phantom and human studies have shown that misregistration can produce errors in the activity distribution of attenuation-corrected perfusion images (3)(4)(5)(6). This change in regional radiotracer distribution may reduce the diagnostic accuracy of myocardial perfusion SPECT.…”

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confidence: 99%

Attenuation Correction in Myocardial Perfusion SPECT/CT: Effects of Misregistration and Value of Reregistration

Goetze¹,

Brown

Lavely

et al. 2007

Journal of Nuclear Medicine

106

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The accuracy of myocardial perfusion SPECT improves with attenuation correction. Algorithms for attenuation correction in hybrid SPECT/CT systems have the potential for misregistration of emission and transmission scans because CT and SPECT are obtained sequentially. Misregistration will influence regional tracer distribution and may reduce diagnostic accuracy. This study focused on the role of misregistration in cardiac SPECT/ CT and the performance of a software-based approach for reregistration. Methods: We included 105 consecutive patients who underwent clinical myocardial perfusion imaging on a SPECT/ CT system. Images were quantitatively assessed for misregistration using fusion software. Results were recorded in millimeters in the x-, y-, and z-axes. Regional tracer uptake in 6 segments (anterior, septal, inferior, lateral, anteroapical, and inferoapical) for noncorrected and attenuation-corrected images before and after reregistration was obtained from polar maps. To determine the relative influence of misregistration, we correlated individual differences between noncorrected and attenuation-corrected images, as well as between attenuation-corrected images before and after reregistration, with the degree of misregistration in a multivariate analysis including additional clinical variables such as sex and body weight. Results: The difference in regional radiotracer uptake was significant between noncorrected and attenuationcorrected images in all 6 segments and was most pronounced in the inferior wall. On multivariate analysis, misregistration contributed significantly to changes in radiotracer distribution in the anterior (P 5 0.038), septal (P 5 0.011), and inferior (P 5 0.006) segments. The mean misregistration was 8.6 6 3.8 mm (1.25 6 0.55 pixel). Misregistration of one or more pixels was observed in 64% of studies. Reregistration of misalignment significantly affected regional radiotracer distribution in the segments shown to be influenced by misregistration. Conclusion: Misregistration occurs with SPECT/CT systems and influences regional tracer distribution on attenuation-corrected myocardial images. Reregistration of misaligned studies may be a useful tool for correction. The impact of this strategy on the diagnostic and prognostic accuracy of cardiac hybrid imaging needs to be determined. Formyocardi al perfusion SPECT, professional societies recommend incorporation of attenuation correction to improve diagnostic accuracy (1). On standalone SPECT scanners, the transmission scans necessary for determining tissue density maps for attenuation correction are obtained with an external radionuclide line or point source. With the advent of SPECT/CT hybrid systems, however, CT is now increasingly used for transmission scanning. Advantages of the CT method include higherquality attenuation maps secondary to higher photon flux, lower noise, and improved resolution (2). Additionally, especially when using multislice CT in SPECT/CT systems, coronary calcium scoring or coronary angiography can be performed t...

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“…Frequent misregistration artifacts in standard cardiac PET/CT using helical CT scans (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11) are eliminated by cine CT and manual coregistration of attenuation-emission data to achieve proper coregistration (10,11). With systematically correct attenuation-emission coregistration, cardiac PET is suitable for assessing the severity of coronary artery disease (CAD) as the basis of invasive procedures, for stratifying risk, for following progression or regression of CAD after intense risk factor treatment, and for predicting coronary events in relation to the intensity of medical treatment (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26).…”

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Reducing Radiation Dose in Rest–Stress Cardiac PET/CT by Single Poststress Cine CT for Attenuation Correction: Quantitative Validation

et al. 2008

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Cardiac PET/CT is optimized by cine CT with dedicated shift software for manual correction of attenuation-emission misregistration. Separate rest and stress CT scans incur greater radiation dose to patients than does standard helical PET/CT or ''pure'' PET using rotating rod attenuation sources. To reduce radiation dose, we tested quantitative accuracy of using a single poststress cine CT attenuation scan for reconstructing rest perfusion images to eliminate resting CT attenuation scans. Methods: A total of 250 consecutive patients underwent diagnostic rest-dipyridamole myocardial perfusion PET/CT with 82 Rb and a 16-slice PET/CT scanner using averaged cine CT attenuation data during breathing at rest and stress. After correcting for any attenuation-emission misregistration, we quantitatively compared resting perfusion images reconstructed using rest cine CT attenuation data with the same resting emission data reconstructed with poststress cine CT attenuation data. Automated software quantifying average regional quadrant activity, severity, size, and combined size and severity of perfusion defects was used for this comparison. Results: Resting perfusion images reconstructed using rest cine CT attenuation data were quantitatively comparable to resting images reconstructed with poststress cine CT attenuation data with no clinically significant differences. Twenty-five (10%) of 250 cases required shifting of stress cine CT attenuation data to achieve optimal attenuationemission coregistration with resting perfusion data. Eliminating rest CT attenuation scans reduced CT radiation dose by 50% below rest-plus-stress cine CT protocols. Conclusion: Resting perfusion images reconstructed using poststress cine CT attenuation data are quantitatively comparable to resting images reconstructed with resting cine CT attenuation data. Eliminating the rest CT scan reduces CT radiation dose by 50%. Cardi ac PET is the most accurate noninvasive technology for assessing myocardial perfusion. Frequent misregistration artifacts in standard cardiac PET/CT using helical CT scans (1-11) are eliminated by cine CT and manual coregistration of attenuation-emission data to achieve proper coregistration (10,11). With systematically correct attenuation-emission coregistration, cardiac PET is suitable for assessing the severity of coronary artery disease (CAD) as the basis of invasive procedures, for stratifying risk, for following progression or regression of CAD after intense risk factor treatment, and for predicting coronary events in relation to the intensity of medical treatment (12-26). Mild reductions in relative coronary flow reserve by PET indicate early nonobstructive or diffuse CAD as the basis for treatment before significant stenosis develops (13,20,21).However, radiation dose to patients undergoing CT has become an important issue (27-30). Current standard PET/ CT protocols acquire separate rest and poststress CT scans for attenuation data to reconstruct rest and stress emission images. Cardiac PET/CT involves substantially great...

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Effect of misalignment between transmission and emission scans on attenuation-corrected SPECT

Cited by 16 publications

References 0 publications

Directions and Magnitudes of Misregistration of CT Attenuation-Corrected Myocardial Perfusion Studies: Incidence, Impact on Image Quality, and Guidance for Reregistration

Directions and Magnitudes of Misregistration of CT Attenuation-Corrected Myocardial Perfusion Studies: Incidence, Impact on Image Quality, and Guidance for Reregistration

Attenuation Correction in Myocardial Perfusion SPECT/CT: Effects of Misregistration and Value of Reregistration

Reducing Radiation Dose in Rest–Stress Cardiac PET/CT by Single Poststress Cine CT for Attenuation Correction: Quantitative Validation

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