Original ArticleSemi-automated algorithm for calculating heart-to-mediastinum ratio in cardiac Iodine-123 MIBG imaging
Introduction
Iodine-123 (123I)-labeled meta-iodobenzylguanidine (MIBG) is a radiopharmaceutical for cardiac sympathetic nerve imaging which has been used to assess heart failure, dilated cardiomyopathy, and cardiac arrhythmia.1, 2, 3, 4, 5, 6 Recently, 123I-MIBG cardiac scintigraphy has played an important role in evaluation of neurodegenerative disease such as dementia with Lewy bodies.7,8 For quantitative assessment of cardiac 123I-MIBG uptake, planar imaging has been utilized, and its usefulness has been supported by a large amount of evidence.1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
The heart-to-mediastinum (H/M) ratio and washout rate in the planar image have been used for quantifying cardiac 123I-MIBG uptake. These indices, however, are considerably influenced by both the choice of collimator and the location and size of the cardiac and mediastinal regions of interests (ROIs).10,12, 13, 14, 15, 16, 17, 18 The reason for quantitative variation is that 123I-MIBG planar image acquisition and processing have not been standardized.12,15,18 The use of institution-specific criteria for interpreting 123I-MIBG imaging limits the generalizability of published results.
Therefore, the purpose of this study is to develop a semi-automated method for standardizing the size and positioning of the myocardial and mediastinal ROIs. We validated intra- and inter-observer variations of the H/M ratio and assessed reproducibility with a semi-automatic method instead of using the manual method.
Section snippets
Study Population
A total of 37 clinical studies of 18 females and 19 males who underwent early and delayed 123I-MIBG scintigraphy were retrospectively selected between October 2007 and May 2008. The characteristics of the subjects are shown in Table 1. Indications for 123I-MIBG scintigraphy included patients with cardiac disease (n = 13), neurodegenerative and psychiatric diseases (n = 12), and normal volunteers (n = 12). The subjects with disease were selected randomly and the volunteers were selected from the
Cardiac ROI
A preliminary study was performed to evaluate the appropriate cardiac ROI size. When we compared the average counts between the polygonal ROI (average 73 ± 43 count/pixel) and circular ROI with the radii of 20, 30, 40, and 50 mm, the differences of average count between the circular and polygonal ROIs were 1.7 ± 3.1, 1.5 ± 2.0, −1.1 ± 2.3, and −3.8 ± 4.8 counts/pixel, respectively. Since the circular ROIs with 20 and 30 mm radii did not include the hepatic and pulmonary uptakes in all the
Discussion
In this study, we have developed an algorithm for calculating the H/M ratio, which automatically determined the mediastinal ROI by using information of a manually defined circular cardiac ROI. The aim of this study is to assess reproducibility of the H/M ratio using the semi-automated method in intra- and inter-observer studies. According to the results of ICCs, Bland-Altman analyses and κ statistics, the semi-automated method improved reproducibility of calculating the H/M ratio in comparison
Conclusion
We developed software for semi-automatically determining the H/M ratio and assessed its reproducibility. The H/M ratio obtained from the semi-automated method had good intra- and inter-observer reproducibility. The application of the semi-automated method in 123I-MIBG planar image processing yielded a quantitative H/M ratio.
Acknowledgments
We thank Drs Junichi Taki and Kawano Masaya for their scientific advices, and Masato Yamada, RT, Minoru Tobisaka, RT, Shigeto Matsuyama, RT and Hiroto Yoneyama, RT for their technological assistance. We also thank Ryo Maeda, Shunsuke Nagare, Tsuyoshi Kouke and Hiroyuki Yamanishi (FUJIFILM RI Pharma Co., Ltd., Tokyo, Japan) for their research assistance.
References (23)
- et al.
Cardiac death prediction and impaired cardiac sympathetic innervation assessed by MIBG in patients with failing and nonfailing hearts
J Nucl Cardiol
(1998) - et al.
123I-mIBG scintigraphy to predict risk for adverse cardiac outcomes in heart failure patients: Design of two prospective multicenter international trials
J Nucl Cardiol
(2009) - et al.
Segmental pattern of myocardial sympathetic denervation in idiopathic dilated cardiomyopathy: Relationship to regional wall motion and myocardial perfusion abnormalities
J Nucl Cardiol
(2002) - et al.
Optimized acquisition and processing protocols for I-123 cardiac SPECT imaging
J Nucl Cardiol
(2006) - et al.
Normal values and within-subject variability of cardiac I-123 MIBG scintigraphy in healthy individuals: Implications for clinical studies
J Nucl Cardiol
(2004) - et al.
Prognostic value of cardiac metaiodobenzylguanidine imaging in patients with heart failure
J Nucl Med
(1992) - et al.
Neuronal imaging using SPECT
Eur J Nucl Med Mol Imaging
(2007) - et al.
I-123-mIBG myocardial imaging for assessment of risk for a major cardiac event in heart failure patients: Insights from a retrospective European multicenter study
Eur J Nucl Med Mol Imaging
(2008) - et al.
Cardiac 123I-metaiodobenzylguanidine imaging allows early identification of dementia with Lewy bodies during life
Eur J Nucl Med Mol Imaging
(2008) - et al.
Iodine-123-MIBG sympathetic imaging in Lewy-body diseases and related movement disorders
Q J Nucl Med Mol Imaging
(2008)
Characterization of Japanese standards for myocardial sympathetic and metabolic imaging in comparison with perfusion imaging
Ann Nucl Med
Cited by (0)
This work was supported in part by Grants-in-Aid for Scientific Research in Japan (No. 22591320, PI: Kenichi Nakajima).