Inter-Site Validations of the Pixel-Wise Method for Cardiac T2* Analysis in Transfusion-Dependent Thai Thalassemia Patients
Pairash Saiviroonporn PhD*, Vip Viprakasit MD, DPhil**, Adisak Maneesai MD***, Noppadol Siritanaratkul MD****, Bunchoo Pongtanakul MD**, John C. Wood MD, PhD*****, Rungroj Krittayaphong MD***
Affiliation : * Department of Radiology, Siriraj Hospital, Mahidol University, Bangkok, Thailand ** Haematology/Oncology Division, Department of Pediatrics and Thalassemia Center, Bangkok, Thailand *** Division of Cardiology, Department of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand **** Division of Hematology, Department of Medicine, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand ***** Divisions of Cardiology, Department of Pediatrics, Children’s Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
Objective : To compare inter-site observer variability of the Pixel-Wise (PW) method for cardiac T2* analysis in thalassemia
patients using the mono-exponential with a constant fitting (offset) model and to compare the cross-model variability of the
offset model to the mono-exponential (typical) model.
Material and Method: Eighty-eight cardiac T2* measurements were performed on 72 Thalassemia major patients. Both
bright- and black-blood techniques were acquired and analyzed at both the reference (REF) and local (LOC) sites using the
PW method by defined region of interest on the whole (at the REF site) and partial (at the LOC site) septum. The offset model
was analyzed at the reference site while both the offset and typical models were performed at the local site. The inter-site
variability of the T2* values were analyzed by independent observers blinded to the results.
Results : The T2* values from the REF-offset, LOC-offset and LOC-typical methods were statistically comparable on both
scanning techniques. The inter-site variations of the offset model were about 5.2% and 4.4% on the bright- and black-blood
techniques, respectively, which was about 1.7% higher than from the intra-site, but was still in a reasonable range compared
to the conventional method of around 5.4%. The cross-model comparisons presented with 0.4 ms of bias and variation of
about 6.9% and 4.7%, respectively, which is about 1.4% higher than from the intra-site.
Conclusion : The observer variability on the PW method using the offset or typical model provided equivalent coefficient of
variation on both scanning techniques, which was also comparable to the previous reports. The inter-site variability of the
offset and cross models was also in a reasonable range, being less than 2% higher than the intra-site with bias of about 0.4
ms.
Keywords : CMR, Myocardial T2* analysis, Pixel-Wise method, Thalassemia; Iron overload; The offset model, The mono- exponential model
