Dear Editor,
It is with great interest that we reply to the letter of questions and comments of Dr. Prof. Xiao Li to the article “Evaluation of normality and reproducibility parameters of 99mTc-MAA scintigraphy in the diagnosis of intrapulmonary vascular dilatations”. However, we do not agree with the criticism regarding the group evaluated and the protocol used for scintigraphy with technetium-99 m-labeled macroaggregated albumin (99mTc-MAA).
Our aim was to assess normal values for scintigraphy with 99mTc-MAA and not to compare scintigraphic findings among patients with hepatosplenic schistosomiasis and normal subjects. So we chose, as the group to be assessed, individuals without liver, heart or lung diseases, previously excluded by clinical, echocardiographic and abdomen ultrasound assessment.
The second point to be discussed is the time of image acquisition, considered too long. In the literature, the time between intravenous injection of 99mTc-MAA and the acquisition of images has varied from acquisition immediately after injection of the radiopharmaceutical to 60 min [1–3]. The passage of 99mTc-MAA from pulmonary capillaries to the systemic circulation is not immediate in intrapulmonary vascular dilatation, and so we believe that the interval between injection of 99mTc-MAA and the image acquisition is important to increase the test sensitivity.
In the discussion of our article, we consider that the use of different methodologies in the performance of tests for the analysis of control groups can be the cause of differences and we draw attention to the lack of a standard protocol for the performance of scintigraphy with 99mTc-MAA in pulmonary vascular dilatation studies.
Best regards,
Andrea Simone Siqueira de Queiros
References
Abrams G, Jaffe C, Hoffer P, Binder H, Fallon MB. Diagnostic utility of contrast echocardiography and lung perfusion scan in patients with hepatopulmonary syndrome. Gastroenterology. 1995;109:1283–8.
Krowka MJ, Wiseman GA, Burnett OL, Spivey JR, Therneau T, Porayko MK, et al. Hepatopulmonary syndrome: a prospective study of relationships between severity of liver disease, PaO(2) response to 100% oxygen, and brain uptake after (99m)Tc MAA lung scanning. Chest. 2000;118(3):615–24.
Hosono M, Machida K, Honda N, Takahashi T, Kashimada A, Osada H, et al. Quantitative lung perfusion scintigraphy and detection of intrapulmonary shunt in liver cirrhosis. Ann Nucl Med. 2002;16(8):577–81.
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de Queiro´s, A.S.S. Reply to ‘Accurate measurement of the normality values of macroaggregated albumin lung perfusion scan in hepatopulmonary syndrome’. Ann Nucl Med 29, 756 (2015). https://doi.org/10.1007/s12149-015-1004-4
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DOI: https://doi.org/10.1007/s12149-015-1004-4