A method is proposed for accurate quantification of lung uptake during shunt studies for liver cancer patients undergoing radio-embolization. The current standard for analysis of [⁹⁹mTc]-MAA shunt studies is subjective and highly variable. The technique proposed in this work involves a small additional peripheral intravenous injection of macroaggregated albumin (MAA) and two additional static acquisitions (before and after injection) to quantify the absolute activity in the lungs as a result of arterio-venous shunting. Such quantification also allows for estimates of absorbed dose to lung tissue at the time of treatment based on MIRD formalism. The method was used on six radio-embolization patients attending the department for lung shunt analysis. Quantitative values for each were compared to a previously validated technique using fully quantitative SPECT/CT imaging, treated as the gold standard. The average difference between absolute activity shunted to the lungs calculated by the proposed technique compared to the previously validated technique was found to be 2%, with a range of (1–8)%. The proposed method is simple and fast, allowing for accurate quantification of lung shunting and estimates of absorbed dose to lung tissue at treatment, and may one day be used in a one-stop procedure for planning and therapy in a single interventional procedure.