The purpose of this study was to develop a novel open-window needle aspiration method and evaluate its efficacy in drainage and sclerotherapy of cystic thyroid nodules that cannot be aspirated with an 18-gauge needle. Two rectangular windows 5.0 mm in length and 1.0 mm wide were placed at the end of the percutaneous transhepatic cholangiography (PTCA) needle trocar to develop a new open-window intervention needle. The efficiency of the open-window intervention needle was compared either to a porous interventional needle or to an ordinary PTCA needle by assessing the aspiration efficiency. The efficacy of the modified open-window approach was tested by carrying out sclerotherapy and drainage on 21 thyroid cystic nodules that could not be aspirated with an 18-gauge needle and comparing it to aspiration with an 18-gauge PTCA needle of 50 cystic thyroid nodules. The efficacy of aspirating coupling agents of various specifications using the new open-window intervention was superior to aspiration using the PTCA trocar needle or a porous needle (p<0.05). Ethanol ablation efficacy in the treatment of 21 cystic thyroid nodules that could not be aspirated with an 18-gauge needle and the aspiration efficacy of 50 cystic thyroid nodules with an 18-gauge PTCA needle were not significantly different (p>0.05). The new open-window intervention needle approach was highly effective in conducting ethanol ablation of cystic thyroid nodules that could not be aspirated using conventional methodologies.