Background Various pulmonary diseases can be evaluated by ventilation and perfusion scintigraphy with a continuous inhalation of 81mKrypton. Leak of radionuclide during inhalation is a major issue for image quality and requires the intervention of a technician, exposing him-her to gamma radiation from the patient.
Purpose To compare two masks: the DAR breathing system (Covidien) and the Performa Trak VNI (Philips Respironics) including a harness for ventilation scintigraphy and to develop an automatic method for evaluating the quality of 81 mkr inhalation.
Materials and Methods We enrolled and randomised 48 patients to breathe through two types of masks: DAR (n = 25) or VNI (n = 23). After intravenous injection of 99mTc-labelled macroaggregated human albumin (LyoMAA, Covidien) and during continuous inhalation of 81mKr extracted from a 81Rb-81mKr generator (Kryptoscan, Covidien), eight incidences were acquired on a dual-head gamma camera. Three parameters were automatically computed by an automatic segmentation method: the mean ventilation counts (mcounts), an index of constancy of the inhalation rates (Cvent/perf) reflecting variations of the ventilation counts [(maximum-minimum)/median] between incidences compared to perfusion and an index of inhalation leak (mBN, the maximum background noise mean on the profiles incidences). Non-parametric tests of comparison of variance and proportion were used (Mood test and Fisher exact Test).
Results Variance of Cvent/perf and mBN were significantly higher (P = 0.03) in the DAR group. In this group 6/25 (24%) patients had parameters out of the distribution of the VNI group and 11/25 (44%) needed the help of a technician to hold their mask. No difference in the mcounts rate was observed.
Conclusions Index of variability of the ventilation rate as well as background noise were significantly higher in the DAR group and involved about 24% of the patients. Support with VNI masks improved the image quality, decreased exposure to radiation and guaranteed constancy in care compared to DAR. Nevertheless high costs restrict their use.
No conflict of interest.
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