A balloon catheter is provided with engagement elements disposed within the balloon so that, upon inflation of the balloon, the engagement elements move in the proximal to distal direction of the catheter so as to abut one another and form a substantially rigid column to maintain alignment of the distal end of the balloon with the proximal end of the balloon and with the catheter. The two dimensional spectra of two images are found using Fourier like transforms. The rear bushing includes a limiter portion and a receiver portion, the limiter portion being secured to the shaft and defining an increased diameter relative to the shaft to form a stop surface the receiver portion having a bore and being coaxially received over the shaft such that the receiver portion is abutted against the stop surface and rotatable about the shaft. If dissociation is indicated, a pulse generator stimulates at least one of the corresponding chambers to restore inter-chamber synchrony. Said closed chamber is set in communication with a source of vacuum so as to empty the bottle or container of the air contained therein before completion of application of the cap. The shoulder has a duct for dosage air, wherein the duct connects the upstream catching nozzle section to the downstream catching nozzle section.