Spurious Pattern Research Articles

Complications resulting from spurious fields produced by a microwave applicator used for hyperthermia

Microwave hyperthermia applicators are generally characterized at two or three frequencies. These frequencies usually are at the extremes of the applicator's operating range. However, such applicators are often used at arbitrary frequencies within their range. The most common reason for choice of frequency is to achieve acceptable coupling in the clinical configuration with a given patient. Occasionally a spurious transmission pattern will result from the frequency chosen that can lead to undetected high power densities well away from the target volume. In the present report, such a situation is discussed. The transmission pattern resembled “horns” reported at the field edge of certain accelerators. This pattern resulted in the inability to heat the target volume and the production of thermal blisters outside that volume. Such an occurrence underscores the need to characterize the transmission characteristics of a microwave hyperthermia applicator at all the frequencies used.

False Electrocardiographic Diagnosis of Atrial Flutter

To the Editor.— The simulation of atrial by electrocardiographic artefacts may be of varied origin, including a broken wire in an extremity electrode, 1 myoclonic contractions of the pectoralis major muscle secondary to cold, 2 and the muscle tremor of Parkinson disease. 3-5 While the electrical artefact produced by the tremor of Parkinson disease is usually easily recognized, a well-defined flutter may occasionally be produced. This simulated may appear only in the standard leads with bilateral tremor, or may be confined to certain of the standard leads when unilateral. 3 However, the spurious pattern may also be seen in the chest leads in some cases, increasing the difficulty of diagnosis. 4 Various methods have been proposed to eliminate these false patterns such as warming the patient in the case of cold-induced tremor, 2 and holding the affected extremity in parkinsonism. 3 Saint-Pierre 5 has suggested placing

Speckle free redundant holography

A new technique with experimental results for producing speckle free redundant holograms without a spurious back ground pattern is reported.

New design for laser image—speckle interferometer

A new laser image—speckle interferometer, a device used for looking at vibrational modes on defusely reflecting surfaces, has been designed. The design makes it possible to provide a reference field in the instrument that is substantially free from spurious pattern. This field interferes with a speckled image so giving a more intense image field. As larger surfaces may be viewed with lower power lasers, the method offers an attractive alternative to strictly holographic methods.

A Vertical Aperture Equalizer for Television

A vertical aperture equalizer employing delays of one scanning line has been built and has been used on commercial broadcasts to increase the subjective sharpness of television pictures. By using both vertical and horizontal aperture equalization, optical aperture defects can be corrected. By the use of vertical aperture equalization and scanning apertures with suitable responses, television in the future may be practically free of line structure and spurious pattern effects due to the scanning-line structure.