Highly directional pressure sensing using the phase gradient.

Many methods of two-microphone directional sensing have limited bandwidth. For active intensity, finite-difference error can be removed by using the phase and amplitude gradient estimator method. Using similar principles, a directional pressure sensor based on the phase gradient is developed that is accurate up to the spatial Nyquist frequency, and beyond if phase unwrapping is applied. A highly directional frequency-independent array response of arbitrary order can be achieved with two microphones. The method is compared against beamforming and traditional gradient sensing for single and multiple sources and is found to have improved localization capabilities and increased bandwidth.

Three-microphone probe bias errors for acoustic intensity and specific acoustic impedance.

In acoustic intensity estimation, adding a microphone at the probe center removes errors associated with pressure averaging. Analytical bias errors are presented for a one-dimensional, three-microphone probe for active intensity, reactive intensity, and specific acoustic impedance in a monopole field. Traditional estimation is compared with the Phase and Amplitude Gradient Estimator (PAGE) method; the PAGE method shows an increased bandwidth for all three quantities. The two- and three-microphone methods are compared experimentally, showing reduced bias errors with three-microphone PAGE for active and reactive intensity, whereas using two microphones is preferred for specific acoustic impedance.

Bias error analysis for phase and amplitude gradient estimation of acoustic intensity and specific acoustic impedance.

Sound intensity measurements using two microphones have traditionally been processed using a cross-spectral method with inherent error in the finite-sum and finite-difference formulas. The phase and amplitude gradient estimator method (PAGE) has been seen experimentally to extend the bandwidth of broadband active intensity estimates by an order of magnitude. To provide an analytical foundation for the method, bias errors in active intensity and specific acoustic impedance are presented and compared to those of the traditional method. Bias errors are reported for a plane-wave field and sound radiated from a monopole and a dipole. Additionally, bias errors are reported for reactive intensity, the estimation of which is unchanged by the PAGE method for the two-microphone case.

An orbital metastasis of prostate adenocarcinoma: A rare case report

A patient with known prostatic cancer presented with left supraorbital swelling with proptosis and restricted eye movements on left eye. Contrast enhanced computed tomography scan revealed dural and bone metastases with soft tissue component extending to the left orbit. Serum prostate specific antigen was markedly elevated at >100 ng/ml. Incision biopsy of the orbital tumor revealed only lymphocytic inflammatory cells within the fibrous stroma attributed mainly to the deeper location of the tumor or shallow locus of the biopsy. Incisional biopsy of the frontal bone revealed atypical looking cells in sheet cluster with nuclear enlargement, hyperchromatic in irregularity confirming the diagnosis of orbital metastasis of prostate carcinoma.Metastasis of prostate cancer to the orbit is rare. One should have a high index of suspicion of orbital metastasis when presented with an elderly patient with ocular symptoms and a history of prostate adenocarcinoma. A thorough clinical, radiological and histological evaluation is necessary to establish the diagnosis.