Patent Application
20130018277
1. Field of the Invention
The invention relates to apparatuses of measuring intracranial pressure and more particularly to a piezoresistor based non-invasive intracranial pressure monitor.
2. Description of Related Art
Intracranial pressure (ICP) of an individual may increase suddenly due to brain swelling, obstruction of cerebral spinal fluid passageways, or brain bleeding because of traffic accident. The intracranial hypertension may painfully press blood vessels and nerves within the brain. This is a life threatening event. Doctors specializing in neurosurgery are aware of the danger and thus many drugs and surgery techniques have been proposed to effectively decrease ICP. The criticality of dispensing such drug to a patient and/or performing a surgery to the patient is that an accurate ICP must be known prior to any treatment.
Various apparatuses and methods for ICP measurement are known in the art. For example, one technique involves inserting a catheter through skull into a cerebral spinal fluid passageway for sucking fluid for analysis. Such implantation is invasive and has danger of infection, patient discomfort, and other adverse effects.
Taiwan Patent Number 1318,569 discloses a method of for measuring ICP by comparing agents by transmitting ultrasonic waves into brain. In detail, the method comprises transmitting an ultrasonic wave signal of band width toward a target in the brain, receiving a signal reflecting from micro bubbles filled with comparison agents in the target of the brain, analyzing spectrum of the reflecting signal to obtain a low frequency response having a band width substantially equal to that of the transmitting signal, calculating a resonance frequency of the micro bubbles based on band width and strength of the low frequency response, calculating sizes of the micro bubbles based on the resonance frequency and properties of the comparison agents, and obtaining an ICP of the target by performing a calculation.
U.S. Pat. No. 4,026,276 discloses a pressure monitoring apparatus implantable in the cranium to measure intracranial pressure. The apparatus comprises a passive resonant circuit having a natural frequency influenced by ambient pressure. The resonant circuit has inductance and capacitance capability for comparing the local environmental pressure to that of a volume of gas trapped inside the apparatus, the environmental pressure being measured by observation of the frequency at which energy is absorbed from an imposed magnetic field located externally of the cranium.
While above patents are directed to non-invasive apparatus and methods, they are disadvantageous due to complicated components, inconvenience in use, inaccurate positioning of the target in the brain, low utility in diagnosis, and high cost.
Notwithstanding the prior art, the invention is neither taught nor rendered obvious thereby.
It is therefore one object of the invention to provide a non-invasive apparatus for sensing intracranial pressure comprising an annular flexible headband member comprising a crossing arcuate rail member and a hook and loop fastener having a fastener portion at one end of the headband member and a cooperating fastener portion at the other end of the headband member; and a monitoring assembly comprising an inverted T-shaped, hollow seat slidably mounted on the rail member, a fastener driven through two ends of the seat for retaining the seat on the rail member, a receptacle extending downward from the seat opposing the fastener, a biasing member disposed in the receptacle, and a microsensor having one end secured to the biasing member and the other end moveably projecting out of the receptacle.
The above and other objects, features and advantages of the invention will become apparent from the following detailed description taken with the accompanying drawings.
Referring to
An annular headband member 10 is formed of flexible material (e.g., plastic or metal) and comprises a Velcro fastener 11 formed on both ends, and an arcuate rail member 12 crossing portions of the headband member 10 other than both ends. A monitoring assembly 20 comprises an inverted T-shaped, hollow seat 21 slidably mounted on the rail member 12, a fastener (e.g., screw) 22 driven through two ends of the seat 21 for retaining the seat 21 on the rail member 12, a short cylindrical receptacle 23 extending downward from the bottom of the seat 21, a torsion spring 24 disposed in the receptacle 23, and a microsensor 25 having one end secured to the torsion spring 24 and the other end projecting out of the receptacle 23 due to the expansion of the torsion spring 24. That is, the microsensor 25 is a spring depressible member.
The microsensor 25 is electrically connected to an external processor (not shown) and is a piezoresistive pressure sensor. The microsensor 25 comprises a membrane 251, a flexible substrate 252 formed of plastic, the substrate 252 being disposed on the top of the membrane 251, a cavity 253 in the substrate 252 communicating with the membrane 251, and a plurality of (e.g., two piezoresistors) 254 formed on the bottom of the membrane 251. Pressure can deflect the membrane 251 and the deflection is proportional to pressure. Further, resistance of the piezoresistor 254 may change in proportional to the deflection as detailed later. The provision of a plurality of piezoresistors 254 can increase accuracy of the pressure measured by the microsensor 25.
As shown in
As shown in
Operation of the microsensor 25 will be described in detail below. Pressure of the target (i.e., injured portion of the brain 31 or diseased portion thereof) may increase greatly. The pressure deflects the membrane 251 by applying through the hole 34 and the scalp 33 and the deflection is proportional to the pressure (see
Alternatively, the monitoring assembly 20 (i.e., the spring depressible microsensor 25) can be replaced with an ultrasonic based monitor in another embodiment. In detail, the ultrasonic based monitor comprises a transmission module for transmitting an ultrasonic wave signal of band width toward a target in the injured or diseased portion of the brain, the signal being a short pulse signal, a receiving module for receiving a signal reflecting from the target in the brain, the reflecting signal being very accurate due to minimum decay, and a sending module for sending the reflecting signal to an external processor. The processor can analyze spectrum of the reflecting signal to obtain a base frequency response, a first resonance response, a second resonance response, and a low frequency response. A resonance frequency can be obtained by analyzing and calculating the above responses. Finally, an accurate ICP of the target can be measured by performing a calculation with respect to the resonance frequency.
The invention has the following advantages: Non-invasive. No injury to the brain. No infection to the brain. Accurate ICP measurement due to precise positioning of the microsensor by both Velcro fastener and spring based adjustments.
While the invention has been described in terms of preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modifications within the spirit and scope of the appended claims.
