Single Photon Emission Computed Tomography –SPECT

What is SPECT?

        SPECT is short for single photon emission computed tomography. As its name suggests (single photon emission) gamma rays are the sources of the information rather than X-ray emission in the conventional CT scan.

Introduction

        Emission Computed Tomography is a technique where by multi cross sectional images of tissue function can be produced , thus removing the effect of overlying and underlying activity. The technique of ECT is generally considered as two separate modalities. SINGLE PHOTON Emission Computed Tomography involves the use single gamma ray emitted per nuclear disintegration. Positron Emission Tomography makes use of radio isotopes such as gallium-68, when two gamma rays each of 511KeV, are emitted simultaneously where a positron from a nuclear disintegration annihilates in tissue.

 Brain Imaging 

        This figure is a transverse SPECT image of the brain. The hot spots present in the right posterior region are seen clearly using SPECT. SPECT examines cerebral function by documenting regional blood flow and metabolism.

Positron Emission Tomography (PET)

        The distribution of activity in slices of organs can be obtained in a more accurate way using PET. In the simplest PET camera two modified sophisticated cameras called Anger cameras are placed on opposite sides of the patient. This increases the collection angle and reduces the collection times which are the limitations of SPECT .In PET, radiopharmaceuticals are labeled with positron emitting isotopes. A positron combines rather quickly with an electron. As a result the two gamma quanta are emitted almost in opposite directions .In PET scanners, rings of gamma ray of gamma ray detectors surrounding the patient are used. Each detector interacts electronically with the other detectors in the field of view. When a photon arrives within a short time frame, it is clear that a pair of quanta was generated and that these were created somewhere along the path between the detectors. Conventional PET tomography makes use of standard filtered back projection techniques used in computed tomography and SPECT.

Back Projection 

                The main reconstruction step involves a process known as ‘Back Projection’. As the original data was collected by only allowing photons emitted perpendicular to the camera face to enter the camera, back projection smears the camera bin data from the filtered sonogram back along the same lines from where the photon was emitted from. 

Conclusion

        It is reasonable to speculate about a constant by perhaps a slower rate of increase of clinical applications of SPECT. It is safe to conclude that SPECT has reached the stage where it will be a valuable and also an unavoidable asset to the medical world.

Read More

Redundant Array of Independent Disks - RAID

What is RAID?

A technique was developed to provide speed, reliability, and increased storage capacity using multiple disks, rather than single disk solutions. RAID takes multiple hard drives and allows them to be used as one large hard drive with benefits depending on the scheme or level of RAID being used. The better the RAID implementation, the more expensive it is. There is no one best RAID implementation. Some implementations are better than others depending upon the actual application. It used to be that RAID was only available in expensive server systems. 

About

Information has become a commodity in today's world, and protecting that information has become mission critical. The Internet has helped push this information age forward. Popular websites process so much information, that any type of slowdown or downtime can mean the loss of millions of dollars. 

RAID 3 

This level uses byte level striping with dedicated parity. In other words, data is striped across the array at byte level with one dedicated parity drive holding the redundancy information. The idea behind this level is that striping the data increases performance and using dedicated parity takes care of redundancy. Three hard drives are required, two for striping and one as dedicated parity drive. Although the performance is good, the added parity does slow down writes. The parity information has to be written to the parity drive whenever a write occurs.

Raid 5 

RAID 5 uses block level striping and distributed parity. This level tries to remove the bottleneck of the dedicated parity drive. With the use of a distributed parity algorithm, this level writes the data and parity data across all the drives. Basically, the blocks of data are used to create the parity blocks, which are then stored across the array. This removes the bottleneck of writing to just one parity drive. However, the parity information still has to be calculated and written whenever a write occurs, so the slowdown involved with that still applies. The fault tolerance is maintained by separating the parity information for a block from the actual data block. 

Parity

This is the method by which a check bit is added to data so that errors can be detected. In a computer, data is organized into bytes, which consist of a series of eight bits. These bits are transmitted as a series of on or off signals that represent the binary values of 1 or 0. A series of O's or 1's can represent an alphanumeric character or some other type of data. When the simplest form of parity is used it is usually referred to as Even Parity or Odd Parity. These two methods add an additional bit to each byte that indicates whether the number of 1 's in the byte is even or odd.

Conclusion 

RAID is a good solution for companies or individuals craving more transfer performance, redundancy, and storage capacity in their data storage systems.

Read More

Smart Quill

Working Of Smartquill

                             SmartQuill is slightly larger than an ordinary fountain pen. Users can enter information into these applications by pushing a button on  the pen and writing down what they would like to enter .The SmartQuill does not need a screen to work. The really clever bit of the technology is its ability to read handwriting not only on paper but on any flat surface – horizontal or vertical. There is also a small three-line screen to read the information stored in the pen; users can scroll down the screen by tilting the pen slightly. 

Abstract

The introduction of SmartQuill has solved some of these problems. Lyndsay Williams of Microsoft, UK is the inventor of SmartQuill,a pen that can remember the words that is used to write, and then transform them into computer text. The pen is slightly larger than ordinary fountain pen, with a screen on the barrel. User can enter information into these applications by pushing a button .Information can be entered using his/her own handwriting. User can use any platform for writing like paper, screen, tablet or even air. There is also a small three-line screen to read the information stored in the pen. Users can scroll down the screen by tilting the pen. 

About

  

         Lyndsay Williams of Microsoft Research's Cambridge UK lab is the inventor of the Smartquill,a pen that can remember the words that it is used to write, and then transform them into computer text . The idea that "it would be neat to put all of a handheld-PDA type computer in a pen," came to the inventor in her sleep. “It’s the pen for the new millennium,” she says. Encouraged by Nigel Ballard, a leading consultant to the mobile computer industry, Williams took her prototype to the British Telecommunications Research Lab, where she was promptly hired and given money and institutional support for her project. 

Accelerometer Technology

        This technology uses a device called Accelerometer which is used  for measuring motion. A tiny accelerometer in a pen could be used to  detect the stops and starts, arcs and loops of handwriting, and transmit this  information to a small microprocessor that would make sense of it as text.  There's also the possibility of viewing a full page of text through a special monocular magnified "virtual" screen that could be built into the end of the pen.

Communication With Other Devices

        Earlier SmartQuill models  developed by BT laboratories communicated with the PC via a radio transmitter, but the current prototype hooks up to a PC via a cable and electronic docking station called an "inkwell." .The data stored in the memory is uploaded to the personal computer when it is placed in to a docking station. An electronic docking station is a small cabinet to which a laptop or notebook computer can be attached for use as a desktop computer ,usually have a connector for externally connected devices, such as hard drives or scanners and ports that can be linked to components such as keyboard, monitor and printer. 

Conclusion

               The estimated cost of this futuristic pen is around $200.SmartQuill supports two factors: small size and convenient use. The future of SmartQuill ensures all computation power the user needs right inside the pen.  Reducing the size of handheld computers can only be taken so far before they become unusable.

Read More

VoCable

About

                Voice (and fax) service over cable networks is known as cable-based Internet Protocol (IP) telephony. Cable based IP telephony holds the promise of simplified and consolidated communication services provided by a single carrier at a lower cost than consumers currently to pay to separate Internet, television and telephony service providers. Cable operators have already worked through the technical challenges of providing Internet service and optimizing the existing bandwidth in their cable plants to deliver high speed Internet access. 

Voice Activation Detector

        This monitors the received signal for voice activity. When no activity is detected for a specific period of time, the software informs the IP. This prevents the encoder output from being transported across the network when there is silence so as to save the bandwidth. This software also measures the idle noise characteristics of the telephony interface. 

PCM Interface (Pulse Code Modulation Interface)

        This interface receives pulse code modulation (PCM) samples from the digital interface and forwards them to the appropriate DSP software modules for processing. 

Embedded Software Architecture

        Texas Instruments and its subsidiary, Telogy Networks, have developed one implementation of embedded VoIP software for cable-based IP telephony. The software supports cable modems and BTIs (up to four ports), as well as the telephony gateway (up to several thousand ports), at the cable head end. The software supports MGCP (Media Gateway Control Protocol) as well as the session protocol (SIP). The basic purpose of the two protocols, which is to process packetized voice traffic, is the same. However, the software supports both because standard bodies are divided as to the relative merits of each. 

Conclusion

        With the merging of telecom carriers, cable operators, and Internet service providers (ISPs), most experts agree that convergence is not merely a trend but an inevitability. The potential cost savings, consolidated billing, streamlined network management, and overall convenience are too compelling for service providers and customers to ignore.

Read More

Wireless Fidelity

Abstract

        Wi-Fi, which stands for “Wireless Fidelity”, is a radio technology that networks computers so they connect to each other and to the Internet without wires. It refers to wireless LAN products based on the IEEE 802.11b specification. Users can share documents and projects, as well as an Internet connection among various computer stations. A Wi-Fi network operates just like a wired network, without restrictions imposed by wires .Not only does it enable users to move around and be mobile at home and at work, it also provides easy connections to the internet and business networks while travelling.

Virtual Private Networks (VPNs) 

        It provide the most robust security solutions for corporate LANs and are already widely used for intranets and remote access. A VPN typically utilizes a dedicated server that provides both authentication and confidentiality. Wireless Access Points are also beginning to include VPN technologies within their devices, allowing simplified VPN deployment.A VPN works through the VPN server at the company head quarters, creating an encryption scheme for data transferred to computers outside the corporate offices.

Technology

        Wi-Fi uses radio technology called IEEE 802.11b to provide secure ,reliable,fast wireless connectivity. A Wi-Fi network can be used to connect computers to each other, to the internet and to the wired networks. Though WLANs are easy to deploy, the network administrator or IT professional will benefit from some basic knowledge about radio wave propagation.

Introduction

Wi-Fi, or Wireless Fidelity is freedom: it allows you to connect to the internet from your couch at home, in  a  hotel room or a conferance room at work without wires . Wi-Fi is a  wireless technology like a cell phone. Wi-Fi enabled computers send and  receive data indoors and out; anywhere within the range of a base station. And the best thing of all, it is fast. However  you only have true freedom  to be connected any where if your computer is configured with a Wi-Fi CERTIFIED radio (a PC card or similar device). Wi-Fi certification  means that you will be able able to  connect anywhere there  are other Wi-Fi  CERTIFIED products – whether you are at home ,office , airports, coffee shops and other public areas equipped  with a Wi-Fi access availability.Wi-Fi will be a major face behind hotspots , to a much greater extent.More than 400 airports and hotels in the US are targeted as Wi-Fi  hotspots.

Conclusion

        Wi-Fi  provides freedom: freedom to physically move around your home or business and still stay connected to the internet or local network; freedom to grow and move an office or business without having to install new cables and wires, freedom to be connected while travelling and on the road .Wireless ‘hotspots’(airports, hotels, coffee shops, convention centers and any  other place where someone can connect to a wireless network ) are being installed world while .

Read More