e-DIOLA Scan2009

Outline e-DIOLA Scan• Motivation:

– SON– Statistical Analysis

• A-Scan• Design Approach• Features • Block Diagram:

– Higher level Block Diagram– Lower level Block Diagram

• Algorithm & Simulation• Devices selection• Hybrid Design Model:

– Hardware– Firmware– Software– Interfacing

• System Validation– Simulation-based Testing– Audio Signal-based Testing

• Limitations• Demo• Future Work

• WHY• WHAT• HOW• System Validation• Limitations• Demo• Future Work

Statement of need• Recent Studies show a remarkable prevalence of ophthalmic

diseases.

• Cataracts leading cause of blindness in the world

• Cataract surgery involves substitution of natural lens by an artificial (IOL)

• Lens power is a function of eye dimensions and curvature values.

• Accuracy level is crucial

• In order to motivate the local market & adapt to changes in the global industry, we will follow a progressive approach to reach our prospective goal:

Enhance A-scan biometry systems

A-Scan Biometry Systems

Physicians Opinion

A-Scan Probe

1/10/2008 Graduation Project - Milestone I 4

Ophthalmic A-scan Uses US to measure the length (dimension) of the eye. Ophthalmologist uses these measurements to evaluate eyes prior to cataract surgery. provides a one-dimensional image of deflections of varying amplitude along a baseline

Height : intensity of the returning impulse Position: indicates time of receiving the echo

IOL : implanted lens – replaces existing crystalline lens since it is clouded over by a cataractDimensions:

Axial Length (AL)Anterior Chamber Depth (ACD)Length Thickness (LT)Vitreous Cavity Depth (VCD)

Techniques: Applanation/Contact ↔ Immersion

Design Approach

We propose an enhanced relatively-low-cost A-scan Biometry system which connects via USB cable to any Windows XP/Windows Vista laptop or desktop computer

Featuresadded

Automatic Diagnosis

best scan selection

optimization of A-Scan Gain & TGC

Adjustable Layer-specific velocity

misalignment & corneal compression check

Manual & automatic selection of IOL formula

Manual labeling

Adjustments for dense cataract & trauma

Manual TGC adjustment

Accurate measurements of AL, LT, VD,&VCD

IOL power calculation

Lens correction factorContinuous Display Freeze

Thresholding all IOL formulae

Automatic & Manual modes

Fixed and TGC

Ribbon Display

Compare IOL formula

3 modes

Avg. & Std

Accurate Peak detection

Block diagrams

• High level BD• Low level BDs

– Acquisition– Preprocessing– TGC

• How we calculated it (each interface & attenuation)• Function

Higher-Level Block Diagram

Lower-Level Block Diagram

Signal Acquisition Module:

Input: Signal from probeOutput: Digitized signal

Pre-processing Module:

• Input: Digitized Signal• Output: Amplified signal

Region Cornea Aqueous Lens Vitreous Retina-Sclera

Attenuation at 9MHz 0.234 0.091 1.82 0.091 0.364

Max Distance (mm) 0.8901098 4.6153846 5.9109893 22.12088 2.03077

Attenuation (dB) 0.208285 0.419999 10.75800 2.013000 0.739200

Classification Module

• Input: Amplified Signal

• Output: Thresholded spikesTime

Voltage

Threshold

Mode Selection

1. Auto-detection & Signal Validation • Input: Spikes from eye Interfaces• Output: identified peaks, while: • Valid Spikes are sent to Eye Measurement Module.• Abnormal Spikes are sent to Auto-diagnosis.• Invalid Spikes are sent to the Reset to rescan.

Mode Selection

B. Manual Mode & Gates:• Input: Spikes from eye Interfaces• Output: identified peaks

Eye Calculations Module

• Input: Time & Amplitude Arrays from Manual or Automatic modes

• Output: Eye Measurements (AL, VCD, LT, VCD)

IOL Measurement Module

• Input: IOL Formula from Manual or Automatic modes

• Output: Calculated IOL Power

Display Module

• Patient Name• Date of Test• Eye Mode (phakic, Aphakic, pseudophakic)• Axial Length• ACD• VCD• Identified Interface-Peaks

Auto-diagnosis Module

• Input: Abnormal Spikes from Automatic Mode• Output:

Non-Axial Scanning

• Input: Spikes from Manual Mode • Output: Tumor Location

θ = cos-1 And the radius at which the tumor is located by:

R = L sin (θ)

Algorithm and Simulation

Algorithm and Simulation0 0.5 1 1.5 2 2.5

x 10-5

-50

0

50

Am

plit

ude

Returning Echo

0 0.5 1 1.5 2 2.5

x 10-5

-500

0

500

Am

plit

ude

Echo after fixed gain

0 0.5 1 1.5 2 2.5

x 10-5

-50

0

50

Am

plit

ude

Echo after TGC

0 0.5 1 1.5 2 2.5

x 10-5

-500

0

500

Am

plit

ude

Echo after fixed gain & TGC

0 0.5 1 1.5 2 2.5

x 10-5

0

200

400

Am

plit

ude

Enveloping

0 0.5 1 1.5 2 2.5

x 10-5

0

2000

4000

Am

plit

ude

No. of Samples

Extracted Spikes

Device Selection• MCU

ASIC DBB µP and µC DSP chipChip count 1 >1 1 1Flexibility None limited programmable programmableDesign time long mdeium short shortPower consumption low Medium-high medium Medium-highProcessing speed High high Low-medium Mediu-highReliability high Low-medium high HighDevelopment cost high medium low LowProduction cost low high Low-medium Low-mdeium

Criteria Required ProvidedEfficient data flow Real time data transmission YESComputational power Medium HighResolution Medium (8bits) High (up to 12 bits)Processing speed High HighMemory size Medium MediumSignal type Mixed signal (Analog and digital) Mixed signalAvailability of a full set of development tools and supports

C compiler, linker, logic analyzer, development assistance, real time debugging tool

All available with the kit

Device Selection• Java

– Java is simple– Java is object-oriented– Java is platform-independent– Java is distributed– Java is interpreted– Java is secure– Java is robust– Java is multithreaded

Devices Selection

• Supporting Tools– Keil + SiliconLabs– MatLaB– NetBeans– Orcad– Proteus– Edge

Data Collection

Device SelectionHybrid comparison table

Standalone system Microcontroller - PC based Software

Advantages1-No compatibility issue 1-Friendly UI 1- Friendly UI2-Independent on electrical problems 2-Independent processing 2-Faster processing3- No interfacing problems 3-Extended data storage 3-Extended data storage

4-More acquired knowledge(e.g.: power supply)

4-More compact 4-More features

5-More acceptable 5-More Features by software 5-More compact (probe + CD)

6-Needs little training 6-Portable(battery) 6-Inexpensive7-Inexpensive

Disadvantages

1-Difficult to implement 1-Dependent on PC or laptop 1-Specific requirements of processor

2-Limited data storage 2-Restricted by complex multitasking

2-Higher risk of computer freezing or limitation

3-Not friendly software 3-Compatibility issues 3-Compatibility issues4-Limited processing 4-Dependent on laptop power

supply4-Upgrading

5-Integrated printer (so more complex) 5-Specific requirements of laptop or PC

5-Dependent on laptop power supply

6-Viruses’ problem(no windows network )

Votes 28.3% 51.7% 20%

Hybrid model diagram

Hardware

Probe

Digital Oscilloscope

Pulser

T/R SwitchVcn Vcp Pulser BPF Probe Simulation

Case 1 high low operating 0 Vpulse from the Pulser circuit

Case 2 low highZero input

signal

signal from the

probe

receives signal from tissue

Enveloping

Returning Echo

Time Envelope-Detector Response to a realistic A-Scan Pulse

Time

Voltage

Bandpass Filter (anti-aliasing)

• Band-lited signal undersampling• Bessel Filter:

– Sharper cutoff frequencies.– Removing ripples in the pass band.– Eliminating overshooting and ringing problems

Badpass Filter

Frequency (MHz)

OutputOutput Amplitude

(V)

25 2 V

4.38 MHz 0.5V

Power Supply

Required Obtained Required Obtained Required Obtained

25 V 15 V

3.3 V

- 15 V 5 V

Overall schematic from ORCAD

• Hyperlinks to each part’s proteus simulation• Bandpass:

– Bandlimited signal not nyquist– Why Bessel– Illustration image – Simulation only 2 pic (4. MHz and 25 MHz)

• Power Supply output voltage– 25,15,-15,5,3.2 V

Firmware Flowchart

Firmware performance analysis

• Blue bars picture• Last 2 rows of performance analysis table• Memory distribution part

Firmware performance analysis

Firmware performance analysisCode Segment Total # of

Instructions# of Calls msec Percentage per Scan

Time

Initializations 64 1 0.087 0.2%

Trigger 8 1 -- ~0%

ADC Interrupt Service Routine 51 260 0.916 4.0%

UART Interrupt Service Routine 128 -- -- --

UART Transmission 755 1 0.416 1.8%

Amplification (FIXED) 78 1 2.311 10.1%

Amplification (TGC) 385 1 12.570 54.7%

Peak Detection 1037 1 3.784 16.4%

Thresholding 369 1 0. 267 1.2%

Check for normality 2602 1 0. 129 1.2%

Main 591 1 0. 170 1.5%

Mathematical Calculations 307 -- -- --

Dynamic Allocation 320 70 1.451 6.7%

Total Time/ scan 6694 -- 26.70 100%

Total Time/ 10 scans -- -- 251.76 --

Firmware performance analysis

Memory Distribution

• • Code Space: 14138 Bytes• RAM space• Internal: 65 Bytes• External: 3509 Bytes

Java Flow chart

Interfacing High level protocol• Java-to-MCU packet image

0xAA

0x00

Ltype DC M/A Type

0xAA

0x01

a

b

c

d

0xAA

0x02

RST STP F/C

Initial Data TGC Control Word

Interfacing High level protocol• MCU-to-Java packet images not kalam

HEADER

# of SPIKES

STATUS

DATA

…

…

…

0xCC

STATUS

Data packet Status Packet

Validation

Acquisition ADC MCU Laptop

Simulation-basedSample-based

Overall Testing

Sample of initial testing of FIrmware

Normal

Sample of initial testing of FIrmware

Aphakic no lens

Sample of initial testing of FIrmware

Mild Asteroid

Sample of initial testing of software by simultion

Sample of initial testing of software by simultion

Coat’s disease

Sample of initial testing of software by simultion

Testing by audio signal

0 50 100 150 200 2500

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Am

plitu

de

No. of Samples

Analog Audio Signal - Normal Scan

Demo goes here =)

LimitationsLimitation Reason

unable to acquire a real ultrasound echo signal

to hardware deficiencies

unable to detect overlapping envelopes that are not separated by at least 1 sample (0.29usec)

limited resolution

perform the designed corneal compression test

limited resolution

the angle algorithm was not implemented as Java code and stayed as pseudo code due to.

time restriction

automatic labeling: the system is unable to transfer to the manual labeling mode in case of more spikes in the retina region.

for phantom materials shortage of materials

Wireless probe design and difficulty to purchase high level electronic components small enough to be on a probe PCB

Future work -Wireless

Future work -Phantom

• Interpretation Eye Interface Velocity (m/s) Density (kg/m3) Acoustic impedance

(MRayl)Attenuation Coefficient

at 9 MHZ (dB/mm)Equivalent Material

Cornea 1620 1062+5 34 0.234 Donated human cornea

Aqueous 1500 1040 1.56 0.091 Saltwater

Lens 1620 or 1641 1000-1050 1.67125 1.82 Lucite

Cow’s eye: 1140+33

Vitreous 1520 or 1532 1005.3 1.534 0.091 Water

Retina 1540 0.364 biopolymer

hydrogels

Sclera 1613 -1622 1000 1.6175 0.7826 ---

Future work -Phantom

• Problem Definition• System Background• Function of Parameters• Model

Project CostItem Cost (L.E)

A-Scan Probe 10,000

Microcontroller Kit 233

PCB 660

USB Cable 12

Notebook 1,500

FTDI chip (USB-Serial IC) 30

Components 70

Total 12,505

Timeplan – Gantt Chart

Thank you