Inventive Problem Solving
Ideation Process
Project Initiation
1. Project objectives
The specific aims are:
· modification of existing infrared visualization system,
· optimization of design specifications for integration into a surgical setting,
· verification of designed system both in vitro and in vivo.
2. Importance of the Situation
This system would improve performance in preserving the parathyroid and thyroid
glands during endocrine surgery by mitigating the impact of surgeon enperience in a
low-cost, time-saving way.
Innovation Situation Questionnaire
1. Brief description of the situation
Complications from incomplete or accidental removal of the parathyroid glands are a
major concern associated with endocrine surgery. Current localization techniques are
primarily preoperative and only applicable in select surgeries. The proximity of the
various tissues encountered in the neck during surgery and the tendency of these tissues
to blend together serve as confounding factors for surgeons. There is a need for a
sensitive, real-time, intra-operative diagnostic tool to assist with anatomical guidance.
Previous studies have shown the ability of near-infrared (NIR) autofluorescence to
differentiate between the parathyroid and the surrounding tissue based on the intrinsic
optical properties. The parathyroid exhibits stronger fluorescence than all other tissues
in the neck. Near-infrared imaging would provide spatial context as a more intuitive
approach for the surgeon. Here we present the first application of an autofluorescencebased imaging system for real-time intra-operative use in endocrine surgery. A 785nm
diode laser is used to excite the tissue and a converter tube is employed to detect the
NIR fluorescence and render it in the visible wavelengths. The image is then captured
by CCD and processed to apply a false color gradient for distinction between tissue
types. We demonstrate the utility of the NIR fluorescence imaging system in vivo and
in vitro. Preliminary results indicate that imaging is able to capture the higher level of
autofluorescence exhibited by the parathyroid differentiating it from the surrounding
tissue.
2. Detailed description of the situation
2.1. Supersystem - System - Subsystems
2.1.1. System name
Parathyroid Intra-operative Visualization System
2.1.2. System structure
This system consists of a diode laser, expanding optical elements, an infrared viewer, CCD camera, and
Innovation WorkBench® software. Apr/09/2010, 11:31
1
Inventive Problem Solving
Labview interface. The optical elements include focussing, expanding lenses and a liquid-light guide. The
infrared viewer uses a telephoto c-mount camera lens and photomultiplier tube. The CCD camera
connects to the NI DAQ board via BNC cables. NI Labview program handles data
processing.
2.1.3. Supersystems and environment
The system will function within an endocrine surgery operating room; nearby systems
include surgical tools, patient monitoring equipment, and other devices used in surgery.
The system will be operated by the surgeron, handled a surgical aide, nurse, or
technician. Requires a computer interface and power supply. Must be located outside
of surgical halo. Dimensions must not interfere with surgical protocol or equipment.
2.1.4. Systems with similar problems
Other imaging devices used for intraoperative modeling have similar restrictions and
issues, necessitating use of collimated light to span the distance of the sterile field.
2.2. Input - Process - Output
2.2.1. Functioning of the system
The system emits near-infrared light onto the tissue and detects the light emitted from
the fluorescing parathyroid glands which it displays in visible wavelengths. The
purpose of this function is to increase surgeon's ability to discriminate between tissues
by using relative brightness as an indicator.
2.2.2. System inputs
Infrared autofluorescent light that has scattered from the parathyroid and thyroid tissues
is the system input.
2.2.3. System outputs
A real-time image of the surgical field is displayed through a labview controlled
computer interface.
2.3. Cause - Problem - Effect
2.3.1. Problem to be resolved
The problem that exists is the inability to establish absolute levels of fluorescence to
use as a threshold for parathyroid gland emission.
Innovation WorkBench® software. Apr/09/2010, 11:31
2
Inventive Problem Solving
2.3.2. Mechanism causing the problem
Cause: Each patient has different physiology and variations existed with emitted signal
intensity.
Effect: No absolute value can be arbitrarily assigned as a threshold that will always
work for all patients.
Cause: Location of parathyroid glands varies for all patients, sometimes not on thyroid
surface.
Effect: Resolution decreases and light is further attenuated by scattering-- decreased
light emission.
2.3.3. Undesirable consequences if the problem is not resolved
If not addressed, technology would give little help to surgeon. Also, if not addressed,
system must be calibrated for each patient before use.
2.3.4. Other problems to be solved
2.4. Past - Present - Future
2.4.1. History of the problem
This problem has existed since the inception of the system: fluorescence has strong
patient variability and must be accounted for.
2.4.2. Pre-process time
Pre-surgical levels of autofluorescence cannot be tested in a non-invasive method, thus
the variability must be accounted for on a patient to patient basis during each surgery.
2.4.3. Post-process time
This is not an option as the device is intended for use in the surgery and after the
process wiol have no effect.
3. Resources, constraints and limitations
3.1. Available resources
Substance resources: 785nm Diode laser, ex vivo thyroid, parathyroid tissue, filters,
lenses, IR Viewer, Computer, DAQ board
Field Resources: EM light filed from laser
Space Resources: Surgeon's field of view, imagng field
Time Resources: preliminary surgical planning, intra-operative time, post-surgical time
Informational Resources: fluorescence of tissue, measured and fed to computing
interface
Functional resources: Identification of fluoresceing cancer tissue in an unexpected area.
3.2. Allowable changes to the system
Small changes to the system are allowed: Imaging device and software can be altered if
improved technology is available. Excitation method, image processing also allowed to
be changed if the improvements can be attained.
3.3. Constraints and limitations
IR viewer and computer interface must remain constant, can be altered if better
technology is affordably attained. Cost must not significantly increase. Excitation
wavelength and power must remain constant for safety considerations.
3.4. Criteria for selecting solution concepts
Finished device should operate with >80% sensitivity and specificity.
Innovation WorkBench® software. Apr/09/2010, 11:31
3
Inventive Problem Solving
Problem Formulation and Brainstorming
IR V Diagram
4/9/2010 11:14:24 AM.
8. Find a way to eliminate, reduce, or prevent Interpatient fluorescence variation in
order to avoid Complications exist.
Enhance useful parameters
Universality
Use software interface to select region of thyroid tissue to use as a baseline. This will
account for inter-patient variability of fluorescence and remove need for absolute
fluorescence levels.
Develop Concepts
1. Categorize preliminary ideas
Use arbitrary threshold levels to quantify fluorescence.
Innovation WorkBench® software. Apr/09/2010, 11:31
4
Inventive Problem Solving
Determine method of relative evaluation using patient specific baseline normalization.
2. Combine ideas into concepts
Method for real-time visualization to detect differential fluorescence of tissues:
Idea: use head-mounted apparatus for surgeon- hands free, can focus on patient without
looking away from working field.
Short-coming: current technology is cost-prohibitive, difficult to apply processing
interface, must apply filtering optics, different excitation light source necessary
Idea: use mounted IR viewer outside surgical field that outputs to video screen in OR-Still hands free, allow image processing programs, simple mounted excitation source,
can apply necessary filters, cheap, zoom capabilities.
Short-comings: bulky, may require adjusting to focus on patient or region of interest.
Idea: Use program interface to select region of interest for patient baseline.
Short-comings: Fluorescence baseline will be dependent upon surgeon's discretion and
experience.
Evaluate Results
1. Meet criteria for evaluating Concepts
Improve sensitivity and specificity of process compared to current values.
Do not reduce surgical performance.
Reduce time required for endocrine surgery.
2. Reveal and prevent potential failures
System does not excite tissue beyond surface-- surgeon must decide where to begin
resecting based on experience.
3. Apply Patterns/Lines of Evolution
Increasing ideality
Ensure reduction of surgical time requirement while improving surgical results
Increasing controllability
Allow adaptable lenses for use with a hands free system that will auto-focus.
Element universalization
Allow for this system to be used in other surgeries if IR excitation is found useful for
tissue discrimination.
4. Plan the implementation
Create a software interface that will allow the user to select a region as a baseline,
based on suregeon experience and environmental factors,
Use external light source for co-registration purposes.
Innovation WorkBench® software. Apr/09/2010, 11:31
5