3D printing in medicine: design and manufacture of hearing aids
Today we will talk about the use of 3D printing and related software in such a branch of medicine as the production of hearing aids.
In the sign language, putting your hand to your ear has long meant: “I can't hear you!”
This gesture appeared not only because we hear through the ears (i.e., with a gesture we point to the organ of hearing), but also because putting the palm to the ear we use it as the simplest resonator that amplifies the sound, as a result we hear better .
')
It was on this mechanical principle that the first hearing aids were based. They were too bulky for use in everyday life and gave only a slight increase in volume:
The military, whom we don’t get tired of thanking for the massive Internet, personal computers and civilian air transport, it turns out, have left their mark in this area. The fact is that the predecessors of radars that use radio waves to register air, sea and ground objects were the so-called acoustic locators and sound mirrors :
American dvuhrozhkovy system, army college Fort McNair (Fort McNair), 1921
Acoustic locators actively developed and were used during the First World War. In the late 30s, it was in military technology that the principle of mechanical amplification of sound reached its peak:
Japanese Emperor Khorokhito inspects the combat hearing tube unit
Meanwhile, in the 1920s, the first electrical (carbon) hearing aids appeared. The action of these devices was based on the principle of the phone. Why this principle was not used in military technology - for the author remains a mystery, the resolution of which is beyond the scope of this short review.
Hearing aids are being improved both in the quality of sound transmission and amplification, and in compactness and portability.
The invention of transistors led to one of the most significant steps in the development of the industry.
In the early 50s, transistor hearing aids, more compact and high-quality, supplanted tube lamps (by the way, radars, i.e. radars, had already driven out acoustic locators during World War II).
Early models of these hearing aids were designed to fit in the eyeglass frame. Later, the ear models, which are familiar to us today, appeared.
Pocket transient hearing aid company OTICON, Denmark - T3, 1953
In the second half of the 20th century, the compactness of hearing aids increased significantly.
The first BTE was released in 1954. In the early 1980s, the in-ear devices familiar to us became popular - they completely fit in the outer ear and are almost invisible from the outside. In 1993, a new, intra-channel apparatus was developed, which was entirely located in the auditory canal. Today all three models are relevant; we will look at them below.
It also becomes possible to make individual, i.e., more ergonomic, ear and ear aids, the shape of which is based on the patient's ear cast.
In the 1990s, digital sound processing was used in medicine - the first digital hearing aids from companies such as Phonak, Siemens, Bernafon, and others appeared. These devices exceeded analog models by an order of magnitude in quality of transmission and sound amplification.
The latest generation of hearing aids can continuously analyze the sound environment and also continuously adapt to it to improve sound quality and reduce background noise.
Today, digital devices are almost completely ousted from the market analog.
The following table shows the most popular varieties of hearing aids today.
In all of the above types of hearing aids, except for intracanal, there is an intra-ear liner - a part of the apparatus that is placed directly in the auricle.
The liner can be universal or individual:
Universal inserts are made by conveyor and cost only $ 1-2.
Individual inserts are made using the impression of the patient's ear canal; therefore, they do not press, do not whistle, do not fall out of the ear canal, and practically do not distort the sound of the hearing aid, which the client's hearing aid specialist has configured to the client. They cost about $ 10 and are subject to restoration.
Inserts can be made of various materials: hard, soft, combined, made of silicone or biopore. Materials differ in their technical characteristics, anti-allergenicity, durability, price, etc.
In this section, directly related to my daily work, I will move from impersonal presentation to a first-person narrative.
Hello :)
As you have guessed, of course, 3D printing is used for the individual manufacture of the in-ear insert of the hearing aid.
Our company, Materialize , was one of the pioneers of this industry and remains at the forefront today. We are developing RSM (Rapid Shell Modeling) - full-featured software for prototyping a hearing aid and the subsequent printing of individual in-ear inserts for ear, intra-ear and Open Ear devices.
Even 15 years ago, the manufacture of individual dental prostheses, dental tabs for reliable surgical operations on the jaw (by the way, our patent), individual inserts for hearing aids - all this was jewelry work and required several hours of work by a high-class specialist, and the slightest mistake could make the patient an invalid (in particular, when introducing a denture, there is a danger of hitting the nerve that passes at the base of the lower jaw, as a result of which a person can no longer manage it).
Our specialized software allows you to minimize the time to manufacture the prosthesis / device, the requirements for personal professionalism / experience of the doctor, and the risk to the patient's health.
My colleague will tell you about dental prosthetics in a separate article, and now we will return to hearing aids.
Consider the earpiece near:
It consists of a plastic case with electronics, a silicone in-ear liner and a connecting tube.
Automated liner manufacturing begins with a patient ear scan.
Heated wax is placed in the ear of the client, which almost instantly takes the form of the auricle and hardens. The resulting impression is digitized using a 3D scanner, resulting in a "cloud" of points - a set of points that accurately describe the inner surface of the auricle.
It is this point cloud (more precisely, two clouds - one for each ear) from the scanner to the RSM operator input (we support all modern types of 3D scanners), and the specialist performs all subsequent transformations of the impression already virtually.
The point cloud is automatically triangulated and smoothed, after which the operator semi-automatically grinds the model and gives it the desired shape using an extensive set of convenient 3D tools.
Here you see the original triangulated model (left) and the same model after giving the shape required for the liner (right). The original shape of the ear model is shown as translucent.
For the convenience of the operator, the liner on the screen is usually located as follows:
To increase the stability of the liner, an additional fixing form is generated, which will pass along the contour of the inner surface of the outer ear:
The form is generated on the basis of automatically constructed guides, which the operator can correct to obtain a more accurate result.
Model with a fixing shape (and a translucent source model)
The ventilation channel serves both for the free circulation of air, which is necessary for the healthy state of the inner ear, and for the prevention of various acoustic defects in hearing aids.
In the case of an intra-ear apparatus, the ventilation duct is automatically placed so as to occupy as little space as possible in the model (leaving space for electronics), after which the operator has enough freedom in choosing his form (tube, cone, letter D, etc.) and changing the location .
In the case of the BTE, optimization of the space occupied by the ventilation duct is not necessary, since the electronics (see the next section) are outside.
In the earpiece and in the “Open ear” apparatus, the electronics (microphone, amplifier, transmitter) are located in an external plastic case.
In the case of an intra-ear apparatus, the electronics are placed in the insert, and therefore when designing the apparatus, the shape of the electronics must be taken into account.
We work with a constantly replenished base containing forms corresponding to the existing types of electronics for hearing aids of all global manufacturers.
The operator specifies the brand of electronics selected for the client, and the RSM automatically places the transmitter with an amplifier in the model optimally and completes the necessary connecting walls around the receiver, again, leaving enough freedom for the operator to manipulate.
The fixing form in intra ear hearing aids is not needed.
1 - microphone
2 - digital processor
3 - transmitter
4 - center line (used to automatically locate components)
An automatic quality check is performed at all stages.
The device is checked for potential cracks due to the thinness of the walls, as well as for the presence of cavities in the material.
The presence of even a small cavity in the model is unacceptable, since with 3D printing on some types of printers, liquid will remain there, which can then get into the patient’s ear through a crack in the wall, which is extremely dangerous.
A check is also performed on the correctness of the relative position of the elements (collision detection).
In this example, the color gamut marks the discrepancies between the original and the processed models.
After the above steps, the model is exported to one of the standard formats (supported by all of today's 3D printers) and sent to print.
In the printed insert, the operator is left to insert the electronics and add a little glue.
All projects are saved, and in case of loss or breakage of the insert, you can print it again on the previously saved layout.
Due to the maximum automation of the process, an experienced operator takes just minutes to complete the design cycle of a single machine! In one working day, the operator sends hundreds of inserts to print, whereas 15 years ago such figures seemed absolutely fantastic, since they exceeded the possibilities of the most experienced craftsmen by two orders of magnitude.
The project is almost ten years old.
Over the years, the range of possibilities at each of the above stages of model processing is rapidly growing, and the processing time decreases (both due to better algorithms and convenient tools, and through annual trainings conducted for new operators in the USA, France and other countries).
Speaking of automation - I probably managed to bother you with the word “automatically” in this post?
The fact is that for me, as a developer of algorithms, it is of most interest in this product, and as a developer of algorithms, that is, as a person who is used every day to deal primarily with abstract entities, I find deep satisfaction in the work, which gives me the opportunity to apply my experience and knowledge for the benefit of living people.
On this major note, thank you for your attention and waiting for questions on the topic.
An article about dentures - soon.
The following resources were used in the preparation of the article:
http://www.otoskop.ru/rus/muzej-sluxovyx-apparatov/
http://www.vabos.com.ua/bernafon_ha_history.html
http://www.siemens-hearing.ru/client/page.asp?id=104
http://www.hearingaids.ru/istoriya-sluxovogo-apparata
http://nnm.ru/blogs/mrecka_/akusticheskie_lokatory/
http://en.wikipedia.org/wiki/Japanese_war_tuba
http://m.habrahabr.ru/post/78486/
http://www.akystik-sluh.ru/
http://en.wikipedia.org/wiki/Hearing_aid
http://www.phonak.com
A bit of history
In the sign language, putting your hand to your ear has long meant: “I can't hear you!”
This gesture appeared not only because we hear through the ears (i.e., with a gesture we point to the organ of hearing), but also because putting the palm to the ear we use it as the simplest resonator that amplifies the sound, as a result we hear better .
')
Mechanical sound amplification
It was on this mechanical principle that the first hearing aids were based. They were too bulky for use in everyday life and gave only a slight increase in volume:
American dvuhrozhkovy system, army college Fort McNair (Fort McNair), 1921
Acoustic locators actively developed and were used during the First World War. In the late 30s, it was in military technology that the principle of mechanical amplification of sound reached its peak:
Japanese Emperor Khorokhito inspects the combat hearing tube unit
First electrical apparatuses
Meanwhile, in the 1920s, the first electrical (carbon) hearing aids appeared. The action of these devices was based on the principle of the phone. Why this principle was not used in military technology - for the author remains a mystery, the resolution of which is beyond the scope of this short review.
Hearing aids are being improved both in the quality of sound transmission and amplification, and in compactness and portability.
Implementation of transistors
The invention of transistors led to one of the most significant steps in the development of the industry.
In the early 50s, transistor hearing aids, more compact and high-quality, supplanted tube lamps (by the way, radars, i.e. radars, had already driven out acoustic locators during World War II).
Early models of these hearing aids were designed to fit in the eyeglass frame. Later, the ear models, which are familiar to us today, appeared.
Achievements of the last decades
Compactness, aesthetics, ergonomics
In the second half of the 20th century, the compactness of hearing aids increased significantly.
The first BTE was released in 1954. In the early 1980s, the in-ear devices familiar to us became popular - they completely fit in the outer ear and are almost invisible from the outside. In 1993, a new, intra-channel apparatus was developed, which was entirely located in the auditory canal. Today all three models are relevant; we will look at them below.
It also becomes possible to make individual, i.e., more ergonomic, ear and ear aids, the shape of which is based on the patient's ear cast.
Sound quality
In the 1990s, digital sound processing was used in medicine - the first digital hearing aids from companies such as Phonak, Siemens, Bernafon, and others appeared. These devices exceeded analog models by an order of magnitude in quality of transmission and sound amplification.
The latest generation of hearing aids can continuously analyze the sound environment and also continuously adapt to it to improve sound quality and reduce background noise.
Today, digital devices are almost completely ousted from the market analog.
Hearing aids today
The following table shows the most popular varieties of hearing aids today.
Inner ear liners
In all of the above types of hearing aids, except for intracanal, there is an intra-ear liner - a part of the apparatus that is placed directly in the auricle.
The liner can be universal or individual:
Universal inserts are made by conveyor and cost only $ 1-2.
Individual inserts are made using the impression of the patient's ear canal; therefore, they do not press, do not whistle, do not fall out of the ear canal, and practically do not distort the sound of the hearing aid, which the client's hearing aid specialist has configured to the client. They cost about $ 10 and are subject to restoration.
Inserts can be made of various materials: hard, soft, combined, made of silicone or biopore. Materials differ in their technical characteristics, anti-allergenicity, durability, price, etc.
And where is the 3D printing?
In this section, directly related to my daily work, I will move from impersonal presentation to a first-person narrative.
Hello :)
As you have guessed, of course, 3D printing is used for the individual manufacture of the in-ear insert of the hearing aid.
Our company, Materialize , was one of the pioneers of this industry and remains at the forefront today. We are developing RSM (Rapid Shell Modeling) - full-featured software for prototyping a hearing aid and the subsequent printing of individual in-ear inserts for ear, intra-ear and Open Ear devices.
Even 15 years ago, the manufacture of individual dental prostheses, dental tabs for reliable surgical operations on the jaw (by the way, our patent), individual inserts for hearing aids - all this was jewelry work and required several hours of work by a high-class specialist, and the slightest mistake could make the patient an invalid (in particular, when introducing a denture, there is a danger of hitting the nerve that passes at the base of the lower jaw, as a result of which a person can no longer manage it).
Our specialized software allows you to minimize the time to manufacture the prosthesis / device, the requirements for personal professionalism / experience of the doctor, and the risk to the patient's health.
My colleague will tell you about dental prosthetics in a separate article, and now we will return to hearing aids.
Liner manufacturing steps
Consider the earpiece near:
It consists of a plastic case with electronics, a silicone in-ear liner and a connecting tube.
Automated liner manufacturing begins with a patient ear scan.
1. Scan the client's ear
Heated wax is placed in the ear of the client, which almost instantly takes the form of the auricle and hardens. The resulting impression is digitized using a 3D scanner, resulting in a "cloud" of points - a set of points that accurately describe the inner surface of the auricle.
It is this point cloud (more precisely, two clouds - one for each ear) from the scanner to the RSM operator input (we support all modern types of 3D scanners), and the specialist performs all subsequent transformations of the impression already virtually.
2. Grinding and shaping the model
The point cloud is automatically triangulated and smoothed, after which the operator semi-automatically grinds the model and gives it the desired shape using an extensive set of convenient 3D tools.
Here you see the original triangulated model (left) and the same model after giving the shape required for the liner (right). The original shape of the ear model is shown as translucent.
For the convenience of the operator, the liner on the screen is usually located as follows:
3. Fixing Form
To increase the stability of the liner, an additional fixing form is generated, which will pass along the contour of the inner surface of the outer ear:
The form is generated on the basis of automatically constructed guides, which the operator can correct to obtain a more accurate result.
Model with a fixing shape (and a translucent source model)
4. Ventilation duct
The ventilation channel serves both for the free circulation of air, which is necessary for the healthy state of the inner ear, and for the prevention of various acoustic defects in hearing aids.
In the case of an intra-ear apparatus, the ventilation duct is automatically placed so as to occupy as little space as possible in the model (leaving space for electronics), after which the operator has enough freedom in choosing his form (tube, cone, letter D, etc.) and changing the location .
In the case of the BTE, optimization of the space occupied by the ventilation duct is not necessary, since the electronics (see the next section) are outside.
5. Electronics
In the earpiece and in the “Open ear” apparatus, the electronics (microphone, amplifier, transmitter) are located in an external plastic case.
In the case of an intra-ear apparatus, the electronics are placed in the insert, and therefore when designing the apparatus, the shape of the electronics must be taken into account.
We work with a constantly replenished base containing forms corresponding to the existing types of electronics for hearing aids of all global manufacturers.
The operator specifies the brand of electronics selected for the client, and the RSM automatically places the transmitter with an amplifier in the model optimally and completes the necessary connecting walls around the receiver, again, leaving enough freedom for the operator to manipulate.
The fixing form in intra ear hearing aids is not needed.
1 - microphone
2 - digital processor
3 - transmitter
4 - center line (used to automatically locate components)
6. Quality control
An automatic quality check is performed at all stages.
The device is checked for potential cracks due to the thinness of the walls, as well as for the presence of cavities in the material.
The presence of even a small cavity in the model is unacceptable, since with 3D printing on some types of printers, liquid will remain there, which can then get into the patient’s ear through a crack in the wall, which is extremely dangerous.
A check is also performed on the correctness of the relative position of the elements (collision detection).
In this example, the color gamut marks the discrepancies between the original and the processed models.
7. Export and print. Reuse
After the above steps, the model is exported to one of the standard formats (supported by all of today's 3D printers) and sent to print.
In the printed insert, the operator is left to insert the electronics and add a little glue.
All projects are saved, and in case of loss or breakage of the insert, you can print it again on the previously saved layout.
8. Operator productivity
Due to the maximum automation of the process, an experienced operator takes just minutes to complete the design cycle of a single machine! In one working day, the operator sends hundreds of inserts to print, whereas 15 years ago such figures seemed absolutely fantastic, since they exceeded the possibilities of the most experienced craftsmen by two orders of magnitude.
The project is almost ten years old.
Over the years, the range of possibilities at each of the above stages of model processing is rapidly growing, and the processing time decreases (both due to better algorithms and convenient tools, and through annual trainings conducted for new operators in the USA, France and other countries).
Thanks for attention!
Speaking of automation - I probably managed to bother you with the word “automatically” in this post?
The fact is that for me, as a developer of algorithms, it is of most interest in this product, and as a developer of algorithms, that is, as a person who is used every day to deal primarily with abstract entities, I find deep satisfaction in the work, which gives me the opportunity to apply my experience and knowledge for the benefit of living people.
On this major note, thank you for your attention and waiting for questions on the topic.
An article about dentures - soon.
Sources
The following resources were used in the preparation of the article:
http://www.otoskop.ru/rus/muzej-sluxovyx-apparatov/
http://www.vabos.com.ua/bernafon_ha_history.html
http://www.siemens-hearing.ru/client/page.asp?id=104
http://www.hearingaids.ru/istoriya-sluxovogo-apparata
http://nnm.ru/blogs/mrecka_/akusticheskie_lokatory/
http://en.wikipedia.org/wiki/Japanese_war_tuba
http://m.habrahabr.ru/post/78486/
http://www.akystik-sluh.ru/
http://en.wikipedia.org/wiki/Hearing_aid
http://www.phonak.com
Source: https://habr.com/ru/post/90757/
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