Plated Hole Polygons

Vias
Vias connect the tracks from one side of your board to another, by way of a hole in your board. On all but cheap
home made and low end commercial prototypes, vias are made with electrically plated holes, called Plated
Through Holes (PTH). Plated through holes allow electrical connection between different layers on your board.
What is the difference between a via and a pad? Practically speaking there is no real difference, they are both
just electrically plated holes. But there are differences when it comes to PCB design packages. Pads and Vias
are, and should be, treated differently. You can globally edit them separately, and do some more advanced
things to be discussed later. So don’t use a pad in place of a via, and vice-versa.
Holes in vias are usually a fair bit smaller than component pads, with 0.5-0.7mm being typical.
Using a via to connect two layers is commonly called “stitching”, as you are effectively electrically stitching both
layers together, like threading a needle back and forth through material. Throw the term stitching a few times into
a conversation and you’ll really sound like a PCB professional!

Polygons

“Polygons” are available on many PCB packages. A polygon automatically fills in (or “floods”) a desired area with
copper, which “flows” around other pads and tracks. They are very useful for laying down ground planes. Make
sure you place polygons after you have placed all of your tacks and pads.
Polygon can either be “solid” fills of copper, or “hatched”

Clearances
Electrical clearances are an important requirement for all boards. Too tight a clearance between tracks and pads
may lead to “hairline” shorts and other etching problems during the manufacturing process. These can be very
hard to fault find once your board is assembled. Once again, don’t “push the limits” of your manufacturer unless
you have to, stay above their recommended minimum spacing if at all possible.
At least 15 thou is a good clearance limit for basic through hole designs, with 10 thou or 8 thou being used for
more dense surface mount layouts. If you go below this, it’s a good idea to consult with your PCB manufacturer
first.
For 240V mains on PCB’s there are various legal requirements, and you’ll need to consult the relevant standards
if you are doing this sort of work. As a rule of thumb, an absolute minimum of 8mm (315 thou) spacing should be
allowed between 240V tracks and isolated signal tracks. Good design practice would dictate that you would have
much larger clearances than this anyway.
For non-mains voltages, the IPC standard has a set of tables that define the clearance required for various
voltages. A simplified table is shown here. The clearance will vary depending on whether the tracks are on an
internal layers or the external surface. They also vary with the operational height of the board above sea level

Component Placement & Design
An old saying is that PCB design is 90% placement and 10% routing. Whilst the actual figures are of no
importance, the concept that component placement is by far the most important aspect of laying out a board
certainly holds true. Good component placement will make your layout job easier and give the best electrical
performance. Bad component placement can turn your routing job into a nightmare and give poor electrical
performance. It may even make your board unmanufacturable. So there is a lot to think about when placing
components!
Every designer will have their own method of placing components, and if you gave the same circuit (no matter
how simple) to 100 different experienced designers you’d get a 100 different PCB layouts every time. So there is
no absolute right way to place your components. But there are quite a few basic rules which will help ease your
routing, give you the best electrical performance, and simplify large and complex designs.
At this point it is a good idea to give you an idea of the basic steps required to go about laying out a complete board:
Ø Set your snap grid, visible grid, and default track/pad sizes.
Ø Throw down all the components onto the board.
Ø Divide and place your components into functional “building blocks” where possible.
Ø Identify layout critical tracks on your circuit and route them first.
Ø Place and route each building block separately, off the board.
Ø Move completed building blocks into position on your main board.
Ø Route the remaining signal and power connections between blocks.
Ø Do a general “tidy up” of the board.
Ø Do a Design Rule Check.
Ø Get someone to check it
This is by no means a be-all and end-all check list, it’s highly variable depending on many factors. But it is a
good general guide to producing a professional first-class layout.

Cartisian Nano Pneumatic Grids

Pneumatic Grids

The second major rule of PCB design, and the one most often missed by beginners, is to lay out your board on a
fixed grid. This is called a “snap grid”, as your cursor, components and tracks will “snap” into fixed grid positions.
Not just any size grid mind you, but a fairly coarse one. 100 thou is a standard placement grid for very basic
through hole work, with 50 thou being a standard for general tracking work, like running tracks between throughhole
pads. For even finer work you may use a 25 thou snap grid or even lower. Many designers will argue over
the merits of a 20 thou grid vs a 25 thou grid for instance. In practice, 25 thou is often more useful as it allows
you to go exactly half way between 50 thou spaced pads.
Why is a coarse snap grid so important? It’s important because it will keep your components neat and
symmetrical; aesthetically pleasing if you may. It’s not just for aesthetics though - it makes future editing,
dragging, movement and alignment of your tracks, components and blocks of components easier as your layout
grows in size and complexity.
A bad and amateurish PCB design is instantly recognisable, as many of the tracks will not line up exactly in the
center of pads. Little bits of tracks will be “tacked” on to fill in gaps etc. This is the result of not using a snap grid
effectively.
Good PCB layout practice would involve you starting out with a coarse grid like 50 thou and using a progressively
finer snap grid if your design becomes “tight” on space. Drop to 25 thou and 10 thou for finer routing and
placement when needed. This will do 99% of boards. Make sure the finer grid you choose is a nice even division
of your standard 100 thou. This means 50, 25, 20, 10, or 5 thou. Don’t use anything else, you’ll regret it.
A good PCB package will have hotkeys or programmable macro keys to help you switch between different snap
grid sizes instantly, as you will need to do this often.
There are two types of grids in a PCB drafting package, a snap grid as discussed, and a “visible” grid. The visible
grid is an optional on-screen grid of solid or dashed lines, or dots. This is displayed as a background behind your
design and helps you greatly in lining up components and tracks. You can have the snap grid and visible grid set
to different units (metric or imperial), and this is often very helpful. Many designers prefer a 100 thou visible grid
and rarely vary from that.

Some programs also have what is called an “Electrical” grid. This grid is not visible, but it makes your cursor
“snap” onto the center of electrical objects like tracks and pads, when your cursor gets close enough. This is
extremely useful for manual routing, editing and moving objects.
One last type of grid is the “Component” grid. This works the same as the snap grid, but it’s for component
movement only. This allows you to align components up to a different grid. Make sure you make it a multiple of
your Snap grid.
When you start laying out your first board, snap grids can feel a bit “funny”, with your cursor only being able to
be moved in steps. Unlike normal paint type packages which everyone is familiar with. But it’s easy to get used
to, and your PCB designs will be one step closer to being neat and professional.

There is no recommended standard for track sizes. What size track you use will depend upon (in order of
importance) the electrical requirements of the design, the routing space and clearance you have available, and
your own personal preference. Every design will have a different set of electrical requirements which can vary
between tracks on the board. All but basic non-critical designs will require a mixture of track sizes. As a general
rule though, the bigger the track width, the better. Bigger tracks have lower DC resistance, lower inductance, can
be easier and cheaper for the manufacturer to etch, and are easier to inspect and rework.
The lower limit of your track width will depend upon the “track/space” resolution that your PCB manufacturer is
capable of. For example, a manufacturer may quote a 10/8 track/space figure. This means that tracks can be no
less than 10 thou wide, and the spacing between tracks (or pads, or any part of the copper) can be no less than
8 thou. The figures are almost always quoted in thou’s, with track width first and then spacing.
Real world typical figures are 10/10 and 8/8 for basic boards. The IPC standard recommends 4thou as being a
lower limit. Once you get to 6thou tracks and below though, you are getting into the serious end of the business,
and you should be consulting your board manufacturer first. The lower the track/space figure, the greater care
the manufacturer has to take when aligning and etching the board. They will pass this cost onto you, so make
sure that you don’t go any lower than you need to. As a guide, with “home made” PCB manufacturing processes
like laser printed transparencies and pre-coated photo resist boards, it is possible to easily get 10/10 and even
8/8 spacing.
Just because a manufacturer can achieve a certain track/spacing, it is no reason to “push the limits” with your
design. Use as big a track/spacing as possible unless your design parameters call for something smaller.
As a start, you may like to use say 25 thou for signal tracks, 50 thou for power and ground tracks, and 10-15
thou for going between IC and component pads. Some designers though like the “look” of smaller signal tracks
like 10 or 15 thou, while others like all of their tracks to be big and “chunky”. Good design practice is to keep
tracks as big as possible, and then to change to a thinner track only when required to meet clearance
requirements.
Changing your track from large to small and then back to large again is known as
“necking”, or “necking down”. This is often required when you have to go between IC
or component pads. This allows you to have nice big low impedance tracks, but still
have the flexibility to route between tight spots.
In practice, your track width will be dictated by the current flowing through it, and the maximum temperature rise
of the track you are willing to tolerate. Remember that every track will have a certain amount of resistance, so
the track will dissipate heat just like a resistor. The wider the track the lower the resistance. The thickness of the
copper on your PCB will also play a part, as will any solder coating finish.

The thickness of the copper on the PCB is nominally specified in ounces per square foot, with 1oz copper being
the most common. You can order other thicknesses like 0.5oz, 2oz and 4oz. The thicker copper layers are
useful for high current, high reliability designs.
The calculations to figure out a required track width based on the current and the maximum temperature rise are
a little complex. They can also be quite inaccurate, as the standard is based on a set of non-linear graphs based
on measured data from around half a century ago. These are still reproduced in the IPC standard.
A handy track width calculator program can be found at www.ultracad.com/calc.htm, and gives results based on
the IPC graphs.
As a rule of thumb, a 10degC temperature rise in your track is a nice safe limit to design around. A handy
reference table has been included in this article to give you a list of track widths vs current for a 10degC rise. The
DC resistance in milli ohms per inch is also shown. Of course, the bigger the track the better, so don’t just
blindly stick to the table.

Pads

Pad sizes, shapes and dimensions will depend not only upon the component you are using, but also the
manufacturing process used to assemble the board, among other things. There are a whole slew of standards
and theories behind pad sizes and layouts, and this will be explained later. Suffice it to say at this stage that
your PCB package should come with a set of basic component libraries that will get you started. For all but the
simplest boards though, you’ll have to modify these basic components to suit your purpose. Over time you will
build up your own library of components suitable for various requirements.
There is an important parameter known as the pad/hole ratio. This is the ratio of the pad size to the hole size.
Each manufacturer will have their own minimum specification for this. As a simple rule of thumb, the pad should
be at least 1.8 times the diameter of the hole, or at least 0.5mm larger. This is to allow for alignment tolerances
on the drill and the artwork on top and bottom layers. This ratio gets more important the smaller the pad and hole
become, and is particularly relevant to vias.
There are some common practices used when it comes to generic component pads. Pads for leaded
components like resistors, capacitors and diodes should be round, with around 70 thou diameter being common.
Dual In Line (DIL) components like IC’s are better suited with oval shaped pads (60 thou high by 90-100 thou
wide is common). Pin 1 of the chip sould always be a different pad shape, usually rectangular, and with the
same dimensions as the other pins.
Most surface mount components use rectangular pads, although surface mount SO package ICs should use oval
pads. Again, with pin 1 being rectangular.
Other components that rely on pin numbering, like connectors and SIP resistor packs, should also follow the
“rectangular pin 1” rule.

Bio-medical Pneumatics

The Schematic Medical PneumaticS

Before you even begin to lay out your PCB, you MUST have a complete and accurate schematic diagram. Many
people jump straight into the PCB design with nothing more than the circuit in their head, or the schematic
drawn on loose post-it notes with no pin numbers and no order. This just isn’t good enough, if you don’t have an
accurate schematic then your PCB will most likely end up a mess, and take you twice as long as it should.
“Garbage-in, garbage-out” is an often used quote, and it can apply equally well to PCB design. A PCB design is
a manufactured version of your schematic, so it is natural for the PCB design to be influenced by the original
schematic. If your schematic is neat, logical and clearly laid out, then it really does make your PCB design job a
lot easier. Good practice will have signals flowing from inputs at the left to outputs on the right. With electrically
important sections drawn correctly, the way the designer would like them to be laid out on the PCB. Like putting
bypass capacitors next to the component they are meant for. Little notes on the schematic that aid in the layout
are very useful. For instance, “this pin requires a guard track to signal ground”, makes it clear to the person
laying out the board what precautions must be taken. Even if it is you who designed the circuit and drew the
schematic, notes not only remind yourself when it comes to laying out the board, but they are useful for people
reviewing the design.
Your schematic really should be drawn with the PCB design in mind.
It is outside the scope of this article to go into details on good schematic design, as it would require a complete
article in its own right.

Imperial and Metric Designs :

The first thing to know about PCB design is what measurement units are used and their common terminologies,
as they can be awfully confusing!
As any long time PCB designer will tell you, you should always use imperial units (i.e. inches) when designing
PCBs. This isn’t just for the sake of nostalgia, although that is a major reason! The majority of electronic
components were (and still are) manufactured with imperial pin spacing. So this is no time to get stubborn and
refuse to use anything but metric units, metric will make laying out of your board a lot harder and a lot messier. If
you are young enough to have been raised in the metric age then you had better start learning what inches are
all about and how to convert them.
An old saying for PCB design is “thou shall use thous”. A tad confusing until you know what a “thou” is.
A “thou” is 1/1000th of an inch, and is universally used and recognised by PCB designers and manufacturers
everywhere. So start practicing speaking in terms of “10 thou spacing” and “25 thou grid”, you’ll sound like a
professional in no time!
Now that you understand what a thou is, we’ll throw another spanner in the works with the term “mil” (or “mils”). 1
“mil” is the same as 1 thou, and is NOT to be confused with the millimeter (mm), which is often spoken the
same as “mil”. The term “mil” comes from 1 thou being equal to 1 mili inch. As a general rule avoid the use of
“mil” and stick to “thou”, it’s less confusing when trying to explain PCB dimensions to those metricated non-PCB
people.
Some PCB designers will tell you not to use metric millimeters for ANYTHING to do with a PCB design. In the
practical world though, you’ll have to use both imperial inches (thous) and the metric millimeter (mm). So which
units do you use for what? As a general rule, use thous for tracks, pads, spacings and grids, which are most of
your basic “design and layout” requirements. Only use mm for “mechanical and manufacturing” type
requirements like hole sizes and board dimensions.

NANO Circuit Design

Nano-tech Introduction

You've designed your circuit, perhaps even bread boarded a working prototype, and now it's time to turn it into a
nice Printed Circuit Board (PCB) design. For some designers, the PCB design will be a natural and easy
extension of the design process. But for many others the process of designing and laying out a PCB can be a
very daunting task. There are even very experienced circuit designers who know very little about PCB design,
and as such leave it up to the "expert" specialist PCB designers. Many companies even have their own
dedicated PCB design departments. This is not surprising, considering that it often takes a great deal of
knowledge and talent to position hundreds of components and thousands of tracks into an intricate (some say
artistic) design that meets a whole host of physical and electrical requirements. Proper PCB design is very often
an integral part of a design. In many designs (high speed digital, low level analog and RF to name a few) the
PCB layout may make or break the operation and electrical performance of the design. It must be remembered
that PCB traces have resistance, inductance, and capacitance, just like your circuit does.
This article is presented to hopefully take some of the mystery out of PCB design. It gives some advice and
“rules of thumb” on how to design and lay out your PCBs in a professional manner. It is, however, quite difficult to
try and “teach” PCB design. There are many basic rules and good practices to follow, but apart from that PCB
design is a highly creative and individual process. It is like trying to teach someone how to paint a picture.
Everyone will have their own unique style, while some people may have no creative flair at all!
Indeed, many PCB designers like to think of PCB layouts as works of art, to be admired for their beauty and
elegance. “If it looks good, it’ll work good.” is an old catch phrase.
Lets have a go shall we...
The Old Days
Back in the pre-computer CAD days, PCBs were designed and laid out by hand using adhesive tapes and pads
on clear drafting film. Many hours were spent slouched over a fluorescent light box, cutting, placing, ripping up,
and routing tracks by hand. Bishop Graphics, Letraset, and even Dalo pens will be names that evoke fond, or not
so fond memories. Those days are well and truly gone, with computer based PCB design having replaced this
method completely in both hobbyist and professional electronics. Computer based CAD programs allow the
utmost in flexibility in board design and editing over the traditional techniques. What used to take hours can now
be done in seconds.

NANO CIRCUITARY

There are many PCB design packages available on the market, a few of which are freeware, shareware, or
limited component full versions. Protel is the defacto industry standard package in Australia. Professionals use
the expensive high end Windows based packages such as 99SE and DXP. Hobbyists use the excellent freeware
DOS based Protel AutoTrax program, which was, once upon a time, the high-end package of choice in Australia.
Confusingly, there is now another Windows based package also called AutoTrax EDA. This is in no way related
to the Protel software.
This article does not focus on the use of any one package, so the information can be applied to almost any PCB
package available. There is however, one distinct exception. Using a PCB only package, which does not have
schematic capability, greatly limits what you can do with the package in the professional sense. Many of the
more advanced techniques to be described later require access to a compatible schematic editor program. This
will be explained when required.
Standards
There are industry standards for almost every aspect of PCB design. These standards are controlled by the
former Institute for Interconnecting and Packaging Electronic Circuits, who are now known simply as the IPC
(www.ipc.org). There is an IPC standard for every aspect of PCB design, manufacture, testing, and anything else
that you could ever need. The major document that covers PCB design is IPC-2221,

Local countries also have their own various standards for many aspects of PCB design and manufacture, but by
and large the IPC standards are the accepted industry standard around the world.
Printed Circuit Boards are also known (some would say, more correctly known) as Printed Wiring Boards, or
simply Printed Boards. But we will settle on the more common term PCB for this article.

Nano Hydral Micro Lamp Systems

The simplest lamp dimmer circuit consists of a rheostat, in series with the lamp, which one
may adjust to obtain the required brightness. Such linear regulators are quite inefficient since
a lot of power is wasted in them. Moreover, in the rheostat the moving contacts are likely to
get damaged in the long run, as its value is frequently adjusted by moving the slider. Such
linear control circuits provide an overall efficiency of no more than 50 per cent. This wastage
of power can be avoided if one uses pulse width modulation (PWM) which can be made to
control an electronic rheostat. The circuit shown here is based on PWM principle. Gate N1
and its associated components constitute an oscillator producing oscillations of approximately
200 Hz with a pulse width of 0.1 ms. This output is fed to transistor T1 for level shifting. At the
output of this transistor is a potentiometer VR2, using which a DC component can be added
to the pulses emerging from transistor T1. By adjusting this potentiometer/trimmer, one can
have a good linear control of the lamp brightness from completely off state to 100 per cent on
state. The signal is inverted by gate N2 and fed to MOSFET 12N10. IC CD40106 provides six
inverting buffers with Schmitt trigger action. The buffers are capable of transforming slowly
changing input signals into sharply defined jitter-free output signals. They are usually used as
wave and pulse shapers. IC CD40106 possesses high immunity and low power consumption
of standard CMOS ICs along with the ability to drive 10 LS-TTL loads. In this circuit loads up
to 24W can be connected between MOSFET drain and 12V supply without using a heatsink.
The loads can even be DC motors, miniature heating elements, etc. If one uses a low RDS
(on) MOSFET, a higher efficiency can be achieved. By using the components as shown in the
circuit, an efficiency of approximately 95 per cent can be achieved. The flexibility of the design
makes it possible to change the MOSFET with a similar one, in case of non-availability of
12N10. The circuit by itself does not draw much current when the load is disconnected.
Ensure proper ESD protection while handling the MOSFET to prevent damage. Lab note: The
circuit was tested using MOSFET IRF640 with RDS (on)=0.18 ohm.

Nano robotics

it has been observed that only well-motivated, highly
compliant patients are suitable for photoradiation (2). A possible
explanation is that this could depend not only on the exhausting
photo(chemio) therapeutic algorithms, but also on the fact that
systemic irradiation, even when successful, always provokes
transient darkening of the non-affected skin, with a negative
psychological impact related to the increased chromatic difference
with the vitiligo patches. Instead, as repigmentation obtained with
the focused UV-B microphototherapy is limited to the treated
vitiligo areas and the radiation is performed only once or twice per
month, the novel phototherapy treatment is extremely well accepted
by the vitiligo patients.

Follow-up studies are needed to ascertain whether the repigmentation
induced by this limited irradiation method is permanent.

Figure 1 Repigmentation after microphototherapy on actively treated
subjects and controls.

*References*

1. Westerhof W, Nieuweboer-Krobotova L. Treatment of vitiligo
with UV-B radiation vs topical psoralen plus UV-A. Arch
Dermatol 1997;133:1525:1528.
2. Njoo MD, Spuls PI, Bos JD, Westrhof W, Bossuyt MM. Nonsurgical
repigmentation therapies in vitiligo. Arch Dermatol
1998;134:1532-1540.
3. Funasaka Y, Chakraborty AK, Hayashi Y, Komoto M, Ohashi A,
Nagahama M, Inoue Y, Pawelek J. Modulation of
melanocyte-stimulating hormone receptor expression on normal
human melanocytes: evidence for a regulatory role of
ultraviolet B, interleukin-1alpha, interleukin-1beta,
endothelin-1 and tumor necrosis factor-alpha. Br J Dermatol
1998;139(2):216-224.
4. Im S, Moro O, Peng F, Medrano EE, Cornelius J, Babcock G,
Nordlund JJ, Abdel-Malek ZA. Activation of the cyclic AMP
pathway by alpha-melanotropin mediates the response of human
melanocytes to ultraviolet B radiation. Cancer Res
1998;58(1):47-54.
5. Romero-Graillet C, Aberdam E, Clement M, Ortonne JP, Ballotti
R. Nitric oxide produced by ultraviolet-irradiated
keratinocytes stimulates melanogenesis. J Clin Invest
1997;99(4):635-642.
6. Ota A, Park JS, Jimbow K. Functional regulation of tyrosinase
and LAMP gene family of melanogenesis and cell death in
immortal murine melanocytes after repeated exposure to
ultraviolet B. Br J Dermatol 1998 139(2):207-215.
7. Slominski A, Baker J, Ermak G, Chakraborty A, Pawelek J.
Ultraviolet B stimulates production of corticotropin releasing
factor (CRF) by human melanocytes. FEBS Lett
1996;399(1-2):175-176.
8. Lee HS, Kooshesh F, Sauder DN, Kondo S. Modulation of TGF-beta
1 production from human keratinocytes by UVB. Exp
Dermatol;6(2):105-110.
9. Marionnet AV; Chardonnet Y, Viac J, Schmitt D. Differences in
responses of interleukin-1 and tumor necrosis factor alpha
production and secretion to cyclosporin –A and ultraviolet
B-irradiation by normal and transformed keratinocyte culture.
Exp Dermatol 1997; 6(1):22-28.
10. Redondo P, Garcia-Foncillas J, Cuevillas F, Espana A,
Quintanilla E. Effects of low concentration of cis- and
trans-urocanic acid on cytokine elaboration by keratinocytes.
Photodermatol Photoimmunol Photomed 1996;12(6):237-243.
11. Kondo S, Sauder DN. Keratinocytes derived cytokines and
UVB-induced immunosuppression. J Dermatol 1995;22(11):888-893.
12. Assefa Z, Garmyn M, Bouillon R, Merlevede W, Vandenheede JR,
Agostinis P. Differential stimulation of ERK and JNK
activities by ultraviolet B irradiation and epidermal growth
factor in human keratinocytes. J Invest Dermatol
1997;108(6):886-891.
13. Cotton J, Spandau DF. Ultraviolet B-radiation dose influences
the induction of apoptosis and p53 in human keratinocytes.
Radiat Res 1997;147(2):148-155.
14. Henseleit U, Zhang J, Wanner R, Haase I, Kolde G, Rosenbach T.
Role of p53 in UVB-induced apoptosis in human HaCaT
keratinocytes. J Invest Dermatol 1997;109(6):722-727.
15. Benassi L, Ottani D, Fantini F, Marconi A, Chiodino C,
Giannetti A, Pincelli C. 1,25-dhydroxyvitamin D3, transforming
growth factor beta1, calcium, and ultraviolet B radiation
induce apoptosis in cultured human keratinocytes. J Invest
Dermatol 1997;109(3):276-282.
16. Sasaki H, Akamatsu H, Horio T. Effects of a single exposure to
UVB radiation on the activities and protein levels of
copper-zinc and manganese superoxide dismutase in cultured
human keratinocytes.

Erythema dose

Minimal erythema dose (MED) for subject, UVB dose per
session per cm2, total dose of UVB received by affected subjects
and percentage of repigmentation after active and placebo
treatments (controls). *Cumulative dose = Session dose * n° of
sessions



Photographs of the subjects were taken at the beginning of the
therapy and then once a month for six months using Wood’s lamp. One
month after the treatment was finished, the results were evaluated
by planimetry based on two comparable photographs.

*Results.*

The MED of lesional skin was between 200 and 500 mJ/cm^2 . In
general repigmentation started 1 month after the beginning of the
UV-B microphoto-therapy.

After 5 months 5 subjects responded with more than 75%
repigmentation (3 achieved 100% repigmentation), 2 individuals
showed 50-75% repigmentation and one showed repigmentation in less
then 50% of the area treated.

No adverse effects were noted. The compliance was excellent. No pain
or burning or itching sensations were reported by the subjects.
Vitiligo was not aggravated in any subject. The average cumulative
UV-B dose with the treatment was 5.025 J/cm^2 (range 2.4-6 J/cm^2 )
per subject.

*Comments.*

According to the principles of evidence-based medicine,
meta-analysis of all relevant studies in the literature recently
showed that the highest mean success rates in repigmentation of
vitiligo were achieved with narrow band UV-B, followed by broadband
UV-B and oral methoxsalen plus UV-A therapy (2). The same study
showed that oral methoxsalen plus UV-A was associated with the
highest rates of side effects, while no side effects were reported
with UV-B therapy (2). Thus, following the recommendations of Njoo
et al based on the meta-analysis of the literature, it seems that
when patients exhibit generalized vitiligo, UV-B (narrow band or
broad band) therapy or, as a second choice, oral methoxsalen plus
UV-A, should be recommended. For patients with localized vitiligo
(defined as vitiligo affecting less than 20% of the total body
surface) (2) a class 3 corticosteroid is advised as first choice
therapy (2).

On the basis of the present study carried out with a novel device
allowing limited and focused UV-B photoradiation, we suggest that
UV-B therapy limited only to the vitiligo patches could be
considered the first-choice therapy for patients with localized
vitiligo, although more studies will be necessary to confirm the
good results and establish the entity of possible long-term side
effects. The protocol for the use of focused UV-B therapy here
presented show that the therapy need not be continuous and that the
cumulative UV-B doses received by the single patient with the
BIOSKIN^® device is obviously much lower than the cumulative UV-B
dose received by the previously established UV-B treatment intended
to treat the whole, or at least a considerable part, skin surface
independent of the percentage of affected skin. It is implicit that
therapy limited to the vitiligo patches carries substantially less
risk for skin cancer that any other kind of systemic photoradiation,
with or without oral intake of psoralen.

Fitzpatrick’s Bio Skin Device

Bioskin device is a generator of UV-B radiation composed of three
main components:

1. UV-B short arc mercury lamp (100 Watt) which generates UV-B
with a spectrum of 280 to 320 nm with a maximum emission peak
at 311 nm;
2. Specialized liquid component optical fiber which can transmit
and focalize the emitted UV-B in a circular beam 1 cm in diameter.
3. Computerized system which allows the regulation of the
intensity (10-100 mJ/cm^2 /s) and time of single spot emission
(0.1-10 seconds).

/Light spot./

Each single spot produces an energy of 10-100 mJ/cm^2 on a 1 cm
diameter circular area (0.785 cm^2 ) for the time necessary to reach
the optimal dose. The optical fiber terminal is in contact with a
different site of the treated patch during the emission of each
spot. Repetition of single spots make it possible to treat VP areas
completely while avoiding normal skin. Complete treatment of a 10
cm^2 diameter vitiligous area with 100 mJ requires repeating a 2
second 1 cm^2 diameter spot 6 times with 100 mJ/cm^2 intensity.

/Treatment session/

Each treatment session consists of irradiation of the VP with a dose
20% lower than minimal erythema dose (MED) calculated by the
operator before the session. The length of each session depends on
the length of the single light spot and the extension of the VP areas.

/Treatment./

The MED in VP is evaluated 24 hours before the beginning of therapy.
The subjects are treated with the following scheme:

* 5 sessions, one a day for 5 consecutive days.
* 10 days break.
* 1 session every 15 days for 5 months.

The control subjects were treated with the same protocol but with
the UVB generator off. It was impossible for the control subjects to
know if the generator was on or not.

Table 3 shows the MED for each patient, dose per session for cm^2 ,
total dose given each subject per cm^2 and the final results.

Vitiligo Microphototherapy

Vitiligo is a common disease of unknown cause that
produces disfiguring white patches of depigmentation. Previous
studies have suggested the effectiveness of UV-B radiation in
generalized vitiligo (GV) therapy, but there was no evidence to
support the same role for segmental vitiligo (SV).

*Objective:* The purpose of this study was to use UV-B radiation
exclusively on vitiligo patches of individuals affected by SV to
evaluate the effectiveness of this therapy.

*Subjects & Methods:* 8 individuals with SV were treated for six
months with a new device called BIOSKIN ® that can produce a focused
beam of UV-B (microphoto-therapy) on vitiligo patches only.
Photographs of the subjects were taken at the beginning of the
therapy and once a month thereafter for six months. The response to
treatment was estimated in 2 comparable photographs using
planimetry. A control group of 8 individuals matched for sex and age
was treated with placebo, using the same device but not releasing
any kind of detectable light.

*Results:* After six months of microphototherapy 5 subjects of the 8
studied achieved normal pigmentation on more than 75% of the treated
areas. In particular, 3 of these were totally repigmented. Two
individuals achieved 50-75% pigmentation of the treated areas, and
only one showed less than 50% repigmentation (table 3). In the
control group only one patient showed moderate repigmentation (less
than 50%) (table 3) (Figure 1).

*Conclusion:* UV-B microphototherapy seems highly effective in
restoring pigmentation in patients affected by vitiligo. As no side
effects have been observed, this could represent the treatment of
choice in the limited (segmental) forms of vitiligo.

*Keywords:* vitiligo, UV-B, therapy



*Introduction
*
Vitiligo is an acquired hypomelanotic disease of unknown etiology
affecting 1-2% of world population without any racial, geographic or
sex differences (1). Although use of ultraviolet-B (UV-B) radiation
in vitiligo therapy is relatively recent, it is considered presently
the most effective treatment for generalized vitiligo (1,2).

The successful use of UV-B rays is probably due to several direct
and mediated interactions of UV-B with melanocytes, keratinocytes
and skin immune system (Table 1).

Enhancement of pigmentation
- By increase of melanocyte stimulating hormone (MSH) receptor
binding activity and melanocortin receptor gene expression [3]
- By activation of cyclic-AMP pathway by alpha-melanotropin which
increases melanocyte proliferation and melanogenesis [4]
- By irradiated keratinocyte production of nitric oxide (NO)
(paracrine induction of melanogenesis) [5]
- By increase of tyrosinase mRNA expression and enzymatic activity [6]
- By melanocyte production and secretion of corticotropin releasing
factors [7]
lnduction of skin inflammation
- By enhancement of keratinocyte production and release of TGFß-1 [8]
- By enhancement of keratinocyte production and release of IL-1 [9]
Alteration of local (skin) immune system response
- By enhancing production and release of TGFß-1which causes
immunosuppression [8]
- By enhancing release of cis urocanic acid (cis-UCA) [10]
By enhancing keratinocyte production and release of TNFß [11]
Tumor promotion
- By induction of c-jun and c-fos protooncogene transcription in
keratinocytes [12]
- By causing cellular DNA damage
Cellular programmed self destruction
- By increasing keratinocyte levels of tumor suppressor gene p53 [13,14]
- By increasing keratinocyte Ievels of 1.25 dihydroxyvitamin D3,
TGFß-1,Ca ^2+ [15]
Metabolic alteration
- Enhanced production of free radical levels
- Enhanced superoxid dismutase (SOD) levels and activity [16]

Table 1 - The main direct and mediated effects of UV-B irradiation
of the skin

In this study we used a new device called BIOSKIN^® provided with a
focused beam of UV-B adapted to treat selected areas of depigmented
skin.

*Subjects and Methods*

/Subjects/

Subjects with segmental vitiligo were included in the study after
obtaining informed consent to ensure that the procedure of
microphototherapy had been fully explained. The individuals were 4
men and 4 women with a mean age of 17.9 years and skin type III for
6 persons and II for the other 2. The control group was composed of
8 individuals, 5 men and 3 women, affected by SV with a mean age of
22.9 years; skin type was III for 5 persons and II for the other 3.

Table 2 shows the sex, age, Fitzpatrick skin phototype and affected
areas for each subject treated.

Ultraviolet Sensor

This sensor measures the ultraviolet radiation between 250 and
400 namometers in μmol m-2 s-1 (micromoles of photons per sqare
meter second).
Although the relative wavelengths of UV radiation differ among
sunlight and electric lights, our measurements, shown in the graph
below, indicate that this sensor provides a close estimate of the UV
radiation coming from electric lamps. This sensor is particularly useful
for determining the UV filtering capacity of the transparent plastic and
glass barriers that are commonly used below electric lamps.

Attach the sensor to a meter or datalogger
capable of displaying or recording a mV output.
The model, serial number, production date, and
conversion factor are located on the sensor cable.

Mount the sensor as level as possible. Small
changes in level can cause measurement errors. We
recommend using our leveling plate (model LEV) for
the most accurate measurements.
The sensor should be mounted with the cable pointing
toward the nearest magnetic pole to minimize azimuth
error.

Why this sensor cannot selectively
measure UV-B Radiation (280-320 nm)
Our measurements confirm those of others and indicate that less than
0.4 % of the photon flux from sunlight falls below 320 nm; 2.3 % falls
between 320 and 350 nm, and 6 % falls between 350 and 400 nm. Although
the UV radiation between 250 and 320 nm is critically important
in photochemical and photobiological reactions, only about 5 % of the UV
photons are in this range. Because only a small fraction of the photons
are in the UV-B range, this meter cannot be used to selectively measure
UV-B radiation. The sensor is sensitive to UV-B radiation, but it is included
with the UV-A radiation to provide a total measurement of UV radiation.

Effects on Output
Level
The sensor must be exactly horizontal for the most
accurate measurement. The largest error is often
caused by small changes in the position of the sensor.
The sensor should be mounted with the cable pointing
toward the nearest magnetic pole.
Cosine response
Some of the radiation coming into a sensor at low
angles is reflected, which causes the reading to be less
than it should be. The cosine-corrected head helps to
capture radiation at low angles. The cosine error for
typical applications is less than 10 %.
Temperature response
The temperature response is about 0.1 % per degree
celsius. This temperature error is insignificant for most
applications.
Long-term stability
The output of all radiation sensors tends to decrease
over time as the detector ages. Our measurements
indicate that the average decrease of the sensor is
about 1 % per year. We recommend returning the
sensor for recalibration every 3 years.

Specifications
435-792-4700
www.apogeeinstruments.com
techsupport@apogee-inst.com
Absolute accuracy ± 10 %
Uniformity ± 5 %
Repeatability ± 1 %
Output Responsivity Approximately 0.15 mV per μmol m-2 s-1
In full sunlight Approximately 26 mV (170 μmol m-2 s-1)
Linear range 0 to 400 μmol m-2 s-1
Sensitivity Calibrated to approximately 6.5 μmol m-2 s-1 per mV
Input power None, self-powered
Operating environment Can be submerged underwater (with or without
mounting bolt).
Materials PVC head, potted solid
Cable 3 meters of shielded, twisted-pair wire with
Santoprene casing, ending in pigtail leads.
Additional cable $1.95/meter.
Dimensions 2.4 cm diameter, 2.75 cm high
Mass 70 g (with 3 m lead wire)
Warranty 1 year parts and labor

Handheld Readings
1. Turn the dial clockwise to the “on” position.
2. Handheld UV meters should be held level as shown
below. Separate sensors should be mounted on a
horizontal surface.
3. The number displayed is the μmol m-2 s-1
4. Turn the meter off after use to conserve battery
power.

Calibration
Although the relative wavelengths of UV radiation differ
among sunlight and electric lights, our measurements, shown
in the graph below, indicate that this sensor provides a close
estimate of the UV radiation coming from electric lamps. This
sensor is particularly useful for determining the UV filtering
capacity of the transparent plastic and glass barriers that are
commonly used below electric lamps.

Why this Meter cannot selectively
measure UV-B Radiation (280-320 nm)

Our measurements confirm those of others and indicate that less than
0.4 % of the photon flux from sunlight falls below 320 nm; 2.3 % falls
between 320 and 350 nm, and 6 % falls between 350 and 400 nm. Although
the UV radiation between 250 and 320 nm is critically important
in photochemical and photobiological reactions, only about 5 % of the UV
photons are in this range. Because only a small fraction of the photons
are in the UV-B range, this meter cannot be used to selectively measure
UV-B radiation. The sensor is sensitive to UV-B radiation, but it is included
with the UV-A radiation to provide a total measurement of UV radiation

Sources of Error in UV Radiation

The variety of applications of ultraviolet (UV) light and the consequent need for accurate UV measurements
have increased enormously over the last 20 years. In some cases, the UV radiation from a source is of inter
(e.g., tanning booths and solar radiation). At other times, the action or chemical reaction initiated by UV
irradiation of a system is of interest (e.g., water purification,UV curing, and semiconductor photolithography).
Finally, UV radiation has a cumulative deleterious effect on biological systems; there are consequently health
safety requirements for the accurate measurement of UV radiation.

Considerable effort has been made to produce simple instrumentation to meet these wide-ranging UV
measurement needs. The typical UV meter or radiometer is composed of a number of simple optical elements,
as shown in Fig. 1. The incident radiation passes through an aperture that limits the active area of the system.
diffuser is often placed after the aperture and is used to improve the angular response and spatial uniformity
The instrument. An optical filter is then employed to select the spectral region of the incident optical
radiation that strikes the detector.

To fully understand the accuracy of such a UV meter, the optical properties of its components and the spectral
responsivity should be known as well as the relative spectral distribution of the source. Additionally, the UV
meter will seldom perform ideally, and out-of-band, non-linear, and non-ideal geometric or spatial response
must be characterized to achieve the lowest uncertainties. However, most UV meters are supplied from the
manufacturer with a calibration at a specific wavelength, and only a nominal wavelength band is specified. In
addition, the spectral distribution of the source being measured is often unknown. The purpose of this paper
is to illustrate that considerable thought must be given to the utilization and calibration of these simple
devices order to understand and minimize measurement errors

2. Sources of Error

It is important to define, at the outset, the physical quantity that is to be measured and the level of uncertainty
needed to achieve the measurement goals. The measurement requirements for the UV meter can be
very different: spectrally integrated irradiance (W/cm2) in the UV-A (315 nm to 400 nm) or UV-B (280 nm to
315 nm) regions as in the case of solar irradiation; a single wavelength dose or exposure (J/cm2) as in the
case of semiconductor photolithography; or an effective or weighted dose (Effective J/cm2) as in the case of
biological action spectra. The sources of error in optical radiation measurements described here are not new
to radiometry.These errors in addition to measurement techniques and procedures are well documented in the field of
photometry. However, these topics are less well known in the UV radiation measurement community,
especially among novice users of UV measurement instruments.Due in part to increasing UV applications, recent
publications specifically address UV meter calibration and characterization [2, 3]. In the following, we discuss
common sources of error in UV radiation measurements,including out-of-band contributions to the signal,
non-ideal geometric properties (non-ideal cosine response in the meters), and poor matching to a defined
action spectrum. Other sources of error have been discussed in the literature and will not be discussed here.
These include environmental factors such as temperature and humidity,which can lead to wavelength-dependent
responsivity changes in UV meters. In addition, UV radiation itself induces aging of the optical elements of meters.
Finally, optical detectors used in UV meters have a finite range over which they have an output signal linearly
proportional to the incident irradiance. UV meters should be tested to verify that they are in the linear range both
for the irradiance level used in practice as well as for the smaller levels typically used for calibration.

3. Out-of-Band/Non-Ideal Responsivity

An ideal meter would have a well-defined responsivity within a specific spectral region and zero responsivity
outside of this region. For example, an ideal UV-A meter would have a constant responsivity from 315 nm
to 400 nm and no response outside of this region.Figure 3 shows the spectral responsivity, determined
in monochromatic radiation, of two broadband UV meters used in semiconductor photolithography to
determine the total exposure of a photoresist to 365 nm radiation from a filtered mercury source [4]. These
meters have a maximum responsivity in the 365 nm region, and the responsivity then decreases to a much
smaller, though non-zero, value at longer wavelengths. The instruments demonstrate differing amounts of
increased responsivity in the near infrared (IR), with Meter A showing responsivity 2 to 3 orders of magnitude
larger than Meter B in the 700 nm to 1000 nm spectral region. The increased IR responsivity is due to
increased transmission in the IR by the glass filters, and because silicon photodiodes have their peak response
in the near IR. The increased responsivity observed at wavelengths shorter than 300 nm is caused by fluorescence
of the diffuser, which then re-emits longer wavelength radiation that passes through the filter to the
photodiode. This was verified in Meter A by placing the diffuser between the filter and the photodiode. This
effectively eliminated the responsivity near 275 nm.For monochromatic radiation measurements near
365 nm, the out-of-band response is not important and both meters can make measurements with little error.
Many real optical sources that are assumed monochromatic,such as lasers, often emit radiation
at additional wavelengths. If the source to be measured emits flux at wavelengths below 300 nm or above
680 nm, the 365 nm radiation could be overestimated and measurements with these two meters will
disagree. Although these UV meters were designed to measure monochromatic radiation, they are very similar to UV
meters designed and used for broadband UV radiation.To illustrate these errors, we compare the signal
produced by the two UV meters from four typical sources with different spectral power distributions: a
mercury arc lamp, a quartz-tungsten halogen lamp (ANSI designation, FEL), a deuterium lamp, and a
xenon arc lamp. The relative spectral distribution of each source is shown in Fig. 4.
Using Eq. (1), we compare the integrated in-band irradiance signal with the out-of-band signal. The
in-band signal is the product of the spectral distribution of the source and the meter responsivity, integrated over
the spectral region from 315 nm to 400 nm. The out-ofband response is the integral of the product summed
over the 200 nm to 315 nm and 400 nm to 1000 nm spectral ranges.