Dermatological Phototherapy and Photodiagnostic...

Dermatological Phototherapy and Photodiagnostic Methods

Jean Krutmann • Herbert Hönigsmann Craig A. Elmets (Eds.)

Dermatological Phototherapy and Photodiagnostic MethodsSecond Edition

123

ISBN 978-3-540-36692-8 e-ISBN 978-3-540-36693-5

DOI 10.1007 / 978-3-540-36693-5

Library of Congress Control Number: 2008936558Second Edition

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Prof. Dr. Jean KrutmannUniversität DüsseldorfInstitut für Umweltmedizinische Forschung (IUF) gGmbHAuf´m Hennekamp 5040225 Düsseldorf, Germany

Prof. Dr. Herbert HönigsmannUniversitätsklinikum WienDermatologische KlinikAbt. Spezielle DermatologieWähringer Gürtel 18–201090 Wien, Austria

Craig A. Elmets, MDUniversity of Alabama, Birmingham, Department of DermatologyBirmingham AL 35294-0007, USA

v

Preface to the Second Edition

During the past 30 years, phototherapy has greatly influenced treatment concepts in der-matology. Consequently, photomedicine has developed from empiricism into one of the most exciting fields in biomedical research. Studies on the effects of visible and ultravio-let radiation on skin have led to a fruitful collaboration between basic scientists and clini-cians. Thus, phototherapy may be regarded as a prime example of applied skin biology.

UV radiation has been used for decades in the management of common skin diseases such as psoriasis and atopic dermatitis. More recently, the introduction of selective spec-tra in the UVB and UVA range, such as narrowband UVB and UVA-1 phototherapy, as well as the inclusion of new indications, has much stimulated the interest in photoderma-tology. Visible light in combination with photosensitizers is currently in use for diagnosis and treatment of selected tumours. Extracorporeal photochemotherapy has proven to be effective beyond dermatology, in particular in transplantation medicine.

Most phototherapeutic regimes have been developed empirically and without know-ledge about the biological mechanisms involved. Recent progress in the understanding of basic photobiological principles has made phototherapy more effective and, even more importantly, safer at the same time.

The second edition of this handbook takes this dualism into account by presenting clin-ical information on the background of current knowledge of photobiological principles. Besides the detailed description of photo- and photochemotherapy for selected skin dis-eases, this volume contains standardized test protocols for photodermatoses and the diag-nosis of skin tumours.

There exists a variety of phototherapeutic modalities, and clinicians can now select the therapy of choice. A specific disease can thus be treated with the regimen that fits best the particular situation of a given patient. Therefore, the major focus of this volume is on the use of different treatment modalities for a specific disease. The clinically oriented chap-ters are supplemented by practical guidelines for phototherapy that have proven success-ful over many years.

Again, the leading experts have contributed to this project. Most of the authors are not only experienced clinical photodermatologists but also internationally renowned experts in basic photobiological research.

We are very grateful to all authors for their excellent contributions to this second edi-tion. We hope that this monograph will continue to serve as the state-of-the-art reference for dermatological phototherapy and photodiagnostic methods in daily practice, clinical settings, and research.

J. Krutmann, H. Hönigsmann, C.A. Elmets Düsseldorf, Germany; Vienna, Austria; Birmingham, Alabama, USA

Autumn 2008

vii

One form of what was called heliotherapy 2000 years ago consisted of ingestion of an in-fusion (boiled extract) derived from a weed growing in the Nile Delta, Ammi majus L., fol-lowed by exposure to the Egyptian sun for the treatment of vitiligo, a disorder that was a serious disfigurement in this population with brown and black skin colored population. This crude treatment was the very earliest form of what is now called PUVA photochemo-therapy, a treatment for psoriasis, vitiligo, and 34 other diseases and that uses the same chemical, psoralen, derived from the same plant source, Ammi majus L., and followed by exposure to specially designed computerized UVA irradiators.

Phototherapy in the practice of dermatology was, in fact, not an efficacious and practi-cal therapeutic option until as late as the mid-1970s, when lighting engineers, photophys-icists, and dermatologists worked together to develop ultraviolet (UV) irradiators emit-ting high-intensity UVA. The UVA irradiators were designed to deliver uniform irradia-tion from fluorescent tubes lining a vertical cylinder in which the patient stands upright. The dose-delivery was computerized, and the doses were not designated in minutes but in joules (UVA) or in millijoules (UVB). The result was what has been termed photochemo-therapy, which is defined as the use of chemicals that are “activated” by exposure of the molecules to radiant energy. The first example of photochemotherapy was the oral inges-tion of a photoactive chemical, psoralen, followed by exposure to long-wave ultraviolet, UVA. The acronym PUVA was created and the modality represented the first use of light and drug together for a beneficial effect in humans.

The introduction of PUVA was the driving force in the mid-1970s that sparked a whole new series of discoveries during the next two decades, i.e., newly created high-inten-sity ultraviolet sources: UVA (320 – 400 nm) Sylvania of the USA and narrowband UVB (311 – 312 nm) Philips of Holland which has now replaced broadband UVB, as the first-line therapy for psoriasis, and more recently UVA-1 (340 – 400 nm). These new effec-tive therapies have been a boon particularly for patients with generalized psoriasis provid-ing efficacious ambulatory treatments but avoiding the systemic problems of methotrex-ate and cyclosporin.

The successful use of the new ultraviolet techniques for the treatment of disease was the “flywheel” for the development of a new sub-specialty called photomedicine, which encompasses all of the applications of the diagnosis and treatment of photoinduced dis-orders as well as the use of the new modalities such as photodynamic therapy for therapy of skin tumors and other diseases. There is now a Photomedicine Society and specialized journals of photodermatology.

We should be aware that the modern methods of phototherapy and photochemotherapy are part of a whole new discipline requiring special equipment and special knowledge of photophysics and photochemistry, and there are at present a limited number of photother-apy centers in the world. In a manner of speaking, present-day phototherapy is compara-

Foreword to the First Edition

ble to the use of X-radiation therapy in dermatology with special hardware, specific indi-cations, the selection of patients, and the need for careful and precise dosimetry.

The practicing dermatologist needs to be educated to correctly use these sophisticated techniques, which have been evolved by large (over 5,000 patients using prospective ran-domized clinical trials in the United States and Europe), beginning in 1974. Alas, in the last two decades, although there was a new impetus for phototherapy, there has not been enough specialized training in phototherapy. Therefore, this updated practical manual is welcome. In this impressive volume, the indications and methodology of these various light sources are presented by an excellent international cadre of dermatologists experi-enced in the use of these various modalities.

It is fitting that one of the editors is from Vienna because the Dermatology Department of the Vienna General Hospital was the second in the world to use PUVA in 1975. This de-tailed and up-to-date practical monograph is a “must” for any group doing phototherapy or contemplating a phototherapy unit. It is also a handy instruction manual for training per-sonnel (technicians and residents) in phototherapy.

Boston, USA, July 2000 Thomas B. Fitzpatrick †, M.D. Ph.D.

viii Foreword to the First Edition

ix

During the past 25 years, phototherapy has greatly influenced treatment concepts in der-matology. Consequently, photomedicine has developed from empiricism into one of the most exciting fields in biomedical research. Studies on the effects of visible and ultravio-let radiation on skin have led to a fruitful collaboration between basic scientists and clini-cians. Thus, phototherapy may be regarded as a prime example of applied skin biology.

UV radiation has been used for decades in the management of common skin diseases such as psoriasis and atopic dermatitis. More recently, the introduction of selective spec-tra in the UVB and UVA range such as narrowband UVB and UVA-1 phototherapy, as well as the inclusion of new indications, has much stimulated the interest in photoderma-tology. Visible light in combination with photosensitizers is currently in use for diagnosis and treatment of selected tumors. Extracorporeal photochemotherapy has proven to be ef-fective beyond dermatology, in particular, in transplantation medicine.

Most phototherapeutic regimens have been developed empirically and without knowl-edge about the biological mechanisms involved. Recent progress in the understanding of basic photobiological principles has made phototherapy more effective and, even more importantly, safer at the same time.

The present handbook takes this dualism into account by presenting clinical informa-tion on the background of current knowledge of photobiological principles. Besides the detailed description of photo- and photochemotherapy for selected skin diseases, this vol-ume contains standardized test protocols for photodermatoses and the diagnosis of skin tu-mors.

There exists a variety of phototherapeutic modalities, and clinicians can now select the therapy of choice. A specific disease can thus be treated with the regimen that fits best the particular situation of a given patient. Therefore, the major focus of this volume is on the use of different treatment modalities for a specific disease. The clinically oriented chap-ters are supplemented by practical guidelines for phototherapy that have proven success-ful over many years.

The leading experts have contributed to this project. Most of the authors are not only experienced clinical photodermatologists but also internationally renowned experts in basic photobiological research.

We are very grateful to all authors for their excellent contributions. We hope that this monograph will serve as a state-of-the-art reference for “Dermatological Phototherapy and Photodiagnostic Methods” in daily practice, clinical settings, and research.

Kitzbühel, Spring 2000 Jean Krutmann Herbert Hönigsmann Craig A. Elmets Paul R. Bergstresser

Preface to the First Edition

Part I Basic Mechanisms in Photo(chemo)therapy . . . . . . . . . . . . . . . . . . . . . 1

UV Radiation, Irradiation, and Dosimetry1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3L. Endres, R. Breit Revised by W. Jordan, W. Halbritter

Part II Photo(chemo)therapy in Daily Practice . . . . . . . . . . . . . . . . . . . . . . . . . 61

Mechanisms of Photo(chemo)therapy2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63J. Krutmann, A. Morita, C. A. Elmets

Photo(chemo)therapy for Psoriasis3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79H. Hönigsmann, A. Tanew, W. L. Morison

Photo(chemo)therapy for Atopic Dermatitis4 . . . . . . . . . . . . . . . . . . . . . . . . . . 103J. Krutmann, A. Morita

Phototherapy and Photochemotherapy 5 of the Idiopathic Photodermatoses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119A. Tanew, J. Ferguson

Photo(chemo)therapy for Cutaneous T-Cell Lymphoma6 . . . . . . . . . . . . . . . 135H. Hönigsmann, A. Tanew

Phototherapeutic Options for Vitiligo7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151B. Ortel, V. Petronic-Rosic, P. Calzavara-Pinton

Photo(chemo)therapy of Graft-versus-Host Disease (GvHD)8 . . . . . . . . . . 185B. Volc-Platzer

Phototherapy and Photochemotherapy: 9 Less Common Indications for Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205T. Schwarz, J. Hawk

Phototherapy and HIV Infection10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229H. McDonald, P. D. Cruz, Jr.

xi

Contents

Part III Special Phototherapeutic Modalities . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

Photodynamic Therapy in Dermatology11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241R-M. Szeimies, S. Karrer, C. Abels, M. Landthaler, C. A. Elmets

Extracorporeal Photoimmunochemotherapy12 . . . . . . . . . . . . . . . . . . . . . . . . . . 281R. Knobler

Ultraviolet A-1 Phototherapy: Indications and Mode of Action13 . . . . . . . . 295J. Krutmann, H. Stege, A. Morita

Part IV Photoprotection in Daily Practice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311

Acute and Chronic Photodamage 14 from Phototherapy, Photochemotherapy, and Solar Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313B. H. Mahmoud, I. H. Hamzavi, H. W. Lim

Photoprotection15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333P. Wolf, A. Young

Part V Photodiagnostic Procedures in Daily Practice . . . . . . . . . . . . . . . . . . . 365

Photodiagnostic Modalities16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367N. J. Neumann, P. Lehmann

The Photopatch Test17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377E. Hölzle

Fluorescence Diagnosis in Dermatology18 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387C. Fritsch, K. Gardlo, T. Ruzicka

Practical Guidelines for Broadband UVB, Narrowband UVB, UVA-1 19 Phototherapy, and PUVA Photochemotherapy—A Proposal . . . . . . . . . . . 415H. Hönigsmann, J. Krutmann

Technical Equipment20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427R. Mang, H. Stege

Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433

xii Contents

Christoph AbelsMedizinisch-wissenschaftliche AbteilungDr. August Wolff GmbH & Co. ArzneimittelSudbrackstraße 5633611 BielefeldGermanyEmail: [email protected]

Reinhard BreitTheodor-Körner-Straße 682049 PullachGermanyEmail: [email protected]

Piergiacomo Calzavara-PintonChief of the Department of DermatologyAzienda Spedali Civili di BresciaBresciaItalyEmail: [email protected]

Ponciano D. Cruz, Jr.Department of DermatologyUniversity of Texas Southwestern Medical Center5323 Harry Hines Blvd.Dallas, 75390-9069 TXUSAEmail: [email protected]

Craig A. ElmetsUniversity of AlabamaDepartment of DermatologySDB 67Birmingham, 35294-0007 ALUSAEmail: [email protected]

James FergusonHead of Photobiology Unit, Department of DermatologyNinewells Hospital & Medical SchoolDundee, DD1 9SY, ScotlandUKEmail: [email protected]

Clemens FritschBankstraße 640476 DüsseldorfGermanyE-mail: [email protected]

Kerstin GardloHauptstraße 10853474 Bad Neuenahr-AhrweilerGermanyEmail: [email protected]

xiii

List of ContributorsContributors

Werner HalbritterOSRAM GmbHCentral Laboratory for Light Measurements (QM CL-M)Hellabrunner Straße 181543 MünchenGermanyEmail: [email protected]

Iltefat H. HamzaviSenior Staff Physician, Multicultural DermatologyDepartment of DermatologyHenry Ford Medical CenterNew Center One3031 West Grand Boulevard, Suite 800Detroit, 48202 MIUSAEmail: [email protected]

John HawkDepartment of PhotobiologySt. Thomas HospitalLondon SE1 7EHUKEmail: [email protected]

Erhard HölzleStädtische KlinikenKlinik für Dermatologie und AllergolgieDr.-Eden-Straße 1026133 OldenburgGermanyEmail: [email protected]

Herbert HönigsmannUniversitätsklinikum WienDermatologische KlinikAbt. Spezielle DermatologieWähringer Gürtel 18–201090 WienAustriaE-mail: [email protected]

Werner Jordan OSRAM GmbHCentral Laboratory for Light Measurements, (I OSR QM CL-M)Hellabrunnerstraße 181543 MunichGermanyEmail: [email protected]

Sigrid KarrerDepartment of DermatologyUniversity of RegensburgFranz-Josef-Strauss-Allee 1193053 RegensburgGermanyEmail: [email protected]

Robert KnoblerDepartment of DermatologyDivision of Special and Environmental DermatologyUniversity of Vienna Medical SchoolVienna General Hospital – AKHWaehringer Gürtel 18–201090 ViennaAustriaEmail: [email protected]

Jean KrutmannUniversität DüsseldorfInstitut für Umweltmedizinische Forschung (IUF) gGmbHAuf´m Hennekamp 5040225 Düsseldorf GermanyEmail: [email protected]

Michael LandthalerHead of Department of DermatologyUniversity of RegensburgFranz-Josef-Strauss-Allee 1193053 RegensburgGermanyEmail: michael.landthaler@ klinik.uni-regensburg.de

xiv Contributors

Percy LehmannKlinikum Wuppertal GmbHHautklinikArrenberger Straße 2042117 WuppertalGermanyE-mail: [email protected]

Henry W. LimDepartment of DermatologyHenry Ford Medical CenterNew Center One3031 West Grand Blvd., Suite 800Detroit, 48230 MIUSAEmail: [email protected]

Bassel H. MahmoudPost-doctoral Research FellowDepartment of DermatologyHenry Ford Medical CenterNew Center One3031 West Grand Boulevard, Suite 800Detroit, 48202 MIUSAE-mail: [email protected]

Renz MangGemeinschaftspraxis für Dermatologie, Venerologie, Allergologie, ProktologieHauptstraße 3642349 WuppertalGermanyEmail: [email protected]

Hallie McDonaldDept. of DermatologyUniversity of Texas Southwestern Medical Center5323 Harry Hines Blvd.Dallas, 75390-9069 TXUSAEmail: [email protected]

Warwick L. MorisonJohns Hopkins at Green Spring10753 Falls Road, Suite 355Lutherville, 21093 MDUSAEmail: [email protected]

Akimichi MoritaDepartment of Geriatric and Environmental DermatologyNagoya City University Graduate School of Medical SciencesNagoya 467-8601JapanEmail: [email protected]

Norbert J. NeumannUniversitäts-Hautklinik Moorenstraße 540225 DüsseldorfGermanyEmail: [email protected]

Bernhard OrtelSection of DermatologyUniversity of Chicago 5841 S. Maryland, MC 5067Chicago, 60637-1470 ILUSAEmail: [email protected]

Vesna Petronic-RosicPDP Director, Section of DermatologyUniversity of Chicago5841 S Maryland, MC-5067Chicago, 60637-1470 ILUSAEmail: [email protected]

Contributors xv

Thomas RuzickaUniversitäts-Hautklinik Postfach 10 10 0740001 DüsseldorfGermanyEmail: [email protected]

Thomas SchwarzHead of Department of Dermatology, Venerology and AllergologyUniversity Hospital of the Christian Albrechts University KielSchittenhelmstraße 7 24105 Kiel GermanyEmail: [email protected]

Helger StegeChefarzt der DermatologieKlinikum Lippe-LemgoRintelner Straße 8532657 LemgoGermanyEmail: helger.stege@klinikum–lippe.de

Rolf-Markus SzeimiesDepartment of DermatologyUniversity of RegensburgFranz-Josef-Strauß-Allee 1193053 RegensburgGermanyEmail: rolf-markus.szeimies@ klinik.uni-regensburg.de

Adrian TanewDivision of Special & Environmental DermatologyDepartment of DermatologyMedical University of Vienna 1090 ViennaAustria Email: [email protected]

Beatrix Volc-PlatzerDepartment of DermatologyDonauspital/SMZ OstLangobardenstrasse 1221220 ViennaAustriaEmail: [email protected]

Peter WolfResearch Unit for PhotodermatologyDepartment of DermatologyMedical University GrazAuenbruggerplatz 88036 GrazAustriaEmail: [email protected]

Antony YoungPhotobiology Department St. Johns Institute of DermatologyGuy’s King/St. Thomas HospitalLondon SE1 7EHUKEmail: [email protected]

xvi Contributors

Basic Mechanisms in Photo(chemo)therapy

Part I

3

Contents

Concerning the Nature of Optical Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Characterization of Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Spectral Composition of Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Quantitative Features of Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Distinctive Features of UV Radiators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Influences That Can Change the Radiation of a Lamp . . . . . . . . . . . . . . . . . . . . . . . 40Daylight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46Dosimetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Core Messages

› Basic principles on the behavior of light and radiation› Important properties of light and UV radiation with respect to photobiology› Definitions and explanations of quantities used in dosimetry› Technical properties of radiators and lamps› Basic principles of spectroradiometric instruments and presentation of spectrally

resolved data

Werner Jordan, Dr. rer. nat. ()OSRAM GmbH, Central Laboratory for Light Measurements, (I OSR QM CL-M),Hellabrunnerstraße 1, 81543 Munich, [email protected]

Jean Krutmann et al. (Eds.), Dermatological Phototherapy and Photodiagnostic MethodsDOI: 10.1007/978-3-540-36693-5, © Springer 2009

1UV Radiation, Irradiation, and Dosimetry

L. Endres*, R. Breit Revised by W. Jordan, W. Halbritter

*This article is dedicated with regard, respect, and gratefulness to Mr. Ludwig Endres, who passed away in January 2008.

1Concerning the Nature of Optical Radiation

The existence of invisible rays in sunlight was not known until the beginning of the nine-teenth century. First, in 1800, by studying the rainbow-colored solar spectrum adjoining to the red side, Friedrich Wilhelm Herschel was able to detect invisible rays generating heat when they impinged on absorbent surfaces. Shortly thereafter, in 1802, Johann Wilhelm Ritter likewise discovered radiation at the other end of the visible spectrum, beyond the vi-olet, that was capable of initiating “intense chemical effects.”

By reason of the detection processes and the geometric positions within the spectrum, it was accordingly an obvious idea to designate these two newly discovered radiation ranges as infrared and ultraviolet radiation respectively. (With regard to wavelengths, it would have been correct to refer to ultra red and infra violet.)

But there were not yet any clear concepts concerning the nature of those kinds of radi-ation, their propagation, or in particular the manner in which light is able to generate ef-fects [16, 20]. Certainly there were various theories, the best known of these being the em-anation theory of Isaac Newton, dating back to the year 1669, and the undulatory theory of Christiaan Huygens, dating back to the year 1677. Newton, in his theory, postulated that light consists of small particles that, when absorbed in material, were capable of generat-ing the known effects. In contrast, Huygens took the view that light was a wave that, just like a water wave, required a medium for its propagation. He named this medium the op-tical ether, which was omnipresent in his opinion but was not detectable with the means available to him.

Each one of these theories was able to offer conclusive explanations for specified phe-nomena—Newton’s for the radiation effects, Huygens’s for the interference phenomena—but neither was capable of offering an all-inclusive solution.

It is therefore understandable that these contradictory matters led to many discussions and attempts to set up a theory of light that was valid for all types of phenomena. How-ever, for almost two centuries, there were no further noteworthy findings in this matter.

A decisive advance took place in 1871, when James Maxwell propounded an electro-magnetic theory of light that inspired Heinrich Hertz to the experiments that led to the dis-covery of electrical oscillations (1888). These results furnished the proof that any electro-magnetic radiation, including the complete optical radiation (light and UV and IR radia-tion), propagates in the manner of waves and does not need any medium for this purpose. He found that all electromagnetic waves, independent of wavelength or frequency, prop-agate in a vacuum with the velocity of light, which was already known at that time. How-ever, attempts to explain the generation and absorption of these waves continued to be un-satisfactory.

The processes implemented in this connection were not established until the beginning of the past century: In 1900, Max Planck published the radiation laws in which light is considered not as a steady process, but as a discontinuous sequence of small energy states that cannot be further divided. In 1902, in the course of investigations of the photoelectric effect, Philipp Lenard discovered particular properties of light that led him to formulate an optical quantum hypothesis. And in 1905, Albert Einstein was able to show that the exper-imental results of Lenard may be fully explained by the quantum theory of Planck.

4 L. Endres, R. Breit

Thus, starting at this time, two theories standing side by side were necessary to provide a complete description of the behavior of electromagnetic waves. With regard to all ques-tions concerned with the creation, absorption, and effect of radiation, whether it be the vi-sual process, the perception of heat, or the reactions to ultraviolet radiation, it was neces-sary to apply the laws of quantum theory, while the processes involved in the propagation of electromagnetic radiation and its behavior in optical systems could be described only by the wave theory.

Not until the second half of our century did new findings of quantum physics provide a connection between these two theories, which, in a mathematical presentation, form ini-tial principles appertaining to a generally valid theory of radiation [16]. Nevertheless, as so frequently occurs in modern physics, even when applying this model, all attempts for explanation go beyond the conceptual power of non-specialists for whom—although it is omnipresent—the manifestation of light continues even nowadays to be a mysterious pro-cess.

Characterization of Radiation

In spite of the very complicated interrelationships that underlie the various manifestations of electromagnetic waves, for the purpose of many technical applications, their behavior can be described with sufficient accuracy by just a few formulae [12, 16, 20]. These con-cern, on the one hand, features such as wavelength, frequency, photon energy, and spectral composition of a mixed radiation, while in the second main group, statements are made that are concerned with the quantitative recording of the transferred radiation intensity and its spatial distribution.

Features of a Wave

Wavelength and Frequency

Electromagnetic radiation propagates in an undulatory form within a wide range of differ-ing shapes. But mathematics (Fourier analysis) proves to us that any possible shape can be built up from a number of sinusoidal curves [16]. So, for understanding the points treated in this chapter, it is sufficient to consider only the properties of a simple sinusoidal wave.

Figure 1.1 shows how a sinusoidal wave can be created. A rotating arrow describes a circle around a central point. By transferring several positions of the arrowhead within a full turn to an axis divided into rotation angles, a graph with a sinusoidal shape can be formed. In this way, the length of the arrow corresponds to the maximum amplitude of the wave. The distance between the points at the beginning and the end of a full revolution is called one period or cycle of the wave.

If the arrow is rotating with constant velocity, one can transfer the points of the arrow-head to a time axis in the same manner. The higher the speed, the more cycles there will be within a given time section (Fig. 1.2a). By knowing at least the propagation velocity of a

1 UV Radiation, Irradiation, and Dosimetry 5

1

wave, one can transform the ordinate axis to length segmentation (Fig. 1.2b). With the ex-amples of Fig. 1.2, we are now able to deduce the basic characterizing quantities of a si-nusoidal wave:

Frequency means cycles per second (cps); in Fig. 1.2a, frequencies of 2, 4, and 8 cps • have been plotted. Wavelength denotes the distance between the beginning and the end of a period. In Fig. • 1.2b, wavelengths of 0.5, 0.25, and 0.125 m have been plotted.

Fig. 1.1 Construction of a sinusoidal wave

Fig. 1.2a,b Frequency and wavelength of a sinusoidal wave a on a time scale and b on a distance scale


• Propagation velocity is defined by the distance that covers an optional point (P) in a specified time period; the dimension is m/s. (In Fig. 1.2, the propagation velocity of all three waves is 1 m/s.)

These quantities are associated with each other:

frequency ν(/s) = propagation velocity v(m/s)wavelenght λ(m)

ν = vλ

(1.1)

wavelength λ(m) = propagation velocity v(m/s)frequency ν(/s)

λ = vν

(1.2)

propagation velocity v(m/s) = wavelength λ(m) � frequency ν(/s) v = λ � ν propagation velocity v(m/s) = wavelength λ(m) � frequency ν(/s) v = λ � ν (1.3)

These equations are valid for all types of electromagnetic waves, independent of fre-quency, wavelength, and intensity [11, 12, 16, 20, 22].

Optical radiation has shorter wavelengths and higher frequencies, as in the examples shown above. In order to avoid inconveniently large or small numbers, derived units are frequently used for the numerical characterization of electromagnetic waves. It is con-ventional to denote the wavelengths of light, UV, and IR radiation in one of the follow-ing units:

1 angstrom (Å) = 1 × 10• −10 m1 nanometer (nm) = 1 × 10• −9 m1 micrometer (• µ) = 1 × 10−6 m

In characterizing frequencies, it is common practice to use the following units (cps means cycles per second):

1 kilohertz (kHz) = 1 × 10• 3 cps1 megahertz (MHz) = 1 × 10• 6 cps1 gigahertz (GHz) = 1 × 10• 9 cps

Propagation Velocity

Any electromagnetic radiation energy propagates in the vacuum with the “velocity of light.”

velocity of light c = 299,792.458 km/s (exact definition) (1.4)

The emphasis is on the word “vacuum.” In all other cases, if radiation enters a medium, the propagation velocity is reduced in accordance with the refractive index n of the perti-nent substance. (For examples of velocities in different media, see Table 1.1.)


1

Normally, this fact is without any influence for common measurement practice. The propagation velocity in earth’s atmosphere differs so little from that in vacuum that the difference is negligible in the vast majority of cases of laboratory work.

Equation 1.3, which states that the propagation velocity equals the product of frequency and wavelength, is also valid for radiation passing through a medium. At a reduced veloc-ity, therefore, either the frequency or the wavelength must vary. Physics tells us [16] that the frequency remains constant in all media, and that the wavelength becomes shorter in proportion to the reduced velocity. Hence, it should be more evident to characterize a radi-ation by its frequency. Nevertheless, within the optical spectral range, the characterization of radiation by stating the wavelength (in a vacuum) has become established, while within the range of the longer waves, for instance radio waves, stating the frequency of radiation is in most cases customary.

Table 1.1 Velocity of light

Medium Refractive index Symbol Velocity Percent of c

Vacuum n = 1 c = 299,792 km/s

Air n = 1.0003 cair = 299,690 km/s 99.9%

Water n = 1.33 cwater = 225,410 km/s 75.2%

Quartz glass n = 1.46 cquartzglass = 205,337 km/s 68.5%

The different velocities given here refer to visible radiation with a wavelength of 500 nm.

Fig. 1.3 Beam model of optical radiation


Energy of an Electromagnetic Wave

A single beam of optical radiation can be imagined—very simplified—as an arrow in space (mathematically, as a vector; see Fig. 1.3, gray straight line) with electric (E, red line) and magnetic (B, green line) sinusoidal wave components [16]. Based on electrodynamics theory, this vector (the so-called Poynting vector S) represents the flux of energy density of an electromagnetic wave in space. In terms of physics nota-tion, it is written as a vector equation:

�S = εc �E � �B (ε = electric constant) (1.5)

The dimension of S (J/m² s) represents the energy density of a beam passing through an ar-bitrary surface within a time interval and results in the well-known term of irradiance Ee (W/m²) in laboratory practice when incident on a detector surface (for common units, see also Table 1.3):

��S� = εc EB = εc E (W/m) (1.6)

Note: All the other models we use to explain the behavior of radiation (Gaussian optics, straight-lined propagation of radiation) and many other “macroscopic”-based calculations are mainly founded on the wave nature of optical radiation.

Photon Energy

Electromagnetic waves transport energy. In the particle view of radiation (quantum me-chanics), the porters of the energy are photons. According to the Einstein relation, the en-ergy E of a photon has a fixed relationship to its frequency ν [16, 20]:

Ephoton = h × ν (h = 6.626 × 10−34 J s, Planck constant) (1.7)

Related to wavelength in a vacuum, equation (1.7) may also be written as:

Ephoton = hν =hcλ

(1.8)

Another common unit for the energy of radiation is the so-called electron volt (eV); 1 eV corresponds to the kinetic energy acquired by an electron passing through a potential dif-ference of 1 V in a vacuum. Since 1 watt second (W s) = 1 joule (J) = 0.624 × 1019 electron volt (eV), it is also possible to write:

Ephoton (eV) =, ( eV

nm)

number of wavelength (1.9)

As can be easily seen from this relationship, photon energy (energy of electromagnetic ra-diation) increases as wavelength decreases. Therefore, UV radiation has a greater energy content than visible light (Ephoton, 250 nm = 4.96 eV > Ephoton, 550 nm = 2.25 eV).


1 Classification of Electromagnetic Waves

The wavelengths of the electromagnetic spectrum cover the enormous range of roughly 10−16 m to 107 m. Accordingly, the whole spectral range is subdivided into various divisions based on the nature of the generation of the radiation [11]. Table 1.2 shows only a coarse classification on this basis.

Thus, within the regions of overlap, X-ray radiation can be generated using both X-ray tubes and the processes of generation of ultraviolet radiation, or electric waves can be gen-erated using oscillator circuits and by thermal processes.

According to international standardization [11], infrared, visible, and ultraviolet radia-tion form the range of optical radiation. These wavelength ranges are classified even more finely with regard to their chemical and physical effects.

Infrared Radiation

Long-Wavelength Infrared—IR-C (3 µ–1 mm) This spectral range denotes a low-en-ergy radiation with little biological significance.

Medium-Wavelength Infrared—IR-B (1,400 nm–3 µ) This is the main emission range of heated glasses (lamp bulbs). IR-B is not perceived as heat by humans, since it is already absorbed in the outermost layer of the skin. Staying under intense IR-B radiation is per-ceived as an unpleasant feeling, since no regulation of the body temperature takes place.

Short-Wavelength Infrared—IR-A (780–1,400 nm) This represents the main emission range of the thermal radiation of the sun. The radiation penetrates deeply into the skin and, within broad limits, is perceived as pleasant. The range 780 nm–1,400 nm is also referred to as the therapeutic thermal octave.

Table 1.2 Coarse overview of the electromagnetic spectrum

Designation Wavelength Frequency Generation

Electric waves 107–10−3 m 101–1011 Hz Oscillator circuits

Infrared radiation 10−3–8 × 10−7 m 1011–4 × 1014 Hz Thermal radiators

Visible radiation 8 × 10−7–4 × 10−7 m 4 × 1014–8 × 1014 Hz Thermal excitation, electron transition

Ultraviolet radiation 4 × 10−7–1 × 10−7 m 8 × 1014–3 × 1015 Hz Electron transition

X-ray radiation 5 × 10−8–1 × 10−13 m 6 × 1015–3 × 1021 Hz Electron transition (inner atomic orbits)

Nuclear radiation 1 × 10−13–1 × 10−16 m 3 × 1021–3 × 1024 Hz Nuclear reaction

Hertz (Hz) is an official SI unit and denotes a periodic oscillation per second (1 Hz = s−1)


Visible Radiation—Light

The main distinctive feature of visible radiation is the visual stimulus and the color im-pression generated by the individual wavelength ranges in the human eye. The sensitivity of the eye to different colors differs in magnitude. The eye is most sensitive to shades of green and least sensitive to violet and red colors. Since the eye’s sensitivity has quite es-sential significance with regard to the economy of light sources, a standard eye response in regard to brightness sensitivity was determined on the basis of experimental investiga-tions. This sensitivity progression is incorporated into international standardization as the spectral luminosity factor, or V (λ) curve [6].

In the psychological area as well, the wavelength—and thus the color—can be rele-vant. Bluish colors are intended to increase activity, while reddish color shades are in-tended to have a calming and relaxing effect.

Although color impressions merge continuously into each other as the wavelength in-creases, it is nevertheless possible to stipulate approximate limits for the individual color ranges:1

Ultraviolet Radiation

Long-Wavelength UV Radiation—UV-A1 (340–380 nm) This is a definite component of all natural and artificial, unfiltered light and UV sources and is not absorbed by un-stained types of glass. This part of UV radiation has the lowest energy properties, and con-cerning its chemical effectiveness, it can be combined with the short-wavelength visible radiation (up to 440 nm) because of its photobiological effects, especially in safety consid-eration with regard to the eye (blue light hazard) [7].

1 In international literature, the boundaries are frequently defined differently: UV-A1 340 nm–400 nm; UV-A2 320 nm–340 nm; UV-B 280 nm–320 nm.

Table 1.3 Color description and the corresponding wavelength range

Common color description Wavelength range

Violet 380–420 nm

Blue 421–495 nm

Green 496–566 nm

Yellow 567–589 nm

Orange 590–627 nm

Red 628–780 nm


1 Long-Wavelength UV Radiation—UV-A2 (315–340 nm) This denotes the transitional range between UV-A and UV-B, in which effects of both spectral ranges can be found.

Medium-Wavelength UV Radiation—UV-B (280–315 nm) This was defined in accor-dance with the erythema action curve for human skin on the basis of the fundamental in-vestigations made by Karl Wilhelm Haußer and Wilhelm Vahle.

Short-Wavelength UV Radiation—UV-C (100–280 nm) This represents the short-est wavelength and thus the highest energy part of UV radiation. In physical definition, UV extends to 15 nm and thus directly adjoins X-ray radiation. But the short-wavelength boundary of UV radiation of the optical range was stipulated as 100 nm in order to avoid conflicts with radiation protection regulations. Between 100 and 200 nm air absorbs UV radiation. Thus, radiation of this wavelength range (also designated as vacuum-UV) can-not occur in air [16, 20, 22].

Spectral Composition of Radiation

Only in exceptional cases, e.g., in the case of lasers, does optical radiation consist of radi-ation that can be described by one single wavelength. Normally, a mixture of many wave-lengths of different intensities is emitted. The spectral composition of radiation determines its effects; therefore, to evaluate the efficacy of radiation, it is necessarily to know the por-tions of the power emitted in the various wavelength domains. The representation of a wavelength-related composition of a mixture of radiation is designated as spectrum, or, if listed in a numerical manner, as spectral power distribution (SPD).2

Spectroscopic Instruments

Investigations and analysis of such mixtures of optical radiation are performed with spec-trometers or spectrographs [14]. A principle construction is shown in Figs. 1.4 and 1.6.

Functionally, one can subdivide these instruments into the following components:

Entrance Area The radiation to be analyzed is collected at the aperture of the spectrom-eter, generally shaped as a slit.

2 Spectral power distributions can be analyzed with spectroscopic equipment (physical methods) only. The eye can perceive only one impression at one place of the retina. Of course, this im-pression primarily depends on the spectral distribution of the light, but it allows no conclusion to the structure of the spectrum. Different spectral power distributions can cause identical im-pressions called metameric color stimuli.


Imaging Optics Concave mirrors transform the divergent incident beam coming from the entrance slit to a parallel incidence. After passing the dispersing elements, they retrans-form them into a convergent bundle, focused in the exit plane of the spectrometer.

Dispersing Elements (Either a Prism or Gratings) Prisms refract the radiation, depend-ing on the wavelength, into different angles. This basic principle may be represented in a simple manner. If a prism is held in sunlight and a piece of paper is placed behind the exit surface, one can see the well-known colors of the rainbow appearing on the paper (see Fig. 1.5). Accordingly, the rainbow is the spectrum of sunlight, but the eye cannot separate the spectral composition of sunlight. The visual process only states the impression “white”.

Gratings reflect the radiation into different directions (optical diffraction). Generally, the shorter the wavelength, the greater the direction is changed. Blue is deflected more greatly than red, and ultraviolet radiation is deflected more greatly than visible.

Exit Area The exit area is defined by a virtual plane on which the spectral dispersed ra-diation is focused.

Fig. 1.4 Principle of spectral dispersion

Fig. 1.5 Spectral refraction seen with a prism


1

To record the intensities of radiation in this area, three main procedures of mounting de-tectors are in use.

Photographic Detector After exposing and developing a photographic material, one can find a very fine structured picture of the spectrum. The blackening of the photographic layer is typically for the spectral intensity at this point. A quantitative interpretation takes pains, because the blackening of the material is not linear with respect to intensity.

Narrow (Exit) Slit with a Single Detector Turning the dispersing element in tempo-ral sequences, the whole spectrum will move through the slit and can be recorded step by step, but a lot of time is necessary to carry out these sequential measurements. Addition-ally, rotating prisms or gratings necessitate high precision of the mechanical construction and stability, which can be very costly.

Pixel Detectors Arranged as an array, pixel detectors are closely packed on a disk and placed directly in the image plane of the spectrum so that each pixel position is assigned to a definite wavelength range. The response (exposure) time with such an arrangement is within a tenth of a second. By evaluating the distribution with electronic equipment, it is possible to perform measurements on spectral power distributions in a very short time.The width of the exit slit and respectively the dimensions of the detector are the limiting factors of spectral resolution. The narrower the slit, or the more packed the pixel detec-tor, the smaller is the selected range and the higher is the spectral resolution that can be achieved. It is primarily limited by the signal intensities picked up, which become pro-gressively weaker the smaller the wavelength area has been sized. In practice, therefore, it is recommended to stay with a resolution that is necessary for the respective application

Fig. 1.6 Principle of the optical path in a prism monochromator


or task to be done. In most cases, it is sufficient to record a value every 5 nm in the visible range, while in the ultraviolet range, the spectrum must be recorded at least in 1 nm steps to guarantee a sufficiently precise allocation of the spectral radiation intensities.

Representation of Spectral Power Distributions

Spectral power distributions can be represented in the form of a table or as a diagram. The intensity of the spectral dispersed radiation is plotted against wavelength (or frequency). The unit of spectral radiation conforms to the unit of the radiation entering the spectral equipment supplemented with the unit of wavelength, which for the UV region usually is the nanometer [12]. For example, measuring irradiance, the unit is W/m²; the correspond-ing spectral unit is then W/(m² nm), according to the wavelength to be characterized.3

In Fig. 1.7, three graphic possibilities are shown of how to plot spectral power distribu-tions. For this purpose and for comparison, a radiation source is selected that emits a radi-ation power of 100 W in the wavelength range from 295 to 405 nm and that has been mea-sured in steps of 10 nm.

3 In some diagrams, the spectral unit is W/m³. This is based on mathematics: one can combine m² and nanometer (10−9m), resulting in 10−9m³.

Fig. 1.7a–c Presenting spectral power distributions: a lines, b continuous, and c staircase


1 In the first example (Fig. 1.7a), the intensities measured are plotted as lines drawn in the center of the wavelength range (the line at 300 nm encloses the range from 295 to 305 nm).The ordinate unit is W, supplemented with the index “in a range of 10 nm”.

If one can be sure the measured spectrum is continuous, one can connect the top of the lines to form a curve (Fig. 1.7b). The characterization of the ordinate now is spec-tral power with the unit W/nm. Note that the numerical values are 10 times lower than in Fig. 1.7a.

If we intend to plot the spectrum by hand, it is more favorable to draw the distribution in the shape of a staircase (Fig. 1.7c).

In Fig. 1.7b, one can seen a so-called continuous spectrum, which is characterized by the fact that radiation is emitted in the whole wavelength range. If we are analyzing a con-tinuum, the shape of the distribution stays nearly the same, independent from the spectral solution chosen. But especially if we are dealing with low pressure discharge lamps, we will find spectral power distributions with emission located in a few definite wavelength regions while the neighborhood is free of any emission. Figure 1.8 shows a line spectrum, which was recorded with different spectral resolutions.

You can see that the lower the spectral resolution, the broader the shape of the line con-tour becomes. Through evaluating the line intensity, you will find the same result, inde-pendent of resolution, but the deceptive shift from parts of the line intensity to adjoining wavelength can lead to errors if one calculates the efficiency according to actinic effects of radiation. For this reason, it is recommended never to specify a spectrum within smaller wavelength steps than the spectral resolution of the spectral instrument.

In practice, there are continuous spectra, line spectra, and spectra exhibiting both of these characteristics [1, 3, 8] (see Fig. 1.9).

Fig. 1.8 Records of the line spectrum (mercury line at 253.7 nm) with spectral resolution of 10 nm, 1 nm, and 0.1 nm


The spectral distributions of sunlight and of incandescent lamps are typical representa-tives of spectral radiation distributions that have no gaps, i.e., irrespective of how narrow the slit is, radiation intensity can be detected at any wavelength setting. Such spectra are designated as continuous (Fig. 1.9a). This behavior is typical for sources generating their emission through high temperature excitation.

If, however, as in the case of sodium and mercury lamps, gases or vapors are excited to emit, then a spectral power distribution is found in which at preferred wavelengths, radi-ation of very high intensity occurs, while in the neighboring areas, virtually no emission can be detected. Accordingly, such spectra are designated as line spectra (Fig. 1.9b).

From the majority of artificial radiation sources emerges an SPD that represents a mix-ture of continuous and line distribution. The reason for this is that modern light manufac-turers have been making increasing use of several physical processes for radiation genera-tion. For example, in the case of fluorescent lamps, the fundamental discharge of the mer-cury gives a line spectrum that is distributed over the UV and visible range. The visible lines contribute to light directly, while the ultraviolet lines excite a mixture of luminescent material to fluorescence applied to the internal surface of the bulb. The SPD of the phos-phors is approximately continuous and superposes the line spectrum. This type of distribu-tion is designated as a mixed spectrum (Fig. 1.9c).

Fig 1.9a–c Continuous spectrum (a), line spectrum (b), and mixed spectrum (c)


1 The real quality of a spectrum is of great interest for physicists and chemists. From this, fundamental information about the structure and/or the elements of a radiator can be ob-tained. In the case of continuous radiating sources, the type of distribution gives an indi-cation of the temperature of the radiator (see Thermal Radiators); in the case of line and mixed spectra, the position of the lines and the form of the continuum give indications of the components that are excited for emission in a source (spectral analysis).

If the primary interest is with the effectiveness of specific radiation, the presentation of an SPD like a staircase, showing the intensity within definite wavelength ranges, is suffi-cient and can be well handled.

Spectral radiation distributions are of great importance for all investigations that are concerned with arithmetic determination of irradiation effects [19]. To this end, there is a need not only for the emission spectrum of the radiation source (absolute values for the wavelength intervals chosen) but also for an action spectrum that defines the spectral sen-sitivity within the individual wavelength ranges. Action spectra are known from many ef-fects and have in some cases also been published in national and international standards. Examples of frequently used action spectra are, within the visible range, the luminos-ity factor of the eye and the spectral value curves for color computation or, in the photo-biological sector, the activity spectra of erythema, pigmentation, or destruction of bacte-ria [12].

Actinic effective radiation is calculated by multiplying the intensity value of each wavelength interval (SPD) with the associated value of the action curve, and—for practi-cal purposes—these arithmetic products are summed rather than integrated. The result is one number that is typical for the efficiency of the radiation mixture under investigation and for this actinic effect [12]:

SPDeffective actinic radiation = �λSPDλ � sλ , action curve � ∆λ (1.10)

Actinic Radiometers

Radiometric measurements concerning actinic radiation are costly and time consuming. In particular, field measurements or measurements for controlling working places are not yet practicable with monochromator systems. Therefore, in the last 10 years, handheld actinic radiometers, like illuminance meters, have been developed. Such a radiometer normally consists of a detector head and a combined signal processing and display unit. The detec-tor head is adjusted to the respective action spectrum by use of appropriate optical filter-ing. But this adaptation to an action spectrum is also the main source of error in measure-ments with such a system, because the spectral sensitivity is often very bad compared to the ideal action curve. Therefore, only when spectral distributions of the radiation mea-sured are similar to the source used for calibration is there a good agreement with spec-trally resolved radiation analysis. Measurements done concerning different spectral power distributions reveal that systematic errors up to a factor of two or three can be stated, con-trary to the simple use of actinic radiometers. In order to rank measurements done with these systems and to help the user with some guidance, a standardization attempt is made concerning the properties and the features of actinic radiometers [13].


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