Increase of surface dose using wound dressings during percutaneous radiotherapy with photons and electrons

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Radiotherapy and Oncology 40 (1996) 181-184

Short communication

Increaseof surface dose using wound dressingsduring percutaneous radiotherapy with photons and electrons C. Thilmann*, I.A. Adamietz, S. Mose, F. Saran, U. Ramm, H.D. B6ttcher Lkpartment of Radiotherapy and Oncology, J. W. Goethe-Universikit, 60590 Frankurt, Germany Received 19 Ikeember 1995;revised 19 April 1996,accepted 13 May 1996

Different wound dressingsare used for the supportive treatment of patients with radiation-induced skin lesions. Depending on beam quality and energy, an increase of the dose administcrcd to the skin and thus an aggravated skin reaction is to be expected irradiation. The increaseof the skin doseduring irradiation with photons(Co60,6MV, 42 MV) andelectrons during percutaneous (7 MeV, 20 MeV, 42 MeV) was deal usingthermoluminescence dosimetry.Theuseof wounddressingsduring electronirradi-

ation and during soft irradiation therapydoesnot significantlyincreasethe doseadmiuisteredto the skin and doesnot therefore causeany problems.During irradiation with high energyphotonsonly extremelythin dressingsshouldbe used,if thereis an aggravatedskin reaction,the dressingshould be taken off beforeirradiation commences. Keywords:Dosimetry;Skin dose;Wound dressing

1. Imtmhth

A fractionated percutaneous radiotherapy can often lead to the development of radiation-induced acute skin lesions. Highly damagedskin requires a mechanical surface protection. This is particularly true with threatening or present epitheliolyses. For this application several wound draings have been tested. Thus, the simple application and cfliciency of non-adhesive siliconccoatedwound dressingsusedfor the trca-t of acute radiation-inducedskin ksions could be shown in a pro-

increase of the dose in the depth of the stratum basale dependson the thickness of the wound dressing used, on the beamqualityand beam energy [3]. Data is not yet available. It is therefore not known whether, and if so, in which casea wound dressing can be left on the skin during irradiation. This study was aimed at quantifying the increase of the dose on the skin through different wound dressings during irradiation for different beam qualities and beam energies.

2. Methods

spectivestudy [l]. An algina& wound dressing is particularly suited for heavily oozing cpithclioly8es, whereasfor the preventionof moist cpitheliolyscsa aclfadhesive hydrocolloid dressing is used. The applied radiation dose to the stratum germinativum is important for the radiation-induce+ acute skin lesions [2,6]. If a wound dressing is left on the skin during irradiation it is expected that this dose increases due to the dose build-up effect. The extent of the l

Corresponding author.

The increaseddose administered to the skin during irradiation was determined using a silicone-coated wound dressing made of polyamide, a silkacetate dressing, a self-adhesive hydrocolloid dressing and an alginate wound dressing (Table 1). During irradiation with %oq radiation, 6 MV photons and 42 MV photons as well as 7 MeV, 20 MeV and 40 MeV electrons were measured with or without wound dressing. Dosimetry was carried out using a thermoluminescent dosimeter (TLD) from lithium fluoride with a sensitive 90 w thick

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C. Thilmann et al. /Radiotherapy and Oncology 40 (1996) 181-184

Table 1 Properties of the examined wound dressings Trade name

Manufacturer

Material

Indication

Thickness

Remarks

Mepitel

M6llnlycke

Moist desquamation

0.5 mm

Cuticerin Varihesive, extra thin Kaltostat

Beyersdorf Convatec

Silicone-coated polyamid net Silkacetate Hydrocolloid

0.4 mm 0.5 mm

Merck

Ca-Na-alginate

Moist desquamation Mechanical protection, prevention of moist desquamation Heavily oozing lesions

Poor adhesivenesswith oozing lesions Good adhesiveness Self-adhesive

2mma

Thickness depends on the content of water

sWater content 0.2 &cm2 comparable to the water content of a dressing applied to heavily oozing lesions.

layer (TLD 7OOR,Solon Technologies, Ohio, USA). The TLDs were preheated at 100°Cfor 30 min and read out manually (J-Iarshaw 2080TLJSolon Technologies, Ohio USA) at a constant heating rate (30 s, 260°C). Light emissionwas integrated over the whole heating up period. For calibration purposes,all TLDs were initially irradiated five times with 6 MV photons and a target doseof 1 Gy. Only those TLDs were selectedwhose five readings showed a standard deviation of s 2.&y. Thus,

errors in the individual reading were spreadover an interval of ~4% (2 standarddeviations).The meanvalue out of the five calibration readingswas the calibration factor for 6 MV photons for eachTLD. The sameway a specific calibration factor was selected for ail exam-

ined beamqualities and beamenergies.For calibration all TLDs were exposedin the depth of maximumdose. The standarddeviationsof all calibration circlesdid not differ from that of the calibration with 6 MV photons.

the dose at a depth of 45 pm. Therefore, the reading agreeswell with the dose in the area of basal cell layer, whose mean depth is indicated as being 45 pm [5]. The measurementsfor all beam qualities were carried out using a perspexphantom (40 cm x 40 cm x 10cm) and a beam direction which was vertical to the skin. For photon beam irradiation, we used a representative field sixeof15m.n x lScm,forelectrons 1Ocm x 14cm.To determine the doses with or without wound dressings, measurementswere taken simultaneously both above and below the wound dressing. To increase reading accuracy and to estimate the standard deviation of each measurementthree TLDs were positioned both above and below. The maximum reading of the depth dose profile was in each case 1 Gy. 3. Results

The reading of the TLD measurementcorresponds to the integral of the dose over the entire thickness of the sensitivelayer. Since the depth dose profiles of all examined beam qualities and beam energiesare largely linear when it comesto the surface, the reading corresponds to

For the electron therapy, the absolutely measured dose on the surface of the skin is relatively high for all analysed materials (85-96%), the increase of the dose through a wound dressing, however, is small (3-7%) (Table 2).

Table 2 Increase of surface dose due to wound dressingsduring irradiation with photons and electrons 6 MV photons

CO60

42 MV photons

7 MeV electrons

20 MeV electrons 40 MeV electrons

Surface Relative Surface Relative Surface Relative Surface Relative Surface Relative Surface Relative dose dose dose dose dose dose dose dose dose dose dose dose increase increase (Gy) increase (Gy) increase (Gy) increase (Gy) increase KM VW Doseinthemaximum of the depth dose cmve Surface dose without wound dressing Mepitel Cuticerin Kaltostat Varihesive

1

1

I

I

I

1

0.26

0.23

0.15

0.84

0.92

0.95

0.43 0.41 0.69 0.45

65% 58% 165% 73%

0.32 0.31 0.49 0.33

39% 35% 113% 43%

0.20 0.20 0.29 0.21

33% 33% 93% 40%

0.88 0.88 0.90 0.89

5% 5% I% 6%

0.96 0.96 0.91 0.96

4% 4% 5% 4%

0.98 0.98 0.98 0.98

3% 3% 3% 3%

C. Thilmann et al. /Radiotherapy

With regard to the photons, the lowest dose increase (39% with 6 MV and 65% with Co60) and the smallest absolute skin dose (32% with 6MV and 43% with Co60) were measuredfor the silkacetate wound dressing. The polyamide and the hydrocolloid dressing showed slightly, the alginate wound dressing significantly higher readings (Table 2). Using 6oCo-yradiation, this leads to a dose increase of 165%and a dose of 69% in relation to the maximum value of the depth dose profile. The three dose values of each measurement were used to calculate the standard deviation of the mean value. The maximum standard deviation of all mean values was 1.75cGy and the maximum random error of all results (two standard deviations) was less than 3.5 cGy. 4. Discussion The fractionated percutaneous radiotherapy causes an acute reaction of the irradiated skin if the total dose is sufficiently high [S]. An erythema is the first visible sign that the skin reacts to irradiation; it is shown in cumulative total doses of between 20 and 30 Gy. If the basal cell layer of the epidermis is subjected to a total dose of 50 to 60 Gy, the development of moist epitheliolyses is very likely [2,6]. They could hamper the progress of the therapy, and their treatment during radiotherapy is difficult. The application of a nonadhesive silkacetate wound dressing proved a very useful tool during treatment of acute radiation-induced skin lesions. It mechanically protects the damaged skin, aids healing and does not causethe skin to feel more irritated. Considering its good adhesive properties it can be removed trauma free. Thus, it may be easier for the patient to continue radiotherapy without interruptions. On the other hand, the silicon-coated polyamide wound dressing used initially has the disadvantage that it is often removed inadvertently [ 11.Only with heavily oozing wounds, however, is the adhesivenesson the lesion unreliable even with the silkacetate dressing. In this case,alginate wound dressingscan be used. The wound dressing’s absorbent material and the wound secretion form a film which, depending on the stage of secretion of the wound, can be up to 2 mm thick. We use a selfadhesivewound dressing for markedly dry epitheliolyses on mechanically heavily stressed skin areas. Provided the wound dressing is not rejected, the mechanical source of irritation can be removed from the heavily stressed skin and thus prevent oozing epitheliolyses from developing. The dose increase of a silicone-coated polyamide net dressing with obliquely incident beams has been investigated and discussed previously [7]. At an oblique angle, the surface dose without dressing is much higher than at a perpendicular beam [4]. But the relative dose increasecausedof wound dressingsis lower. Beamsobliquely incident on the skin are applied in the irradiation

and Oncology 40 (195%) 181-184

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of the female breast and the head and neck. The intention of treatment is often curative or adjuvant. In these situations wound dressings are mostly applied for radiation- induced lesions on healthy skin. With regard to late effects and the cosmetical result, the dressing should be as thin as possible to keep the dose increase as low as possible. The radiation dose of the basal cell layer responsible for the extent of the radiation-induced acute reaction of the skin dependson beam type and beam energy. With electron therapy, the dose increase through a wound dressing is small (3-7%) considering that the radiation doseof the basal cell layer is already high. Even without the use of a wound dressing the skin does react severely. A significant increaseto the skin reaction is not to be expected with any of the analysed wound dressings. Any of the wound dressings can be left on the skin during electron irradiation, but its thickness should be taken into account when calculating the actually applied dose. With photons the dose increase caused by a wound dressing depends on the thickness of its tissue. Thus, substantial differences in the increase of the skin dose between the individual products were observed. From the point of view of the dosimetry, the polyamide wound dressingand the silkacetate dressing are equal. A slightly higher skin dose was measured for the hydrocolloid wound dressing. A therapy situation in which wound dressings are used for the treatment of radiationinduced moist epitheliolyses is the irradiation of head and neck tumours. As interruptions in the therapy impair the prognosis, particularly in the caseof irradiation treatment of head and neck, the optimal care of the skin is the ultimate aim. Should it becomenecessaryto treat moist epitheliolyses with a wound dressing, we recommend the application of the non-adhesive silkacetate wound dressing. Compared to the polyamide dressing it has the same dosimetric characteristics but superior adhesiveness.For the time being, the irradiation series should be continued using the wound dressing. It then dependson the clinical development of the skin lesions whether the wound dressing can be left in the radiation field. The self-adhesive hydrocolloid wound dressing can be used as a mechanical protection for threatening epitheliolyses. Also in this case, the irradiation series should, for the time being, be continued with a flat wound dressing. When using radiotherapy on an ulcerating tumour it is best for the removal of the lesion to carry out the therapy without any delays. A low surface dose through a high dose build-up effect is not desired. Thus, all nonadhesivewound dressingswhoseclinical aptitude for the treatment of ulcerating tumours has been proven can be used regardlessof their dosimetric characteristics. During external beam therapy with a photon energy level of up to .lOO kV (Weichstrahltherapie) wound dressingsdo not increase the stresson the skin because

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of the small range of secondary electrons [3]. Therefore, wound dressingscan be left on the skin without incurring the risk of an aggravated skin reaction. This, however, has to be taken into account when calculating the actually applied dose. References [I] Adamietx, LA., Mose, S., Haberl, A., Saran, F., Thilmann, C. and Bi%tcher,H.D. Effect of self-adhesive,silicone-coatedpolyamide net dressingon irradiated human skin. Radiat. Oncol. Invest. 2: 277-282, 1995. [2] Goldschmidt, H. and Sherwin, W.K. Reactions to ionizing radiation. J. Am. Acad. Deimatol. 3: 551-579, 1980. [3] ICRU. Radiation dosimetry: electron beams with energies between I and 50 MeV. ICRU Report 35: 16-9, 1984.

141 Khan, F.M. The Physics of Radiation Therapy, 2nd edn. Williams & Wilkins, Baltimore, 1994. PI Orton, C.G. and Seibert, M.S. Depth dose in skin for oblique incident Co60 radiation. Br. J. Radiol. 45: 271-275, 1972. I61 Solan, M.J., Brady, L.W., Binnick, S.A. and Fitzpatrick, P.J. Skin. In: Principles and Practice of Radiation Oncology, 2nd edn., pp. 479-495. Editors: C. A. Perez and L. W. Brady, Lip pincot, Philadelphia, 1992. I71 Thihnann, C., Adamietx, LA., Ramm, U., Mose, S., Saran, F. and BBttcher, H.D. Strahlenbelastung der Haut bei Verwendung einer silikonbeschichteten Wundaullage aus Polyamid wiihrend der Radiotherapie mit Photonen und Elektronen. Strahlentherap. Onkol. 172: 270-274, 1996. PI Tubiana, M., Dutreix, J. and Wambersie, A. Radiobiologie. Herrmann, Paris, 1986.