Research Report

Relative Transmission of Ultrasound by Media Customarily Used for Phonophoresis

The puqlose of this study was to determine the relative transmission of ultrasound by the media commonly used by pkysical therapists to apply phonophoresis. The relative transmission of ultrasound energy through various phonophoresis media was compared with that of degassed water, which is the ideal standard. Transmis- sion was assessed by placing a thin layer of the test medium on the transducer of a therapeutic ultrasound unit and measuring delivery of ultrasound with an ultrasound power meter. The media evaluated produced two significantly dzffer- ent groups of transmission results: ( I ) transmisrion greater than 80% of that of water and (2) transmission less than 40% of that of water Media that optimize the therapeutic eficacy of phonophoresis in both clinical and experimental settings are disczrssed. {Cameron MH, Monroe LC. Relative transmission of ultrasound by media c l~tomady used for phonophoresis. Phys Thm 1992;72:142-I#]

Key Words: Corticosteroid, Phonophoresis, Ultrasound

Phonopboresis is the therapeutic ap- plication of ultrasound with a topical drug, most commonly a cortico- steroid.' The drug is placed on the skin in the form of a gel, cream, oint- ment, or liquid and serves as the ultrasound transmission medium. This procedure is intended to enhance transdermal penetration of the drug while providing the therapeutic effects of ultrasound.'s2 For ultrasound to have the.se effects, it must be transmit- ted through the medium to the skin.

dependent on the physical properties of these materials. Thus, careful selec- tion of the preparations used for ultrasound transmission is required. Some commercially prepared gels, water, mineral oil, and glycerin are effective coupling agents for ultra- sound.3-5 However, although phono- phoresis is a widely used physical therapy p r ~ c e d u r e , ~ the ultrasound transmission by media commonly used for this procedure is not well known.'

Transmission of ultrasound energy Griffin and colleagues published the through one material to another is results of four studies investigating

MH Cameron, BSc, PT, is Physical Therapist, Mount Eden Physical Therapy Center, 2457 Grove Way, Ste 107F, Castro Valley, CA 94546. She was Sta5 Physical Therapist, John Muir Medical Center, 1981 N Broadway, Ste 180, Walnut Creek, CA 94598, when this study was conducted. Address all correspondence to Ms Cameron at 6131 Thornhill Dr, Oakland, CA 94611 (USA).

LG Monroe, MFT, FT, was Sta5 Physical Therapist, John Muir Medical Center, when this study was conducted.

This article was submilled April 22, 1991, and was accepted August 13, 1991

'Ptizer Labs Division, Pfizer Inc, 235 E 42nd St, New York, NY 10017.

Michelle H Cameron Linda G Monroe

the phonophoretic enhancement of hydrocortisone penetration to swine muscle and nerve tissue using Pfizer's CortrilB ointment* as the transmission medium.%" They concluded that in- creasing ultrasound power, applica- tion time, and drug concentration all increased hydrocortisone penetration. Although these studies attempt to identify treatment guidelines for pho- nophoresis, the data analysis and methodology limit the application of these results.

The treatments in the animal studies of Griffin and colleaguess" most ef- fectively increased hydrocortisone penetration but also burned the ani- mals. Such treatments cannot be ap- plied in the clinical setting. Moreover, skin damage alone is known to in- crease transdermal drug penetration and could explain the findings of these and similar studies.'* Heating may have resulted from the conver- sion of ultrasound energy to heat in a

Physical Therapyllrolume 72, Number 2/Februa1-y 1992 142 / 61

poorly transmitting coupling medium.13

A recent study of phonophoresis with rats and guinea pigs showed a fivefold to twentyfold increase in transdermal delivery of D-mannitol, inulin, and physostigmine within 2 hours following ultrasound appli- cation.14 Radiolabeled solutions of these chemicals were used as the transmission media for this study, and drug penetration was assessed by measuring the output of these chemicals in the urine.

Human studies of transdermal pene- tration of an anesthetic15 and a nonsteroidal anti-inflammatory drug16 failed to demonstrate en- hanced penetration with ultrasound. The topical anesthetic was in a cream, and the nonsteroidal anti- inflammatory was a gel documented to have 87% to 139% ultrasound transmission as compared with wa- ter. We believe that with such good transmission, the lack of effect found with the nonsteroidal anti- inflammatory must be due to factors other than poor ultrasound trans- mission. The authors suggest that ultrasound may not affect transder- ma1 penetration because either the drug used is unsuitable for this method of administration o r the method used was not sensitive enough to distinguish a treatment effect. All of these studies evaluated only the effects of ultrasound on drug penetration. Other studies of phonophoresis 17-20 have assessed the therapeutic efficacy of this procedure.

Griffin et a117 found that 68% of adult patients with a wide variety of muscu- loskeletal inflammatory conditions who received hydrocortisone phono- phoresis had increased range of mo- tion and decreased pain compared with 28% of those who received ultra- sound alone (N=102). They used Cor- trilm ointment with either 10% or 0% hydrocortisone as the ultrasound transmission medium. They did not evaluate the effects of topical applica- tion of hydrocortisone alone and thus were unable to compare standard

application of this drug with applica- tion by phonophoresis.

Kleinkort and WoodlH carried out a retrospective study of 285 patients treated for a variety of common in- flammatory conditions and com- pared the results of treatment using a 1% hydrocortisone preparation and a 10% hydrocortisone prepara- tion. The 1% hydrocortisone me- dium used was a water-based cream, and the 10% hydrocortisone medium was micronized hydrocorti- sone powder in petrolatum oint- ment. They found that, on average, the patients in the 10% hydrocorti- sone group received two treatments fewer than those in the 1% hydro- cortisone group, and thus con- cluded that 10% hydrocortisone is more effective.

Two published case studies19JO docu- ment improvement in temporoman- dibular joint dysfunction after treat- ment with phonophoresis. Wing19 used 10% micronized hydrocortisone acetate in petrolatum as the transmis- sion medium, and KahnZO used 0.5% hydrocortisone ointment covered with mineral oil. Both authors reported almost complete resolution of symp- toms after 5 to 10 treatments.

In summary, some studies indicate that phonophoresis may be an effec- tive treatment modality. Most inves- tigators, however, fail to consider ultrasound transmission through the media they use as a factor in their studies.

Benson and McElnay7 studied the transmission of ultrasound through topical pharmaceutical products available in Europe; however, they did not evaluate the media com- monly used in the United States for phonophoresis. Moreover, neither drug concentration nor media com- ponents were sufficiently docu- mented to allow direct comparison with other media. They reported a wide range of results, with gels transmitting ultrasound most effec- tively and several media not trans- mitting any ultrasound.

The purposes of this study were (1) to identify transmission media commanly used by physical thera- pists for phonophoresis, (2) to de- termine the relative transmission of ultrasound by these media and other corticosteroid preparations, and (3) to identify a group of media that transmit ultrasound well.

Method

Determination of Commonly Used Media

A questionnaire regarding the use of phonophoresis was sent to the directors of 125 physical therapy practices in northern California. Directors of practices using phono- phoresis were asked to identify the drugs and types of media they used for this procedure. The types of me- dia were categorized on the survey questionnaire as thick white creams, ointments, gels, mixed media, and other media.

Sixty-two percent (77) of the ques- tionnaires were returned completed. Of the respondents, 77% (59) re- ported regularly using phonophoresis in patient treatment. Hydrocortisone was the most frequently applied drug, with 81% (48) of the respondents using 10% hydrocortisone and 19% (11) of the respondents using 1% hy- drocortisone. Thick white cream (46%) and thick white cream mixed with ultrasound gel (44%) were the most commonly used transmission media. Selection of the media tested for ultrasound transmission in this study was based in part on the re- sponses to this survey.

Analysis of Ultrasound Transmission

The media tested for ultrasound trans- mission are listed in the Appendix. These include media used by the sur- vey respondents for phonophoresis, media used in prior research on pho- nophoresis,sll and some potent corti- costeroid gels selected by these re- searchers. Some nonmedicated media used for therapeutic ultrasound appli- cation were also tested.

Physical TherapyNolume 72, Number 2Pebruary 1992

Flgure 1 . Ohmic UPM-3Opower meter

Ultrasound transmission was deter- mined using an Ohmic UPM-30 ultra- sound power metert and a Chatta- nooga Intelect Model 700 therapeutic ultrasound unit,* as shown in Figure 1. The power meter uses the radiation force balance method to measure ultrasound p ~ w e r . ~ l . * ~ It consists of a conical metal target suspended from a precision balance into a rubber- lined tank filled with degassed water. The transducer of the therapeutic ultrasound unit is immersed approxi- mately 1 cm below the surface of the water, directly above the conical tar- get, and the ultrasound is turned on. The sound waves exert a force on the target, pushing it deeper into the water and thus deflecting the bal- ance. The balance measures the ex- erted force, which is directly propor- tional to the ultrasound energy

used for quantthing ultrasound transmission.

reaching the target. The UPM-30 power meter was evaluated by the National Bureau of Standards and the Division of Electronic Products of the Bureau of Radiological Health to be accurate to +6%, with a reproduc- ibility error of +5%.23 The power meter used for this study was cali- brated with a l-g standard weight and then used to calibrate the ultra- sound unit with degassed water. The ultrasound unit generates 1-MHz fre- quency ultrasound with power from 0 to 3 w/cm2 and an effective radiat- ing area of 8.5 cm2. It does not shut off power with poor ultrasound transmission.

To assess ultrasound transmission by different media, the transducer of the ultrasound unit was covered with a 5-mm-thick layer of test medium. The

+Ohmic Instruments Co, 102 Chew Ave, St Michaels, MD 21663.

*Chattanoc~ga Corp, 101 Memorial Dr, PO Box 4288, Chattanooga, TN 37405

$Saran Wrap", Dow Brands Inc, 9550 Zionsville Rd, Indianapolis, IN 46268.

l i~enley International, 104 Industrial Blvd, Sugar Land, TX 77478.

medium was contained in a plastic cuff, which had been put around the transducer, and the medium was cov- ered with polyethylene wrap.§ Visible air bubbles were removed from the medium with a syringe and needle. To test ultrasound transmission by the l-mm-thick chempad@,ll a single sheet was placed over the transducer head and then covered with polyethylene. The ultrasound transducer, with a layer of test medium, was secured head down 1 cm below the surface of the water in the power meter tank. The transducer head was centered above the conical target. Power was set at 1.5 w/cm2 on the ultrasound unit's power meter for each medium tested, and the reading on the balance was noted after 1 minute. Degassed water was tested first, after every third measurement, and last to verify the consistency of ultrasound output. Ultrasound transmission with just the polyethylene cover was measured to assess its effect on transmission.

Ultrasound transmission relative to water was calculated by dividing gram force exerted through the medium being tested by the average gram force exerted when degassed water alone was used. The transmission by degassed water varied + 2%.

The ultrasound transmission relative to degassed water for each medium tested is displayed in the Table. Trans- mission was not significantly affected by the polyethylene cover. All media tested, except for the Chempada, pro- duced results in one of two transmis- sion groups: (1) good transmission (ie, transmission greater than 80% of that of water) or (2) poor transmis- sion (ie, transmission less than 40% of that of water). Eighty percent was chosen as the lower cutoff for good transmission because most newer therapeutic ultrasound units automati- cally shut off power when they detect less than 60% to 80% transmission.

The media that transmitted ultrasound well were corticosteroid gels, a methyl salicylate cream, and media specifically made for use with ultra-

Physical Therapy/Volume 72, Number 2February 1992

- Table. Ul~rasound (US) Transmission by Phonophoresis Media

sound. Adding an equal amount of medium that transmits well to a me- dium that transmits poorly did not improve transmission. Ultrasound gel

Transmission mixed with either 1% or 10% micron- Relative to Water ized hydrocortisone acetate powder

Product (%) also transmitted poorly.

Media that transmit US well

LidexB gel, fluocinonide 0.05%a

Thera-Gesicm cream, methyl salicylate

Mineral oilC

US geld

US lotione

Betamethasone 0.05%' in US geld

Media that transmit US poorly

Diprolenem ointment, betamethasone 0.05%g

Hydrocortisone (HC) powder 1%" in US geld

HC powder 10%" in US gel

Cortrilm ointment, HC 1%'

Eucer~nB cream'

HC cream 1 %k

HC cream 1 O%k

HC cream 1 0 % ~ mixed with equal weight US geld

Myoflexa cream, trolamine salicylate 10%' 0

Triamcinolone acetonide cream O.l%k

Velva HC cream 10%"

Velva HC cream 10%" with equal weight US geld

White petrolatumm

Other

Chempad-La"

Polyethylene wrapo 98

"Syntex Laboratories Inc, 3401 Hillview Ave, PO Box 10850, Palo Alto, CA 94303.

'~ i ss ion Pharmacal Co, 1325 E Durango, San Antonio, TX 78210.

'Pennex Corp, Eastern Ave at Pennex Dr, Verona, PA 15147

d~ltraphonic@, Pharmaceutical Innovations Inc, 897 Frelinghuysen Dr, Newark, NJ 07114

'Polysonic, Parker Laboratories Inc, 307 Washington St, Orange, NJ 07050.

harmfa fair Inc, 110 Kennedy Dr, Hauppauge, NY 11788

KSchering Corp, Galloping Hill Rd, Kenilwonh, NJ 07033.

'~urepac Pharmaceutical Co, 200 Elmora Ave, Elizabeth, NJ 07207.

'Pfizer Labs Division, Pfizer Inc, 253 E 42nd St, Ncw York, NY 10017.

'Beiersdorf Inc, PO Box 5529, Norwalk, CT 06856-5529.

'E Fougera & Co, 60 Baylis Rd, Melville, NY 11747.

' ~ o r e r Consumer Pharmaceuticals, Div of RhBne-Poulenc Rorer Pharmaceuticals Inc, 500 Virginia Dr, Fort Washington, PA 19034.

"Universal Cooperatives Inc, 7801 Metro Pkwy, Minneapolis, MN 55420.

"Henley International, 104 Industrial Blvd, Sugar Land, TX 77478.

"Saran WrapB, Dow Brands Inc, 9550 Zionsville Rd, Indianapolis, IN 46268.

'~vntex laboratories Inc, 3401 Hillview Ave, PO Box 10850, Palo Alto, CA 94303.

**Mission Pharmacal Co, 1325 E Durango, San Antonio, TX 78210.

This study identified a wide variety of ultrasound transmission media used by physical therapists for phono- phoresis. Most clinicians surveyed reported using 10% or 1% hydrocorti- sone in a thick white cream base. However, all thick white conico- steroid creams tested were found to transmit ultrasound poorly, and trans- mission was not improved by admix- ture of these media with a gel that transmits well. Ultrasound gel mixed with micronized hydrocortisone ace- tate powder also yielded a poorly transmitting medium, possibly be- cause of the reflection of ultrasound by drug particles.

Three of the drug-containing media tested-Lidex@ gel,# betamethasone gel, and Thera-Gesic@ creams*-were found to transmit ultrasound well. It is likely that some other topical drug preparations, particularly gels with low drug concentrations, also transmit ultrasound well. Although the ideal ultrasound power for clinical applica- tion of phonophoresis is not known, whatever power is used, one must use a medium that transmits effec- tively to achieve predictable ultra- sound transfer. When a poor transmis- sion medium is used, much less ultrasound energy reaches the patient than is shown on the ultrasound unit's power meter. Fortunately, there is a wide selection of media that transmit ultrasound well. These media should be used with the ultrasound power and frequency most appropri- ate to the pathology being treated.

When applying phonophoresis, it is also important to select the appropri- ate drug for the pathology. Low- and high-potency corticosteroids, local anesthetics, counterirritants, methyl salicylate, and nonsteroidal anti- inflammatory agents are all available

64 / 145 Physical Therapyllrolume 72, Number 2Pebruary 1992

Figure 2. Demonstration of ineffec- tive ultrasound transmission by poorly transmitting medium.

in topical preparations. The relative clinical potential of these different drug preparations depends on phar- macologic activity, topical potency, and conc.entration.24 The corticoster- oids in Lidex@ and betamethasone gels are highly potent anti- inflammatory drugs that may also produce systemic side effects such as endocrine suppression or the mani- festations of Cushing's symptom com- plex when absorbed in large amounts.25 As phonophoresis may increase drug penetration, it also may increase the clinical benefits and the risks of topical drug application.

Not uncc~mmonly, phonophoresis is administered by putting a poorly transmitting medium on the skin and then placing the area to be treated, and the ultrasound transducer, under water. As water is a good transmitter of ultrasound, this procedure prevents the ultrasound unit from shutting off but also effectively keeps the ultra- sound from reaching the intended treatment area. Thus, we do not rec- ommend the application of phono- phoresis under water except for areas in which a liquid is needed to keep

Figure 3. Demonstration of ultrasou medium.

air from coming between the trans- ducer and an unevenly contoured area of the body. In this circumstance, a medium that transmits ultrasound well should be applied to the skin before the limb and transducer are placed in water.

As many topical drug preparations currently used for phonophoresis transmit ultrasound poorly, we rec- ommend that the clinical physical therapist qualitatively evaluate the ultrasound transmission by any me- dium using this simple technique. First, form an approximately l-cm- deep well above the face of the transducer of an ultrasound ma- chine by placing wide gummed tape around the transducer, as shown in Figure 2. Place a layer of the me- dium to be tested on the transducer surface and fill the remainder of the well with water. Then turn on the ultrasound machine to 1 to 2 w/cm2. If the medium transmits

nd transmission by effective transmission

ultrasound at all, the water will be agitated, as shown in Figure 3. If the medium transmits ultrasound poorly, the water remains still, as shown in Figure 2.

The depth of the medium and the duration of the test used in this study differ from those used clinically. We used a 5-mm thickness of medium, whereas a layer as thin as 0.5 mm may be used clinically. .We do not believe that changes in the thickness of the layer within this range will change transmission through the me- dium; changes in thickness within this range will not affect how well the me- dium couples with water in this ex- perimental model or with the body in the clinical setting. When medium depth is less than the diameter of the sound field, any decrease in transmis- sion will be due to losses across boundaries between materials, rather than to losses within the materials themselves.13 The ultrasound applica-

Physical 'Therapy/Volume 72, Number 2February 1992

tion time used in this study was Conclusions shorter than is typically used clini- cally. This application time was cho- Phonophoresis is an accepted physical sen in order to avoid obscuring our therapy procedure. A variety of media results through heating the compo- are used to allow the coupling re- nents of the experimental system. quired for transmission of ultrasound - Appendlx. Media Tested

Thick White Creams

EucerinQ cream with no druga

Hydrocortisone cream 1 %b

Hydrocortisone cream 1 O%b

Myoflexa cream, trolamine salicylate 10%'

Thera-GesicQ cream, methyl salicylate 15%d

Triamcinolone acetonide cream 0.1 %b

Velva hydrocortisone cream

Olntments

CortrilQ ointmenl, hydrocortisone 1 %'

Diprolene@ ointment, betamethasone 0.05%g

White petrolatumh

Gels

Lidex@ gel, fluocinonide 0.05%'

Betamethasone 0.05%' in ultrasound (US) gelk

US gelk

Mixed Medla

Hydrocortisone cream with equal weight US gelk

Micronized hydrocortisone acetate powder 1 %e in US gelk

Micronized hydrocortisone acetate powder 1 O%e in US gelk

Velva hydrocortisone cream with equal weight US gelk

Other Medla

Chempad-LQ,' lidocaine 2%, menthol 1 %

Mineral oilm

Polyethylene wrap alone"

US lotion0

"Beiersdorf Inc, PO Box 5529, Norwalk, CT 06856-5529

'E Fougera & Co, 60 Baylis Rd, Melville, NY 11747.

'Rarer Consumer Pharmaceuticals, Div of RhBne-Poulenc Rorer Pharmacueticals Inc, 500 Virginia Dr, Fon Washington, PA 19034.

'~ission Pharmacal Co, 1325 E Durango, San Antonio, TX 78210.

ePurepac Pharmaceutical Co, 200 Elmora Ave, Elizabeth, NJ 07207.

f~f izer Labs Division, Pfizer Inc, 253 E 42nd St, New York, NY 10017.

RSchering Corp, Galloping Hill Rd, Kenilwonh, NJ 07033.

'universal Cooperatives Inc, 7801 Metro Pkwy, Minneapolis, MN 55420.

'Syntex Laboratories Inc, 3401 Hillview Ave, PO Box 10850, Palo Alto, CA 94303.

'Pharmfair Inc, 110 Kennedy Dr, Hauppauge, NY 11788.

'ultraphonic", Pharmaceutical Innovations Inc, 897 Frelinghuysen Dr, Newark, NJ 07114.

' ~ e n l e ~ International, 104 Industrial Blvd, Sugar Land, TX 77478.

"Pennex Corp, Eastern Ave at Pennex Dr, Verona, PA 15147.

"Saran Wrap@, Dow Brands Inc, 9550 Zionsville Rd, Indianapolis, IN 46268.

OPolysonic, Parker Laboratories Inc, 307 Washington St, Orange, NJ 07050.

to the body. Phonophoresis media that transmit ultrasound well are identified in this study. Many commonly used media were found to be poor trans- mitters of ultrasound. Prior research using such media concluded that ultra- sound enhances drug penetration, with improved relief of symptoms. As little ultrasound was generated in this study, the results were probably not due to the specific effect of ultrasound on penetration of topical medication. Both experimental evaluation and clinical use of phonophoresis in the future should include selection of media that are known to transmit ultrasound well. Such considerations would allow stud- ies of transdermal drug penetration, depth of penetration, and clinical effi- cacy, which will help to identlfy the ultrasound characteristics and drugs most appropriate for different clinical applications. The identification of good phonophoresis media and the descrip- tion of a quick method for qualitative evaluation of other media in this arti- cle will enable clinicians to select ap- propriate phonophoresis media for their clinical treatment of patients.

Acknowledgments

We thank Ohmic Instruments Com- pany for supplying the wattmeter used in this study. Gratitude is also due to Marcia Hendricks, MA, PT, for her support and to John R Cameron, PhD, MD, for photographic and edito- rial assistance.

References

1 Antich TJ. Phonophoresis: the principles of the ultrasonic driving force and efficacy in treatment of common onhopaedic diagnoses. Journal of Orthopaedic and Sports Physical Therapy. 1982;4:99-102. 2 Tyle P, Agrawala P. Drug delivery by phone phoresis. Pharmaceurical Research. 1989;6: 355361. 3 Warren CG, Koblanski JN, Sigelman RA. Ultra- sound coupling media: their relative transmissiv- ity. Anh Phys Med Rebahil. 1976;57:21%222. 4 Griffin JE. Transmlssiveness of ultrasound through tap water, glycerin, and mineral oil. Phys Ther 1980;60:1010-1016. 5 Docker MF, Foulkes DJ, Patrick MK. Ultra- sound couplants for physiotherapy. Physiother- a&. 1982;68:124125. 6 Pottenger FJ. Utilization of hydrocortisone phonophoresis in United States Army physical therapy clinics. Milit Med. 1989;154:355-358.

66/147 Physical The1 rapyllrolume 72, Number 2Pebruary 1992

7 Benson I W , McElnay JC. Transmission of ultrasound energy through topical pharmaceu- tical products. Physiotherapy. 1988;74: 11-13. 8 Griffin JE, Touchstone JC. Ultrasonic move- ment of cortisol into pig tissues, I: movement into skeletal muscle. Am J Phys Med 1963;42: 77-85. 9 Griffin JE, Touchstone JC, Liu ACY. Ultra- sonic movement of cortisol into pig tissue, 11: movement into paravertebral nerve. Am J Phys Med. 1965;44:2&25. 10 Griffin JE, Touchstone JC. Effects of ultra- sonic frequency o n phonophoresis of cortisol into swine tissues. Am J Phys Med 1972;51: 62-78. 11 Griffin JE, Touchstone JC. Low-intensity phonophoresis of cortisol in swine. Phys Ther. 1968;48:1336-1344. 12 McEvoy J, ed. American Ilospital Fonnu- laly Service. Bethesda, Md: American Society of Hospital Pharmacists; 1990:1720-1729. 13 Frizzel LA, Dunn F. Biophysics of ultra- sound. In: lxhman JF, ed. Therapeutic Heat

and Cold. Baltimore, Md: Williams & Wilkins; 1990:362-397. 14 Levy D, Kost J, Meshulam Y, Langer R. Ef- fect of ultrasound on transdermal drug deliv- ery to rats and guinea pigs. J Clin Invest. 1989;83:2074-2078. 15 McElnay JC, Matthews MP, Harland R, Mc- Cafferty DF. The effect of ultrasound on the percutaneous absorption of lignocaine. Br J Clin Phannacol. 1985;20:421424. 16 Benson HAE, McElnay JC, Harland R. Use of ultrasound to enhance percutaneous ab- sorption of benzydamine. Phys Ther. 1989; 69:11>118. 17 Griffin JE, Echternach JL, Price RE, Touch- stone JC. Patients treated with ultrasonic driven hydrocortisone and with ultrasound alone. Phys Ther. 1967;47:594-601. 18 Kleinkort JA, Wood F. Phonophoresis with 1 percent versus 10 percent hydrocortisone. Phys Thm 1975;55:1320-1324.

19 Wing M. Phonophoresis with hydrocorti- sone in the treatment of temporomandibular joint dysfunction. Phys Ther. 1982;62:32-33. 20 Kahn J. Iontophoresis and ultrasound for postsurgical temperomandibular trismus and paresthesia. Phys Ther. 1980;60:307-308, 21 Roveti D. Measurement of Diagnostic and Therapeutic Ultrasound: Clinical Engineering Notes-A1Y-330. St Michaels, Md: Ohmic Instru- ments Co; 1980. 22 Roveti D. Ultrasound power measurement. Medical Electronics. 1989;12:9%106. 23 Operating Manual: Ultrasound Power Meter Model UPM-30. St Michaels, Md: Ohmic Instruments Co; 1978. 24 Cornell RC, Stroughton RB. The use of top- ical corticosteroids in psoriasis treatment. Der- matol Clin. 1984;2:397409. 25 Physicians' Desk R e f m c e . 45th ed. Ora- dell, NJ: Medical Economics Co Inc; 1991.

Physical 'Therapy/Volume 72, Number 2February 1992 148/67

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