Radiation exposure during percutaneous nephrostomy '.
Summary Radiation doses of radiologists, assistants a n d patierits during 21 percutaneous nephrostornies (PN) (including 11 unilateral a n d 5 bilateral procediires) were measured using an area-exposiire meter and thermoluminescent dosimeters. T h e mean fluoroscopy time pcr PN w a s 1 2 min and the rnean product of a i r kerma a n d the cross-sectioiial a r e a of tlie fluoroscopic beam w a s 8.0 (range 0.41-24) Gycm2. Doses to the radiologists and assistants were generally modest, and the yearly dose limits of ICRP will not be exceeded in practice. The doses to the radiologist's fingers were found to be the most restrictive in this study. Hegardirig the mean dose to the radiologist's firigers (190 pGy). the yearly dose limit of 5 0 0 mSv would be exceeded after about 2600 PNs provided that his fingers a r e not otherwise exposed. With the maximal finger dose of 1 1 0 0 yGy, this would o c w r af'ter about 4 5 0 yearly PNs.
I
Key w o r d s -
Die Strahlenbelastung von Iladiologen. Röntgenassistentinncn u n d Patienten während 2 1 perkutaner Nephrostomien (1 l unilaterale und 5 bilaterale) wurden mittels Flächenbestrahlungsmesser und Therinolumineszenzdosimetern gemessen. Die mittlere Fluoroskopiezeit während einer perkutanen Nephrostomie betrug 1 2 Minuten und d a s mittlere Produkt a u s d e r Kerma in Luft und d e r Querschnittsfläche d e s Fluoroskopstrahls w a r 8 , 0 (Bereich 0,41 -24) Gycm2. Radiologen und Röntgeriassisteriten wurden im allgemeinen n u r mäßigen t3estrahlungsdoseii ausgesetzt; die jährlichen Dosierungsgrenzen d e r ICRP werden iil d e r Praxis nicht iiberschritten. In dieser Studie wurde festgestellt, d a ß die Strahlungsexposition der Finger eines Radiologen a m hochsten war. Hinsichtlich der mittleren Stralilurigsbelastuiig d e r Finger eines Radiologen (190 &Gy) würde die mittlere Dosierui~gsgrenze von 5 0 0 mSv erst nach etwa 2 6 0 0 perkutanen Nephrostomien erreicht, falls seine Finger nicht auch noch a n d e r weitig Strahlen ausgesetzt sind. Bei d e r maximalen Fingerbelastuiig von 1100 ltCy würde dieser Fall nach etwa 4 5 0 perkutanen Neplirostoniien pro J a h r eintreten. Schlüsselwörter
I
-
P P -
Intcrventional Radiology - Dosimetry
-
Nephrostomy
Inlroduction While the number of many radiological examinations ie.g. angiography) involving fliioroscopy has hecn dccrcasing, int,crvcntional proccdures now give a n extra radiation burden to the radiological staf'f. Percutaneous nephrostorily (PN) is orie ol' the most common radiological interventionnl procedures. It may be carried out practically a t every well-equipped radiological dcpartrncnt. Thc nccd fOr a wcll-trained team to avoid excess complicat,ions means that certain mc:rnbcrs
For~sclir.R~iilgriislr.154.3(1991)238-241 Georg'rhiernti Verlag Stuttgart. New York
(C)
S t r a h l u n g s b e l a s l u n g bei p e r k u t a n e r Nephrostomie - - ---
Interventionsradiologir Dosirrietrie
Nephrostomic -
I
of tlie radiological staff will be rcpcatcdly involved in these procedures. Few reporls exist., tiowevcr, considering the radiation doses during PN. This study w a s carried out to rrieasurc-: the radiation doscs to which especially the radiologisl aiid assistant a r e exposad. Patients a n d mclhads Radiation doses during 21 P N s (11 uiiilnternl niid 5 bilateral) were rccordcd. Thcrr: were 14 pntienls (8 irmales and 6 malcs. agcd 25 7 9 ) . Tlir iridicalion ior PN was urinary obstruciioir in all biit two cases: Urinarv lcaka~cin thc firslniid nntegradc pyelography as wcll as subscquent snmplirig o f iiririe via catheler for cytological nnnlysis i i i ltir second.
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BLJ 7,. Vehmnsl. R. Nnuukair~erl', M. 'ibpiouac~ra'. I>.M(inkinrn P. Pibkiirnntc! I , P. 7e1-ualtcrrtinlcrI , S. ~ a u i k r i r k i land . 1.. ~ i r ~ i s a n r i ' I i)t:parliiii:iil of Uiagiiosli(:lladiology. I l ~ l s i i i k iUiiivc:i.sily Ci:iilral I Iospitirl. I i r l s i i i k i . 1:iril;rnd ancl ?17innishCciitrc lor Radiation and Niiclear Safcty (STI !K). Ilclsinki. I:inlaiid
Itadiation exposicre dr~rtngpercc~/«rzc.ous tt~phrostonzcj P -
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Forlsc.hr. Rot~tgertstr1.i4,3 .-
239 -
An arigiography cquipmcnt with Siemens Sirecon 2 K U V irnage intensilier systerri niid Elema-Schönandcr Multix table was used. This unit with under the table tube (Sierneiis ßi 31)/ 50/150 with total liltrntion of 3.5 rnmAl) was powered using a Siemens 'l'ridoros 5s X-ray generator. The kV/mA factors wcrc autornatically controlled and ranged from 60 to 110 kV arid froni 1 to 2 mA. Iii the angiograpliy equiprncnt. the distance from the xray focus to the patient's skiri was 60 ciii and the averagc sizr ofthc fluoroscopy ficld was cstimated to be 6 x 9 crn at the patient's skin level. l'he absorptioii oi' ihn tablc at 80 k V was rneasured to be 1.5 %. The doses of thc radiologist and assistant cvere rncasured with therrnolurniriescerii. dosirneters (TI.Ds) fixcd to thc skin nccording to Fig. 1. Calcium sulphate (CaS04: Dy) TI.-powtler was used. Dosimei.ers were also fixcd to thc paticnt's skin close to thc thyroid gland. to fernale breasts and to male gonnds. The exposure-area product (~crn') was rneasurcd for each procedure and was converted to the product of air kermn nnd bcarn arca using the conversion factor 0.0088 ~ ~ c r n ' / ~ c r n A ' . Doiior Dosex-A cxposurc-arca product rnetcr with a YI'W transrnission ioriisation chainber attached to thc x-ray tube was used. ThcTLDs were analysed and calibrated at tlie Finnish Centre for Radiation and Nuclear Safcty ( S r U K ) . The theriuolurninesccnt output ofCaS04: Dy-powder was ineasured using n Vinten Toledo 654 TLD rcader. l'he background radiation was rneasured and subtracted froiii the nieasurcd doscs. lf thc dosirneter dosc was bclow 1 pCy i t was considered as riil. I r i cases of bilateral PNs. the total doses and cxposure-area products were nieasured and divided by 2 as it would have 1)ee11nwkward to changc dosirncitcrs during a two-phasic procedure.
X
Outside protective clothing
0
Inside protective clothing
@
Both locations
Fig. 1
Placement of dosimeters to the radiologist and to theassistant.
ranged f'rom 7.3 pCy to 1 9 pGy except llie average finger doses oS 190 pCy. The doses under Lhe lead shields were close 10 Zero. The assistant's doses were about half of that received by the radiologist and the finger doses even less. The Skin dose «ver the patient's thyroid (n = 21) avcragcd 41 pGy (range 4.8-170), the female patient's breasts (11 = 12) 620 p(;y (19-3000) and the male patienl's gonads (n = C)) 450 pCy (36-1500).
Discussion The mean fluoroscopy time for PN was 1 2 min (range 0.5-40 rnin). The producl orair kerma and fluoroscopic beam area per procedure ranged from 0.41 to 24 Cycm' (mean 8.0).The radiation doses to the radiologist (Tab. 1 ) and 10 the assistant (Tab. 2) are givcn. Thc radiologist's average Skin dose to various parts of the body
Percutaneous rieplirostomy is one of the most conimon inlervenlional radiologic procedures and is also used a s a p a r t ofmore complicated procedures such a s nephroscopy and percutaneous lithotripsy. Although sometimes only ultrasonic guidance is uscd (9),fluoroscopy
Tab. 1 Radiationdose (pGy)to the radiologist. Nurnber of measurement and mean values; ranges in parentheses. BS = behindthe lead shield, OS = on the lead shield.
Tab. 2 Radiationdose(pGy)to theassistant.Numberof measurementsand mean values; ranges in parentheses.BS = behindthe lead shield, OS = on the lead shield.
- .
.
TLD site
I (n) 1 rnean 1 range
forehead thyroid BS thyroid OS right shoulder left shoulder abdomen BS abdomenOS right 3. finger lefl 3. finger fernale breast US
121 15 18 21 21 21 21 21 21 7
1 ( 0 - 78) ( 0 - 11) ( 1.4- 78) (1.4-29) ( 1.2- 29) ( 0 2.5) 7.3 ( 0 - 62) 190 ( 5.0-1100) 110 (10 - 910) 0 ( 0 3.0)
1 15
1.6 19 11 13 0
TLD site
forehead thyroid BS thyroid OS right shouldei lefl shoulder abdomen BS abdornenOS right 3. finger lefi 3. finger fernale breast
1
(n)
1 mean 1 range
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Iii all cases, the kidney t« be cathetcriscd was localised aiid tlie lowor pole calyx punctured at ultrasonic guidance. After this, a fliioroscopically guidcd rnodified Seldinger I.echniquc (12) was used to dilate sbpwise tlie tract with subscqueritly Iarger dilators and to introdiice thechosen PN catlieter int.0 the renal pelvis. Tlie technique varicd somewhat depending on the type of thc catheter. After the ciitlieter Iiad beeri properly inscrtcd. radiographs wcrc cxposcd to visualise the site oT the callictsr tip. 'I'he operating radiologist was usually assistcd by another doctor. Altogcther six radiologists participated in tlie procedurcs.
240 Fortschr Rorrlgeristr 154,.3 is usually used in assisting the tract dilatation and in Perforrning an antegrade pyelography when nccdcd. Iii spile of the popularity o i PN, we iound I'ew dala concerning its radiation doses. A liinited number of 'I'LDs were used for analysis in a recent study (6).'l'he average doses both to the Sternum (210 yGy) and forehead (14 pCy) of the patient in Krahe's study were less than the mt:an dose to tlie f'einale breasls (620 yGy) or 10 Llie tliyroid (41 CL(;Y) iii our study. 'l'he saine applied 10 the average fluoroscopy time (5.5 rnin in Krahe's study versus 1 2 min i i i our study). However. in other studies (1, 7) 15.1 -16 min fluoroscopy was nccded for ncphrostorny proccdiirc bchrc ncphrolithotorriy. Nthough not proved by this study, factors that are likely to influence the screening tin-ies are tlie degree and technique of the tract dilatation. the radiologist's and assistant's experience. the patient's constitution and condition (including the degree of hydronephrosis) and eqiiiprncnt-rclated factors.
Assurniiig the X-ray field to be static, 6 cm in size. back scatter factor 1.25 (4). the rneasured table top absorption 15 % and the tissue kerrna/air kerma ratio 1.05, the patient's surface dose can be estirnated frorn the area-exposure product to be 0.16 Gy (16 rad or 1 8 R) per PIV. This calculation does riot include the dose frorn radiographs (usually 1 to 3 per PN) which were exposed using a separate x-ray equiprnent. This value is sornewhat higher than the average Skin surface radiation exposure of 17.8 or 10.2 R at extracorporeal shock wave lithotripsy (2, 1I). The mean surface dose of patients was 10.2 m(;y (8) or 250 mSv (1) during percutaneous nephrostolithotorny. Area-exposure products of average 4800 ~ c m have ' been reported during cardiac radiological procedures (3) exceedingour rnean values 01'8.0 Gycrn2(900 ~crn').It is to be noted, however, that rnean exposures during the same procedures carried out by different radiologists with differeilt X-rayequipment have been found to vary by a factor of two or more (10). 9
T Vehmas rt al
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X
The variation in TLD doses (both the radiologist's. assistant's and patient's) was wide. reaching rnaxirnally more than 100fold differences, a fact that has often been noted in this kind of studies. The range is rnainly attributable to fluoroscopy time, to the patient's body constitution and in the case of the patient's TI.Ds, to the number and field size of radiographs exposed. The fluoroscopy beam in our study was moved while contrast was injected, depending on the level of ureteral obstruction. Thus, low ureteral obstructions were likely to cause high gonadal doses. The radiologist's TLDs in our study showed values sornewhat lower to those previously reported (6).As could be assurned, the radiologist's fingers received the greatest radiation doses. The radiation dose to the assistant was about halroi that received by the performing radiologist. The assistants' finger doses showed differences up to more than lO0Ofold indicating great variance in the assistant's activity/skill. The radiation dose behind protective clothes was practically zero. The radiation doses in bilateral PN alrnost doubled that received in unilateral PN.
Lead glasses or gloves wert! riot used iri lliis study. Sterile protective gloves are seldorn used a t least in our country possibly becaiise of the relative curnbersomeness. The bcnelit of a thyroid shicld was evident biit there are still rnariy radiologists wtio do not wear it. 'l'he annual dose lirnits recoinrnended by ICRP are 50 mSv foi the effective dose equivalent and 500 rnSv li)r all tissucs cxccpt thc Icns o l the eye for which lhe corriniissiori recornnierids a liinit ol' 1.50 rnSv in a ycar (5).'l'he limit of the effeclive dose equivalent will mosl likely not restrict the inaximum allowable yearly nurnber of PNs that one radiologist might conduct. The doses to the radiologist's fingers were foiind to be the rnost restrictive factor in thisstudy. At thc mean dosc to the radiologist's lingers (190 p(;y), the yearly dose lirnit of 500 rnSv woiild bc exceeded after aboul2600 PNs. At the maximal linger dose of 1'100 pGy. this would happen after about 450 yearly PNs. Thc dosimeters were placed on the dorsal aspect of the third fingcrs' middle phalanx, for practical reasons. On the palniar aspect of t.hc terminal phalanges thc doscs would most likely have been greater, however.
If finger doses are excluded. the secoiid most rcstrictivc Organ, the lens of the eye, would allow at leasl 1900 PNs peradiologist per year at the maximal dose oT 78 @(;Y arid 10000 PNs at the average dosc of 1 5 pCy (provided he would perforni no olher fiuoroscopic procedures). According to the well-known principle, the radiatiori doses should be kept as low as reasonahly acceptable. Sornetimes the radiologist cannot, howevcr, avoid placing his hands iiear the primary bearn. Iri order to rninimise radiation to hands, proper protective gloves should bc used or better operational techniques should be developed. The shielding effect and usefulness of protective gloves are riow being studied a t our departrnent. The influence o i makirig dose measurernents on the radiologist's perforrnance is not known. however. It is possible that some radiologists have paid special attention to the radiation risks during the study and the doses in real practice rnight be somewhat higher.
Heferences ~-
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Rush. W. H.. G. E. Brannerz. R. P. Gihbons. R. J. Correa jr.. J. S. Elder: Radiation exposure to patient and urologist during percutaneous nephrostolithotomy.J. Urol. 132 (1984)1140-1152 Carler. I.!. B.. E. B. Naslund, R. A. Riehfe: Variables iniluencing
radiation exposiire during extracorporeal shock wave lithotripsy. Review of 298 treatmcnts. Urology 30 (1987)546-550 V a u l k n e r , K.. 1'1. G. Lowe. J. K. Sweeney. R. A . ßardsley: Rndiation doses and sornatic risk to patients during cardiac radiological proccdurcs. Br. J. Radiol. 59 (1986)359-363 Harrison. R. M.: ßackscatter iactors ror diagiiostic radiology (1-4 mmAl HVL). Phys. Med. Biol. 27 (1982) 1465-1474 I(.T?P: Data Tor use for protcction against external radiation. ICRP publication 51 11987) (Pergarriori Press, Oxiord) Krahe uon, Th., K. Ewen, K. Lackner, 0. Köster, V. Nicofas: L)ie Strahlcncxposition dcs Patienten und Untersuchers in der interventionellen Radiologie. Fori.sctir. Röntgeristr. 145 (1986) 217-220
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F. C.. .W. Auster, T. .I. Beck, 11'. Chang, F. t.: ~Marsl~all: Monitoring radiation exposiire lo medical pcrsonnel during perciitaiieous ncphrolithotorny. Urology 28 (1986) 221 -226 "{ao, P. N . . K. Faulkner, J. K. Swceney. D. 1.. Asbury. P. Sarnhrook, N . J . Ulacklock: 1ladia.Lioiidosc to paticnt and s t a n d iiring percutancous ncphrostolitho~oiriy. Er. .I. IJml. 59 (J987) 508 - 5 12 Rcztzck, H. H . . L.. B. Talner: Perciitancous ncphrostomy. Kadiol. Cliii. North A m . 22 (1984) 393-406 "' Howley, K. A . . .T. .I. IlilL, R. A. Watkins. U. M . Moores: Ai1 investigation into the levels ol'rarliation coxposurc in diagnostic exaniiriations involving Iluoroscopy. Br. .I. Kadiol. 60 (1 987) 167 -173 ' I oa,n Suienringen. F. I,., D. L . McC'ullofcgh. H . ßysr. I?. Appel: Radiation cxposlire lo patieiits during cxtracorporeal shock wave lithotripsy. J. Urol. 138 11987) 18-20 Vehrnns, T.. 1.. Kioisauri, P. ~Mankirien.b: Tieralu. K. Sorrter. T. 1.chtonstz. C.-G. Slan.derlskjöld-Nordt!nstanz: Hcsults and complicalions of pcrcutcanous nephrostorriy. Aiiii. Clin. Rcs. 20 (1988)423-427 ; Lowe,
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Dr. 7iipio Vehn~ns . ~C ~Hospital ~ ~ 1+,lsinki ~ or~iagiiostic~adio~ogy ~ ~4 ~ 00290 ,,cls,nki/l:inland
Forischr. Rönlgerrslr. 154.3 ... . -
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241 -
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This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited.
Radialion exposure during percutancous nepl~roslonry
Summary Radiation doses of radiologists, assistants a n d patierits during 21 percutaneous nephrostornies (PN) (including 11 unilateral a n d 5 bilateral procediires) were measured using an area-exposiire meter and thermoluminescent dosimeters. T h e mean fluoroscopy time pcr PN w a s 1 2 min and the rnean product of a i r kerma a n d the cross-sectioiial a r e a of tlie fluoroscopic beam w a s 8.0 (range 0.41-24) Gycm2. Doses to the radiologists and assistants were generally modest, and the yearly dose limits of ICRP will not be exceeded in practice. The doses to the radiologist's fingers were found to be the most restrictive in this study. Hegardirig the mean dose to the radiologist's firigers (190 pGy). the yearly dose limit of 5 0 0 mSv would be exceeded after about 2600 PNs provided that his fingers a r e not otherwise exposed. With the maximal finger dose of 1 1 0 0 yGy, this would o c w r af'ter about 4 5 0 yearly PNs.
I
Key w o r d s -
Die Strahlenbelastung von Iladiologen. Röntgenassistentinncn u n d Patienten während 2 1 perkutaner Nephrostomien (1 l unilaterale und 5 bilaterale) wurden mittels Flächenbestrahlungsmesser und Therinolumineszenzdosimetern gemessen. Die mittlere Fluoroskopiezeit während einer perkutanen Nephrostomie betrug 1 2 Minuten und d a s mittlere Produkt a u s d e r Kerma in Luft und d e r Querschnittsfläche d e s Fluoroskopstrahls w a r 8 , 0 (Bereich 0,41 -24) Gycm2. Radiologen und Röntgeriassisteriten wurden im allgemeinen n u r mäßigen t3estrahlungsdoseii ausgesetzt; die jährlichen Dosierungsgrenzen d e r ICRP werden iil d e r Praxis nicht iiberschritten. In dieser Studie wurde festgestellt, d a ß die Strahlungsexposition der Finger eines Radiologen a m hochsten war. Hinsichtlich der mittleren Stralilurigsbelastuiig d e r Finger eines Radiologen (190 &Gy) würde die mittlere Dosierui~gsgrenze von 5 0 0 mSv erst nach etwa 2 6 0 0 perkutanen Nephrostomien erreicht, falls seine Finger nicht auch noch a n d e r weitig Strahlen ausgesetzt sind. Bei d e r maximalen Fingerbelastuiig von 1100 ltCy würde dieser Fall nach etwa 4 5 0 perkutanen Neplirostoniien pro J a h r eintreten. Schlüsselwörter
I
-
P P -
Intcrventional Radiology - Dosimetry
-
Nephrostomy
Inlroduction While the number of many radiological examinations ie.g. angiography) involving fliioroscopy has hecn dccrcasing, int,crvcntional proccdures now give a n extra radiation burden to the radiological staf'f. Percutaneous nephrostorily (PN) is orie ol' the most common radiological interventionnl procedures. It may be carried out practically a t every well-equipped radiological dcpartrncnt. Thc nccd fOr a wcll-trained team to avoid excess complicat,ions means that certain mc:rnbcrs
For~sclir.R~iilgriislr.154.3(1991)238-241 Georg'rhiernti Verlag Stuttgart. New York
(C)
S t r a h l u n g s b e l a s l u n g bei p e r k u t a n e r Nephrostomie - - ---
Interventionsradiologir Dosirrietrie
Nephrostomic -
I
of tlie radiological staff will be rcpcatcdly involved in these procedures. Few reporls exist., tiowevcr, considering the radiation doses during PN. This study w a s carried out to rrieasurc-: the radiation doscs to which especially the radiologisl aiid assistant a r e exposad. Patients a n d mclhads Radiation doses during 21 P N s (11 uiiilnternl niid 5 bilateral) were rccordcd. Thcrr: were 14 pntienls (8 irmales and 6 malcs. agcd 25 7 9 ) . Tlir iridicalion ior PN was urinary obstruciioir in all biit two cases: Urinarv lcaka~cin thc firslniid nntegradc pyelography as wcll as subscquent snmplirig o f iiririe via catheler for cytological nnnlysis i i i ltir second.
This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited.
BLJ 7,. Vehmnsl. R. Nnuukair~erl', M. 'ibpiouac~ra'. I>.M(inkinrn P. Pibkiirnntc! I , P. 7e1-ualtcrrtinlcrI , S. ~ a u i k r i r k i land . 1.. ~ i r ~ i s a n r i ' I i)t:parliiii:iil of Uiagiiosli(:lladiology. I l ~ l s i i i k iUiiivc:i.sily Ci:iilral I Iospitirl. I i r l s i i i k i . 1:iril;rnd ancl ?17innishCciitrc lor Radiation and Niiclear Safcty (STI !K). Ilclsinki. I:inlaiid
Itadiation exposicre dr~rtngpercc~/«rzc.ous tt~phrostonzcj P -
-
--
- --
-
--
Forlsc.hr. Rot~tgertstr1.i4,3 .-
239 -
An arigiography cquipmcnt with Siemens Sirecon 2 K U V irnage intensilier systerri niid Elema-Schönandcr Multix table was used. This unit with under the table tube (Sierneiis ßi 31)/ 50/150 with total liltrntion of 3.5 rnmAl) was powered using a Siemens 'l'ridoros 5s X-ray generator. The kV/mA factors wcrc autornatically controlled and ranged from 60 to 110 kV arid froni 1 to 2 mA. Iii the angiograpliy equiprncnt. the distance from the xray focus to the patient's skiri was 60 ciii and the averagc sizr ofthc fluoroscopy ficld was cstimated to be 6 x 9 crn at the patient's skin level. l'he absorptioii oi' ihn tablc at 80 k V was rneasured to be 1.5 %. The doses of thc radiologist and assistant cvere rncasured with therrnolurniriescerii. dosirneters (TI.Ds) fixcd to thc skin nccording to Fig. 1. Calcium sulphate (CaS04: Dy) TI.-powtler was used. Dosimei.ers were also fixcd to thc paticnt's skin close to thc thyroid gland. to fernale breasts and to male gonnds. The exposure-area product (~crn') was rneasurcd for each procedure and was converted to the product of air kermn nnd bcarn arca using the conversion factor 0.0088 ~ ~ c r n ' / ~ c r n A ' . Doiior Dosex-A cxposurc-arca product rnetcr with a YI'W transrnission ioriisation chainber attached to thc x-ray tube was used. ThcTLDs were analysed and calibrated at tlie Finnish Centre for Radiation and Nuclear Safcty ( S r U K ) . The theriuolurninesccnt output ofCaS04: Dy-powder was ineasured using n Vinten Toledo 654 TLD rcader. l'he background radiation was rneasured and subtracted froiii the nieasurcd doscs. lf thc dosirneter dosc was bclow 1 pCy i t was considered as riil. I r i cases of bilateral PNs. the total doses and cxposure-area products were nieasured and divided by 2 as it would have 1)ee11nwkward to changc dosirncitcrs during a two-phasic procedure.
X
Outside protective clothing
0
Inside protective clothing
@
Both locations
Fig. 1
Placement of dosimeters to the radiologist and to theassistant.
ranged f'rom 7.3 pCy to 1 9 pGy except llie average finger doses oS 190 pCy. The doses under Lhe lead shields were close 10 Zero. The assistant's doses were about half of that received by the radiologist and the finger doses even less. The Skin dose «ver the patient's thyroid (n = 21) avcragcd 41 pGy (range 4.8-170), the female patient's breasts (11 = 12) 620 p(;y (19-3000) and the male patienl's gonads (n = C)) 450 pCy (36-1500).
Discussion The mean fluoroscopy time for PN was 1 2 min (range 0.5-40 rnin). The producl orair kerma and fluoroscopic beam area per procedure ranged from 0.41 to 24 Cycm' (mean 8.0).The radiation doses to the radiologist (Tab. 1 ) and 10 the assistant (Tab. 2) are givcn. Thc radiologist's average Skin dose to various parts of the body
Percutaneous rieplirostomy is one of the most conimon inlervenlional radiologic procedures and is also used a s a p a r t ofmore complicated procedures such a s nephroscopy and percutaneous lithotripsy. Although sometimes only ultrasonic guidance is uscd (9),fluoroscopy
Tab. 1 Radiationdose (pGy)to the radiologist. Nurnber of measurement and mean values; ranges in parentheses. BS = behindthe lead shield, OS = on the lead shield.
Tab. 2 Radiationdose(pGy)to theassistant.Numberof measurementsand mean values; ranges in parentheses.BS = behindthe lead shield, OS = on the lead shield.
- .
.
TLD site
I (n) 1 rnean 1 range
forehead thyroid BS thyroid OS right shoulder left shoulder abdomen BS abdomenOS right 3. finger lefl 3. finger fernale breast US
121 15 18 21 21 21 21 21 21 7
1 ( 0 - 78) ( 0 - 11) ( 1.4- 78) (1.4-29) ( 1.2- 29) ( 0 2.5) 7.3 ( 0 - 62) 190 ( 5.0-1100) 110 (10 - 910) 0 ( 0 3.0)
1 15
1.6 19 11 13 0
TLD site
forehead thyroid BS thyroid OS right shouldei lefl shoulder abdomen BS abdornenOS right 3. finger lefi 3. finger fernale breast
1
(n)
1 mean 1 range
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Iii all cases, the kidney t« be cathetcriscd was localised aiid tlie lowor pole calyx punctured at ultrasonic guidance. After this, a fliioroscopically guidcd rnodified Seldinger I.echniquc (12) was used to dilate sbpwise tlie tract with subscqueritly Iarger dilators and to introdiice thechosen PN catlieter int.0 the renal pelvis. Tlie technique varicd somewhat depending on the type of thc catheter. After the ciitlieter Iiad beeri properly inscrtcd. radiographs wcrc cxposcd to visualise the site oT the callictsr tip. 'I'he operating radiologist was usually assistcd by another doctor. Altogcther six radiologists participated in tlie procedurcs.
240 Fortschr Rorrlgeristr 154,.3 is usually used in assisting the tract dilatation and in Perforrning an antegrade pyelography when nccdcd. Iii spile of the popularity o i PN, we iound I'ew dala concerning its radiation doses. A liinited number of 'I'LDs were used for analysis in a recent study (6).'l'he average doses both to the Sternum (210 yGy) and forehead (14 pCy) of the patient in Krahe's study were less than the mt:an dose to tlie f'einale breasls (620 yGy) or 10 Llie tliyroid (41 CL(;Y) iii our study. 'l'he saine applied 10 the average fluoroscopy time (5.5 rnin in Krahe's study versus 1 2 min i i i our study). However. in other studies (1, 7) 15.1 -16 min fluoroscopy was nccded for ncphrostorny proccdiirc bchrc ncphrolithotorriy. Nthough not proved by this study, factors that are likely to influence the screening tin-ies are tlie degree and technique of the tract dilatation. the radiologist's and assistant's experience. the patient's constitution and condition (including the degree of hydronephrosis) and eqiiiprncnt-rclated factors.
Assurniiig the X-ray field to be static, 6 cm in size. back scatter factor 1.25 (4). the rneasured table top absorption 15 % and the tissue kerrna/air kerma ratio 1.05, the patient's surface dose can be estirnated frorn the area-exposure product to be 0.16 Gy (16 rad or 1 8 R) per PIV. This calculation does riot include the dose frorn radiographs (usually 1 to 3 per PN) which were exposed using a separate x-ray equiprnent. This value is sornewhat higher than the average Skin surface radiation exposure of 17.8 or 10.2 R at extracorporeal shock wave lithotripsy (2, 1I). The mean surface dose of patients was 10.2 m(;y (8) or 250 mSv (1) during percutaneous nephrostolithotorny. Area-exposure products of average 4800 ~ c m have ' been reported during cardiac radiological procedures (3) exceedingour rnean values 01'8.0 Gycrn2(900 ~crn').It is to be noted, however, that rnean exposures during the same procedures carried out by different radiologists with differeilt X-rayequipment have been found to vary by a factor of two or more (10). 9
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The variation in TLD doses (both the radiologist's. assistant's and patient's) was wide. reaching rnaxirnally more than 100fold differences, a fact that has often been noted in this kind of studies. The range is rnainly attributable to fluoroscopy time, to the patient's body constitution and in the case of the patient's TI.Ds, to the number and field size of radiographs exposed. The fluoroscopy beam in our study was moved while contrast was injected, depending on the level of ureteral obstruction. Thus, low ureteral obstructions were likely to cause high gonadal doses. The radiologist's TLDs in our study showed values sornewhat lower to those previously reported (6).As could be assurned, the radiologist's fingers received the greatest radiation doses. The radiation dose to the assistant was about halroi that received by the performing radiologist. The assistants' finger doses showed differences up to more than lO0Ofold indicating great variance in the assistant's activity/skill. The radiation dose behind protective clothes was practically zero. The radiation doses in bilateral PN alrnost doubled that received in unilateral PN.
Lead glasses or gloves wert! riot used iri lliis study. Sterile protective gloves are seldorn used a t least in our country possibly becaiise of the relative curnbersomeness. The bcnelit of a thyroid shicld was evident biit there are still rnariy radiologists wtio do not wear it. 'l'he annual dose lirnits recoinrnended by ICRP are 50 mSv foi the effective dose equivalent and 500 rnSv li)r all tissucs cxccpt thc Icns o l the eye for which lhe corriniissiori recornnierids a liinit ol' 1.50 rnSv in a ycar (5).'l'he limit of the effeclive dose equivalent will mosl likely not restrict the inaximum allowable yearly nurnber of PNs that one radiologist might conduct. The doses to the radiologist's fingers were foiind to be the rnost restrictive factor in thisstudy. At thc mean dosc to the radiologist's lingers (190 p(;y), the yearly dose lirnit of 500 rnSv woiild bc exceeded after aboul2600 PNs. At the maximal linger dose of 1'100 pGy. this would happen after about 450 yearly PNs. Thc dosimeters were placed on the dorsal aspect of the third fingcrs' middle phalanx, for practical reasons. On the palniar aspect of t.hc terminal phalanges thc doscs would most likely have been greater, however.
If finger doses are excluded. the secoiid most rcstrictivc Organ, the lens of the eye, would allow at leasl 1900 PNs peradiologist per year at the maximal dose oT 78 @(;Y arid 10000 PNs at the average dosc of 1 5 pCy (provided he would perforni no olher fiuoroscopic procedures). According to the well-known principle, the radiatiori doses should be kept as low as reasonahly acceptable. Sornetimes the radiologist cannot, howevcr, avoid placing his hands iiear the primary bearn. Iri order to rninimise radiation to hands, proper protective gloves should bc used or better operational techniques should be developed. The shielding effect and usefulness of protective gloves are riow being studied a t our departrnent. The influence o i makirig dose measurernents on the radiologist's perforrnance is not known. however. It is possible that some radiologists have paid special attention to the radiation risks during the study and the doses in real practice rnight be somewhat higher.
Heferences ~-
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Rush. W. H.. G. E. Brannerz. R. P. Gihbons. R. J. Correa jr.. J. S. Elder: Radiation exposure to patient and urologist during percutaneous nephrostolithotomy.J. Urol. 132 (1984)1140-1152 Carler. I.!. B.. E. B. Naslund, R. A. Riehfe: Variables iniluencing
radiation exposiire during extracorporeal shock wave lithotripsy. Review of 298 treatmcnts. Urology 30 (1987)546-550 V a u l k n e r , K.. 1'1. G. Lowe. J. K. Sweeney. R. A . ßardsley: Rndiation doses and sornatic risk to patients during cardiac radiological proccdurcs. Br. J. Radiol. 59 (1986)359-363 Harrison. R. M.: ßackscatter iactors ror diagiiostic radiology (1-4 mmAl HVL). Phys. Med. Biol. 27 (1982) 1465-1474 I(.T?P: Data Tor use for protcction against external radiation. ICRP publication 51 11987) (Pergarriori Press, Oxiord) Krahe uon, Th., K. Ewen, K. Lackner, 0. Köster, V. Nicofas: L)ie Strahlcncxposition dcs Patienten und Untersuchers in der interventionellen Radiologie. Fori.sctir. Röntgeristr. 145 (1986) 217-220
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F. C.. .W. Auster, T. .I. Beck, 11'. Chang, F. t.: ~Marsl~all: Monitoring radiation exposiire lo medical pcrsonnel during perciitaiieous ncphrolithotorny. Urology 28 (1986) 221 -226 "{ao, P. N . . K. Faulkner, J. K. Swceney. D. 1.. Asbury. P. Sarnhrook, N . J . Ulacklock: 1ladia.Lioiidosc to paticnt and s t a n d iiring percutancous ncphrostolitho~oiriy. Er. .I. IJml. 59 (J987) 508 - 5 12 Rcztzck, H. H . . L.. B. Talner: Perciitancous ncphrostomy. Kadiol. Cliii. North A m . 22 (1984) 393-406 "' Howley, K. A . . .T. .I. IlilL, R. A. Watkins. U. M . Moores: Ai1 investigation into the levels ol'rarliation coxposurc in diagnostic exaniiriations involving Iluoroscopy. Br. .I. Kadiol. 60 (1 987) 167 -173 ' I oa,n Suienringen. F. I,., D. L . McC'ullofcgh. H . ßysr. I?. Appel: Radiation cxposlire lo patieiits during cxtracorporeal shock wave lithotripsy. J. Urol. 138 11987) 18-20 Vehrnns, T.. 1.. Kioisauri, P. ~Mankirien.b: Tieralu. K. Sorrter. T. 1.chtonstz. C.-G. Slan.derlskjöld-Nordt!nstanz: Hcsults and complicalions of pcrcutcanous nephrostorriy. Aiiii. Clin. Rcs. 20 (1988)423-427 ; Lowe,
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Radialion exposure during percutancous nepl~roslonry
