FROM T H E DEPARTMENTS O F DIAGNOSTIC RADIOLOGY A N D RADIATION PHYSICS, AKADEMISKA S J U K H U S E T , S-750 1 4 U P P S A L A , S W E D E N .
RADIATION PROTECTION IN FLUOROSCOPY WITH AN IMAGE INTENSIFIER A . H E M M I N G S S O N a n d P. O . L O F R O T H
W h e n t h e r o e n t g e n tube is m o u n t e d a b o v e t h e patient a n d t h e i m a g e intensifier b e n e a t h t h e e x a m i n a t i o n c o u c h , t h e radiation d o s e s received b y t h e personnel h a v e b e e n f o u n d t o b e considerably larger t h a n w i t h a n o p p o s i t e b e a m direction ( J A C O B S O N 1970,
H O F F M A N et c o l l .
1 9 7 1 , R I L E Y et c o l l .
1 9 7 2 , S T A C E Y et c o l l .
1974, WHOLEY
1 9 7 4 ) . T h u s , with a n o v e r c o u c h t u b e , s e c o n d a r y radiation f r o m t h e site of entry of the b e a m a t the upper surface of the patient is greater t h a n w i t h a n u n d e r c o u c h tube, w h e n scattered radiation c o m e s m a i n l y f r o m t h e site of exit of t h e b e a m f r o m t h e patient ( H O F F M A N et coll.). In this r a d i o l o g y d e p a r t m e n t it h a s b e e n f o u n d that in catheterization, with t h e o v e r c o u c h t u b e , t h e radiation d o s e t o t h e r a d i o l o g i s t per f o r m i n g t h e catheterization m a y b e m o r e t h a n 0 . 0 1 G y o v e r a period of four w e e k s , measured a t s h o u l d e r level a b o v e t h e l e a d rubber a p r o n . T h i s m e a n s a d o s e t o t h e lens, for e x a m p l e , lying c l o s e t o t h e m a x i m u m permissible d o s e e q u i v a l e n t of 1 5 r e m (1 rem = 0 . 0 1 Sv) p e r year ( I C R P 1 9 6 6 ) . Of t h e a p p r o x i m a t e l y 1 8 p e r cent of t h e b l o o d - f o r m i n g b o n e m a r r o w that is n o t p r o t e c t e d b y a l e a d rubber a p r o n ( H O F F M A N et coll.), t h e greatest p r o p o r t i o n is l o c a t e d cranially, a n d t h e d o s e t o this fraction of b o n e m a r r o w w o u l d therefore b e u n a c c e p t a b l y h i g h ( m a x i m u m permissible d o s e e q u i v a l e n t 5 r e m per year, I C R P ) . F o r f l u o r o s c o p y i n e x a m i n a t i o n r o o m s e q u i p p e d w i t h a n o v e r c o a c h tube, special auxiliary devices h a v e b e e n c o n s t r u c t e d t o m i n i m i z e the r a d i a t i o n d o s e received b y parts of t h e b o d y that are n o t p r o t e c t e d b y t h e lead r u b b e r a p r o n . T h e a i m s h a v e been ( 1 ) t o d i m i n i s h t h e r a d i a t i o n t o t h e u n p r o t e c t e d Submitted for publication 7 December 1977. Acta Radiologica
Diagnosis 19 (1978) Fasc. 6
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shielding equipment at 80 kV, 1 mA and a field size of 130 mm x 130 mm with a phantom thickness of 200 mm. b) The shielding device for an overcouch tube. The tube is rotatable and has panels that can be let down.
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h e a d - n e c k - s h o u l d e r r e g i o n , (2) t o p r e v e n t t h a t t h e shielding device h a m p e r s the w o r k of t h e e x a m i n e r , (3) t o p r o m o t e sterile catheterization c o n d i t i o n s , a n d (4) t o m a k e the h a n d l i n g of the device easy a n d n o t u n d u l y h e a v y .
Material and Methods T h e r a d i a t i o n in the l a b o r a t o r y w a s m e a s u r e d w i t h a surveymeter ( N u c l e a r C h i c a g o M o d e l 2 5 8 8 M o n i t o r a n d 2 5 2 6 m e d i u m range i o n i z a t i o n c h a m b e r , v o l u m e 5 0 0 ml). T h e m e a s u r e m e n t i n s t r u m e n t has a linear energy r e s p o n s e ranging f r o m 10 k e V t o o v e r 1 M e V , w i t h a n a c c u r a c y of 10 per cent. S u p p l e m e n t a r y m e a s u r e m e n t s were m a d e w i t h a n E I L i o n i z a t i o n c h a m b e r (37 A ) c o n n e c t e d t o a K e i t h l e y Electrometer 616. A 2 0 0 m m thick a n d 3 0 0 m m square w a t e r p h a n t o m , c o r r e s p o n d i n g roughly t o t h e cross-sectional d i m e n s i o n s of a n o r m a l - s i z e d patient, w a s p l a c e d o n the e x a m i n a t i o n c o u c h in the centre of the r a d i a t i o n field. T h e b e a m w a s oriented at right angles t o the i m a g e intensifier. M e a s u r e m e n t s were p e r f o r m e d during f l u o r o s c o p y
with
a u t o m a t i c d o s e c o n t r o l , in a vertical p l a n e t h r o u g h the b e a m at right angles t o the t u b e . T h e size of the f o c a l s p o t w a s 1.2 m m x 1.2 m m a n d the t u b e p o t e n t i a l w a s 8 0
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Fig. 2
Fig. 3
Fig. 2. The shielding device mounted on the tube. Fig. 3. The shielding device in place. Lead rubber suspended on the compression tube of a remote control apparatus for fluoroscopy with the overcouch tube.
k V (12 p u l s e s p e r p e r i o d ) w i t h t o t a l f i l t r a t i o n of t h e b e a m 3.5 m m A l . T h e field size a t t h e level of m e a s u r e m e n t w a s 130 m m x 130 m m . T h e r a d i a t i o n levels a r e g i v e n a s e x p o s u r e p e r t i m e u n i t a n d p e r m A ( m R / h ; 1 m R ^ 2 . 5 8 10
7
C/kg).
T h e p r o b l e m s of r a d i a t i o n p r o t e c t i o n in c o n n e c t i o n w i t h o v e r c o u c h
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h a s b e e n solved b y s h i e l d i n g e q u i p m e n t s w h i c h a r e m a i n l y b a s e d o n t h e s a m e p r i n c i ples. A t t h i s r a d i o l o g y d e p a r t m e n t a d e t a c h a b l e s h i e l d i n g t u b e h a s b e e n c o n s t r u c t e d t h a t c a n b e fixed o n t o t h e d i a p h r a g m h o u s i n g in t h e c h a n n e l s i n t e n d e d for t h e p e r s p e x p l a t e s o r a d d i t i o n a l filters for u s e in a n g i o g r a p h y l a b o r a t o r i e s a n d o t h e r f l u o r o s c o p y r o o m s e q u i p p e d w i t h a n o v e r h e a d t u b e a n d a f i l m - f o c u s d i s t a n c e of a b o u t 100 c m ( F i g s 1 b , 2). T h e s h i e l d i n g t u b e is r o t a t a b l e a n d is s u p p l i e d w i t h t w o h i n g e d p a n e l s of different sizes t h a t c a n b e let d o w n t o i m p r o v e t h e s h i e l d i n g in t h e d i r e c t i o n of t h e e x a m i n e r . T h e s h i e l d i n g t u b e is c o n s t r u c t e d of a 6 m m t h i c k p l e x i g l a s s f r a m e c o v e r e d w i t h a 0.5 m m t h i c k s h e e t of l e a d . T h e s h e e t of lead is g l u e d t o t h e p l e x i g l a s s . F o r r e m o t e c o n t r o l i n s t a l l a t i o n s w i t h a c o m p r e s s i o n t u b e , a lead r u b b e r
shield
w i t h a lead e q u i v a l e n c e of 0.5 m m h a s been c o n s t r u c t e d . T h i s is s u s p e n d e d a l o n g t h e l o n g side of t h e c o u c h by m e a n s of o p e n h o o k s o n r o d s t h a t a r e fixed t o t h e c o m p r e s s i o n t u b e . In o r d e r t o p r o t e c t t h e a n a e s t h e s i s t , for e x a m p l e , a t t h e h e a d side of t h e c o u c h , a l o n g lead r u b b e r s c r e e n is a l s o s u s p e n d e d s o t h a t it is a l m o s t a t r i g h t a n g l e s t o t h e r a d i a t i o n field a n d shields t h e e x a m i n e r a t t h e l o n g side of t h e t a b l e , a n d a l s o o n e of t h e s h o r t e n d s of t h e t a b l e , f r o m s e c o n d a r y r a d i a t i o n ( F i g . 3). 64-785841
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Fig. 4. The lead quivalence of the lead rubber in Fig. 3 is 0.5 mm. The exposure rate (mR/h) at the couch with the shielding device ( ) is given at 80 kV, 1 mA and a field size of 130 mm x 130 mm with a phantom thickness of 200 mm.
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F o r c a r d i o a n g i o g r a p h y w i t h use of a lateral r o e n t g e n tube, a shielding device has b e e n fixed t o the side of t h e d i a p h r a g m h o u s i n g (Fig. 5 b). T h i s device, w h i c h is m a d e of a sheet of lead rubber w i t h a l e a d e q u i v a l e n c e of 0.5 m m , a n d is s u s p e n d e d o n a n a l u m i n i u m rail, c a n b e l o w e r e d t o shield against s e c o n d a r y radiation f r o m the patient w h i c h o t h e r w i s e i m p i n g e s u p o n the examiner's u n p r o t e c t e d head, n e c k and a r m s and r e d u c e the general radiation level in the laboratory. This shielding device c a n b e fixed in the raised p o s i t i o n w i t h a m a g n e t i c lock and kept in the desired p o s i t i o n w i t h a friction lock.
Results W i t h o u t a n y extra shielding, in f l u o r o s c o p y with the o v e r c o u c h tube, the level of r a d i a t i o n a b o v e a n d at the e x a m i n a t i o n c o u c h is relatively high (Fig. 1 a). T h u s , for t h e s h o u l d e r - n e c k - h e a d r e g i o n , w h i c h is n o t protected b y the lead rubber a p r o n , the e x p o s u r e rate is 100 t o 2 0 0 m R / h . W h e n t h e shielding device is applied, and with the p a n e l let d o w n , t h e r a d i a t i o n in this r e g i o n is r e d u c e d t o less t h a n 5 m R / h (Fig. 1 a). A t l o w e r levels of t h e r o o m t h e s e c o n d a r y r a d i a t i o n is n o t r e d u c e d w i t h s u c h h i g h efficiency, b u t individual p r o t e c t i o n is p r o v i d e d by the lead rubber a p r o n . W i t h this shielding device the r a d i a t i o n d o s e t o the staff, i n c l u d i n g the radiologist performing t h e catheterization, m e a s u r e d at the cervical region, w a s less than 0.5 m G y over a p e r i o d of four w e e k s .
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Fig. 5. a) Lead rubber with a lead equivalence of 0.5 mm for fluoroscopy and cineradio graphy with a lateral tube. The figure gives the exposure rate (mR/h) at the side of the exami nation couch in a horizontal plane about 115 cm above the floor. The exposure rate with ( ) and without ( ) the lead rubber is given at 80 kV, 1 mA and a field size of 130 mm x 130 mm. b) The shielding device for a lateral tube.
W i t h the lead rubber shield attached t o the c o m p r e s s i o n t u b e of the r e m o t e c o n t r o l installation, the trunk is well protected, while the e x p o s u r e rate in t h e s h o u l d e r - n e c k head region is 2 0 to 100 m R / h . T h i s d e p e n d s o n h o w c l o s e to the patient the shield is p o s i t i o n e d (Fig. 4). W i t h the shielding device u s e d w i t h the lateral t u b e at c a r d i o a n g i o g r a p h y , the radiation is r e d u c e d f r o m a b o u t 100 t o 2 0 0 m R / h t o less t h a n 5 m R / h at the level of the device, m e a s u r e d at the p o s i t i o n of the radiologist p e r f o r m i n g the catheterization.
Discussion D u r i n g the t w o years in w h i c h it has n o w been in use, the d e t a c h a b l e t u b e , fixed o n t o the d i a p h r a g m h o u s i n g in f l u o r o s c o p y with the o v e r h e a d tube, has b e e n f o u n d e a s y t o h a n d l e and has caused n o hindrance t o the w o r k of the e x a m i n e r . T h e reduc t i o n by a factor of 2 0 to 4 0 of the radiation reaching the s h o u l d e r - n e c k - h e a d r e g i o n
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m e a n s a substantial i m p r o v e m e n t of the r a d i a t i o n p r o t e c t i o n of u n s h i e l d e d parts of t h e b o d y at a n g i o g r a p h y , and a c o n s i d e r a b l y l o w e r level of general radiation in the l a b o r a t o r y . T h e a n n u a l d o s e t o the lens w h i c h the e x a m i n e r m a y receive during f l u o r o s c o p y w i t h c a t h e t e r i z a t i o n u s i n g this extra shielding device is less than o n e t e n t h of the m a x i m u m permissible d o s e t o the lens, 15 rem per year. O b v i o u s l y , t o a c h i e v e this d o s e r e d u c t i o n , c o n s t a n t use m u s t be m a d e of the shielding device, the r a d i a t i o n fields m u s t be kept as small as p o s s i b l e and l o n g periods of f l u o r o s c o p y s h o u l d be a v o i d e d . T h e lead rubber shield that is a t t a c h e d t o the c o m p r e s s i o n e q u i p m e n t of a r e m o t e c o n t r o l a p p a r a t u s is simple t o m a n u f a c t u r e . It d o e s n o t protect the head a n d shoulder r e g i o n quite as well as the device described b u t p o s i t i o n e d c l o s e t o the object it gives a general r e d u c t i o n of the e n v i r o n m e n t a l radiation in the r o o m . T o p r o v i d e a d d i t i o n a l p r o t e c t i o n t o the h e a d - n e c k - s h o u l d e r region in f l u o r o s c o p y during a l o n g e r t i m e , especially in o b e s e p a t i e n t s , a c o m p l e m e n t a r y t u b e can be attached t o t h e d i a p h r a g m h o u s i n g as described. T h i s lead rubber shield c a n n o t be used unless c o v e r e d b y sterile drapes, w h e n sterile c o n d i t i o n s are necessary. T h e shielding device used with the lateral tube in c a r d i o a n g i o g r a p h y also satisfies the d e m a n d s for clinical a p p l i c a t i o n and d i m i n i s h e s the radiation d o s e ten- t o fiftyf o l d . T h i s d e v i c e s h o w s t h a t an effective radiation shield need n o t b e c o m p l i c a t e d or i m p e d e u p o n the e x a m i n a t i o n p r o c e d u r e . F u r t h e r m o r e , the m e a s u r e m e n t s d e m o n s t r a t e d that a high radiation d o s e t o m e m bers of the staff w i t h the t u b e a b o v e or at the side of the e x a m i n a t i o n c o u c h is pre d o m i n a n t l y d u e t o s e c o n d a r y r a d i a t i o n f r o m the patient. T h u s , n o leakage radiation f r o m the tube or t u b e h o u s i n g w a s f o u n d w i t h the e q u i p m e n t used.
SUMMARY In fluoroscopy and cineangiography with an overcouch tube or with a lateral tube, the radiation dose to the personnel is high. Simple shielding devices reducing, ten- to fifty-fold, the radiation dose to the unprotected shoulder-neck-head region are described.
ZUSAMMENFASSUNG Bei Durchleuchtung und Kinematographie mit einer Obertischrohre oder einer Iateralen Rohre ist die Strahlendosis des Personals hoch. Einfache Schutzanordnungen, die die Strahlendosis der ungeschiatzten Schulter-Nacken-Kopf-Regionen zehn- bis fiinfzig-Fach reduzieren, werden beschrieben.
RESUME La dose de radiation recue par le personnel est elevee au cours de la radioscopie et de la cineangiographie faites avec un tube au-dessus de la table ou avec un tube lateral. Les auteurs decrivent des dispositifs protecteurs simples qui reduisent dans une proportion allant de dix a cinquante fois la dose d'irradiation de la region de l'epaule du cou et de la tete par rapport a la dose sans protection.
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R E F E R E N C E S HOFFMAN J. R., STAIGER J . W . , W O L L A N R. O. and A M P L A T Z K.: The M i n n e s o t a special
procedure room. Radiology 97 (1971), 551. ICRP: Recommendation of the International Commission on Radiological Protection. Publication 9, Pergamon Press, London 1966. JACOBSON A . : Radiation protection considerations of overhead fluoroscopic installations. Hlth Phys. 20 (1970), 55. RILEY R. C , BIRKS J . W . , PALACIOS E. and TEMPLETON A . W . : Exposure of radiologists
during special procedures. Radiology 104 (1972), 679. STACEY A . J . and DAVIS R.: Personnel protection during cardiac catheterization with a comparison of the hazards of undercouch and overcouch X-ray tube mountings. Brit. J. Radiol. 47 (1974), 16. WHOLEY M . H . : Clinical dosimetry during the angiographic examination. Comments o n coronary arteriography. Circulation 50 (1974), 627.
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RADIATION PROTECTION IN FLUOROSCOPY WITH AN IMAGE INTENSIFIER A . H E M M I N G S S O N a n d P. O . L O F R O T H
W h e n t h e r o e n t g e n tube is m o u n t e d a b o v e t h e patient a n d t h e i m a g e intensifier b e n e a t h t h e e x a m i n a t i o n c o u c h , t h e radiation d o s e s received b y t h e personnel h a v e b e e n f o u n d t o b e considerably larger t h a n w i t h a n o p p o s i t e b e a m direction ( J A C O B S O N 1970,
H O F F M A N et c o l l .
1 9 7 1 , R I L E Y et c o l l .
1 9 7 2 , S T A C E Y et c o l l .
1974, WHOLEY
1 9 7 4 ) . T h u s , with a n o v e r c o u c h t u b e , s e c o n d a r y radiation f r o m t h e site of entry of the b e a m a t the upper surface of the patient is greater t h a n w i t h a n u n d e r c o u c h tube, w h e n scattered radiation c o m e s m a i n l y f r o m t h e site of exit of t h e b e a m f r o m t h e patient ( H O F F M A N et coll.). In this r a d i o l o g y d e p a r t m e n t it h a s b e e n f o u n d that in catheterization, with t h e o v e r c o u c h t u b e , t h e radiation d o s e t o t h e r a d i o l o g i s t per f o r m i n g t h e catheterization m a y b e m o r e t h a n 0 . 0 1 G y o v e r a period of four w e e k s , measured a t s h o u l d e r level a b o v e t h e l e a d rubber a p r o n . T h i s m e a n s a d o s e t o t h e lens, for e x a m p l e , lying c l o s e t o t h e m a x i m u m permissible d o s e e q u i v a l e n t of 1 5 r e m (1 rem = 0 . 0 1 Sv) p e r year ( I C R P 1 9 6 6 ) . Of t h e a p p r o x i m a t e l y 1 8 p e r cent of t h e b l o o d - f o r m i n g b o n e m a r r o w that is n o t p r o t e c t e d b y a l e a d rubber a p r o n ( H O F F M A N et coll.), t h e greatest p r o p o r t i o n is l o c a t e d cranially, a n d t h e d o s e t o this fraction of b o n e m a r r o w w o u l d therefore b e u n a c c e p t a b l y h i g h ( m a x i m u m permissible d o s e e q u i v a l e n t 5 r e m per year, I C R P ) . F o r f l u o r o s c o p y i n e x a m i n a t i o n r o o m s e q u i p p e d w i t h a n o v e r c o a c h tube, special auxiliary devices h a v e b e e n c o n s t r u c t e d t o m i n i m i z e the r a d i a t i o n d o s e received b y parts of t h e b o d y that are n o t p r o t e c t e d b y t h e lead r u b b e r a p r o n . T h e a i m s h a v e been ( 1 ) t o d i m i n i s h t h e r a d i a t i o n t o t h e u n p r o t e c t e d Submitted for publication 7 December 1977. Acta Radiologica
Diagnosis 19 (1978) Fasc. 6
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shielding equipment at 80 kV, 1 mA and a field size of 130 mm x 130 mm with a phantom thickness of 200 mm. b) The shielding device for an overcouch tube. The tube is rotatable and has panels that can be let down.
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a
h e a d - n e c k - s h o u l d e r r e g i o n , (2) t o p r e v e n t t h a t t h e shielding device h a m p e r s the w o r k of t h e e x a m i n e r , (3) t o p r o m o t e sterile catheterization c o n d i t i o n s , a n d (4) t o m a k e the h a n d l i n g of the device easy a n d n o t u n d u l y h e a v y .
Material and Methods T h e r a d i a t i o n in the l a b o r a t o r y w a s m e a s u r e d w i t h a surveymeter ( N u c l e a r C h i c a g o M o d e l 2 5 8 8 M o n i t o r a n d 2 5 2 6 m e d i u m range i o n i z a t i o n c h a m b e r , v o l u m e 5 0 0 ml). T h e m e a s u r e m e n t i n s t r u m e n t has a linear energy r e s p o n s e ranging f r o m 10 k e V t o o v e r 1 M e V , w i t h a n a c c u r a c y of 10 per cent. S u p p l e m e n t a r y m e a s u r e m e n t s were m a d e w i t h a n E I L i o n i z a t i o n c h a m b e r (37 A ) c o n n e c t e d t o a K e i t h l e y Electrometer 616. A 2 0 0 m m thick a n d 3 0 0 m m square w a t e r p h a n t o m , c o r r e s p o n d i n g roughly t o t h e cross-sectional d i m e n s i o n s of a n o r m a l - s i z e d patient, w a s p l a c e d o n the e x a m i n a t i o n c o u c h in the centre of the r a d i a t i o n field. T h e b e a m w a s oriented at right angles t o the i m a g e intensifier. M e a s u r e m e n t s were p e r f o r m e d during f l u o r o s c o p y
with
a u t o m a t i c d o s e c o n t r o l , in a vertical p l a n e t h r o u g h the b e a m at right angles t o the t u b e . T h e size of the f o c a l s p o t w a s 1.2 m m x 1.2 m m a n d the t u b e p o t e n t i a l w a s 8 0
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Fig. 2
Fig. 3
Fig. 2. The shielding device mounted on the tube. Fig. 3. The shielding device in place. Lead rubber suspended on the compression tube of a remote control apparatus for fluoroscopy with the overcouch tube.
k V (12 p u l s e s p e r p e r i o d ) w i t h t o t a l f i l t r a t i o n of t h e b e a m 3.5 m m A l . T h e field size a t t h e level of m e a s u r e m e n t w a s 130 m m x 130 m m . T h e r a d i a t i o n levels a r e g i v e n a s e x p o s u r e p e r t i m e u n i t a n d p e r m A ( m R / h ; 1 m R ^ 2 . 5 8 10
7
C/kg).
T h e p r o b l e m s of r a d i a t i o n p r o t e c t i o n in c o n n e c t i o n w i t h o v e r c o u c h
installations
h a s b e e n solved b y s h i e l d i n g e q u i p m e n t s w h i c h a r e m a i n l y b a s e d o n t h e s a m e p r i n c i ples. A t t h i s r a d i o l o g y d e p a r t m e n t a d e t a c h a b l e s h i e l d i n g t u b e h a s b e e n c o n s t r u c t e d t h a t c a n b e fixed o n t o t h e d i a p h r a g m h o u s i n g in t h e c h a n n e l s i n t e n d e d for t h e p e r s p e x p l a t e s o r a d d i t i o n a l filters for u s e in a n g i o g r a p h y l a b o r a t o r i e s a n d o t h e r f l u o r o s c o p y r o o m s e q u i p p e d w i t h a n o v e r h e a d t u b e a n d a f i l m - f o c u s d i s t a n c e of a b o u t 100 c m ( F i g s 1 b , 2). T h e s h i e l d i n g t u b e is r o t a t a b l e a n d is s u p p l i e d w i t h t w o h i n g e d p a n e l s of different sizes t h a t c a n b e let d o w n t o i m p r o v e t h e s h i e l d i n g in t h e d i r e c t i o n of t h e e x a m i n e r . T h e s h i e l d i n g t u b e is c o n s t r u c t e d of a 6 m m t h i c k p l e x i g l a s s f r a m e c o v e r e d w i t h a 0.5 m m t h i c k s h e e t of l e a d . T h e s h e e t of lead is g l u e d t o t h e p l e x i g l a s s . F o r r e m o t e c o n t r o l i n s t a l l a t i o n s w i t h a c o m p r e s s i o n t u b e , a lead r u b b e r
shield
w i t h a lead e q u i v a l e n c e of 0.5 m m h a s been c o n s t r u c t e d . T h i s is s u s p e n d e d a l o n g t h e l o n g side of t h e c o u c h by m e a n s of o p e n h o o k s o n r o d s t h a t a r e fixed t o t h e c o m p r e s s i o n t u b e . In o r d e r t o p r o t e c t t h e a n a e s t h e s i s t , for e x a m p l e , a t t h e h e a d side of t h e c o u c h , a l o n g lead r u b b e r s c r e e n is a l s o s u s p e n d e d s o t h a t it is a l m o s t a t r i g h t a n g l e s t o t h e r a d i a t i o n field a n d shields t h e e x a m i n e r a t t h e l o n g side of t h e t a b l e , a n d a l s o o n e of t h e s h o r t e n d s of t h e t a b l e , f r o m s e c o n d a r y r a d i a t i o n ( F i g . 3). 64-785841
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Fig. 4. The lead quivalence of the lead rubber in Fig. 3 is 0.5 mm. The exposure rate (mR/h) at the couch with the shielding device ( ) is given at 80 kV, 1 mA and a field size of 130 mm x 130 mm with a phantom thickness of 200 mm.
—I
1— I 0
1 0.2
1
1
1
0.4
0.6
0.8
1 1.0
m
F o r c a r d i o a n g i o g r a p h y w i t h use of a lateral r o e n t g e n tube, a shielding device has b e e n fixed t o the side of t h e d i a p h r a g m h o u s i n g (Fig. 5 b). T h i s device, w h i c h is m a d e of a sheet of lead rubber w i t h a l e a d e q u i v a l e n c e of 0.5 m m , a n d is s u s p e n d e d o n a n a l u m i n i u m rail, c a n b e l o w e r e d t o shield against s e c o n d a r y radiation f r o m the patient w h i c h o t h e r w i s e i m p i n g e s u p o n the examiner's u n p r o t e c t e d head, n e c k and a r m s and r e d u c e the general radiation level in the laboratory. This shielding device c a n b e fixed in the raised p o s i t i o n w i t h a m a g n e t i c lock and kept in the desired p o s i t i o n w i t h a friction lock.
Results W i t h o u t a n y extra shielding, in f l u o r o s c o p y with the o v e r c o u c h tube, the level of r a d i a t i o n a b o v e a n d at the e x a m i n a t i o n c o u c h is relatively high (Fig. 1 a). T h u s , for t h e s h o u l d e r - n e c k - h e a d r e g i o n , w h i c h is n o t protected b y the lead rubber a p r o n , the e x p o s u r e rate is 100 t o 2 0 0 m R / h . W h e n t h e shielding device is applied, and with the p a n e l let d o w n , t h e r a d i a t i o n in this r e g i o n is r e d u c e d t o less t h a n 5 m R / h (Fig. 1 a). A t l o w e r levels of t h e r o o m t h e s e c o n d a r y r a d i a t i o n is n o t r e d u c e d w i t h s u c h h i g h efficiency, b u t individual p r o t e c t i o n is p r o v i d e d by the lead rubber a p r o n . W i t h this shielding device the r a d i a t i o n d o s e t o the staff, i n c l u d i n g the radiologist performing t h e catheterization, m e a s u r e d at the cervical region, w a s less than 0.5 m G y over a p e r i o d of four w e e k s .
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Fig. 5. a) Lead rubber with a lead equivalence of 0.5 mm for fluoroscopy and cineradio graphy with a lateral tube. The figure gives the exposure rate (mR/h) at the side of the exami nation couch in a horizontal plane about 115 cm above the floor. The exposure rate with ( ) and without ( ) the lead rubber is given at 80 kV, 1 mA and a field size of 130 mm x 130 mm. b) The shielding device for a lateral tube.
W i t h the lead rubber shield attached t o the c o m p r e s s i o n t u b e of the r e m o t e c o n t r o l installation, the trunk is well protected, while the e x p o s u r e rate in t h e s h o u l d e r - n e c k head region is 2 0 to 100 m R / h . T h i s d e p e n d s o n h o w c l o s e to the patient the shield is p o s i t i o n e d (Fig. 4). W i t h the shielding device u s e d w i t h the lateral t u b e at c a r d i o a n g i o g r a p h y , the radiation is r e d u c e d f r o m a b o u t 100 t o 2 0 0 m R / h t o less t h a n 5 m R / h at the level of the device, m e a s u r e d at the p o s i t i o n of the radiologist p e r f o r m i n g the catheterization.
Discussion D u r i n g the t w o years in w h i c h it has n o w been in use, the d e t a c h a b l e t u b e , fixed o n t o the d i a p h r a g m h o u s i n g in f l u o r o s c o p y with the o v e r h e a d tube, has b e e n f o u n d e a s y t o h a n d l e and has caused n o hindrance t o the w o r k of the e x a m i n e r . T h e reduc t i o n by a factor of 2 0 to 4 0 of the radiation reaching the s h o u l d e r - n e c k - h e a d r e g i o n
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m e a n s a substantial i m p r o v e m e n t of the r a d i a t i o n p r o t e c t i o n of u n s h i e l d e d parts of t h e b o d y at a n g i o g r a p h y , and a c o n s i d e r a b l y l o w e r level of general radiation in the l a b o r a t o r y . T h e a n n u a l d o s e t o the lens w h i c h the e x a m i n e r m a y receive during f l u o r o s c o p y w i t h c a t h e t e r i z a t i o n u s i n g this extra shielding device is less than o n e t e n t h of the m a x i m u m permissible d o s e t o the lens, 15 rem per year. O b v i o u s l y , t o a c h i e v e this d o s e r e d u c t i o n , c o n s t a n t use m u s t be m a d e of the shielding device, the r a d i a t i o n fields m u s t be kept as small as p o s s i b l e and l o n g periods of f l u o r o s c o p y s h o u l d be a v o i d e d . T h e lead rubber shield that is a t t a c h e d t o the c o m p r e s s i o n e q u i p m e n t of a r e m o t e c o n t r o l a p p a r a t u s is simple t o m a n u f a c t u r e . It d o e s n o t protect the head a n d shoulder r e g i o n quite as well as the device described b u t p o s i t i o n e d c l o s e t o the object it gives a general r e d u c t i o n of the e n v i r o n m e n t a l radiation in the r o o m . T o p r o v i d e a d d i t i o n a l p r o t e c t i o n t o the h e a d - n e c k - s h o u l d e r region in f l u o r o s c o p y during a l o n g e r t i m e , especially in o b e s e p a t i e n t s , a c o m p l e m e n t a r y t u b e can be attached t o t h e d i a p h r a g m h o u s i n g as described. T h i s lead rubber shield c a n n o t be used unless c o v e r e d b y sterile drapes, w h e n sterile c o n d i t i o n s are necessary. T h e shielding device used with the lateral tube in c a r d i o a n g i o g r a p h y also satisfies the d e m a n d s for clinical a p p l i c a t i o n and d i m i n i s h e s the radiation d o s e ten- t o fiftyf o l d . T h i s d e v i c e s h o w s t h a t an effective radiation shield need n o t b e c o m p l i c a t e d or i m p e d e u p o n the e x a m i n a t i o n p r o c e d u r e . F u r t h e r m o r e , the m e a s u r e m e n t s d e m o n s t r a t e d that a high radiation d o s e t o m e m bers of the staff w i t h the t u b e a b o v e or at the side of the e x a m i n a t i o n c o u c h is pre d o m i n a n t l y d u e t o s e c o n d a r y r a d i a t i o n f r o m the patient. T h u s , n o leakage radiation f r o m the tube or t u b e h o u s i n g w a s f o u n d w i t h the e q u i p m e n t used.
SUMMARY In fluoroscopy and cineangiography with an overcouch tube or with a lateral tube, the radiation dose to the personnel is high. Simple shielding devices reducing, ten- to fifty-fold, the radiation dose to the unprotected shoulder-neck-head region are described.
ZUSAMMENFASSUNG Bei Durchleuchtung und Kinematographie mit einer Obertischrohre oder einer Iateralen Rohre ist die Strahlendosis des Personals hoch. Einfache Schutzanordnungen, die die Strahlendosis der ungeschiatzten Schulter-Nacken-Kopf-Regionen zehn- bis fiinfzig-Fach reduzieren, werden beschrieben.
RESUME La dose de radiation recue par le personnel est elevee au cours de la radioscopie et de la cineangiographie faites avec un tube au-dessus de la table ou avec un tube lateral. Les auteurs decrivent des dispositifs protecteurs simples qui reduisent dans une proportion allant de dix a cinquante fois la dose d'irradiation de la region de l'epaule du cou et de la tete par rapport a la dose sans protection.
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R E F E R E N C E S HOFFMAN J. R., STAIGER J . W . , W O L L A N R. O. and A M P L A T Z K.: The M i n n e s o t a special
procedure room. Radiology 97 (1971), 551. ICRP: Recommendation of the International Commission on Radiological Protection. Publication 9, Pergamon Press, London 1966. JACOBSON A . : Radiation protection considerations of overhead fluoroscopic installations. Hlth Phys. 20 (1970), 55. RILEY R. C , BIRKS J . W . , PALACIOS E. and TEMPLETON A . W . : Exposure of radiologists
during special procedures. Radiology 104 (1972), 679. STACEY A . J . and DAVIS R.: Personnel protection during cardiac catheterization with a comparison of the hazards of undercouch and overcouch X-ray tube mountings. Brit. J. Radiol. 47 (1974), 16. WHOLEY M . H . : Clinical dosimetry during the angiographic examination. Comments o n coronary arteriography. Circulation 50 (1974), 627.
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