m P h a s e - c o n t r a s t T o m o g r a p h y u s i n g X - r a y I n t e r f e r o m e t e r h a v i n g 4 0 - μ L a m e l l a Fig. 1. X-ray interferometer w ith a 40 μ m lamella (a) and experimental setup for phase-contrast X-ray tomography (b ) . Fig. 1(a) Fig. 1(b) Figure 2(a) Figure 2(b) Recently , various imaging techniques t hat produce c ontrast i m age s from X -ray phas e information have been proposed. Biologica l imaging is t heir m ain target because of expecte d sensitivity u p to 1000 times higher than absorption- c ontrast X -ray imaging, w hose performance is insufficient for soft tissues. Th r ee-dimensional to mographic imaging using X-ray phase informatio n has also been achieved [1,2] using an X -ra y interferometer [3]. Its high sensitivity enabl es us to observe tissue structures, such as vessels, cancerous lesions, fibrous tissues, without the use of contras t media. T he method’s spatial resolution (roughly 30 μ m × 30 μ m × 60 μ m) , however, was not satisfactory fo r histological observatio n; t he spatial resolution wa s not limited by our image detecto r, but by the X-ray interferometer itself, which was made by cutting th e body out of a crystal. T he interferometer produces interference fringes by generating and recombining two c oherent X -ray beams using t he dynamica l diffraction at a set of lamellae. A blurring mechanism is involved in this process; that is, the wave field of X-rays downstream of the sample is altered by th e third l amella, which f unctions as an X -ray hal f - mirror, due to the process of d ynamical diffraction. We therefore fabricated a new X-ray interferometer with a 40 - μ m lamella ( ), which was effectiv e for suppressing the image blurring. T he interferometer successfully produced interference fringes and was installed at beamlin e BL20X U , w here we developed an apparatus fo r phase-contrast tomography. In the measurements, we used 12.4 keV X-rays with a CCD-based image detector, w hose pixel size was 6.5 μ m × 6.5 μ m. Tissue pieces (2 ~ 3 mm in diameter) were observe d in a cell filled with formalin. The experimental setu p shown in . s hows tomographic images obtained for a piece cut out of the cortex of a rat kidney fixe d in formalin [4]. C onvoluted tubules and vessels are revealed. s hows an optical image of (a) (b) 40 μ m Undulator Monochromator Phase shifter X-ray interferometer Sample Image detector 116 A t s u s h i M o m o s e a , b , I c h i r o K o y a m a a , b a n d T o h o r u T a k e d a c ( a ) T h e U n i v e r s i t y o f T o k y o ( b ) S P r i n g - 8 / J A S R I ( c ) U n i v e r s i t y o f T s u k u b a E - m a i l : m o m o s e @ e x p . t . u - t o k y o . a c . j p t h e c o r r e s p o n d i n g s p e c i m e n s l i c e d a f t e r t h e X - r a y m e a s u r e m e n t f o r c o m p a r i s o n . G l o m e r u l i c a n a l s o b e i d e n t i f i e d i n F i g . 2 ( a ) i n c o m p a r i s o n w i t h F i g . 2 ( b ) . F i g u r e 2 ( c ) s h o w s a 3 - D r e n d e r e d v i e w o f t h e t o m o g r a p h i c d a t a . I n e a r l i e r e x p e r i m e n t s [ 5 ] , t h e s t r u c t u r e s c o u l d n o t b e r e v e a l e d a s c l e a r l y a s t h e p r e s e n t i m a g e . R e f e r e n c e s [ 1 ] A . M o m o s e , N u c l . I n s t r u m . M e t h . A 3 5 2 ( 1 9 9 5 ) 6 2 2 . [ 2 ] A . M o m o s e e t a l . , N a t u r e M e d i c i n e 2 ( 1 9 9 6 ) 4 7 3 . [ 3 ] U . B o n s e a n d M . H a r t , A p p l P h y s . L e t t . 6 ( 1 9 6 5 ) 1 5 5 . [ 4 ] A . M o m o s e , I . K o y a m a , Y . H a m a i s h i , H . Y o s h i k a w a , T . T a k e d a , J . W u , Y . I t a i , K . T a k a i , K . U e s u g i a n d Y . S u z u k i , P r o c . 7 t h I n t . C o n f . X - r a y M i c r o s c o p y , t o b e p u b l i s h e d i n J . d e P h y s i q u e I V . [ 5 ] A . M o m o s e e t a l . , S P I E P r o c . 3 6 5 9 ( 1 9 9 9 ) 3 6 5 . F i g . 2 . P h a s e - c o n t r a s t t o m o g r a p h i c i m a g e o f a c o r t e x p a r t o f a r a t k i d n e y ( a ) a n d a n o p t i c a l i m a g e o f t h e c o r r e s p o n d i n g s p e c i m e n s l i c e d a f t e r X - r a y m e a s u r e m e n t ( b ) . G : g l o m e r u l i . ( c ) 3 - D r e n d e r e d t o m o g r a p h i c v i e w . S t r u c t u r e s c o r r e s p o n d i n g t o 2 o r 3 p i x e l s c o u l d b e r e s o l v e d i n t h e t o m o g r a m . T h u s , p r e s e n t s p a t i a l r e s o l u t i o n i s e s t i m a t e d t o b e b e t w e e n 1 3 μ m a n d 2 0 μ m . I t i s s p e c u l a t e d , h o w e v e r , t h a t t h e i n f l u e n c e o f t h e d e t e c t o r ’ s s p a t i a l r e s o l u t i o n w a s n o t n e g l i g i b l e ; t h e r e f o r e , i n p a r a l l e l w i t h e m p l o y i n g a b e t t e r i m a g e d e t e c t o r , X - r a y i n t e r f e r o m e t e r s w i l l b e f u r t h e r i m p r o v e d t o a c h i e v e h i g h e r s p a t i a l r e s o l u t i o n . ( a ) 2 0 0 μ m G ( b ) ( c ) 8 0 0 μ m ( c ) 117
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