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AUTOMATIC SEGMENTATION AND THREE-DIMENSIONAL RENDERING FOR CT IMAGE SETS OF THE FLUID-FILLED STOMACH , D. Ress. Ph.D.. 1L F. Thoeni, M.D., Univezsity of California, Department of Radiology, San Francisco, CA . . . . . . . Pureose: Three-dimensional rendering o f the stomach, offers.an a!ternabve .methoa ~ as.ses, s .rag gasmc tun(ors, but commercially available techniques are seriously nnpalred when mtraluminai flmdrs.prese~t; In this investigation, a computer code was written to perform 3D-rendenng of the stomaen mstenaen with air and/or fluid. Methods: Ten patients underwent a helical CT consisting .of 3-to-7 mm slices obttt~ed t ~ u g h , th~ s~mach. Noaionie contrast material was administ~'ed at 5 m[/. sec fo( 150 ml. (scan aelay: ao sec) an the stomach distended with effervescent agents. For 3D-rendering, an mt.etaetxve t~.mputer code with an extensive graphical usar interface was written to allow rapid . s~m~tat ton o f C T onage sets.of hofi~ow organs. The code uses several strategies to detect the tuner wall o t me stomaca ennancen wire contrast material even in the presemce of residual gastric fluid. Results All sets of CT images were successfully segm.ented and rendered in 3D:d%~nffi~patients with gastriefluid. Threeintr insictumurrnassesandtwoaxmnsmmas.seswerect ._canl/mentm • . . Conclusions: Automatic segmentation and 3D-rendering of the mteaaor wall ot the stomach is feastble and may become a useful tool for the diagnosis and treatment planning of intraluminal gastric tumors.

SENSITIVITY OF VIRTUAL COLONOSCOPY FOR SMALL SIMULATED POLYPS OF PIG COLON. A.H. Dachrnan, M.D., lames Lieberrnan. M.D.. R. B. Osiris, M.D., S-Y. J. (::hen, Ph.D., K. Hoffmann, Ph.D.G. M7 Newmark, M.D., J. McGill, Department of Radiology, The University of Chicago, Chicago, IL 60637

Puroose: Virtual colonoscopy is a method of three-dimensional rendering of the mucosai surface of the colon from CT-generated data in a manner that simulates an eadoscopic view. We investigated the sensitivity of virtual cofonoscopy for small lesions anti how the sensitivity changes with position of the lesions in the colon with respect to the gantry, pitch and collimation. Mpthad s: Pig colon was resected and cleansed. Polyps of 3, 5, 7 and 10 millimeters were simulated. The insufflated colon was placed in a water bath within a plastic container. Images were obtained at 3 ram, 5 rrma, mad 7 ram collimation at pitches of 1, t.6 and 2. In order to simulate polyps in vertical, oblique and transverse segments of the human colon, the colon was oriented at angles of 0 °, 45 ° and 9(P to the gantry. The images were reconstructed at 1 mm intervals. We compared the ease of interpretation (time) for the 2-D and real time 3-D rendered images at angles of 45 ° and 90 ° to the gentt y. We correlated the lesion conspicuity on a scale of 0 to 2 and the number of views on which the lesion was seen for variables of axis, pitch and collimation. Results: All lesions were visible on 2-D and 3-D viewings, although 3 ram polyp was less well seert than the others. The 5 rnm polyp was fairly well seen in most views. All 7 rmn and 10 nun polyps were well seen. Increasing the pitch decreased the number of views seen of the prospecSves and increased the number of views seen on the 1 mm reconstructed retrospectives. Conclusions: Lesinn consplcuity does not seem to vary with the speciraen orientation w i ~ lesions 3 mm or greator. 3-I:) renderings are reviewed as fast as 2-D images. Lesions of 5 mm or greater are appropriate for accurate analysis using virtual colonascopy. The number of views on which the lesion was seen was directly related to pitch on the reirospective I ram reconstructions and inversely related in prospective views.

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CT F L U O R O S C O P Y : IMPLICATIONS F O R T H E S E L E C T I O N O F IMAGING T E C H N I Q U E IN RADIOLOGICALLY G U I D E D A B D O M I N A L P R O C E D U R E S . Nial l G W a r n o c k . F . tLC .R . . D a v i d E M e l l e n b e r g , P h . D . , B r a d H T h o m p s o n , M.D. , Y u t ~ k a S a t o , M.D. , U n i v e r s i t y of Iowa, Iowa City, IA P u r o o s e : To e v a l u a t e t h e ro le of CT g u i d a n c e w i t h n e a r r e a l t i m e r e c o n s t r u c t i o n i n p e r c u t a n e o u s a b d o m i n a l p r o c e d u r e s . M e t h o d s : CT F l u o r o s c o p y a t 6 i m a g e s p e r s e c o n d w a s c o m p a r e d w i t h c o n v e n t i o n a l C T for a b d o m i n a l n e e d l e p l a c e m e n t s i n h u m a n c a d a v e r s . R e s u l t s : N e a r r e a l - t i m e d i s p l a y f ac i l i t a t e s n e e d l e g u i d a n c e w i t h i n t h e i m a g i n g p l ane . P a t i e n t r a d i a t i o n e x p o s u r e i s s i m i l a r to c o n v e n t i o n a l CT. U s i n g s i m p l e n e e d l e h o l d e r s t h e o p e r a t o r s h a n d e x p o s u r e i s 1 - 2 m R / s . C o n c l u s i o n s : CT f l u o r o s c o p y i s a r o b u s t g u i d a n c e s y s t e m . W i t h i n t h e a b d o m e n a p p l i c a t i o n s wi l l b e l i m i t e d b y t he ava i l ab i l i t y of o t h e r m e t h o d s n o t i n v o l v i n g o p e r a t o r e x p o s u r e . L ike ly u s e s i n c l u d e s i t e s w h i c h a r e n o t we l l s e e n a t u l t r a s o u n d a n d w h i c h a r e s m a l l a n d m o b i l e , h a v e a h a z a r d o u s a c c e s s t r ac t , o r a r e o n l y v i s i b l e t r a n s i e n t l y w i t h c o n t r a s t e n h a n c e m e n t . C o n t i n u i n g d e v e l o p m e n t of i m p r o v e d o r r e m o t e l y m a n i p u l a t e d n e e d l e h o l d e r s a n d of r iva l M R g u i d a n c e s y s t e m s wi l l a l s o i n f l u e n c e u s e .

E F F E C t O F BI O PSY N E E D L E S I Z E I N ABILITY T O ASSESS G E N E E X P R E S S I O N BY P O L Y M E R A S E C H A I N R E A C F I O N (PCR), Will iam Waddil l III. M.D.. E. Uoger , M.D., The University of Arizona, Tucson, AZ. Purpose: Evaluation of gene expression by PCR in gene therapy for cancer. Methods: In a phase I clinical trial approved by the H uman Subjects Commit tee , the R A C and the FDA, ten pat ients (4 women and 6 men) with metastatic me lanoma were t reated with C-f-guided intratumoral injection of HLA-B7 gene with l iposemal vector. All patients underwent serial CT scans post gene therapy with repeat CT-guided core biopsies of the injected tumor for assessment of gene~ localization and expression by the polymerase chain reaction (PCR), RT-PCR, flow eytometly and , immunohistochemish'y. Results: Tissue specimens from 18 gauge core needle biopsies were adequate for analyzing gene expression by PCR. Smal le r needle sizes provided insufficient tissue specimens for PCR analysis regardless of the number of tissue specimens. Conclusions: Needle size does affect ability to assess gene expression by PCR.

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QUANTITATIVE ANALYSIS OF CORTICAL CNS ATROPHY VIA AN AUTOMATED APPROACH, Leonard B. Kolodny, M.D., J.P. Cousins, Ph.D., W.A. Wagle, M.D., Albany Medical College, Albany, NY Purpose: To compare a computer analysis with neuroradiologist's interpretation of cortical atrophy on axial MRI images. Methods: Standard clinical axial image sets FSE/T2 (TE/TR/ETL 102/4000/8) or Spin Echo T2 (TE/TR 85/2500) were obtained on a G.E. Signa 1.5 clinical system. Five, 5mm thick slices per study, through the region of the ventricles, were analyzed with a volume and segmentation program calculating the CSF and total brain volumes. Neuroradiological readings were used to determine the category of clinical atrophy. Four groups were evaluated: normal (n=30), mild atrophy (n=30), moderate atrophy (n=3O) and severe atrophy (n=9). Results: The mean (standard deviation) and [range] of %CSF for the groups were: normal 5.97%(1.90%), [2.91-9.86%]; mild atrophy 11.80%(4.56%), [5.17-22.19%]; moderate atrophy 18.17%(4.87%), [10.54-31.32%]; and severe atrophy 29.87%(3.98%), [21.53-35.62%]. The 95% confidence intervals of % CSF for the groups were: normal 5.29-6.65, mild atrophy 10.17-13.43, moderate atrophy 16.43-19.91, and severe atrophy 27.27-32.47. ConcIusion: Neuroradiologicai assessment of CNS atrophy is subjective and shows a great deal of variability. Automated assessment is fast, accurate, reproducible and can be used to evaluate for subtle changes over time. This technology can be used to set age related standards which eventually may be used to diagnose early degenerative CNS disease.

THE NON-CONTRAST HEAD CT AND AIDS IN THE EMERGENCY ROOM, A USELESS EXAM?, Kenneth I~ Tomkovich, M.D., H J . Lee, M.D., D. Ghanekar, M.D., L Wolansky, M.D., AZ. Kainln, M.D., S.R. Baker, M.D., LrMDNJ-New Jersey Medical School, Newark, NJ.

Purpose: Much at tent ion has been paid to the optimal way to image the brain for pat ients wi th HIV infectiorCAIDS and neurologic symptoms. Our objective is to deterinine if non-cont~mt head CT is a useful sc~ening test in the emergency setting.

Methods: We reviewed a total of 250 cases of non-contrast CT scans of the head from October 1994 through November 1995. All pat ients had the diagnosis of HIV infection or AIDS. All cases were reviewed by one or more neuroradiologists.

Results: A total of 169 males and 81 females were included. The mean age was 89.5 years. Findings included mass lesion 16.4%, encephalomalacla 7.5%, white ma t t e r disease 7.5%, hydrocephalus 7.5%, sinusitis 4.5%. 23.9°/0 had more than one finding. 23.1% were normal.

Conclusions: 'I]ae non-contraat head CT is a useful screening study which can rapidly evaluate HIV infected or AIDS pat ients who have neurologic signs and symptoms. Of those exams which are positive, a relatively small percentage will require addi t ional diagnostic examination. Especially in the emergency setting, the non- omatrast head CT can quickly eliminate the possibility of life threatening intracradial disease while narrowing the group of pat ients requiring additional studies.