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the catheter in real time, the section level and position must be tracked continuously. Meth- ods for accomplishing this are being devel- oped by Dr. Wolfgang Nitz and Dr. Peter Speier in the Applications Development de- partment at Siemens Med. One of their devel- opments is a prototype MR-compatible catheter that carries a micro-coil at its tip. That makes it possible to determine the loca- tion of the catheter tip in MR scanners. A soft- ware program developed by Speier and coworker Dr. Sven Zühlsdorff uses this infor- mation to track the position of the sectional image, so that a clear view of the catheter tip can always be obtained. “This puts us two or three years ahead of the competition,” asserts Nitz.
3D Images During Surgery. Siemens is also taking a new approach in 3D imaging during emergency operations. For instance, previ- ously, a patient suspected of having suffered a cerebral hemorrhage had to be transported from a sterile angiographic room to a differ- ent room for a verification CT scan, and then returned to the angio room. In a life-threaten- ing situation, this meant having to waste pre- cious time before the hemorrhage could be stopped. “With the new generation of angio- graphic C-arm systems, like the AXIOM Artis dBA DynaCT, the verification CT scan is ob- tained while performing treatment — and without relocating the patient,” reports Dyna- CT Product Manager Michael Martens.
In DynaCT, the X-ray source of the angio- graphic system revolves around the patient and generates sectional images, as in com- puted tomography. The imaging process is carried out by an advanced version of syngo Inspace 3D that’s capable of depicting even low-contrast regions such as soft tissues and liquids, so that cerebral hemorrhages and tu- mors can be discerned.
“Although the resolution of low-contrast tissues isn’t quite as good as in conventional CT, it’s sufficient for intervention in the angio lab,” says Dr. Hideyuki Takano of Chiba Cancer Center in Chiba, Japan, who has already used DynaCT in examining brain tumors and liver carcinomas.
With a 60 percent market share, Siemens is the market leader in angiographic systems for neuroradiology. Martens is confident that this new technology will become widely ac- c e p t e d a s t h e s t a n d a r d m e t h o d d u r i n g t h e ■ M i c h a e l L a n g coming year.
Patients benefit because hybrid systems deliver more accurate diagnoses faster.
Hybrid systems such as Siemens’ Symbia deliver the best of both worlds — in this case, a cross-section of a thyroid gland (with benign tumor). In the com- bined image (center image, below) anatomical details (CT, left image) and functional information (SPECT, right image) are superimposed.
Until now, physicians have used two dif- ferent devices — one for SPECT and one for CT. However, since the patient’s position may differ slightly from one examinations to the other, an exact superimposition of the image information is difficult to achieve. Only when CT and SPECT are combined can the two sets be flawlessly fused. Using Symbia, the two ex- posures are made in quick succession while the patient remains in the same position. The SPECT signal not only demonstrates the posi- tion of the tumor but also provides clues as to its physiology. Very active tumors accumulate high concentrations of radioactive material and therefore emit strong signals. But some of the radiation emitted by this radioactive substance in the body is absorbed or scat- tered by surrounding tissue. This can degrade the image and make localization and inter- pretation difficult.
Hybrid CT-SPECT technology can solve this problem. “With the CT data, the software we’ve developed can estimate the amount of atten-
Localizing Tumors in 3D. Another hybrid system, the biograph, works much like Sym- bia. It combines CT with Positron Emission Tomography (PET). In PET, too, the patient is injected with a small amount of a radioactive substance. But, unlike SPECT, the radioactive substance does not emit photons but ele- mentary particles called positrons. The posi- trons collide with electrons in nearby atoms. Each such interaction creates two photons. These photons can be identified, and their point of origin precisely localized by detec- tors.
“Nuclear medicine is a service provider for specialists, such as surgeons, which supplies important image information for use in ther- apy or during surgical intervention,” explains Stefan Käpplinger, manager of the Physics Group at Medical Solutions (Med) in Erlan- gen, where he is also responsible for Molecu- lar Imaging. “Radiologists in nuclear medicine are accustomed to interpreting tomograms. Surgeons, on the other hand, prefer three-
became the first institution in Europe to start using the new Symbia System from Siemens, a hybrid CT-SPECT (computed tomography and single photon emission computed to- mography) system (above).
uating tissue through which the radiation has traveled and, as a result, determine the actual level of radioactivity in the tumor,” notes Keith Andress, manager of the Software Department for Molecular Imaging at Siemens Medical So- lutions in Hoffmann Estates, Illinois. The CT data can also serve to estimate the depth of the at- tenuating tissue between the tumor and the detector, thereby improving the precision of tumor localization. The Symbia system benefits patients in yet another way. In the past, they had to make separate appointments in two different departments at different times. As a result, days or even weeks might pass before a diagnosis was finally available. Now, both ex- aminations are performed in quick succession.
dimensional images.” That’s why biograph systems have been provided with FusedVision 3D software. This program assembles 2D sec- tional CT images into a three-dimensional im- age that can be viewed from any angle.
In CT, an X-ray source rotates around the patient to create sectional images of the body. On the other hand, in SPECT, patients are injected with small doses of slightly ra- dioactive substances that accumulate for a short time in certain organs, such as the heart, or in tumor tissues. The emitted radia- tion is sensed by a detector to create images that reveal biological activity and metabolism in damaged areas of the heart or in malignant tumors.
The tumor data generated by PET is incor- porated within this image. This combination improves physicians’ ability to check the progress of therapy. Checking a tumor’s re- sponse to therapy requires follow-up exami- nations at regular intervals. The biograph can swiftly and accurately superimpose images from different exams, so that the physician can easily compare the position and size of the tumor, as well as the level of radioactivity in it.
One Plus One Is a Lot More
Fast computer programs have opened the door to a new category of medical imaging systems — hybrids. These combine different systems to achieve images of unprecedented quality. The result: improved diagnoses and more efficient procedures in hospitals.
H igh-tech makes it possible. State-of-the- art computer tomography (CT) produces images of the heart in a matter of seconds with a resolution of under 0.4 millimeters, and ultrasound devices generate real-time 3D pictures of a fetus in the mother’s womb. But ultimately it’s software that integrates high- tech components into a smoothly functioning whole. This is clearly demonstrated by a new generation of medical devices — hybrid sys- tems. These systems amalgamate gigantic data volumes generated by different imaging methods. The result is improved image qual- ity and more efficient diagnostic procedures. In the spring of 2005, for instance, the Uni- versity Medical Center in Erlangen, Germany,
Pictures of the Future | Fall 2005