Electron-beam CT in the noninvasive assessment of coronary stent patency.

RATIONALE AND OBJECTIVES: Coronary artery stents reduce the rate of restenosis in patients who have undergone balloon angioplasty; therefore, the implantation of coronary stents represents an important method in the treatment of coronary stenoses. The authors' purpose was to investigate the usefulness of electron-beam computed tomography (CT) as a noninvasive means of assessing the patency of coronary artery stents in patients who had undergone balloon angioplasty and stent placement. MATERIALS AND METHODS: Electron-beam CT was used to assess stent patency in 177 patients with 285 stents. Contrast material-enhanced multisection flow studies were performed, and the images were evaluated by three investigators and compared with the findings of coronary angiography. RESULTS: Cine loop evaluations and time-attenuation curve analysis led to the correct diagnosis in 167 (94.3%) patients, as confirmed with coronary angiography. Stenoses had occurred in 18 of the 194 vessels with stents, and 14 of these were detected with electron-beam CT. CONCLUSION: Electron-beam CT appears to be a valuable imaging modality in the noninvasive assessment of stent patency in coronary arteries.

Two- and three-dimensional imaging for interventional MRI and CT guidance.

Minimally invasive techniques using endoscopes for image guided therapy are common in the surgical field and in internal medicine. Interventional procedures in the past were performed with either fluoroscopic, sonographic or CT-guidance, but now MRI-guided interventional procedures are being developed. Combining these technologies will improve surgical access and reduce complications. Today, tomographic 2 D and 3 D imaging (CT, EBT, MRI) can be used for precise and transparent guidance of endoscopes and surgical instruments inside the body for the field of minimally invasive therapy. 3 D imaging is helpful for anatomical, but not for morphological understanding. It has to be used interactively with actual cross sectional imaging for instrument guidance. This will offer a safe and effective access into the body, especially in high risk areas and lead to the new field of "Surgical Tomography".

Image-guided minimally invasive therapy.

From its beginning surgical tomography developed rapidly. The possibility to identify every structure inside the body and to guide instruments with monitoring of tissue changes increase safety. Different therapies have been performed under CT and MRI guidance and evaluated in studies, like biopsies, tumor pain therapy and treatments of tumors as well as treatments of the spine. The results show that surgical tomography is an accurate guiding technique. Especially in combination with micro endoscopy offers a new way of surgery. The complication rate as well as the frequency of side effects is very low.

Technique for CT guided microendoscopic dissection of the spine.

The indications for percutaneous nucleotomy techniques are limited to disk herniation without dislocated free fragments. In cases with free fragments we have developed a new technique for percutaneous sequestrectomy. Under CT and fluoroscopic guidance spinal endoscopy was performed. In the past, percutaneous diskectomies were X-ray-guided with or without endoscopy. In this paper we describe the combination of CT-scanning, fluoroscopy and microendoscopy for guidance of nucleotomes, lasers, microendoscopes and micro-instruments. The technique was performed on 20 patients (17 outpatients) with chronic back pain. To date no major complications occurred. The method offers an effective outpatient treatment of small free fragments and scar tissue in the spinal canal and the foramen.

[Immunoglobulins for the prevention of radiation pneumonitis following large-volume irradiation in bronchial carcinoma]. / Immunglobuline zur Prophylaxe der Strahlenpneumonitis nach grossvolumiger Bestrahlung beim Bronchialkarzinom.

In a randomized study 20 patients with non small cell lung cancer were treated for cure at a linear accelerator. Before, during and after treatment levels of immunoglobulins were measured. At the end of radiation therapy levels of IgA, IgG and IgM decreased. After therapy they increased slowly. 3 months after irradiation the average immunoglobulin levels showed a reduction of 16%. After substitution of immunoglobulins no decrease of the levels was seen. After substitution of immunoglobulins the Karnofsky index was significantly higher. Substituted patients showed a lower rate of radiation pneumonitis.

[Microinvasive CT-controlled tumor therapy of soft tissue and skeletal metastases]. / Mikroinvasive CT-gesteuerte Tumortherapie von Weichteil- und Skelettmetastasen.

Micro-invasive CT-guided intratumoral therapy (MIC-ITT) when used in combination with sympathectomy can be an excellent palliative treatment with little impairment of the patient. Rapid as well as complete reduction of pain without systemic side effects can be achieved under local anesthesia in patients in advanced tumor stages by the direct instillation of 50 to 96% alcohol and/or a locally efficacious low toxic cytostatic (Mitoxantron) under CT guidance. CT enables not only exact puncture without injuring endangered structures but also a controlled application of medication. The interventions can be performed with special probes with a diameter of 18 to 25 G. The study population consisted of 145 patients who received a total of 434 treatments. Repeated micro invasive intratumoral treatment was performed on 110 patients with bone and soft tissue metastases (Group I, 335 single treatments) and on 35 patients with vertebral metastases (Group II, 109 single treatments). In all patients conventional therapeutic strategies had been exhausted or were no longer applicable on the basis of a reduced Karnofsky Index. Treatment was performed in combination with sympathetic neurolysis at the upper tumor pole in all cases. The maximum follow-up time was 30 months. Pain reduction was estimated on a visual analogic scale. In Group I up to time of death a pain reduction of 75% or better was achieved in 88 patients (80%). A reduction in tumor size concomitant with a stabilization of the tumor region could be shown in 25% in this group, no change in 62% and progression in 13%. In Group II a pain reduction greater than 75% was achieved in 84% as well as a reduction in tumor size (< 50%) in 18% of the patients. Necrotic zones could be shown in 27% and calcification of tumor area in 35%. No change in tumor size was found in 66% of the patients, progression in 16%. All treatments were free of complications. On the whole the results of this therapeutic approach are encouraging. In particular one aspect should be mentioned: with respect to palliative treatment the reduction of tumor size is not crucial. The decisive factor is the improvement in quality of life of the patient using an intervention which impairs the patient only minimally. Furthermore this micro invasive approach should always involve the combination of local tumor treatment with treatment or lysis of the autonomic sympathetic nervous system in tumor vicinity.(ABSTRACT TRUNCATED AT 400 WORDS)

Interventional MRI: update.

Interventional MRI is in its early stages of development. Nevertheless, the design of new interventional MRI scanners that allow maximum direct access to the patient combined with the development of new interventional MRI pulse sequences and localization systems, means that the archetypal operating rooms of the 21st century may well contain dedicated interventional MRI units for combined radiological and surgical procedures. The present article looks at the state of interventional MRI today and looks ahead to what may be forthcoming in the not-too-distant future. After briefly discussing the instrumentation necessary for practical interventional MRI, the article will go on to describe a number of different approaches to, and clinical applications for, interventional MRI. The use of MRI in guiding and controlling tumor ablation, aspiration cytology and surgical biopsy of different body parts is described.

Percutaneous nucleotomy with CT and fluoroscopic guidance.

Automated percutaneous diskectomy was performed with use of computed tomographic (CT) and fluoroscopic monitoring. Degenerative disease of the intervertebral disk was treated with local administration of anesthesia and use of a nucleotome. One hundred ten patients with neurologic symptoms and morphologic changes of one segment were selected for treatment. Previous conservative therapy had been unsuccessful. Patients with completely prolapsed and sequestered fragments of herniated disks ("uncontained disk"), narrow intervertebral spaces, posterior osteophytes, diseased facet joints, and spinal stenoses were not considered candidates for percutaneous nucleotomy (PNT). After PNT, 82% of the patients had complete remission of their neurologic symptoms; Lasègue sign was negative or improved in 92%. In 18% (20 patients), the symptoms did not improve sufficiently; 11% (12 of 110) of these patients underwent surgical nucleotomy. There were no serious complications, in particular, no injuries to vital structures (nerves, thecal sac, arteries, veins), except for one case of spondylodiskitis. Guiding PNT with CT and fluoroscopy provides a safe procedure with good clinical results. The addition of CT has shortened the operation but increased over-all procedure time. In the future, a shift to outpatient treatment may offset the additional time and cost of including CT guidance.

[Security aspects on the Internet]. / Sicherheitsaspekte im Internet.

AIM OF THE STUDY: Is it possible to use the Internet as a secure media for transport of telemedicine? Which risks exist for routine use? In this article state of the art methods of security were analysed. Telemedicine in the Internet has severe risks, because patient data and hospital data of a secure Intranet can be manipulated by connecting it to the Web. CONCLUSIONS: Establishing of a firewall and the introduction of HPC (Health Professional Card) are minimizing the risk of un-authorized access to the hospital server. HPC allows good safety with digital signature and authentication of host and client of medical data. For secure e-mail PGP (Pretty Good Privacy) is easy to use as a standard protocol. Planning all activities exactly as well as following legal regulations are important requisites for reduction of safety risks in Internet.

Image-guided access techniques.

For increasing safety in access and guidance of endoscopes and instruments, fast real-time radiologic imaging should be integrated. Open designed Magnetic Resonance Imaging (MRI), Computer Tomography (CT), and Electron Beam Tomography (EBT) scanners permit adequate transparency of the operative field. CT and EBT as hybrid scanners can be combined with fluoroscopy. MRI avoids X-ray exposure and entails the possibility of 3D localisation, while open access and keyhole imaging allows nearly real-time guidance of instruments. EBT has the largest gantry (90 cm) for using long instruments, and the image acquisition requires only 50 msec (34 images/sec at 8 levels). However, computed reconstruction of the data takes about 3 times longer than conventional CT. Until EBT can be accelerated, CT will be the golden standard of guidance-techniques in high risk areas, because the tips of the instruments can be precisely visualised within +/- 0.5 mm (MRI: 3.5 mm). MRI-guidance can be used for low risk access techniques. This safe interactive transparent guidance technique has the potential to reduce complications, and it adds significant advantages to micro-invasive operative procedures such as percutaneous diskectomies, pain and cancer therapy with ethanol, or gene-technology implants in the new field of "surgical tomography".

Prevalence and clinical significance of accidental findings in electron-beam tomographic scans for coronary artery calcification.

AIMS: To analyse the prevalence, and diagnostic and therapeutic consequences, of accidental findings in electron-beam tomographic scans performed for evaluation of coronary artery calcification. METHODS AND RESULTS: A total of 1812 consecutive patients with known or suspected coronary artery disease underwent electron-beam tomography. In 583 (32%) of the patients, i.v. contrast was also administered for non-invasive coronary angiography. A total of 2055 non-coronary pathological findings were observed in 953 (53%) of the patients. The prevalence of extra-cardiac disease, as shown in native scans and contrast studies, was assessed separately. In 583 (32%) patients, cardiac structures or the pericardium were affected, in 423 (23%) aortic disease was found. Lung disease was found in 357 (20%), and pathology of other organs in 273 patients (15%). The most frequent findings were aortic calcium in 423 (23%) patients and heart valve calcification in 317 patients (17%). Malignant disease could be detected in three patients. Further diagnostic investigations were done in 191 (11%) patients, 141 (74%) of which concerned the heart. In 22 (1.2%) patients, specific therapy was initiated following electron-beam tomographic findings. CONCLUSION: Accidental non-coronary pathology is a frequent finding in electron-beam tomographic calcium scanning, and often requires diagnostic or therapeutic action. Profound knowledge of the radiological differential diagnosis of the thoracic organs is necessary for reporting electron-beam tomographic scans, in order to avoid misdiagnosis and to receive a high quality interpretation.

[New possibilities and aspects of low-field magnetic resonance tomography]. / Neue Möglichkeiten und Gesichtspunkte der Low-Field-Kernspintomographie.

Worldwide, MRI is going up to higher field-strength. For imaging, magnets with field-strength between 0.2 and about 2.5 Tesla are installed. Below 0.2 Tesla, Low-Field-systems have been used in research-projects to optimize image quality. New developments of 0.064 Tesla Permanent-Magnet-MRI are hopeful for clinical work. Future possibilities of Low-Field-MRI are shown. The advantages of this system are good image quality by low initial start-up and operating costs as well as ease of sitting and lack of need for cryogens. The open design has excellent patient acceptance and allows to examine patients with claustrophobia feelings. It allows easier monitoring during the examination-especially children and patients with cancer or polytraumatic diseases. The introduction of more affordable MRI-systems of low-field-strength may decrease the cost of MRI to the point where it is competitive with computer tomography.

[Pelvimetry using various magnetic resonance tomography techniques vs. digital image enhancement radiography: accuracy, time requirement and energy exposure]. / Pelvimetrie mittels verschiedener kernspintomographischer Techniken vs. digitale Bildverstärkerradiographie: Genauigkeit, Zeitbedarf und Energiebelastung.

In 50 patients with suspected or proven cephalo-pelvine disproportion pelvimetry was performed with MR-tomography using a gradient-echo-sequence (FLASH 2D) before or after labour. Results were compared with measurements using digital radiography. In principle, both methods are exchangeable. The sagittal pelvic in- and outlet bispinous diameters are well reproducible. On the other hand, the transverse pelvic inlet and the distance between the ischiatic tubera are not so reliably reproduced. The accuracy of measurement does not depend on individual pelvic distances. Critical statistical analysis demonstrates, that in the worst case differences between the two methods might become unacceptable. Our results indicate two major reasons: 1. there are interobserver problems which cannot be neglected, and 2. the anatomical definition of referential landmarks for the measurements is unsafe. In 10 volunteers, a comparison was made between a T1-weighted spin-echo sequence (SE), a fast gradient echo sequence (FLASH-2D) and an ultrafast gradient echo technique (Turbo-FLASH). For the examination techniques presented here, the high-frequency exposure load or specific absorption rate (SAR loc and SAR total) is below the values permitted by the German Federal Health Bureau (Bundesgesundheitsamt). Whereas the exposure load in case of spin-echo takes (SE) is 22fold higher than with the gradient echo technique (GHE), the load values of ultra-fast GE (usGE) are only about 16% of the 2D-FLASH sequence or about 0.007% of SE. The difference in image quality does not affect the accuracy of measurement.

Minimally invasive evaluation of coronary stents with electron beam computed tomography: In vivo and in vitro experience.

We sought to describe the value of electron beam computed tomography (EBCT) to detect stent restenoses at follow-up and to identify characteristic EBCT features of coronary stents. Six coronary stents (GRII, Jostent, NIR, PS, Micro, Wiktor) were scanned in vitro (10 1. 5-mm-thick slices, 15-cm FoV, 100-ms AT) before and after inflation with 3.0-, 3.5-, and 4.0-mm balloons to study intensity values and different stent dimensions in comparison to caliper measurements. In 44 patients (60 +/- 10 years, 4 females) we prospectively compared EBCT findings [eight 8-mm-thick slices in the flow mode, 26-cm field of view (FoV), 50 ms acquisition time (AT)] with 6-month angiographic outcome after placement of 86 stents in 49 vessels. For the detection of significant angiographic luminal narrowing (>/=75%) that occurred in 17/49 vessels (35%), we found a sensitivity of 65%, a specificity of 84%, and a positive and negative predictive value of 69% and 82%, respectively. The in vitro data show significant differences in image intensity between the stents and a significant gradual decrease in image intensity with increasing stent diameters. The mean differences between EBCT and caliper measurements for the length and diameter were 0.17 +/- 0.18 mm and -0.32 +/- 0.25mm, respectively. EBCT is currently the only noninvasive technique that allows the assessment of stent dimensions and stent geometry, which may prove useful in patients when intravascular ultrasound cannot be performed. Contrast-enhanced EBCT is a promising tool for minimally invasive stent patency evaluation at follow-up, especially in patients that are unable to exercise. Cathet. Cardiovasc. Intervent. 48:39-47, 1999.

Reproducibility of two coronary calcium quantification algorithms in patients with different degrees of calcification.

PURPOSE: To evaluate the reproducibility of coronary calcium quantification algorithms by electron beam CT (EBT) in patients with different amounts of calcified plaque using the conventional (Agatston) score and an area score and to demonstrate a potential application of these results for evaluation of follow-up scans. METHODS: In 50 consecutive patients. the conventional calcium score (CCS = Agatston score) and the area score (AS) were summed for each artery and patient. Data were analyzed in four groups according to degrees of calcification: 0 (absent-minimal): CCS 0-9, I (mild): CCS 10-99, II (moderate): CCS 100-399, III (severe): CCS > or = 400. We determined and compared the reproducibility for each algorithm within and among groups. RESULTS: Median percent reproducibility improved with increasing amounts of calcified plaque for the CCS and the AS (p = 0.002 and p = 0.004, respectively). We demonstrate how these reproducibility values can be used to evaluate long-term follow-up studies. The reduction of median reproducibility per patient using the AS vs. the CCS was 32% (13 vs. 19%, respectively). On a vessel-by-vessel basis, the reduction of median reproducibility was 7% (24.3 vs. 22.6%, CCS vs. AS, p < 0.02), which was attributable to a 45% reduction in reproducibility in arteries with mild scores (46.1 vs. 25.5%, CCS vs. AS, p < 0.005). CONCLUSION: The AS has an improved reproducibility compared with the CCS, especially in patients with small amounts of coronary calcifications which may prove clinically useful. Different reproducibility values in different degrees of calcification can be used for an individual assessment of changes in amounts of coronary calcification.

Coronary arterial stent patency: assessment with electron-beam CT.

PURPOSE: To evaluate electron-beam computed tomography (CT) for stent localization and noninvasive assessment of stent patency in patients with coronary arterial stents and coronary bypass stents. MATERIALS AND METHODS: CT in the single-section volume mode was performed in 202 patients with 321 coronary arterial stents in 221 vessels to localize the stents. Patency was evaluated in the multisection flow mode with an intravenous bolus injection of contrast material. All electron-beam CT images were reviewed by an observer who had no knowledge of the coronary angiographic results. Electron-beam CT findings were then compared with coronary angiographic findings. RESULTS: The stents could be visualized and related to the coronary arterial segments in 216 of 221 vessels with electron-beam CT. Of the 221 vessels, 207 were correctly evaluated with electron-beam CT. Compared with coronary angiography, electron-beam CT permitted the detection of 18 of 23 high-grade stenoses (sensitivity, 78%) and correctly depicted the absence of high-grade stenoses in 189 of 193 vessels with stents (specificity, 98%). Altogether, 18 stenoses were detected correctly at electron-beam CT; the interpretation was false-positive in four vessels (positive predictive value, 82% [18/22 vessels]) and false-negative in five (negative predictive value, 97% [189/194 vessels]). CONCLUSION: Electron-beam CT may be helpful in localizing intracoronary stents and assessing stent patency noninvasively to delay the intervals between catheterizations in an increasing number of patients.

Compatible instrumentation for intraoperative MRI: expanding resources.

Steadfast progress has been made from biopsy to surgery with interventional MRI (iMRI). Such image-guided interventions require specialized instrumentation due to the unusual elements of the MR environment. Suppliers/manufacturers of MR-compatible instrumentation were few in 1994, but now there are more than 50. We present fundamental issues of MR compatibility and a list of known suppliers/manufacturers.