Biomedical subjects
C D Claussen
Publications and source records attributed to C D Claussen.
[Excimer laser angioplasty. I. The tissue effects of a ring catheter system on peripheral arterial vessels].
We have carried out an experimental study using a new laser catheter on 28 cadaver femoral arteries in 14 subjects and on six aortas. This ring catheter system consists of 12 circular quartz fibres with a central lumen and allows the application of energies up to 20 mJ through a 7F flexible catheter in vivo. The laser emits ultraviolet light of a wave-length of 308 nm, in pulses of 60 ns and a frequency of 2-40 Hz. The energy within a single fibre is 5 J/cm2 and exceeds the intensity required to ablate calcifications. Histologically it has been shown that, depending on the type of tissue, 1 to 2.4 microns of tissue per pulse is removed. Experimentally, rate of progress in a calcified occlusive lesion in the femoral artery, using 20 Hz and energy transmission of 20 mJ, was 3 to 5 mm per minute. Perforation of vessel wall if the catheter tip was at right angles to it depended on the degree of atherosclerosis and was between nine and 116 seconds. Marginally, there was only minimal thermal damage.
[Excimer laser angioplasty. II: Initial clinical experience with peripheral arterial occlusive diseases].
First clinical experiences in the treatment of chronically occluded arteries with 7F-multi-fiber catheter systems transmitting pulsed laser light are presented. 16 patients (7 stadium IIb, 4 stadium III, 5 stadium IVa Fontain) underwent the procedure. 14 of 16 lesions (distance: 0.5-10 cm), most of them with visible calcification, could be recanalized successfully. After the catheter had passed lesions several times, remaining stenoses of 48% (mean value) could be reduced by balloon angioplasty. By moving the catheter with less speed than the experimentally determined speed of laser light ablation and by guiding it over a safety wire, perforation and embolization could be avoided. In one case, occlusion material was pressed into collateral vessels and in two cases groin hematomas had to be observed.
Laser ring catheters in excimer laser angioplasty.
Percutaneous excimer laser angioplasty is dependent on a reliable and effective energy transmission through fiberoptic devices. Compared with bare fibers, ring catheters provide improved flexibility and a central channel for insertion of guide wires. Peripheral laser catheters (7-9 F) were used in 32 patients with arterial occlusive disease in the lower limbs. The technical success rate was 91%. Vessel wall dissections occurred in nine cases but caused no clinical sequelae in the preliminary follow-up period (1-6 months). The clinical application of the catheter devices proved to be safe.
[Computed tomography of the pancreas].
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[Thermoluminescent dosimetry of panoramic zonography].
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[Determination of hematocrit and iodine concentrations following intravenous bolus administration of ionic and nonionic monomeric and dimeric contrast media--an animal experimental study].
A monomeric ionic (meglumine diatrizoate), a monomeric non-ionic (iopromide) and a dimeric non-ionic contrast medium were intravenously administered (V. jugularis) to 15 rabbits. Blood iodine concentration as well as haematocrit were determined from blood samples taken from the femoral artery immediately after injection until the 90th second p.i. The contrast media showed clear differences concerning the haematocrit, i.e. the isotonic non-ionic dimer induced its lowest decrease. The direct determination of the blood iodine concentration revealed no significant deviations between the contrast media studied. Only non-ionic dimers are iso-osmolar with plasma at the iodine concentrations employed in diagnostic radiology. Compared with monomeric compounds this study provides fundamental evidence that isotonic, non-ionic dimeric contrast media cause only slight effects on blood cells. This confirms experimentally the clinically reported good tolerance of dimeric contrast media in patients.
[Clinical application of panoramic zonography].
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Bolus geometry and dynamics after intravenous contrast medium injection.
Studies of contrast medium bolus geometry and dynamics were carried out to provide data for optimizing the use of contrast medium in digital subtraction angiography (DSA) and dynamic CT. Apparatus for fast digital recording of x-ray attenuation profiles was used; this is a new digital imaging mode (Chronogram) available on a CT scanner. Variables studied were injection site, injection speed, contrast medium volume, and subsequent saline injection; peak time, full width at half maximum, and maximum contrast enhancement were recorded. Positioning of the catheter in the vena cava reduced peak time and increased enhancement. High injection speeds led to shorter peak times. An increase in speed from 4 to 8 ml/s caused markedly higher enhancement, while further increase did not add significantly to enhancement. For a given injection speed, enhancement was increased and the peak time delayed by using larger injection volumes. Injection of saline solution after intravenous contrast medium did not change results significantly. There was a statistically significant correlation between pulse rate and peak time; the faster the pulse rate the shorter the peak time.
[Diagnosis of aortic aneurysm: new considerations (author's transl)].
Computed tomography was employed in 37 patients suspected of having an aortic aneurysm: it was demonstrated in 32. Additional angiography was performed in 13, in eight of whom thoracic or thoracic-abdominal aneurysm was diagnosed, in five with dissection. Computed tomography gave a more exact measure of length and width of the aneurysm than angiography. The renal arteries were involved in four instances, pelvic arteries in seven. Both arteriography and computed tomography demonstrated dissection of the thoracic aneurysm.
[Bolus geometry and dynamics after intravenous injections of contrast media Studies using chronography].
Studies of contrast bolus geometry and dynamics were carried out by means of a chronogram - a digital serial radiographic method. Four situations were considered - contrast volume, speed of injections, subsequent saline injections and rapidly repeated contrast boli. Peak values, maximum duration and half-life of the bolus and maximum contrast enhancement were recorded. The results have shown that a larger volume of contrast with reduced injection speed leads to a lengthening of the peak period. More rapid injection speed up to 8 ml/sec leads to a higher peak and increased contrast enhancement. Further increases of injection speed beyond 8 ml/sec does not further increase contrast enhancement. The subsequent injection of saline has no recognisable effect on bolus geometry or dynamics.
[CT diagnostic of ovarial tumors].
The diagnostic value of computed tomography was examined in 34 patients by the clinical diagnosis of an ovarial tumor established immediately before the operation. In 78,9% of all cases, a carcinoma could be surely recognized, often only by indirect signs of malignancy. Benign processes were correctly recognized in 83,3% of all cases. The staging of carcinomas was correct in 57,9%. A disadvantage of CT lies in the fact that it does not show peritoneal disseminations of smallest metastases as well as metastatic formations in not enlarged lymph nodes, which often leads to an understaging.
Immersion ultrasound of testicular pathology.
A water-coupled free-immersion ultrasound scanner, the Octoson, was used to study 70 patients with scrotal masses. Scrotal swelling can be identified accurately as intrascrotal fluid collections of solid lesions, and an intra- or extra-testicular origin can be determined precisely. In most cases, testicular tumors can be distinguished from inflammatory conditions. Immersion testicular ultrasound can disclose the site, delineate the extent, and characterize the nature of intra- and extra-testicular lesions.
Immersion ultrasonography of scrotal and testicular pathology.
A water-coupled free-immersion ultrasound scanner, the Octoson, was used to study 70 patients with scrotal disease. The main advantage of the immersion technique is the perfect overview of the whole male genital organ. Scrotal masses could be differentiated to a high percentage into intrascrotal fluid collections and intra- or extra-testicular solid lesions. In some cases, testicular tumors could be distinguished from inflammatory conditions on the basis of the ultrasound examination alone. According to out present experience, immersion ultrasound of the scrotum proved to be an effective method in disclosing the site, delineating the extent and characterizing the nature of extra- and intra-testicular disease.
The diagnosis of congenital spinal disorders in computed tomography (CT).
9 patients (8 girls, 1 boy) with dysraphic disorders of the spinal column were examined by CT. In 6 cases no diastematomyelia was established. Among the 8 girls, an intraspinal bony septum was identified in 7 instances and a splitting of the cord without identifiable septum was seen in 1 girl. In 6 patients with symptoms dysplastic changes of the cord independent of the segmental level could be identified, such as variable thickness and a heterogenous absorption pattern of the cord. Three girls with symptomless diastematomyelia showed no striking absorption pattern of the spinal cord. Asymptomatic diastematomyelia indicates that frequently concomitant orthopaedic and neurological disorders cannot be referred to a mechanically obstructed ascent of the cord alone, but infer complex etiologies, probably including abnormal medullary vascularization Dural sac and subarachnoid fixation of the spinal cord cannot be identified by CT. Unless there is a possibility of a low lumbar medullary conus or of spinal cord dysplasia or intraspinal lipoma, cyst or fistula, one can assume that the normal ascent of the cord is obstructed with subsequent pull on the cord elements. From our preliminary experience which takes into account conventional radiological procedures, the appropriate task of CT consists of identifying even a minimally calcified septum in radiologically suspected diastematomyelia. Further, with CT one can exclude a splitting of the cord without a calcified septum. CT provides a noninvasive method for assuring diagnosis of diastematomyelia at an early stage and enables one to make the differential diagnosis from pseudodiastematomyelia.
Computed tomography of trauma involving brain and facial skull (craniofacial injuries).
Among head injuries, frontobasal fractures play an important role due to frequently concomitant intracranial complications. Intracranial hematomas, cerebral contusions, depressed fractures, and intracranial air are readily detected by computed tomography (CT). Traumatization of intraorbital structures often associated with blowout fractures and herniation of cerebral parenchyma into the ethmoidal, frontal, or sphenoidal sinuses are best demonstrated by CT. In assessing soft tissue structures, CT is superior to multidirectional tomography, which tends to be more suitable for fine detail study of bony structures. Furthermore, CT is helpful for diagnosing inflammatory processes due to bacterial invasion not infrequently following traumatic communication between the paranasal sinuses and the cranial cavity. Sequelae of head trauma such as posttraumatic porencephaly are clearly demonstrated by CT.
Mn-DPDP-enhanced MR imaging of malignant liver lesions: efficacy and safety in 20 patients.
Twenty patients with malignant liver lesions underwent magnetic resonance (MR) imaging with manganese (II) DPDP [N,N'-dipyridoxylethylenediamine-N,N'-diacetate 5,5'-bis(phosphate)] to evaluate the safety and efficacy of the contrast agent. In two groups of 10 patients each, 5 mumol/kg Mn-DPDP was administered intravenously (3 mL/min) at a concentration of either 50 or 10 mumol/mL. T1- and T2-weighted images were obtained with a 1.5-T imager. Six patients reported a total of eight instances of side effects (flush, feeling of warmth, metallic taste) of which seven occurred at the 50 mumol/mL concentration. A significant decrease in alkaline phosphatase levels 2 hours after injection was recorded. On T1-weighted images, the 10 mumol/mL formulation yielded significantly greater increases in contrast-to-noise ratio (79.8%-137.5%) than the 50 mumol/mL formulation (46.2%-86.6%). In a blinded reader study of 10 patients with one to five lesions each, no lesion was missed on Mn-DPDP--enhanced T1-weighted images; however, four false-positive foci were identified. The authors conclude that slow administration of 5 mumol/kg Mn-DPDP at a concentration of 10 mumol/mL is safe and efficient enough to proceed to further clinical trials.
Hematopoietic reconstitution after bone marrow transplantation: assessment with MR imaging and H-1 localized spectroscopy.
Magnetic resonance (MR) studies were performed in 14 patients as early as possible (21-110 days) after bone marrow transplantation (BMT). MR characteristics of lumbar vertebral bone marrow were studied with T1-weighted spin-echo imaging, water- and fat-selective imaging with a frequency-selective excitation technique, and point-resolved spatially localized proton spectroscopy. Signals from water and fat protons and their T1 and T2 values were analyzed. Water proton signal intensity correlated well with cellularity within bone marrow, as determined with parallel iliac crest biopsies. The fraction of signal from water in red bone marrow of patients with allogeneic transplants from siblings (four cases) was significantly higher than in four patients with autologous transplants. The latter showed very low cellularity in the period of about 4 weeks after BMT because of the cytotoxic pretreatment of the bone marrow. The MR results in six patients with allogeneic transplants from unrelated donors ranged widely, depending on the complications after BMT. Analysis of data obtained with the different techniques showed that water- and fat-selective MR imaging and spectroscopic methods are useful for noninvasive monitoring of hematopoietic reconstitution after BMT.