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Biomedical subjects

N Hosten

Publications and source records attributed to N Hosten.

At least 55 records · Page 3Linked to original sources
PubMed2000

Perfusion abnormalities of kidney parenchyma: microvascular imaging with contrast-enhanced color and power Doppler ultrasonography--preliminary results.

The purpose of this study was to evaluate the feasibility of microvascular imaging using contrast-enhanced color and power Doppler sonography. Ten patients with a focal lesion of the kidney were examined. Three patients were investigated with the polymeric butylcyanacrylate-based contrast agent SHU 563A, and the remaining patients were investigated with the galactose-based agent Levovist. It was possible to observe the microvascularization with Levovist during the blood pool phase of the agent over a period of 1 to 3 s at 1 min and 2 min after injection. With SHU 563A, microvascular imaging was possible 0.50 s after injection and lasted for 10.35 min. No intratumoral signals were seen in cysts (n = 6) and the investigated abscess. Weak intratumoral polychromatic effects were observed in both renal cell carcinomas in this series. Metastasis could be differentiated from healthy parenchyma due to lack of the polychromatic effect. SHU 563A is appropriate for performing microvascular imaging. The Levovist-induced polychromatic effects are smaller, of shorter duration, and observable only during the blood pool phase; thus, the expected diagnostic benefit is limited.

Blood Vessels↗
PubMed2000

CSF flow studies of intracranial cysts and cyst-like lesions achieved using reversed fast imaging with steady-state precession MR sequences.

BACKGROUND AND PURPOSE: Differentiating between intracranial cysts or cyst-like structures and communicating or noncommunicating cysts is often not possible with cranial CT or nonfunctional MR imaging. We evaluated a retrospective ECG-gated fast imaging with steady-state precession (PSIF) MR sequence with optional cine mode to differentiate cystic masses from enlarged CSF spaces and to determine the accuracy of detecting communication between cysts and neighboring CSF spaces. METHODS: Fourteen patients with intracranial cystic masses underwent CSF flow studies with an ungated and a retrospective ECG-gated cine-mode PSIF sequence in addition to spin-echo imaging. Findings were evaluated retrospectively by using a five-point rating scale and without knowledge of clinical or other imaging findings. Results were compared with intraoperative findings or with results of intrathecal contrast studies. RESULTS: Eighteen arachnoid cysts and one enlarged cisterna magna were diagnosed. Improved differentiation between cysts and enlarged CSF spaces was obtained with cine-mode PSIF imaging in six lesions (six patients). Increased diagnostic certainty as to communication between cysts and CSF spaces was obtained in 18 cysts (13 patients). Diagnoses were verified by membranectomy in five lesions, by CT cisternography in five lesions, and indirectly by shunting in one cystic lesion. In one case, MR diagnosis was not confirmed by CT cisternography. CONCLUSION: Cine-mode MR imaging with a retrospective ECG-gated flow-sensitive PSIF sequence contributed to the certainty of communication between arachnoid cysts and neighboring CSF spaces with an accuracy of 90%, using surgical findings or intrathecal contrast studies as reference. Differentiation between intracranial cysts and enlargement of CSF spaces and other cystic masses was improved in 25% of cases.

Adolescent↗
PubMed1999

Contribution of color and power Doppler sonography to the differential diagnosis of acute and chronic rejection, and tacrolimus nephrotoxicity in renal allografts.

The aim of the present study was to differentiate acute rejection, chronic rejection, and tacrolimus nephrotoxicity with color and power Doppler imaging of renal transplants. One hundred examinations were obtained from 45 patients. Pulsatility and resistive indices were calculated from color Doppler images. The grade of renal vascularization was quantified using computer-assisted pixel analysis in a rectangular region-of-interest. The percentage of vessel-covered renal parenchyma (POV) was calculated using a histogram that discriminated renal vessels from renal parenchyma via power Doppler images. Furthermore, the distance from the most peripherally located vessels to the renal capsule (PVD) was measured. A reduced POV < or = 55% proved to be the best discriminator when chronic rejection was suspected (sensitivity 79%, specificity 87%). Tacrolimus nephrotoxicity showed not only a moderate elevation of the Doppler signal but also an increased PVD > or = 3.9 mm and a normal POV. We conclude that the evaluation of renal vessels by power Doppler images improves diagnostic accuracy for patients with renal allografts.

Acute Disease↗
PubMed1999

High-resolution conjunctival contrast-enhanced MRI dacryocystography.

We assessed high-resolution MRI of the lacrimal system with conjunctival contrast enhancement in patients with suspected stenosis. We studied 18 patients with epiphora affecting 22 eyes, using a surface coil, before and after conjunctival and intravenous Gd-DTPA. Stenosis or obstruction of the ducts was found in 18 of 22 cases: at canalicular level in 3 cases, at the sac in 7 cases, and in the nasolacrimal duct in 8 cases. Periductal pathology following surgery to the maxillary sinus or dacryocystorhinostomy was seen in three cases. In conjunction with the findings on syringing and/or conventional dacryocystography, the narrowing was classified as stenosis or obstruction.

Adult↗
PubMed1999

Focal liver lesions: Doppler ultrasound.

Echo patterns of focal liver lesions as well as other morphological criteria do not suffice for differential diagnosis. In an attempt to increase the specificity of ultrasound of focal liver lesions, several years of Doppler-flow information was evaluated. Recent advances in ultrasound technology (power Doppler imaging, second harmonic imaging) as well as commercial availability of an intravenous signal enhancer (contrast agent) have additionally improved results of this technique.

Aged↗
PubMed1999

[Evaluation of polyurethane stent implantation for the treatment of complete obstruction of the nasolacrimal system: 8-month follow-up and complications].

UNLABELLED: Dacryocystorhinostomy is still the standard procedure complete stenosis of the nasolacrimal duct. New methods try to preserve the natural lacrimal pathway. Song implanted in 1995 a nasolacrimal polyurethane stent through the nasolacrimal duct. The results and complications of this new method are described in this prospective study. METHODS: Thirty consecutive patients with complete obstruction of the nasolacrimal duct or lacrimal sac were included in the study. The stenosis was localized by dacryocystography. The ages ranged from 22 to 87 years (mean, 58.9 +/- 16 years). Dacryocystography was performed immediately, 4 weeks and 8 months after the procedure to verify the position and patency of the stent. RESULTS: Twenty-five short (35 mm) and 5 long (45 mm) stents were implanted. Twenty-four of 30 patients after 4 weeks and 9 of 10 patients after 8 months had reduced or no complaints. In 1 patient the stent was obstructed. Forceful irrigation with saline solution permitted recanalization. In 1 patient the stent had moved into the upper canaliculus. Because of irritation of the canaliculus it had to be pulled out after 2 months. CONCLUSION: The follow-up is still too short to recommend stent implantation as a real alternative to dacryocystorhinostomy. The main advantages are that the procedure is faster, no incision is necessary, and the local anesthesia is easier. The disadvantage is the need for X-ray examination.

Adult↗
PubMed1999

[Automated speech recognition for the generation of medical records in computed tomography].

PURPOSE: A study was performed to compare the performance of automatic speech recognition (ASR) with conventional transcription. MATERIALS AND METHODS: 100 CT reports were generated by using ASR and 100 CT reports were dictated and written by medical transcriptionists. The time for dictation and correction of errors by the radiologist was assessed and the type of mistakes was analysed. The text recognition rate was calculated in both groups and the average time between completion of the imaging study by the technologist and generation of the written report was assessed. A commercially available speech recognition technology (ASKA Software, IBM ViaVoice) running on a personal computer was used. RESULTS: The time for the dictation using digital voice recognition was 9.4 +/- 2.3 min compared to 4.5 +/- 3.6 min with an ordinary Dictaphone. The text recognition rate was 97% with digital voice recognition and 99% with medical transcriptionists. The average time from imaging completion to written report finalization was reduced from 47.3 hours with medical transcriptionists to 12.7 hours with ASR. The analysis of misspellings demonstrated (ASR vs. medical transcriptionists): 3 vs. 4 for syntax errors, 0 vs. 37 orthographic mistakes, 16 vs. 22 mistakes in substance and 47 vs. erroneously applied terms. CONCLUSIONS: The use of digital voice recognition as a replacement for medical transcription is recommendable when an immediate availability of written reports is necessary.

Algorithms↗
PubMed1999

[The value of magnetic resonance tomography (MRT) for evaluating ventricular and anastomotic functions in patients with an extra- or intracardiac total cavopulmonary connection (TCPC)-modified Fontan operation].

PURPOSE: To evaluate different MR methods (ventricle and flow measurements) for the postoperative follow-up of hemodynamics in patients with extra- or intracardial TCPC. MATERIALS AND METHODS: Twenty-eight consecutive patients (14 female, 14 male) within the ages of two to thirty-eight years were examined using a 1.5 T Gyroscan ACS-NT scanner (Philips, Best, Netherlands). 7 patients had an extracardial (eTCPC), and 21 an intracardial (iTCPC) tunnel. The calculation of the ventricular function and muscle mass was performed using "multislice-multiphase" technique by summing up the end-diastolic and end-systolic areas; the flow measurements were evaluated by phase shift velocity mapping in the superior vena cava (SVC), inferior vena cava (IVC), right (RPA) and left (LPA) pulmonary artery. Besides peak and mean velocity, the mean and maximal flow volumes (ml/min) were calculated. RESULTS: Ejection fraction (EF) of the functionally single ventricle was within the normal range (mean 57%) in 22/28 patients while mean muscle mass was elevated in the group with eTCPC (mean 121 g/m2). The mean flow volumes and the peak velocities in all vessels were higher in the group with iTCPC as compared to the one with eTCPC. Clinically relevant retrograde flows in the IVC were only found in the group with iTCPC (7/21), as well as a significant predominant flow distribution towards the RPA (p < 0.05; Wilcoxon signed-rank test); in the group with eTCPC towards the LPA (n.s.). CONCLUSIONS: MRI is a useful method for the assessment of ventricular function and muscle mass in the follow-up after the modified Fontan operation. MRI flow measurements additionally provided clinically relevant information about the hemodynamics in Fontan patients.

Adolescent↗
PubMed1999

[Malignant lymphoma: magnetic resonance tomography findings in residual supradiaphragmatic space-occupying lesions].

PURPOSE: Evaluation of MR imaging in patients with Hodgkin's lymphoma and high grade non-Hodgkin's-lymphoma and mediastinal residual mass after first line chemotherapy. MATERIALS AND METHODS: MR imaging (1.5 T) was performed in 36 patients (Hodgkin's lymphoma n = 26, NHL n = 10) after first line chemotherapy). Twenty patients had inactive residual mass, 16 patients had residual lymphoproliferative lesions. T1- and T2-weighted spin echo images were visually analysed by a score index (range 1-5) as well as quantification of enhancement by signal-intensity-ratios SImax/SIplain). RESULTS: For the differentiation between residual lymphoproliferative activity and inactive residual mass, the highest accuracy was obtained for the signal intensity of residual mass on T2-w-SE compared to pectoralis muscle (94% sensitivity, 80% specificity, likelihood ratios: 4.0 [LR+]; 0.3 [LR-]). The cut-off value of the SI ratio was calculated retrospectively at 1.96 (p > 0.05). CONCLUSIONS: Differentiation between inactive (fibrotic) and lymphoproliferative (active) residual mediastinal mass is possible by MR imaging using as parameter the size reduction after therapy and the signal intensity on T2-w-SE in comparison to pectoralis muscle. Thus study suggests an additional value using the SI ratio for the differentiation.

Adult↗
PubMed1999

[Diagnostic value of signal-enhanced color Doppler ultrasound in space-occupying lesions of the skin and skin appendages].

PURPOSE: Prospective evaluation of the diagnostic outcome of plain and signal-enhanced color Doppler sonography for the differentiation between benign and malignant cutis-involving lesions. MATERIALS AND METHODS: 39 patients with 40 suspected malignant skin lesions received an preoperative ultrasound examination before and after application of 4 g Levovist i.v. Spectral Doppler, conventional color and power Doppler were performed. The images were analyzed semiquantitatively using a specially developed software. The diagnoses were confirmed by histological analysis (37 cases) or by follow up controls (3 cases). RESULTS: Whereas the B-mode criteria such as echogenoity, borderline and homogenecity, and the spectral Doppler analysis were not useful for differentiation between malignant and benign lesions, the analysis of the intratumorously visible number of vessels and of the ratio of the vascularized area using a special software, especially after injection of the signal enhancing agent, provided valuable information. In 10 of 18 benign but only in 1 of 22 malignant lesions, no intratumorous vessels were visible after application of Levovist (plain: 10/18 benign and 6/22 malignant lesions). The number of visible vessels increased strongly after signal enhancement. Using a "ratio of the vascularized area (percentage vessel area) > 5%" as a criterion of malignancy, 2 false positive and 2 false negative results were observed after application of Levovist (without/with Levovist sensitivity 73%/91%, specificity 89%/89%). CONCLUSIONS: The signal-enhanced color Doppler sonography provides useful additional information for the differentiation between benign and malignant cutis-involving lesions, especially the semiquantitative vascularization analysis. The latter is superior to B-mode ultrasound and to spectral Doppler analysis. The signal enhancer increases the sensitivity, whereas the specificity remains unchanged.

Adolescent↗
PubMed1999

[Fat-saturated, contrast-enhanced spin-echo sequences in the magnetic resonance tomographic diagnosis of peritoneal carcinosis].

PURPOSE: To evaluate contrast-enhanced, fat-saturated spin echo sequences for the detection of peritoneal carcinosis with MRI. MATERIALS AND METHODS: 61 patients, 35 with and 26 without peritoneal carcinosis, were examined with abdominal MRI. Fat-saturated, T1-weighted spin echo sequences were performed before and after administration of Gd-DTPA. In addition, 22 patients with peritoneal carcinosis were examined with contrast-enhanced abdominal CT. RESULTS: 32 of 35 patients with peritoneal carcinosis demonstrated contrast enhancement of the visceral and 30 of 35 enhancement of the parietal peritoneum (91 and 86%, respectively). Wall thickening of the intestine or parietal peritoneum were noted in 21 and 20 of 35 patients (60 and 57%, respectively), ascites in 18 of 35 patients (51%). False positive contrast enhancement of the peritoneum was noted in 4 of 26 patients (15%). In the direct comparison of MRI and CT, 22 of 22 patients versus 7 of 22 patients showed contrast enhancement of the visceral peritoneum (100 and 32%, respectively). For other signs of peritoneal carcinosis (e.g., ascites, peritoneal seedings), no differences in diagnostic reliability were demonstrated. CONCLUSIONS: The use of fat-saturated, spin echo sequences facilitates the diagnosis of peritoneal carcinosis by artifact reduction and improved detection of peritoneal contrast enhancement. MRI with fat-saturated sequences was superior to CT.

Adult↗
PubMed1999

[Retroperitoneal recurrence of non-seminomatous testicular tumors: computerized tomography findings before retroperitoneal lymph node excision].

PURPOSE: In relapsing testicular cancer, additional chemotherapy is followed by abdominal CT. If residual lesions are found, retroperitoneal lymphadenectomy is considered. We studied retrospectively whether morphological criteria can help in selected cases in deciding about lymphadenectomy by distinguishing between vital tumor, scarring and mature teratoma. METHODS: In 26 patients who had been treated by salvage chemotherapy and retroperitoneal lymphadenectomy for non-seminomatous testicular cancer between 1990 and 1997, abdominal computed tomography and histology were correlated. RESULTS: Histological examination found scarring in 10 patients, vital tumor in 6, mature teratoma in 4, and simultaneous teratoma and vital tumor in 6. A single CT criterion for distinguishing between these histologies was not identified. In two patients with large masses which were partly cystic and partly solid vital tumor and teratoma were verified. Scarrings may be expected in cystic lesions at the level of the renal hilus which are lined by a thin and smooth wall. Size did not matter. CONCLUSION: Accurate differentiation between vital tumor and necrosis was not possible. Before lymphadenectomy CT, however, localised lesions.

Adolescent↗
PubMed1999

Comparison of four magnetic resonance methods for mapping small temperature changes.

Non-invasive detection of small temperature changes (< 1 degree C) is pivotal to the further advance of regional hyperthermia as a treatment modality for deep-seated tumours. Magnetic resonance (MR) thermography methods are considered to be a promising approach. Four methods exploiting temperature-dependent parameters were evaluated in phantom experiments. The investigated temperature indicators were spin-lattice relaxation time T1, diffusion coefficient D, shift of water proton resonance frequency (water PRF) and resonance frequency shift of the methoxy group of the praseodymium complex (Pr probe). The respective pulse sequences employed to detect temperature-dependent signal changes were the multiple readout single inversion recovery (T One by Multiple Read Out Pulses; TOMROP), the pulsed gradient spin echo (PGSE), the fast low-angle shot (FLASH) with phase difference reconstruction, and the classical chemical shift imaging (CSI). Applying these sequences, experiments were performed in two separate and consecutive steps. In the first step, calibration curves were recorded for all four methods. In the second step, applying these calibration data, maps of temperature changes were generated and verified. With the equal total acquisition time of approximately 4 min for all four methods, the uncertainties of temperature changes derived from the calibration curves were less than 1 degree C (Pr probe 0.11 degrees C, water PRF 0.22 degrees C, D 0.48 degrees C and T1 0.93 degrees C). The corresponding maps of temperature changes exhibited slightly higher errors but still in the range or less than 1 degree C (0.97 degrees C, 0.41 degrees C, 0.70 degrees C, 1.06 degrees C respectively). The calibration results indicate the Pr probe method to be most sensitive and accurate. However, this advantage could only be partially transferred to the thermographic maps because of the coarse 16 x 16 matrix of the classical CSI sequence. Therefore, at present the water PRF method appears to be most suitable for MR monitoring of small temperature changes during hyperthermia treatment.

Body Temperature↗
PubMed1999

Differential diagnosis of lymph node lesions. A semiquantitative approach with power Doppler sonography.

RATIONALE AND OBJECTIVES: To assess the value of power Doppler for distinguishing reactive from malignant lymph node disease. METHODS: In a prospective study, 48 untreated patients with palpable cervical lymph node enlargement (n = 211) underwent examination with power Doppler sonography. The perfusion sites were subdivided into three groups: central, peripheral, and hilar perfusion. In addition, the authors qualified the intensity of perfusion using a semiquantitative scale from 0 (no perfusion) to III (high perfusion). Finally, the overall perfused lymph node area was measured and the percentage of perfused nodal area was calculated. RESULTS: Power Doppler sonography showed perfusion in 183 of 211 lymph nodes. Histologic examination revealed 67 reactively enlarged lymph nodes, 72 metastases, and 44 lymphomas. Reactively enlarged lymph nodes showed characteristically intense hilar perfusion (82.1%), whereas nodal metastases exhibited mainly peripherally located flow (84.7%) of grade intensity I to III. Lymph nodes invaded by malignant lymphoma were highly perfused, displaying color signals in the center as well as in the nodal periphery (90.9%). CONCLUSIONS: The perfusion patterns of lymph nodes provide useful additional information in the differential diagnosis of cervical lymphadenopathy.

Adolescent↗
PubMed1999

Radiologic anatomy of ventricular assist devices.

Ventricular assist devices (VAD) allow for long-term circulatory support of patients with end-stage heart failure. With the increasing duration of circulatory support, diagnostic imaging plays an important role in the management of patients on a VAD. The aim of our review was to analyze the radiologic features of different VADs. From 1987 to 1996, 319 patients (mean age 42 years, range 3 to 74 years) were treated with a VAD. A Berlin Heart VAD was implanted in 263 of the patients, the univentricular Baxtor Novacor was implanted in three patients, and the univentricular CI Heartmate was implanted in 19 patients. All patients were studied by serial chest radiographs. In addition, 70 patients underwent computed tomography (CT), and five patients underwent electron beam CT. The Berlin Heart VAD was used as a biventricular support system in 218 patients. In all cases, the position of the wire-directed cannulae was identified on the chest radiographs, while the exact position of the cannula tip could be visualized by CT only. The plastic cannulae of both the Novacor and the Heartmate were not discernible on radiographs, but required CT for evaluation. Computed tomography also resolved the metal components of the pumps. The titanium-made pump housing of the Heartmate caused beam-hardening artefacts that might conceal fluid accumulations in the pump pocket. Computed tomography is the standard of reference for examinations of cannula position, pump position, and pump components of ventricular assist devices.

Adolescent↗
PubMed1999

Uveal melanoma: correlation of histopathologic and radiologic findings by using thin-section MR imaging with a surface coil.

PURPOSE: To evaluate whether the different signal intensities at magnetic resonance (MR) imaging of melanoma are associated with a higher content of melanin. MATERIALS AND METHODS: In a prospective study, MR imaging and ophthalmoscopic examination findings in 42 patients (19 women, 23 men; age range, 30-87 years) with uveal melanoma were compared with histopathologic examination findings obtained after enucleation. MR imaging was performed with 2-mm sections by using a 5-cm surface coil. T1- and T2-weighted images were obtained before and after contrast material administration. RESULTS: In 33 (79%) of the patients, there was homogeneous tumor pigmentation, whereas in nine (21%) patients, there was inhomogeneous bipartite tumor pigmentation. Compared with the histopathologic data, the results of qualitative evaluation were accurate in 29 (58%) of 50 and in 26 (53%) of 49 tumorous areas on T1- and T2-weighted images, respectively. Quantitative evaluation yielded better results, especially at T1-weighted imaging; an 86% correlation was found. Because of methodological reasons, only the superficial pigmentation of inhomogeneous tumors could be evaluated with ophthalmoscopy. CONCLUSION: Thin-section MR imaging of the eye enables an accurate prediction of melanomatous pigmentation with quantitative evaluation of plain T1-weighted images and is superior to ophthalmoscopy in cases of inhomogeneous pigmentation.

Adult↗
PubMed1999

1H and 31P NMR characterisation of a double breast coil for spectroscopic measurements and imaging.

For the first time a double turn breast coil has been described which can be used for 1H imaging, 1H spectroscopy and 31P spectroscopy. The paper describes basic technical features of the coil, coil design, B1 field/excitation field distribution for 1H and 31P, sensitivity, and feasibility for 31P spectroscopic in vivo studies. The main advantage of the double frequency tuneable coil is that 1H imaging for tumor localization and 31P spectroscopy for response control can be done without an additional repositioning of the patient.

Breast Neoplasms↗