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Biomedical subjects

P Hilfiker

Publications and source records attributed to P Hilfiker.

12 recordsLinked to original sources
PubMed2000

Temperature mapping of magnetic resonance-guided laser interstitial thermal therapy (LITT) in lymphangiomas of the head and neck.

BACKGROUND AND OBJECTIVE: Lymphangiomas of the tongue and neck are uncommon benign congenital lymphatic tumors. These vascular lesions are difficult to treat, frequently recur, and can cause patients significant morbidity. Treatment may also be complicated by adjacent vital anatomic structures. Magnetic resonance (MR)-controlled laser-induced interstitial thermotherapy (LITT) has been proven to be a noninvasive safe treatment. Real-time monitoring of tissue temperature with thermosensitive sequences allows controlled coagulation necrosis. STUDY DESIGN/MATERIALS AND METHODS: LITT was performed in a lymphangioma specimen ex vivo. In four patients (eight procedures) with lymphangiomas of the tongue and neck, MR-guided LITT was performed with a percutaneous approach in a multiapplicator technique. The laser system consisted of a titanium catheter and a protective catheter. The dome of the fiber end had a diameter of 1.4 mm with an active length of 20 mm. Temperature sensitive sequences were used in a 0.5 T open-configured MR scanner with the proton frequency shift technique to map the spatial and temporal distribution of Nd:YAG laser effects (7 Watts, 30 pulses per second, 10 minutes/location). Postoperative MR follow-up was performed at 1 week and at 3 months. In three patients, partial resection of the tumor was performed 6 months after LITT. RESULTS: In three patients, MR clearly showed a diminished tumor volume. All four patients reported subjective amelioration and in three patients former functional problems, such as speech and swallowing were improved. MR thermometry allowed accurate demarcation of changes by heat and distinction of affected tumor volume (3.0 cm +/- 0.3 cm). The histology of the patients 6 months after LITT showed laser-induced fibrosis of former lymphatic tissue. CONCLUSION: The results suggest that LITT can be performed safely with tissue preserving of vital structures and can be effective in the treatment of deep tumors, such as lymphangiomas. However, given the nature of the lesion, the potential for recurrence exists no matter what modality is chosen.

Adult↗
PubMed2000

From clinical observation to long-term monitoring: diagnostic developments in conservative epileptology.

The diagnostic goals in nonsurgical (conservative) epileptology differ from presurgical diagnostic aims. The resulting development of diagnostic methods in a tertiary-level epilepsy center is shown and the major technical and organizational consequences of this difference for diagnostic long-term monitoring (LTM) as opposed to presurgical LTM are investigated. A total of 133 consecutive daytime LTM investigations using radio telemetry were reviewed and seizure parameters such as type, duration, method of seizure detection, and need of mobility were evaluated and compared to presurgical LTM. Compared to presurgical LTM, partial seizures were relatively rare (17.8%) and short epileptic or nonepileptic motor events lasting <1 s, such as myoclonic, atonic, short tonic seizures, spasms, tics, or startle reactions, are frequent (34.9%). Of all seizures, 23% had no or minor ictal EEG changes, subtle symptomatology without signaling by a patient or accompanying person, and could be detected only by continuous online surveillance by an experienced EEG technician. Due to the nature of the patient population in diagnostic LTM, there is an increased need for ictal and interictal mobility (radio telemetry). LTM in conservative epileptology requires more intense human surveillance for seizure detection and increased patient mobility compared to presurgical LTM.

Adolescent↗
PubMed2000

Twenty years of ictal EEG-EMG.

This study aimed to evaluate the use of ictal EEG recordings combined with simultaneous surface EMG in the diagnosis and analysis of motor events, both epileptic and nonepileptic. All ictal registrations were performed utilizing radio/cable telemetry. Routine recordings consisted of 18-channel EEG plus 8-channels bipolar surface EMG in freely moving patients. Combined ictal EEG-EMG recordings in freely moving patients enabled us to identify and define the following pathomechanisms of epileptic drop seizures, epileptic axial spasms, atonic, myoclonic-atonic, and akinetic seizures. Precise differentiation could be made between tonic and nontonic postural seizures and between startle-induced reflex seizures and hyperekplexia. The findings from telemetered ictal recordings in freely moving patients with combined EEG and surface EMG offer the only means of identifying, defining, and differentiating motor events, both epileptic and nonepileptic, of a short duration that cannot be properly differentiated by clinical examination alone.

Diagnosis, Differential↗
PubMed1999

[Endovascular treatment of the abdominal aortic aneurysm: assessment, implantation technique, after-care and results].

BACKGROUND: Endovascular treatment of abdominal aortic aneurysm (AAA) is a new minimally invasive alternative to surgical repair. Patient selection, perioperative management, the procedure itself and postoperative follow-up are new aspects. PATIENTS: From June 1997 to June 1998, 37/70 patients (53%) with AAA were treated by the endovascular method. There were 35 males and two females, mean age 74 +/- 7 years, with a mean ASA class of 3.5 +/- 0.5. Graft repair was performed in 33 patients, due to inappropriate aortic anatomy for the endovascular technique in 24 and leaking aneurysm in 9. METHODS: Feasibility is based upon computed tomography and angiography. The procedure was performed in the operating room, under general, regional and local anaesthesia in 14, 3 and 20 patients, respectively. 36 bifurcated and one tube endoprosthesis were implanted. An open access on one femoral or iliac artery and, in case of bifurcated prosthesis, usually a percutaneous access (10 Fr) on the other side were performed. Positioning and delivery were monitored under fluoroscopy. RESULTS: All the AAA could be sealed by the endovascular technique. In one patient, an iliac limb was removed surgically because of proximal misplacement, but the procedure was completed by the endovascular technique. Mean operation time was 140 +/- 67 minutes. ICU stay was 1.4 +/- 1.6 days and patients were discharged after 6.5 +/- 3.5 days. Postoperative radiological follow-up showed totally sealed aneurysms in 34/37 patients (91%). In 3 patients a residual perfusion originating from a lumbar artery was observed. In 7/14 patients with AAA diameter > 6 cm and without residual leakage on the control CT scan, aneurysm pulsation remained after endovascular treatment. There was no early or late death after endovascular repair. During the follow-up period of 4 +/- 3 months patients are doing well. One patient needed balloon dilatation of an iliac limb. CONCLUSIONS: Endovascular treatment of AAA is a minimally invasive technique with short recovery time. This technique seems to be particularly advantageous in elderly or severely ill patients. Long-term controls are mandatory to identify potential complications, particularly when residual perfusion or aneurysm pulsation persists.

Aged↗
PubMed1999

Abdominal pulsatile tumor after endovascular abdominal aortic aneurysm repair.

A 70 years old patient was successfully treated for infrarenal aortic aneurysm by an endovascular bifurcated prosthesis. Three months later, because of dysuria, he underwent urological examination revealing an abdominal pulsatile tumor. Thereafter, the patient was sent to our emergency ward with suspected symptomatical endoleak. Radiological screening by computer tomography and magnetic resonance angiography showed good post-operative results without endoleak. Patient was treated with antispasmodic medication and is doing well today. Because endovascular repair of aortic aneurysm, in contrast to an open approach, does not eliminate the aneurysm itself, post-operative abdominal palpation can be ambiguous. Magnetic resonance angiography--without the need of nephrotoxic contrast medium--compares favourably to CT and provides excellent pictures with less artefacts for post-operative screening of endoleak. If reperfusion can be excluded, pulsation is due to the transmission of the blood-pressure wave to the thrombosed aneurysm.

Aged↗
PubMed1999

Magnetic resonance angiography versus duplex sonography for diagnosing renovascular disease.

Noninvasive testing for renovascular disease is required to identify patients who may benefit from revascularization procedures without exposing an unnecessary amount of patients to the risks of catheter angiography. All available methods of diagnosing renal artery stenosis have significant limitations. We compared a new technique, contrast-enhanced magnetic resonance angiography, with an established technique, duplex ultrasonography, for the detection of renal artery stenosis using catheter angiography as the standard of reference. Eighty-nine patients with clinically suspected renovascular disease underwent duplex renal scanning and contrast-enhanced magnetic resonance angiography. Sixty of these also underwent catheter angiography. All studies were interpreted for the presence of renal artery stenosis blinded to the results of the other imaging modalities. For detection of hemodynamically significant (>/=60% diameter reduction) main renal artery stenosis, sensitivity and specificity were 90% and 86%, respectively, for magnetic resonance angiography and 81% and 87% for duplex sonography. Most false readings involved differential grading of stenoses detected with all 3 techniques. When patients with fibromuscular dysplasia were excluded from the analysis, the sensitivity of magnetic resonance angiography increased to 97%, with a negative predictive value of 98%. Magnetic resonance angiography detected 96% and duplex 5% of accessory renal arteries seen at catheter angiography. Contrast-enhanced magnetic resonance angiography is a useful technique for diagnosing atherosclerotic renovascular disease. It overcomes the major limitations of duplex renal scanning. However, duplex has the advantage of providing hemodynamic information and appears better suited for the assessment of patients with suspected fibromuscular dysplasia.

Adult↗
PubMed1995

Fast spin-echo inversion-recovery imaging versus fast T2-weighted spin-echo imaging in bone marrow abnormalities.

RATIONALE AND OBJECTIVES: The purpose of this investigation is to compare a fat-suppressed T2-weighted fast spin-echo (FSE) sequence in bone marrow abnormalities with an FSE STIR sequence that recently has become commercially available. METHODS: Fast spin-echo images (repetition time [TR], 3500-5000 mseconds; echo time [TE], 96-114 mseconds) and FSE STIR images (TR, 3000-5000 mseconds; TE, 32-40 mseconds; inversion time [TI], 140-150 mseconds) were compared quantitatively and qualitatively calculating signal-to-noise ratios (SNRs), contrast-to-noise ratios (CNRs), and lesion conspicuity and using a qualitative scoring system. RESULTS: Signal-to-noise ratio (mean +/- standard deviation) was 36.4 +/- 19.3 for the FSE and 29.0 +/- 15.9 for the FSE STIR images (P = .002). Contrast-to-noise ratio (mean +/- standard deviation) was 18.7 +/- 14.3 for the FSE and 20.3 +/- 16.0 for the FSE STIR images (P = .45). Lesion conspicuity (mean +/- standard deviation) was 1.7 +/- 1.5 for the FSE and 3.5 +/- 4.0 for the FSE STIR images (P = .025). The most important difference in the qualitative evaluation related to the better signal homogeneity on the FSE STIR images. CONCLUSIONS: Fast spin-echo STIR images may be preferable to FSE images with fat suppression due to better image homogeneity and lesion conspicuity.

Adolescent↗
PubMed1992

Detection and evolution of rhythmic components in ictal EEG using short segment spectra and discriminant analysis.

An automated method for analysis of ictal EEG is described which aims to reliably detect one or several rhythmic components in short EEG segments (2 sec) and to display their presence, frequency, amplitude, location, and temporal evolution. Spectra were estimated and compared using fast Fourier transform (FFT) and autoregressive modelling (AR). A subsequent linear discriminant analysis decided whether a spectral peak is likely to be caused by rhythmic activity or by the inherent statistical variability. FFT was found to perform better than AR in the detection of rhythmic components, yielding a false-positive rate of 0.825%, a false-negative rate of 2% (signal to noise ratio -4.6 dB), a frequency resolution of 2 Hz, and a temporal resolution of 0.5 sec. Seizure analysis revealed that the ictal scalp EEG of even short seizures can show a complex evolution of rhythmic patterns which are impossible or difficult to recognize by visual inspection or conventional spectral analysis. The following phenomena are demonstrated: superposition of two rhythmic components suggesting two cerebral regions discharging simultaneously and independently with their own pacemakers, sudden and gradual change of frequencies, and gradual development of harmonic frequencies. It is suggested that a more precise correlation between rhythmic generators and seizure symptomatology might allow more predictable pharmacological responses in antiepileptic therapy.

Adult↗
PubMed1984

Normal and myopathic propagation of surface motor unit action potentials.

With the aid of a computer-assisted multichannel EMG system, the propagation of motor unit action potentials is analysed during isometric voluntary muscular contraction under normal and myopathic conditions. A linear array of 30 surface electrodes is fixed above the biceps brachii muscle, parallel to the longitudinal muscle axis and centered over the end-plate zone. The EMG is simultaneously recorded on all channels and displays the propagation of surface potentials on both sides of the innervation band. The mean muscle fibre conduction velocity is computed by a cross-correlation technique. Five adult patients in a late stage of progressive muscular dystrophy show a highly altered propagation behaviour of motor unit action potentials without a time shift between potentials of adjacent electrodes. A mathematical model is described which predicts such a behaviour and suggests that it must be due to a pathological longitudinal spread of end-plates in this patient group. In 5 boys with Duchenne muscular dystrophy and only moderate impairment of the biceps muscle the mean muscle fibre velocity was reduced (2.81 +/- 0.34 m/sec) compared to 17 healthy subjects (4.42 +/- 0.37 m/sec). Each myopathic patient examined could be separated clearly from the group of healthy subjects on the basis of the surface EMG analysis.

Adolescent↗
PubMedDate not supplied

Role of duplex color Doppler ultrasound, computed tomography, and MR angiography in the diagnosis of septic puerperal ovarian vein thrombosis.

BACKGROUND: Septic puerperal ovarian vein thrombosis (SPOVT) is one of the underlying etiologies of puerperal fever. A correct diagnosis of this condition is important because adequate treatment requires additional administration of anticoagulants. The purpose of this study was to evaluate the role of duplex color Doppler ultrasound (CDUS), computed tomography (CT), and magnetic resonance angiography (MRA) in the detection of SPOVT. METHODS: Twenty-six patients with puerperal fever suspected to be due to SPOVT and unresponsive to broad antibiotic treatment for at least 48 h were included in a prospective study using CDUS, CT, and MR imaging including MRA. Examinations were analyzed and then correlated to a standard of reference gathered from surgical and clinical follow-up data and from results of imaging. RESULTS: SPOVT was present in nine patients (right side n = 8, bilateral n = 1). CDUS was inconclusive due to gaseous distention of the bowel or obesity in 13 of 26 cases. After counting inconclusive findings as wrong results for statistical purposes, sensitivity, specificity, and accuracy for CDUS were 55.6%, 41.2%, and 46.2%, respectively. CT had a sensitivity of 77.8% with a specificity of 62.5%; accuracy was 68.0%. MRA rendered conclusive results in all evaluated patients, resulting in a sensitivity and specificity of 100%. CONCLUSION: MRA is recommended in all patients with inconclusive CDUS findings and persistent suspicion for SPOVT. CT has the advantage of more rapid access and lower cost and thus will probably remain a sufficiently accurate alternative. Septic puerperal ovarian vein thrombosis (SPOVT)-Computed tomography-Magnetic resonance angiography-Ultrasound.

Adult↗