Terje Tillung

Distribution of local anesthetic in axillary brachial plexus block : A clinical and magnetic resonance imaging study

Background There is an unsettled discussion about whether the distribution of local anesthetic is free or inhibited when performing brachial plexus blocks. This is the first study to use magnetic resonance imaging (MRI) to help answer this question. Methods Thirteen patients received axillary block by a catheter–nerve stimulator technique. After locating the median nerve, a total dose of 50 ml local anesthetic was injected via the catheter in four divided doses of 1, 4, 15, and 30 ml. Results of sensory and motor testing were compared with the spread of local anesthetic as seen by MRI scans taken after each dose. The distribution of local anesthetic was described with reference to a 20-mm diameter circle around the artery. Results Thirty minutes after the last dose, only two patients demonstrated analgesia or anesthesia in the areas of the radial, median, and ulnar nerve. At that time, eight of the patients had incomplete spread of local anesthetic around the artery, as seen by MRI. Their blocks were significantly poorer than those of the five patients with complete filling of the circle, although incomplete blocks were also present in the latter group. Conclusion This study demonstrated that MRI is useful in examining local anesthetic distribution in axillary blocks because it can show the correlation between MRI distribution pattern and clinical effect. The cross-sectional spread of fluid around the brachial–axillary artery was often incomplete–inhibited, and the clinical effect often inadequate.

Experimental application of thermosensitive paramagnetic liposomes for monitoring magnetic resonance imaging guided thermal ablation.

The use of a liposomal paramagnetic agent with a T1‐relaxivity that increases markedly at temperatures above the phase transition temperature (Tm) of the liposomal membrane was evaluated during magnetic resonance imaging (MRI) guided hyperthermia ablation. A neodymium‐yttrium aluminum garnet (Nd‐YAG) laser unit and a radiofrequency ablation system were used for tissue ablation in eight rabbit livers in vivo. One ablation was made in each animal prior to administration of the liposomal agent. Liposomes with a Tm of 57°C containing gadodiamide (GdDTPA‐BMA) were injected iv, and two additional ablations were performed. T1‐weighted scans were performed in heated tissue, after tissue temperature had normalized, and 15–20 min after normalization of tissue temperature. Increase in signal intensity (ΔSI) for ablations prior to injection of the agent was 13.0% (SD = 5.7) for the laser group and 9.1% (SD = 7.9) for the radiofrequency group. Signal intensity after administration of the agent unrelated to heating was not statistically significant (ΔSI = 1.4%, P = 0.35). For ablations made after injection of the agent, a significant increase was found in the laser (ΔSI = 34.5%, SD = 11.9) and radiofrequency group (ΔSI = 21.6%, SD = 22.7). The persistent signal enhancement found in areas exposed to a temperature above the threshold temperature above Tm allows thermal monitoring of MRI guided thermal ablation. Magn Reson Med 52:1302–1309, 2004.

Real time MRI-guided excision and cryo-treatment of osteoid osteoma in os ischii--a case report.

A 36-year-old electrician had not been able towork during the last 8 months due to intense painin his left buttock. Plain radiographs were normal,but scintigraphy, MRI and CT indicated an osteoidosteoma in the left tuber os ischii. The patient wasgiven spinal anesthesia, and placed in a 0.5T GESigna SP/i open MRI (General Electric, Milwau-kee, USA) (Figure 1). With the patient in decubi-tus position, a surface coil was attached and thenidus located. A biopsy needle was placed in thecenter of the lesion, using an optical tracking sys-tem integrated in the magnet gantry, for placementof the needle. A 4 mm cylinder was cored out andfixed in formaldehyde for histologic examinationwhich confirmed the diagnosis osteoid osteoma.Then a 3 mm cryo probe (Galil Medical, Haifa,Israel) was placed centrally in the lesion (Figure2). 4 cycles (1/2–2 min) with cooling to –180€°Cinterrupted by passive thawing were used. ControlMRI showed the defect after the biopsy. The pa-tient was pain-free one day after the operation,soon resumed full-time work, and had no symp-toms 1 year later.

Functional imaging of the thoracic outlet syndrome in an open MR scanner

Abstract. Symptoms due to thoracic outlet syndrome may present only in abduction, a position that cannot be investigated in conventional MR scanners. Therefore, this study was initiated to test MRI in an open magnet as a method for diagnosis of thoracic outlet syndrome. Ten volunteers and 7 patients with a clinical suspicion of thoracic outlet syndrome were investigated at 0.5 T in an open MR scanner. Sagittal 3D SPGR acquisitions were made in 0 and 90 ° abduction. In the patients, a similar data set was also obtained in maximal abduction. To assess compression, the minimum distance between the first rib and the clavicle, measured in a sagittal plane, was determined. In the neutral position, no significant difference was found between patients and controls. In 90 ° abduction, the patients had significantly smaller distance between rib and clavicle than the controls (14 vs 29 mm; p < 0.01). On coronal reformatted images, the compression of the brachial plexus could often be visualised in abduction. Functional MR examination seems to be a useful diagnostic tool in thoracic outlet syndrome. Examination in abduction, which is feasible in an open scanner, is essential for the diagnosis.

Percutaneous cryoablation of colorectal liver metastases: potentiated by two consecutive freeze–thaw cycles

Cryoablation may be beneficial for selected patients with liver tumours. Two freeze-thaw cycles at the same location have been recommended during treatment as this potentiate the effect of ablation in experimental studies. However, single freeze ablations are used by some as double freeze procedures are time-consuming and have been associated with increased risk of complications. Estimation of ice-ball volume is difficult using regularly used monitoring techniques. Magnetic resonance imaging, however, allows excellent and multiplanar visualisation of the frozen region during ablation. We comment on the effect of double freeze cycles in regard to ice-ball volume as estimated from magnetic resonance imaging during percutaneous cryoablation of colorectal liver metastases. The ice-ball volume at the end of the second freeze cycle was median 42% larger than the volume at the end of the first freeze. Double freeze cycles may thus facilitate tumour destruction.

Cryoablation of colorectal liver metastases: minimally invasive tumour control.

Background: Freezing is used for in situ destruction (ablation) of liver tumours not eligible for resection. The procedure is typically done during laparotomy. The objective of this report was to study tumour control at the site of freezing and a minimally invasive approach to cryoablation of colorectal liver metastases. Methods: A prospective study of 19 patients was conducted between 1999 and 2003. Twenty‐five tumours were ablated during 24 procedures (i.e. 5 reablations). Sixteen procedures were performed percutaneously, 5 during laparotomy and 3 laparoscopically. Magnetic resonance imaging (MRI) was used for intraprocedural monitoring during most procedures. Nine patients had concomitant liver resections performed (5 during laparoscopy, 4 during laparotomy). Results: Out of 25 ablations, 18 (72%) were assumed adequate. Total ice‐ball volume during percutaneous procedures was median 62 cm 3 (range 32–114). Excellent imaging of the extent of freezing was achieved using MRI. Hospital stay for patients treated percutaneously was median 4 days (range 3–30). No perioperative mortality occurred. Tumour recurrence at the site of ablation occurred in 8 of 18 (44%) tumours adequately ablated. Actuarial 2‐year tumour‐free survival at site of ablation was 48%. At the time of analyses 12 out of 13 (92%) patients assumed to be adequately ablated were alive. Of all patients, 14 out of 19 (74%) survived. Conclusions: Short‐term tumour control can be achieved following cryoablation of colorectal liver metastases. A minimally invasive approach is feasible but the diameter of metastases considered for percutaneous cryoablation should not exceed 3 cm.

The clinical value of dynamic magnetic resonance imaging in normal and incontinent women--a preliminary study on micturition.

In this preliminary study in nine volunteers and nine women with genuine stress incontinence (GSI) dynamic magnetic resonance imaging (MRI) was used to study the voiding phase in the sitting position after physiological filling of the bladder by urine. The MRI technique has been documented as being useful for this purpose, but in this small group of women it was not possible to determine any specific difference in the voiding pattern between the volunteers and the GIn this preliminary study in nine volunteers and nine women with genuine stress incontinence (GSI) dynamic magnetic resonance imaging (MRI) was used to study the voiding phase in the sitting position after physiological filling of the bladder by urine. The MRI technique has been documented as being useful for this purpose, but in this small group of women it was not possible to determine any specific difference in the voiding pattern between the volunteers and the GSI subjects. Since the present study ended, technical improvement of MRI has appeared and further technical development of the MRI technique is expected, which will widen the diagnostic possibilities of the procedure in incontinent women. In a clinical perspective, dynamic MRI appears to be useful but is recommended to be restricted for research projects.