Novel laser system and laser irradiation method reduced the risk of carbonization during laser interstitial thermotherapy: assessed by MR temperature measurement.

BACKGROUND AND OBJECTIVE: To establish laser interstitial thermotherapy (LITT) for intracranial tumors, the authors investigated a method to regulate localized temperature generated by interstitial laser irradiation using magnetic resonance (MR) temperature mapping. STUDY DESIGN/MATERIALS AND METHODS: A diode laser system and six different types of optical-fiber system were developed for LITT. The characteristics of temperature profiles produced by each laser-fiber system were investigated with MR temperature measurement (the water proton chemical technique), and differences in the temperature profile induced by two laser-irradiation methods (continuous and intermittent) were observed. RESULTS: All fiber systems with the exception of the diffuse-projection fiber system, created a spherical temperature profile. Carbonization sometimes occurred around the bare-end fiber tip upon high power laser irradiation. The diffuse-projection fiber system produced a cylindrical temperature distribution, and the temperature profile showed a more gradual temperature elevation than the bare-end fiber. No carbonization occurred at the tip of the diffuse-projection fiber system. In addition, the utilization of the intermittent irradiation method also increased temperature gradually. Fiber-system modification and intermittent irradiation reduced laser-beam intensity and the risk of carbonization. CONCLUSION: The use of a diffuse-projection fiber system which intermittently transmits a reduced intensity laser beam is an effective tool to regulate temperature during LITT using MR temperature measurement.

Normal brain and brain tumor: multicomponent apparent diffusion coefficient line scan imaging.

Magnetic resonance line scan diffusion imaging of the brain, with diffusion weighting between 5 and 5,000 sec/mm(2), was performed in healthy subjects and patients with a 1.5-T machine. For each voxel, biexponential signal decay fits produced two apparent diffusion constants and respective signal amplitudes. Images based on these parameters show potential for use in the differentiation of gray and white matter, edema, and tumor.

Intraoperative diffusion imaging on a 0.5 Tesla interventional scanner.

Intraoperative line scan diffusion imaging (LSDI) on a 0.5 Tesla interventional MRI was performed during neurosurgery in three patients. Diffusion trace images were obtained in acute ischemic cases. Scan time per slice was 46 seconds and 94 seconds, respectively, for diffusion tensor images. Diagnosis of acutely developed vascular occlusion was confirmed with follow-up scans. White matter tracts were displayed with the principal eigenvectors and provided guidance for the tumor surgery. In all cases, the diagnostic utility of LSDI was established. J. Magn. Reson. Imaging 2001;13:115-119.

Motion robust imaging for continuous intraoperative MRI.

The sensitivity of MR imaging to motion and susceptibility normally requires that the physician using intraoperative MRI cease surgical activity while image data sets are acquired. We demonstrate that line scan imaging allows the physician to continue operating without the delays caused by imaging. Consequently, patient anesthesia, surgery, and operating room time can be reduced. J. Magn. Reson. Imaging 2001;13:158-161.

Influence of alcohol on branched-chain amino acid/tyrosine molar ratio in patients with cirrhosis.

We investigated whether the reduction of plasma tyrosine in alcoholic liver disease would affect the branched-chain amino acid/tyrosine molar ratio (BTR) measured using an enzymatic assay method in alcoholic cirrhosis. BTR values were higher in patients with compensated and decompensated alcoholic cirrhosis (5.68 +/- 2.29 and 3.28 +/- 0.75) due to reduction of the tyrosine level relative to those in patients with nonalcoholic cirrhosis (3.64 +/- 1.22 and 2.53 +/- 0.99). A decrease in tyrosine level and an increase in BTR value were observed after single ethanol administration to healthy subjects. As significant elevation of serum immunoreactive insulin levels followed elevation of serum glucose levels after alcohol loading, it was thought that insulin accelerated intrahepatic metabolism of aromatic amino acids, resulting in reduction of the tyrosine level. The same mechanism may be applied to tyrosine reduction in patients with alcoholic cirrhosis during heavy drinking.

Magnetic resonance cisternography for visualization of intracisternal fine structures.

OBJECT: To assess its usefulness in demonstrating cisternal anatomy, the authors investigated magnetic resonance (MR) cisternography in which a heavily T2-weighted turbo spin-echo method was used to visualize normal anatomical fine structures and lesions in the basal cisterns in 20 healthy volunteers and 43 patients. The authors applied peripheral pulse gating, which had been optimized to reduce artifacts in the cisterns attributable to cerebrospinal fluid (CSF) flow. METHODS: The detectability of each cranial nerve was determined in healthy volunteers. The first, second, and third nerves and the seventh-eighth nerve complex were clearly visualized in all participants; the fifth nerve was clearly seen in 80% and the sixth cranial nerve in 50%. The fourth nerve and the ninth through 12th nerves were difficult to identify individually, except in some volunteers. To reduce artifacts caused by fast CSF flow, we determined the delays as a function of the time elapsed between two consecutive peaks of pulse wave in a peripheral pulse gate (P-P interval) at which there was reversal of flow direction to minimize the CSF flow-related artifact. Using peripheral pulse gating and a time delay of 30% of the R-R interval, the authors succeeded in minimizing the CSF flow-related artifacts. Magnetic resonance cisternography appears to be very useful for demonstrating intracisternal fine anatomy and enhancing the contours of the juxtacisternal lesion. A minute amount of CSF interposed between lesions and normal structures such as nerves, vessels, or bone structures can be detected by means of this sequence. In patients with facial spasm, axial images and oblique coronal images obtained in a plane parallel to the seventh-eighth cranial nerve complex demonstrated vascular compression in all 13 patients. The MR cisternography finding of compression was confirmed in all nine patients who underwent microvascular decompression. CONCLUSIONS: Magnetic resonance cisternography appears to show great promise for evaluation of patients with neurovascular compression or tumors in and around the basal cisterns; the procedure adds only a small amount of imaging time.

[Delayed ischemic neurological deficit that developed over 15 days after subarachnoid hemorrhage].

We retrospectively studied subarachnoid hemorrhage (SAH) patients with delayed ischemic neurological deficit (DIND), and analyzed the factors causing extremely late onset of deficits occurring over 15 days after onset of the SAH. Among 605 patients with SAH, 201 (33%) developed DIND. Among DIND patients, 137 had undergone early aneurysm surgery. In these 137 patients, onset date of DIND was definite in 131 patients. Six patients (5%) developed DIND over 15 days after SAH. All 6 had asymptomatic angiographical vasospasm and infections, most often meningitis, before the onset of DIND. Compared with cases in which there was ordinary onset of DIND, other statistically significant factors among these 6 patients were intracerebral hemorrhage, sepsis and meningitis. We suspect that DIND were manifested subclinically in the early period because of the associated hyperdynamic hemodynamics resulting from sepsis in these patients.

Surgical indications in patients with an intracerebral hemorrhage due to ruptured middle cerebral artery aneurysm.

In this retrospective study, the authors analyzed surgical outcomes in patients who suffered an intracerebral hemorrhage (ICH) as a result of a ruptured middle cerebral artery aneurysm. They studied 47 patients who underwent early aneurysm surgery and hematoma evacuation within 24 hours after onset of ICH. The types of ICH were classified into three groups according to their appearance on computerized tomography scanning: 1) temporal ICH; 2) intrasylvian hematoma; and 3) ICH with diffuse subarachnoid hemorrhage (SAH). Overall, 25 patients (53%) achieved a favorable outcome and 18 (38%) died. Factors that could be used to predict a favorable outcome included age less than 60 years, temporal ICH, World Federation of Neurological Surgeons Grade II or III, absence of a surgical complication, and a hematoma volume less than 25 ml. In the patients with temporal ICH, eight of nine patients achieved a good recovery and no patient developed a surgical complication or delayed ischemic deficit. The significant prognostic factor in patients with an intrasylvian hematoma was surgery within 6 hours after onset of symptoms. In patients with temporal ICH or intrasylvian hematoma, the results of the initial neurological examination did not accurately predict outcome. On the other hand, in patients with ICH and diffuse SAH, those patients who developed an ICH with a volume greater than 25 ml had a poor prognosis. These results indicate that aggressive surgical treatment should be performed in patients with a temporal ICH or an intrasylvian hematoma, regardless of the neurological findings on admission; in patients with ICH and diffuse SAH, a careful review of surgical indications is required.