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Aki Kangasmäki

Publications and source records attributed to Aki Kangasmäki.

8 recordsLinked to original sources
PubMed2007

Brain function during multi-trial learning in mild cognitive impairment: a PET activation study.

We explored functional brain changes with positron emission tomography (PET) in mild cognitive impairment (MCI) patients and elderly normal controls by employing an episodic memory task that included two successive encoding trials of semantically related word-pairs and final retrieval. Both groups demonstrated significant learning across the two trials. The control group showed predominantly left frontal activity during encoding, and right frontal plus left temporal activity during retrieval. However, the MCI patients recruited partly different brain regions. They failed to activate right frontal and left temporal areas during retrieval, and failed to show any different activation for encoding on the first and second trials, whereas the controls activated a region of posterior cingulate. There was indication of compensatory increases in rCBF of the occipital cortex during incremental learning and the left frontal lobe during retrieval in the patients. These results suggest different episodic memory processing in the MCI group, and a possible over-reliance on semantic processing. Subtle functional changes occur in the pre-Alzheimer brain before there are marked structural or behavioural abnormalities.

Aged↗
PubMed2006

Sparing of the submandibular glands by intensity modulated radiotherapy in the treatment of head and neck cancer.

BACKGROUND AND PURPOSE: The submandibular glands produce most of the unstimulated saliva output and are the key in prevention of radiation-related xerostomia. We investigated whether sparing of the submandibular function is feasible with intensity modulated radiotherapy (IMRT). PATIENTS AND METHODS: Thirty-six patients diagnosed with head and neck cancer were treated with IMRT and had at least one parotid gland excluded from the planning target volume. In a subset, of these patients (n=18) where the risk of cancer recurrence in the contralateral submandibular region was judged low, the contralateral submandibular gland was spared from full-dose irradiation. The total unstimulated and stimulated salivary flow rates and adverse effects were monitored. RESULTS: Twelve months following IMRT mean unstimulated saliva flow was 60% of the baseline value among patients who had one submandibular gland spared and 25% among those who did not (P=0.006). Patients whose contralateral submandibular was spared reported less grade two or three xerostomia (4 vs. 11; P=0.018), and used less saliva substitutes. No cancer recurrences were detected at the vicinity of the spared glands during a median follow-up time of 31 months. CONCLUSIONS: Submandibular gland sparing with IMRT is safe in selected patients treated for head and neck cancer. It is effective in prevention of radiation-associated xerostomia.

Adult↗
PubMed2004

Abnormal intravoxel cerebral blood flow heterogeneity in human ischemic stroke determined by dynamic susceptibility contrast magnetic resonance imaging.

BACKGROUND AND PURPOSE: The determination of cerebral blood flow heterogeneity (FH) by dynamic susceptibility contrast (DSC) magnetic resonance imaging has recently been proposed as a tool to predict final infarct size in acute stroke. In this study, we describe the evolution of FH during the first week as well as its correlation to the patients' clinical status. METHODS: Ten patients with ischemic stroke were studied with DSC MRI and diffusion-weighted imaging in hyperacute (<6 hours) phase, at 24 hours, and 1 week after symptom onset. In addition to intravoxel FH, cerebral blood volume (CBV), cerebral blood flow (CBF), and contrast agent mean transit time (MTT) were determined from DSC MRI. All patients were evaluated neurologically with National Institute of Health Stroke Scale concurrently with the imaging sessions. RESULTS: All patients showed infarct growth, judged by diffusion-weighted imaging, during the week with simultaneous decrease in the sizes of FH, CBV, CBF, and MTT abnormalities. The FH abnormality was shown to be larger than CBV and CBF abnormalities at the hyperacute phase and 24 hours, but smaller than MTT abnormality in all 3 imaging sessions. The sizes of hyperacute FH, CBV, CBF, and MTT abnormalities correlated well with infarct size at 24 hours and at 1 week. Additionally, FH was the only perfusion parameter that correlated with the clinical score. CONCLUSIONS: FH predicts infarct size equally well with the other perfusion parameters but is superior in correlation with the clinical score. FH can easily be incorporated to hyperacute stroke imaging without additional efforts.

Aged↗
PubMed2004

Localization of local anesthetic solution by magnetic resonance imaging.

PURPOSE: The aim of this study was to examine the distribution of local anesthetic solution by magnetic resonance imaging (MRI) after combined peribulbar and retrobulbar, superomedial retrobulbar, and sub-Tenon's injection in relation to clinical akinesia. DESIGN: Randomized clinical trial. PARTICIPANTS: Fifteen patients scheduled for cataract surgery, 5 patients in each group. METHODS: Five patients received combined peribulbar and retrobulbar anesthesia, 5 patients received superomedial retrobulbar injection, and 5 patients had sub-Tenon's injection, all with a combination of bupivacaine 0.75%, lidocaine 2%, and hyaluronidase. The MRI scans were performed before the injection and up to 35 minutes after the injection. RESULTS AND CONCLUSIONS: Reliable anesthesia is achieved using a combined peribulbar and retrobulbar block and a relatively great volume of local anesthetic solution, which spreads throughout the orbit, as evidenced by MRI. After superomedial retrobulbar and sub-Tenon's injection, the local anesthetic solution accumulates behind the globe. Sub-Tenon's injection gives good analgesia and slight akinesia with a very small volume. Superomedial retrobulbar injection and combined peribulbar and retrobulbar block provide a similar degree of exophthalmos, which seems to be the result of the volume injected behind the globe.

Aged↗
PubMed2002

Non-linear model for the kinetics of 10B in blood after BPA-fructose complex infusion.

A numerical model with a memory effect was created to describe the kinetics of 10B in blood after a single 4-dihydroxyborylphenylalanine-fructose complex (BPA-F) infusion in boron neutron capture therapy (BNCT). The model formulation was based on the averaged data from 10 glioma patients from the Brookhaven National Laboratory (BNL) BNCT-trials. These patients received a 2 h i.v. infusion of a BPA-fructose complex that delivered 290 mg BPA/kg body weight. The model was validated by fitting the original BNL patient data and new patient data from the Finnish BNCT-trials. The new 3-parameter non-linear model provided mean absolute differences between the measured and estimated 10B concentrations in blood that were less than 3.9% when used to simulate actual patient irradiations that comprised two irradiation fields separated by a break to reposition the patient. The flexibility of the model was successfully tested with two different infusion protocols. The patient data were modelled with a two-compartment model and a bi-exponential fit for comparison. The 3-parameter model is better than previously described models in predicting the time course of blood 10B concentration after cessation of intravenous infusion of BPA-fructose.

Boron↗
PubMed2002

Evaluation of four postprocessing methods for determination of cerebral blood volume and mean transit time by dynamic susceptibility contrast imaging.

Four different postprocessing methods to determine cerebral blood volume (CBV) and contrast agent mean transit time (MTT) by dynamic susceptibility contrast (DSC) MRI were compared. CBV was determined by two different methods that integrate tracer concentration-time curves numerically and by two other methods that take recirculation into account. For the two methods that use numerical integration, one method cuts the integration after the first pass while the other method integrates over the whole time series. For the two methods that account for recirculation, one method uses a gamma-variate fit, whereas the other method utilizes tissue impulse response. All four methods determine MTT as the ratio of CBV and cerebral blood flow (CBF). In each case, CBF was obtained as the height of the impulse response obtained by deconvolving the tissue concentration-time curves with a noninvasively determined arterial input function. Monte Carlo simulations were performed to determine the reliability of the methods and the validity of the simulations was supported by observation of similar trends in 13 acute stroke patients. The method of determining CBV and subsequently MTT was found to affect the measured value especially in areas where MTT is prolonged, but had no apparent effect on the visually determined hypoperfusion volumes.

Aged↗
PubMed2002

Diffusion-weighted MR imaging in normal human brains in various age groups.

BACKGROUND AND PURPOSE: Few studies have concerned the absolute apparent diffusion coefficient (ADC) values in the normal human brain and the effect of aging on diffusion. Therefore, our purpose was to determine whether the average ADC (ADC(av)) values in the various regions of the brain differ with age, sex, or hemisphere and to establish reference values of the absolute ADC(av) for further studies. METHODS: Subjects (40 men and 40 women) were chosen from a healthy population; age groups were 20-34, 35-49, and 50-64 years and 65 years or older (n = 20 each). All subjects were examined with MR imaging, including conventional and diffusion-weighted imaging in three orthogonal directions with two b values (0 and 1000 s/mm(2)) at 1.5 T. Bilateral ADC(av) values were determined in 36 regions of interest encompassing the entire brain. RESULTS: ADC(av) values were highest in the cortical gray matter ([0.89 +/- 0.04] x 10(-3) mm(2)/s; range, 0.78-1.09 x 10(-3)), lower in the deep gray matter ([0.75 +/- 0.03] x 10(-3) mm(2)/s; range, 0.64-0.83 x 10(-3)), and lowest in the white matter ([0.70 +/- 0.03] x 10(-3) mm(2)/s; range, 0.62-0.79 x 10(-3)). The ADC(av) values did not significantly change with aging, except for an increase in the lateral ventricles. No difference was observed between women and men or between the hemispheres. CONCLUSION: The data reported herein are representative, and the ADC(av) values can be used for reference in future studies and in clinical settings.

Adult↗