Biomedical subjects

W Y Guo

Publications and source records attributed to W Y Guo.

At least 19 recordsLinked to original sources

PubMed1999

Pilocytic astrocytoma of the posterior fossa: a follow-up study in 15 patients.

BACKGROUND: The extent of resection in pilocytic astrocytoma of the posterior fossa remains undefined, as the problem of hydrocephalus has not yet been solved. We retrospectively reviewed the data from 15 patients with a pilocytic astrocytoma of the posterior fossa to evaluate the impact of surgical technique, in terms of resection extent, by serial magnetic resonance imaging (MRI) examinations. In addition, the issue of hydrocephalus was considered and related to the different treatment modalities. METHODS: Macroscopic, gross, total resection of the tumor was performed in all 15 patients. Follow-up was obtained in 14 patients for a period ranging between 11 and 119 months (median, 41.5 months). The ages of patients ranged from two to 13 years (mean, 7 +/- 3 years). All patients underwent serial MRI examinations in the first month, every six months for the first two years and then yearly. RESULTS: Outcome was good in 12 patients who had no neurologic deficit and fair in two patients who were slightly handicapped but had an independent life. There were four patients with an abnormally persistent enhancement on MRI, with a median follow-up of 30 months. One of these patients had progressively increasing size of the enhancement. Three of them had the same size of enhancement during the follow-up period. The MRI findings showed residual tumors in four patients. One of them had tumor regrowth one year after surgery. There were 11 cases with pilocytic astrocytoma and hydrocephalus. Five patients were treated with tumor removal and external CSF drainage. Six patients underwent tumor removal only, without perioperative cerebrospinal fluid (CSF) drainage. Only one patient had a permanent ventriculoperitoneal shunt. CONCLUSIONS: Our study illustrated that the extent of tumor resection of pilocytic astrocytoma can be defined by postoperative serial MRI examinations. Long-term follow-up with MRI seems mandatory in cases with abnormal enhancement. Hydrocephalus is a common finding in patients with a pilocytic astrocytoma. A permanent ventriculoperitoneal shunt is required only in patients with postoperative hydrocephalus.

Adolescent↗

PubMed1998

The radiation induced magnetic resonance image intensity change provides a more efficient three-dimensional dose measurement in MRI-Fricke-agarose gel dosimetry.

A detailed methodology has been developed to map the spatial dose distribution in a Fricke-agarose gel based on the radiation induced image intensity change in the gel's magnetic resonance (MR) images. Besides the linear correlation between the change in the gel's spin-lattice relaxation rate and the absorbed dose, it is shown here that the radiation induced image intensity change for T1-weighted spin-echo images with TE << TR correlates exponentially to the absorbed dose. Furthermore, at the lower dose region (< 15 Gy), the correlation is fairly linear and its sensitivity is high. The minimum detectable dose is shown to be equivalent to the one obtained using the conventional R1-based approach. Since only one T1-weighted image is required for the dose evaluation, compared to the R1-based method, the total MR imaging time can be reduced from hours to a few minutes. This extensive time reduction avoids ferric ion diffusion effects and provides a practical way to simply and effectively measure the three-dimensional dose distribution using the Fricke-agarose dosimeter gel.

Gels↗

PubMed1998

The effectiveness and factors related to treatment results of gamma knife radiosurgery for meningiomas.

A retrospective analysis was conducted on 80 patients with intracranial mengiomas treated with Gamma Knife radiosurgery between 1993 and 1996. The purpose was to analyze the efficacy of the treatment and to assess appropriate treatment parameters. The results were assessed by regular MR examinations, and tumor volume was measured at 6-month intervals. Mean follow-up duration was 21 months (range 6-45 months). 63 meningiomas were at the skull base and 17 were distal from the skull base. Tumor volumes <5 ml (n=38), 5-10 ml (n=21), 10-15 ml (n=14), 15-20 ml (n=7). The patients were divided into 3 groups according to the radiation dose. The groups were high-dose (peripheral dose 17-20 Gy, n=19), medium-dose (15-16 Gy, n=33) and low-dose (12-14 Gy, n=28) groups. A statistical method (Generalized Estimation Equation) was applied to compare treatment results in these groups with different doses and tumor volumes. The volume measurement at the latest follow-up showed 74% (59/80) meningiomas decreased in volume, 17% (14/80) had no tumor enlargement and 9% (7/80) had increased in volume. The increased volume was found more frequently in the patients with a short (6-12 months) follow-up period. In this series, the tumors had 32&percnt reduction in average tumor volume at 3 years after radiosurgery. At the range of 12-20 Gy peripheral dose (PD), radiosurgery was effective to reduce tumor volume 0.7% per month (p<0.05). However, higher doses had no significant difference on tumor volume reduction (p>0.05). On the other hand, high-dose (PD>17 Gy) treatment was associated with a higher risk of temporary tumor swelling and the development of adverse radiation effects (AREs). The AREs detected on MR images occurred in (25/80) 31% patients. Only 6/25 AREs were symptomatic and 2 had neurological sequelae. Peripheral doses, tumor volumes and their locations had significant impacts on the ARE (p<0. 05). In conclusion, a peripheral dose of 15-16 Gy may be adequate for meningiomas with small volumes (<5 ml). In larger tumors (>10 ml) a lower PD is preferred (12-14 Gy). To avoid initial tumor swelling and ARE, high-dose irradiation (PD>17 Gy) is not recommended for meningiomas larger than 5 ml.

Adult↗

PubMed1998

Protection of visual pathway in gamma knife radiosurgery for craniopharyngiomas.

Craniopharyngiomas present a major challenge to Gamma Knife radiosurgery (GKRS) due to their proximity to the optic apparatus. Based on observations of the evolving tumoral change on MRI and clinical results, an optimization of the treatment strategy and dose selection is possible. From March 1993 to September 1996, 21 patients with craniopharyngiomas were treated by GKRS. Every patient received stereotactic MRI exclusively for targeting and dose planning. The tumor and adjacent structures, including optic nerves, chiasm, and tracts were carefully identified and delineated on sagittal, coronal and axial films. The tumor volume ranged from 0.3 to 28 ml (average 9 ml). We purposefully apply multiple isocenters (average 9.1 shots) to create an isodose curve that covered the tumor optimally while sparing the optic pathway. The marginal dose prescribed was 9.5 to 16 Gy (50%). The maximal dose was 19 to 32 Gy. The maximal dose to the optic apparatus was 3.2 to 12.5 Gy. After GKRS, all patients were followed up clinically every month. MR studies were conducted every six months with the same techniques on the same scanner to investigate evolution of tumor volume and any adverse radiation effect. The follow-up period ranged from 6 to 40 months (mean: 18.4, median: 19). All patients were followed more than 6 months. Nineteen out of 21 cases (90.5%) achieved tumor control; that is, 18 tumor shrinkage (volume reduction: 15-95%) and 1 stabilized tumor growth. Among these 21 patients, 7 had improved visual acuity or visual field after GKRS, and the rest remained stable. Two patients developed mild T2 change on MRI without any endocrinological disturbance or visual impairment. Protection of the visual pathway can be secured by a sophisticated delineation on 3-dimensional stereotactic images with multiple-shot dose planning. Craniopharyngiomas with tumor volume up to 25 ml were treated safely and effectively, because the dose to the optic apparatus was kept as low as possiby this strategy. Further follow-up is needed to determine the highest tolerable dose to surrounding critical structures and the long-term outcome of tumor control.

Adolescent↗

PubMed1998

Verifying complete obliteration of carotid artery-cavernous sinus fistula: role of color Doppler ultrasonography.

The purpose of this study was to evaluate the role of color Doppler ultrasonography in verifying obliteration of carotid artery-cavernous sinus fistula before and after therapeutic embolization or gamma knife radiosurgery. Before treatment, carotid artery-cavernous sinus fistula showed the following data on color Doppler ultrasonography: (1) increased blood flow in the common carotid artery (220 to 1264 ml/min with mean+/-SD of 728+/-378 ml/min); internal carotid artery (435 to 1097 ml/min with mean+/-SD of 834+/-216 ml/min) in fistulas of the direct type; and external carotid artery (85 to 257 ml/min with mean+/-SD of 170+/-75 ml/min) in fistulas of the indirect type in comparison to the contralateral side; (2) reverse pulsatile flow or spiculated wave form with turbulent flow in the engorged superior ophthalmic vein on the lesion side in all patients. All of the above abnormal hemodynamic changes became normal in six patients immediately after first embolization, in two patients with balloon embolization combined with subsequent direct embolization by direct puncture through the superior orbital fissure or internal carotid artery embolization, and in five patients after gamma knife radiosurgery at 4, 4, 8, 9, and 9 months, respectively. Color Doppler ultrasonography might be a good modality in long-term follow-up of carotid artery-cavernous sinus fistula after gamma knife radiosurgery and embolization.

Adolescent↗

PubMed1998

High resolution computed tomography of temporal bone fracture.

BACKGROUND: High resolution computed tomography (HRCT) is highly efficient in demonstrating the anatomy of the temporal bone. This study evaluates its application to temporal bone fractures (TBF). METHODS: We collected data from 26 cases of TBF in the past two years. All cases underwent HRCT examination. The clinical information was reviewed and correlated with the imaging findings. RESULTS: Eighty-six percent of the cases had longitudinal fractures. Axial scans were the most useful in identifying the fracture line. Mastoid opacification on routine head computed tomography (CT) was also useful in indicating possible TBFs. Complications of TBF, such as ossicular chain disruption, facial nerve damage or otorhino-liquorrhea, were identified clearly using HRCT. CONCLUSIONS: To minimize or prevent the sequelae of TBF, accurate radiologic evaluation is necessary as soon as possible after injury. HRCT of the temporal bone delineates the bony and soft tissue anatomy with high accuracy and we recommend it as the diagnostic modality of choice.

Adolescent↗

PubMed1998

Endovascular embolization of arteriovenous fistulas of the external carotid artery.

BACKGROUND: External carotid arteriovenous fistulas (AVFs) are rare and most hospitals have limited experience with their management. This study was designed to evaluate the effectiveness and safety of endovascular embolization of AVFs of the external carotid artery under angiographic control. METHODS: A series of 13 patients with AVFs involving the branches of the external carotid artery, all treated with endovascular embolization, were reviewed. There were 10 males and three females ranging in age from nine to 46 years, with a mean of 27 years. The most frequent presenting symptoms were pulsatile tinnitus, followed by bruit and/or thrill, ocular problems, headache and a pulsatile mass in the neck. The middle meningeal artery was most often involved, followed by the internal maxillary artery and the occipital artery. The AVFs were caused by trauma in 10 patients and occurred spontaneously in three. N-butyl-2-cyanoacrylate was used to embolize the fistula in 11 patients and a detachable balloon was used in two. RESULTS: All the patients were cured and no significant complications were observed. No recurrence was noted after a clinical follow-up of three months to seven years (mean, 37 months). CONCLUSIONS: Endovascular embolization proved to be a safe and effective procedure. It should be the treatment of choice for repair of external carotid AVFs.

Adolescent↗

PubMed1998

Orbital invasion in nasopharyngeal carcinoma: evaluation with computed tomography and magnetic resonance imaging.

BACKGROUND: Ocular symptoms and tumor cranial nerve involvement are commonly observed in patients with nasopharyngeal carcinoma (NPC). These are primarily due to tumor invasion of the cavernous sinus and/or skull base, as direct tumor invasion of the orbit is very rare. This study was designed to assess computed tomography (CT) and magnetic resonance imaging (MRI) in documenting orbital invasion caused by NPC, with a special emphasis on the route of orbital extension. METHODS: A total of 562 patients with histopathologically prove NPC were examined using CT and/or MRI for tumor staging or post-treatment follow-up. We retrospectively reviewed CT and MRI findings to identify tumor invasion to orbital cavities and to evaluate the pathway of tumor spread. RESULTS: Eighteen patients had tumor extension into the orbital cavities. Seventeen patients had ocular complaints. Fourteen of 18 showed unilateral orbital involvement and four patients showed bilateral orbital involvement. The route from the pterygopalatine fossa and inferior orbital fissure into the orbital cavities was the most common pathway of NPC invasion (n = 13), followed by ethmoid sinus and/or sphenoid sinus into the orbits (n = 4). In one patient, the route of orbital invasion was difficult to determine due to massive tumor extension. CONCLUSION: Direct orbital invasion is rare in NPC. The pterygopalatine fossa and inferior orbital fissure are the most common routes of invasion, followed by invasion via the ethmoid and/or sphenoid sinuses. Coronal sections best show these findings on CT or MRI. Our study also shows that either CT or MRI provide essential information in documenting orbital invasion and determining the pathway of tumor spread.

Adult↗

PubMed1998

Effects of gamma knife radiosurgery for brain tumors: clinical evaluation.

BACKGROUND: Gamma knife radiosurgery is a safe and effective alternative to microsurgery in the management of selected intracranial lesions. In our initial three-year experience with gamma knife radiosurgery, 431 patients were treated using this method. This report presents the treatment results for three different types of brain tumors: benign meningiomas, malignant metastases and gliomas. METHODS: A retrospective study was performed to analyze a consecutive series of 71 meningiomas, 31 metastatic tumors and 21 gliomas treated by gamma knife radiosurgery between March 1993 and May 1996. The treatment results were investigated using regular magnetic resonance examinations and tumor volume measurement at six-month intervals to observe sequential changes of the tumors. Patients with meningiomas were further divided into three groups according to the peripheral radiation doses: high-dose (20-17 Gy, n = 18), medium-dose (16-15 Gy, n = 33) and low-dose (14-12 Gy, n = 20). The Generalized Estimation Equation was applied to compare treatment results in these three groups with different doses and tumor volumes. RESULTS: Volume measurements of the 71 meningiomas showed that 76% decreased in size, 16% stabilized and 8% increased in size. The volumes increased most frequently in the early stage (6-12 months) after treatment and subsequently regressed after the twelfth month. The tumor control rate for meningiomas in our three-year follow-up was over 90%. For meningiomas, the statistical analysis showed that both the radiation dose and tumor volume were significantly related to the development of adverse radiation effects (p < 0.05). In metastatic tumors, rapid tumor regression after radiosurgery was found in 87% of the patients. In gliomas, radiosurgery effectively inhibited tumor growth in selected patients with small, circumscribed, less infiltrative tumors. Ependymomas and low-grade astrocytomas had more favorable outcomes than other gliomas. CONCLUSIONS: Gamma knife radiosurgery is effective for controlling tumor growth in benign meningiomas for up to three years after surgery. In selected cases of malignant metastasis and gliomas, most patients appeared to benefit from the treatment with symptomatic improvement and prolonged survival. Treatment strategy and dose selection in radiosurgery should be adjusted to optimize tumor control and avoid adverse radiation effects.

Brain Neoplasms↗

PubMed1997

Primary cerebellar extramedullary myeloid cell tumor mimicking oligodendroglioma.

Extramedullary myeloid cell tumors (EMCTs) are tumors consisting of immature cells of the myeloid series that occur outside the bone marrow. Most of them are associated with acute myelogenous leukemia or other myeloproliferative disorders, and a small number occur as primary lesions, i.e., are not associated with hematological disorders. Occurrence inside the cranium is rare, and there has been only one case of primary EMCT involving the cerebellum reported in the literature. The case we report here is a blastic EMCT occurring in the cerebellum of a 3-year-old boy who had no signs of leukemia or any hematological disorder throughout the entire course. The cerebellar tumor was at first misdiagnosed as an "oligodendroglioma" because of the uniformity and "fried egg" artifact of the tumor cells. The tumor disappeared during chemotherapy consisting of 12 treatments. However, it recurred and metastasized to the cerebrospinal fluid (CSF) shortly after the therapy was completed. A diagnosis of EMCT was suspected because of the presence of immature myeloid cells in the CSF, and was confirmed by anti-myeloperoxidase and anti-lysozyme immunoreactivity of the cerebellar tumor. The patient succumbed 1 year and 3 months after the first presentation of the disease.

Cerebellar Neoplasms↗

PubMed1997

Magnetic resonance imaging of obliterated arteriovenous malformations up to 23 years after radiosurgery.

The authors report outcomes in 18 patients with arteriovenous malformations (AVMs) who were treated with gamma knife radiosurgery and in whom magnetic resonance (MR) imaging was obtained a mean of 14 years (range 8-23 years) after treatment and 10 years (range 4-17 years) after confirmed obliteration of the AVM. All patients were asymptomatic after radiosurgery and during the time of the study. In five patients (28%), cyst formation was observed that corresponded to the site of the obliterated AVM. Cyst formation and contrast enhancement on MR imaging could not be statistically correlated to the radiation dose. In 11 (61%) of the 18 patients, contrast enhancement that was not related to a recanalization of the nidus was observed in the target area. In three patients (17%), an increased T2-weighted signal was detected at the site of previous AVM; this was interpreted as gliosis or demyelination, which appeared to be dose dependent. The study illustrates that cyst formation, contrast enhancement, and an increased T2-weighted signal can be observed in asymptomatic patients in the area that was targeted for AVM radiosurgery up to 23 years after the procedure. The report provides new and essential information about long-term effects on normal tissue after radiosurgery and provides a basis for the interpretation of MR studies in the follow up of small AVMs treated by radiosurgery.

Adolescent↗

PubMed1997

Intracranial ganglioglioma: CT and MRI findings.

Thirteen cases of pathologically proved intracranial gangliogliomas were reviewed in order to define the characteristic computed tomography (CT) and magnetic resonance image (MRI)-features. All patients were evaluated with CT and four of them were studied by MRI. Six tumors were cystic dominant mixed masses with remarkable focal contrast enhancement (6/13, 46%); and seven were solid in nature with variable contrast enhancement (7/13, 54%). Nine of them contained calcification (9/13, 69%). The temporal lobe was affected in six patients (6/13, 46%); the posterior fossa in four patients; the frontal lobe in two; the remaining huge one in the frontal, temporal and basal ganglion. On MRI, the findings were similar to those of the CT. Gangliogliomas do not have a characteristic CT and MRI features. They may appear as pure cystlike tumors, cystic dominant mixed tumors with remarkable focal contrast enhancement, solid tumors with variable contrast enhancement or diffuse involving the brain parenchyma and/or subarachnoid spaces. However, radiologists should include ganglioglioma in the differential diagnosis when we find patient has a long-standing process as well as a calcified tumor in the temporal lobe with following characteristic; cystic dominant mixed tumor with remarkable focal contrast enhancement, or a solid mass without hemorrhage or significant surrounding edema.

Adolescent↗

PubMed1996

Do we need conventional angiography? The role of magnetic resonance imaging in verifying obliteration of arteriovenous malformations after Gamma Knife surgery.

Sixteen cerebral arteriovenous malformations (AVMs) were examined to determine the role of magnetic resonance (MR) imaging in verifying obliteration. The AVMs (mean volume 7.5 cm3, range 2-17 cm3) were treated with Gamma Knife surgery between March 1993 and May 1994. Integration of stereotactic MR and stereotactic conventional X-ray angiography (XRA) was used for targeting in the Gamma Knife surgery. All MR examinations both for targeting and follow-up, were performed on a 1.5-Tesla superconductive MR scanner (Signa). Multiple pulse sequences (spin echo T1- and T2-weighted MR imaging, and three-dimensional time-of-flight MR angiography) were used. The mean maximum target dose was 37.4 Gy (range 25.0-44.0 Gy). The mean minimum target dose was 20.1 Gy (range 17.5-25.2 Gy). Follow-up imaging was performed about every 6 months or when clinically warranted. XRA was performed when the AVM was no longer seen on MR images. The time from the last MR image to the XRA was within 1 month in nine patients, and longer in seven. MR imaging demonstrated regressing AVMs in all patients as early as 3 months after Gamma Knife surgery. For seven of the nine patients total obliteration on MR was confirmed on XRA within 1 month. In the other two, previous hemorrhage and adverse radiation effects probably caused overestimation of AVM obliteration. In the remaining seven patients, XRA confirmed the MR observation although the time intervals were longer. It is concluded that, for medium- to large-volume AVMs, MR can demonstrate not only the regressing AVMs but also verify total obliteration. However, verification has to be based on an integration of MR imgaging and MR angiography. The use of MR reduces the invasiveness of Gamma Knife surgery for cerebral AVMs.

Adolescent↗

PubMed1996

An evaluation of the accuracy of magnetic-resonance-guided Gamma Knife surgery.

An evaluation of the systematic accuracy of magnetic resonance (MR)-guided Gamma Knife surgery was performed. In two experiments, a cylinder phantom filled with dosimeter gel containing ferrous sulfate was fixed to a stereotactic frame. The gel phantom was irradiated with the Gamma Knife with a single shot using 4-mm collimators. The target point was set at the frame center of the stereotactic system giving coordinate values of X = 100, Y = 100, Z = 100. The maximum target dose was 15 Gy. MR imaging was undertaken immediately after the irradiation, using a superconductive 1.5-T MR scanner. Spin echo T1-weighted images, with transaxial, coronal, and sagittal views, were obtained. On the images, points with the highest signals were defined as the target point which received the maximum dose. Within the dose range of the experiment, this definition is based on a linear relationship between the dose to the gel and the T1 relaxation shortening after irradiation. The distances between the frame center and the target point defined on the MR images in the experiments were 0.12 mm (0.2375 pixels) and 0.43 mm (0.8515 pixels), respectively. Both are within the mechanical accuracy of the Gamma Knife. The imaging study confirms the accuracy of the Gamma Knife surgery used in the institution.

Evaluation Studies as Topic↗

PubMed1995

The additive effects of quinine on antidepressant drugs in the forced swimming test in mice.

The aim of this study was to investigate if quinine plus antidepressant drugs (ADS) leads to an additive effect in the forced swimming test. Quinine (0.125, 0.5 mg/kg) and ADS (subactive doses) were given IP 45 and 30 min, respectively, before the test. When combined with QUIN, all drugs that act via inhibition of 5-HT uptake (imipramine, amitriptyline, citalopram, paroxetine, fluoxetine and fluvoxamine) significantly increased the swimming time of mice. Among trazodone, mianserin and iprindole (atypical ADS), only iprindole combined with quinine decreased the immobility (increased swimming) of the animals. The specific noradrenaline (NA) uptake inhibitors, desipramine and viloxazine, but not maprotiline, were also found to reduce the immobility time when pretreated with quinine. The mixed monoamine oxidase (MAO) inhibitor (pargyline) and MAO-A inhibitor (moclobemide) also shortened the period of immobility whereas the MAO-B inhibitor (nialamide) and the dopamine (DA) uptake inhibitor (bupropion) did not. Quinine's additive effects on several types of ADS is likely a result of blockade of potassium channels.

Animals↗

PubMed1995

Embolization of carotid cavernous fistula by means of direct puncture through the superior orbital fissure.

PURPOSE: To embolize carotid cavernous fistulas (CCFs) by means of transorbital puncture of the cavernous sinus (CS) and the cavernous segment of the internal carotid artery (ICA) through the superior orbital fissure. MATERIALS AND METHODS: Five patients with CCF were treated with embolization of the CS, and six were treated with embolization of both the CS and the cavernous portion of the ICA after transorbital puncture. All except one had previously undergone occlusion of the ipsilateral proximal ICA before direct transorbital puncture. RESULTS: The fistulas in these cases were all obliterated completely. Only two patients had temporary ptosis. No other remarkable complications were noted. The patent ICA on the side of the fistula in one patient remained patent after embolization. CONCLUSION: Direct transorbital puncture through the superior orbital fissure is an alternate treatment for CCF, especially when the ipsilateral ICA has been occluded.

Adult↗

PubMed1995

Early effects of Gamma Knife surgery on malignant and benign intracranial tumors.

To assess the early response of intracranial tumors to Gamma Knife surgery, we performed a prospective investigation of 42 patients treated by Gamma Knife surgery for different types of intracranial tumors. The clinical condition, tumor volume, treatment results and their temporal correlation with the irradiation were analyzed, based on MRI performed on the same MR scanner. Volume reduction in the tumors measured at the latest follow-up ranged from 0.2 to 100%. All except 1 malignant tumor showed decreasing size and improving peritumoral edema 1-7 months after radiosurgery. In 30 benign tumors, 13 showed either a decrease or no change in volume. However, an initial volume increase was observed in 17 tumors, with a maximum at 3-9 months, which subsequently regressed. In 2 meningioma patients, peritumoral edema increased and needed steroid treatment. Sequential PET-FDG imaging of the patients showed decreasing FDG uptake, indicating a decrease tumor in metabolism. The PET findings correlated well with the loss of contrast enhancement on MR images. In conclusion, intracranial tumors respond to Gamma Knife surgery from an early stage. Different tumors have different responses to radiosurgery. It is too early to offer a prognosis of long-term effects based on the limited material. However, sequential clinical, MR and PET follow-ups provide an excellent opportunity to investigate the evolving irradiation effects in vivo.

Brain Neoplasms↗

PubMed1995

Early irradiation effects observed on magnetic resonance imaging and angiography, and positron emission tomography for arteriovenous malformations treated by Gamma Knife radiosurgery.

In 14 patients (7 males and 7 females, age 16-49, mean 29 years), medium-to-large arteriovenous malformations (AVMs; nidus volume 3.5-17.5 cm3, mean 9.4 cm3) were treated by Gamma Knife radiosurgery. Stereotactic MR and conventional angiography were included for targeting to improve targeting accuracy and tissue content in the irradiation volume. Maximum irradiation doses to the nidi were 36-40 Gy (mean 38.9 Gy) and minimum target doses were 18-24 Gy (mean 20 Gy). MR images and MR angiography demonstrated decreasing caliber of feeding vessels and AVM nidus volumes from an early stage, 3 months after radiosurgery, which indicated improvement in cerebral hemodynamics. The improvement correlated well with that observed on PET using [18F]fluorodeoxyglucose (FDG) and with the patients' clinical condition. MR creates an opportunity to monitor treatment effects in a completely noninvasive manner, while conventional angiography remains necessary for verifying complete obliteration of AVMs. More patients and longer follow-ups are needed for clarifying the role of MR techniques in radiosurgery for AVMs.

Adolescent↗