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W Y Guo

Publications and source records attributed to W Y Guo.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1995

Radiobiology of radiosurgery for refractory anxiety disorders.

The neuroradiological manifestations of bilateral single-session gamma (gamma)-irradiation to normal tissue contained in the internal capsule after gamma knife capsulotomy for otherwise intractable anxiety disorders were studied. In nine consecutive patients, a target maximum dose of 200 Gy was administered in a target volume of 276 +/- 42 mm3 (mean +/- SD) within the 50% isodose level. Serial computed tomographic and magnetic resonance imaging scans were undertaken from 3 to 44 months after irradiation. After surgery, a necrotic lesion appeared on computed tomographic scans, reaching its maximum volume (900 +/- 800 mm3) at 6 to 9 months, then decreasing (to 457 +/- 400 mm3) over the first postoperative year. This volume correlated with the mean isodose level of 91 (range, 41-143) Gy. On T2-weighted magnetic resonance imaging scans, the reaction tissue volumes were considerably larger and took longer to disappear than expected. In 15 targets, maximum reaction volumes were recorded at 1 to (approximately) 2 years after irradiation. In the remaining seven targets, smaller reaction volumes were observed, with no clear maxima appearing during 3 years of observation. In a pilot case, a lower target maximum dose of 160 Gy and a radiation volume of 275 mm3 within the 50% isodose gave only minimal surrounding tissue reactions. This report serves to alert clinicians that the tissue reaction volumes and the time course of their development after high irradiation doses may be less predictable than expected from previous observations in smaller radiation volumes. For this reason, lower irradiation doses and smaller volumes should be used in the future, and the time factor should be taken into account when interpreting computed tomographic and magnetic resonance images of gamma-knife-induced lesions.

Adult↗
PubMed1995

Midbrain hemorrhage presenting as bilateral ptosis without hemiplegia: a case report.

A 66-year-old man suddenly developed bilateral ptosis after awaking from a nap. He did not experience nausea, vomiting or headache. In the emergency room, high blood pressure was noted. On examination, his consciousness was clear. Ptosis was present bilaterally and worse on the right side. The pupils promptly constricted to light. He could fully adduct his eyes during conjugate gaze movements, but convergence was impaired in the right eye. There was no diplopia or nystagmus. The assessment of the motor and sensory systems revealed no significant findings. Computed tomographic scanning and magnetic resonance imaging of the brain showed a small hematoma in the midbrain. Six months later, ptosis improved; however, the convergence deficit remained.

Blepharoptosis↗
PubMed1995

Startle epilepsy presenting as drop attacks: a case report.

A case of startle epilepsy, induced by an unexpected touch on the left shoulder of a 3.5 year old boy, was investigated. The startle epilepsy manifested as an atonic drop attack. Neurological examination revealed a mild hemiparesis on the left side. Computed tomography (CT) scanning demonstrated an enhancement over the right parieto-frontal region, suggesting a hemangioma. Interictal electroencephalography (EEG) showed diffuse slowing and asymmetry of background activities with lower amplitude over the right centro-parieto-temporal region. The ictal EEG showed a paroxysmal bilaterally synchronized high amplitude single spike followed by a few slow waves lasting about one second over the bilateral centro-parieto-temporal regions. The seizure resisted anticonvulsant therapy and no significant responses were observed despite the use of combined therapy with valproic acid, phenytoin, primidone and clonazepam.

Child, Preschool↗
PubMed1994

Haemorrhagic pituitary tumours.

In a group of 69 patients with pituitary tumours, 12 were found to have evidence of intratumoral haemorrhage on MRI, characterized by high signal intensity on short TR/TE sequences. This was verified in all but 1 patient. The majority of the bleedings occurred in macroadenomas. Five (42%) were prolactinomas and 4 (33%) were non-functioning adenomas. There were 2 GH- and 1 ACTH-secreting tumours. All 5 patients with prolactinomas were on bromocriptine medication. Two of the patients had a clinical picture of pituitary apoplexy. The haemorrhage was not large enough to prompt surgery in any of the patients. However, surgical verification of the diagnosis was obtained in 5 cases, while 6 patients were examined with follow-up MRI.

Adenoma↗
PubMed1994

Multiple intracranial arteriovenous malformations: a case report.

Multiple intracranial arteriovenous malformations are rare. There are a few cases in the literature with up to three malformations in one patient. A child with seven separate cerebral malformations is now described. There was no history of haemorrhage, but only of febrile seizures. The malformations were discovered at CT and verified at angiography. Six were selected for stereotaxic irradiation with the multi-cobalt unit. The seventh was considered too big for irradiation and suitable for surgery.

Cerebral Angiography↗
PubMed1993

Gamma knife surgery of cerebral arteriovenous malformations: serial MR imaging studies after radiosurgery.

PURPOSE: To investigate the temporal sequence of post radiosurgery magnetic resonance imaging changes in cerebral arteriovenous malformations. METHODS AND MATERIALS: Eighteen patients were regularly followed up after gamma knife surgery. The follow-up intervals ranged from one day to 44 months. High signal lesion in or around arteriovenous malformations on T2-weighted magnetic resonance images corresponding to the treatment volume and developing after radiosurgery were defined as the adverse reaction of the irradiation. This high signal and the regression of arteriovenous malformations nidus after radiosurgery were evaluated. RESULTS: Adverse reaction of irradiation was observed in nine cases. Seven of them were symptomatic. The reactions presented as focal high signal in three cases and focal high signal with extension along the neural tracts in six cases. The reactions were seen either immediately after treatment (one case), between 3 and 14 months (seven cases), and 40 months after treatment (one case). The regression of the adverse reaction was observed to start 5 +/- 3 months after its appearance. Regression of the arteriovenous malformations' nidus was found in 16 cases. In two cases the AVMs became invisible on magnetic resonance images but the angiogram still demonstrated abnormal shunts. In another one case with angiogram showing total obliteration, the nidus was erroneously interpreted as incomplete obliteration on magnetic resonance images. CONCLUSION: It is concluded that magnetic resonance imaging is a sensitive in vivo method for detecting cerebral radiation injury. Magnetic resonance imaging offers a method for evaluating the regression of arteriovenous malformations' nidus, but the diagnosis of complete obliteration of the nidus after radiosurgery still relies on the angiogram.

Adolescent↗
PubMed1993

Even the smallest remnant of an AVM constitutes a risk of further bleeding. Case report.

A case with an ill-defined arteriovenous malformation in the parieto-occipital region is presented. Open surgery was unsuccessful in removing the AVM totally, and treatment with gamma knife radiosurgery was then attempted. At 14 months after this treatment the AVM was believed to be obliterated. The patient had a new intracranial haemorrhage 59 months after radiosurgery. Renewed angiography showed an obvious AVM outside the previously irradiated area. Retrospective analysis of the angiogram at 14 months after radiosurgery revealed early filling of a draining vein as a sign of residual AVM at this time. Renewed radiosurgical treatment was performed. It is believed that an ill-defined margin, laminar flow, and effects of previous surgery might add to difficulties in a proper visualisation and delineation of an AVM. Further, a small remaining shunt may be overlooked if the angiogram is not carefully analysed or if the angiogram is of inferior quality. It should be stressed that partial or almost total obliteration of an AVM is no protection against rebleeding.

Cerebral Angiography↗
PubMed1993

Radiosurgery for venous angiomas.

Radiosurgical treatment with the gamma knife for venous angiomas was used as an alternative to microsurgical removal in order to avoid abrupt cessation of venous drainage, which may be shared by the venous angioma and important parts of the brain. Thirteen cases of venous angioma were treated between 1977 and 1991. In two cases cavernous angiomas were also present and in one case a distant arteriovenous malformation (AVM) was also found. In two cases the angioma shared the venous drainage with an adjoining AVM; this is the first description of such pathology. For venous angiomas irradiation was prescribed to cover at least the convergence of the medullary veins. For AVM's close to a venous angioma the treatment was exclusively prescribed to the AVM nidus. After treatment, complete obliteration of the venous angioma was observed in one case, partial obliteration was observed in three cases, and five venous angiomas were unaffected by the treatment. Undue effects of radiation occurred in four cases: one focal edema and three radionecroses. Extirpation of the radionecrotic tissue 6 months after radiosurgery was necessary in one case. In the other three cases, the venous angioma was observed to be completely or partially obliterated, or unaffected by the treatment (one case each). In two cases of combined AVM and venous angioma, complete obliteration of the treatment AVM nidus was obtained. It is concluded that radiosurgery for venous angioma, although conceptually attractive, still does not fulfill the rigid criteria of minimal risk which must be set for the treatment of a lesion with a benign natural history.

Adult↗
PubMed1993

[Pharmacokinetics of moracizine and moracizine sulfoxide in healthy volunteers].

The pharmacokinetics of moracizine (Mor) and moracizine sulfoxide (Mor-SO) determined by reversed phase HPLC was reported. The data in 6 volunteers after a single oral dose (600 mg) showed an one-compartment open model. The peak concentration in plasma (2.1 +/- 0.4 micrograms.ml-1) of Mor reached within 1-2 h. The Mor-SO concentration in plasma was much lower (0.19 +/- 0.06 micrograms.ml-1) than that of Mor, but its elimination T1/2 (2.3 +/- 1.0 h) was similar to that of Mor (1.5 +/- 1.0 h). The recoveries of Mor, Mor-SO, moracizine sulfone (Mor-SO2) in urine within 48 h were 0.07%, 0.25%, and 0.06% of the total dose, respectively. The Mor and Mor-SO concentration ranges in plasma for 9 arrhythmic patients after 2-wk therapeutic trial were 0.09 +/- 0.07 to 0.9 +/- 0.5 microgram.ml-1 and 0.040 +/- 0.023 to 0.15 +/- 0.06 micrograms.ml-1, respectively. These results suggested that cumulative doses would not result in accumulation of the drug and the anti-arrhythmic effect of Mor-SO might not be realized.

Adult↗
PubMed1993

Combined embolization and gamma knife radiosurgery for cerebral arteriovenous malformations.

In a study of 46 patients with cerebral arteriovenous malformations (AVMs) the value of combining embolization and gamma knife radiosurgery was assessed. In 35 patients with large grade III to V AVMs (Spetzler-Martin system) staged combined treatment was planned. In 11 patients, radiosurgery complemented embolization for a residual AVM. The number of embolization sessions ranged from 1 to 7 (median 2). Twenty-six patients needed multiple embolization sessions. In 28 patients the grade of AVMs decreased as a result of embolization. In 16 patients collateral feeding vessels developed after embolization which made delineation of the residual nidus difficult. The time lag between the last embolization and radiosurgery ranged from 1 to 24 months (median 4). Nineteen of 35 large grade III to V AVMs were possible to treat by radiosurgery following embolization. In the 46 patients complications occurred in 9 from embolization and in 2 from radiosurgery. Two patients had transient and 9 had permanent neurologic deficits. It is concluded that embolization facilitates radiosurgery for some large AVMs and therefore this combined treatment has a role in the management of AVMs.

Adolescent↗
PubMed1993

Target delineation in radiosurgery for cerebral arteriovenous malformations. Assessment of the value of stereotaxic MR imaging and MR angiography.

A study of 6 selected arteriovenous malformation (AVM) patients was performed to investigate the feasibility of delineating an AVM on MR images and to compare the AVM volume outlined on different images. Conventional stereotaxic angiograms, stereotaxic MR images and MR angiograms using several different pulse sequences were obtained prior to radiosurgery. Treatment plans were made from the conventional stereotaxic angiograms. These plans were then transferred to a separate dose planning computer which displayed the MR images with the superimposed isodose lines. The radiated volumes of AVM and brain tissue were measured from these MR images. Last, an assessment was made of the radiation volume needed for an appropriate treatment of the AVM if the treatment plan was made from the MR images rather than from the conventional stereotaxic angiogram. It was possible to delineate medium and large size AVM nidi on stereotaxic MR images based on an integration of information obtained from various pulse sequences. The estimated volumes of the AVM nidi were found to be larger on the conventional stereotaxic angiograms than on the stereotaxic MR images. Consequently, a dose plan based on a conventional stereotaxic angiogram would result in a higher integral dose to the brain with the same target dose. By using reliable MR information it is expected that the volume of brain exposed to radiation could be decreased and the adverse effects of stereotactic radiosurgery for AVM thereby minimized.

Adult↗
PubMed1993

Radiological aspects of gamma knife radiosurgery for arteriovenous malformations and other non-tumoural disorders of the brain.

The aims of the thesis were to investigate stereotaxic procedures in radiosurgery for cerebral arteriovenous malformations (AVMs) and radiation effects of single session high-dose irradiation delivered by gamma knife on the human brain. Investigation of gamma knife radiosurgery in 1,464 patients constitutes the data base of this thesis. High quality stereotaxic angiography is the gold standard targeting imaging in radiosurgery for cerebral AVMs, particularly for small AVMs or residual AVMs after other treatments. For medium and large size AVMs, stereotaxic MR techniques can improve targeting precision and decrease irradiation volume as compared to stereotaxic angiography in selected cases provided that proper pulse sequences are used. Combined treatments, where embolization precedes radiosurgery, can improve amenability of the treatment for large AVMs. This is on condition that the partially embolized nidi are well delineated and the volume of the residual nidi has been decreased to a level where an optimum irradiation can be safely prescribed. Radiologically, adverse radiation effects (ARE) of gamma knife radiosurgery for cerebral AVMs are observed in 16% (131/816) of the patients. The ARE are observed as a focal low attenuation on CT or as a focal high signal on MR image without enhancement in 47% (61/131), and as a peripheral or homogeneous enhancing lesion in 48% (63/131). MR imaging is more sensitive than CT in detecting the ARE. 91% of the ARE are observed within 18 months after radiosurgery and 89% are seen to regress within 18 months. Clinically, symptomatic ARE are only observed in 6% (51/816) and only in half of them, i.e. 3%, are the symptoms permanent. The risk of ARE in radiosurgery for venous angiomas is higher as compared to AVMs. Other mechanisms have probably been employed. In gamma capsulotomy, the necrotic lesions and reaction volumes created by using multiple isocentres of 4 mm collimators are less predictable as compared to that by single isocentre. Volume effects and depreciation of the steep isodose gradient are hypothesised as the leading factors of the inconsistency. Based on the in vivo assessment of the radiation effects observed on the basically normal human brain it is concluded that irradiation volume is strongly related to the radiation effects and is one of the important considerations in decision making for radiosurgery. Volume of brain tissue exposed to irradiation could be minimised and precision of targeting could be maximised provided that a proper stereotaxic imaging is used.(ABSTRACT TRUNCATED AT 400 WORDS)

Anxiety Disorders↗
PubMed1991

Percutaneous reposition of dislodged coils in the treatment of a vertebral arteriovenous fistula--with CT follow-up.

We report a case of vertebral arteriovenous fistula in which embolization was complicated by migration of two coils and a partially inflated balloon. In order to relieve compression to the spinal cord, the displaced balloon was punctured percutaneously. For both relieving compression to the spinal cord and obliterating the residual fistula, the dislodged coils in the partially thrombosed epidural venous sinus were removed percutaneously and placed in the fistula, and more coils were implanted in the fistula percutaneously through the needle. CT follow-up half a year later showed complete resolution of compression of the spinal cord and complete recovery from myelopathy was clinically apparent.

Adult↗
PubMed1991

Stereotactic radiosurgery with the cobalt-60 gamma unit in the treatment of growth hormone-producing pituitary tumors.

Stereotactic radiosurgery on the pituitary given with the cobalt-60 gamma unit was used in the treatment of 21 patients with growth hormone (GH)-producing pituitary adenomas and acromegaly. All but one patient had locally invasive macroadenomas, and in the majority of cases, there was parasellar growth. Radiosurgery was the initial treatment for seven patients. Fourteen patients were previously treated by pituitary surgery, eight of whom had undergone conventional external pituitary irradiation as well. All patients had clinical signs of active acromegaly before radiosurgery. The radiation doses given to the previously untreated patients or those who only underwent surgery were 40 to 70 Gy in each of one to three irradiations. The patients with previous external irradiation received a lower dose of 30 to 50 Gy in each of one or two irradiations. The patients were observed during a period of 1 to 21 years from the first radiosurgical session. Two young patients had a clinical remission with a substantial decline of GH levels to near normal serum profiles. Another eight patients obtained reduction of GH levels and clinical activity. More than half of the patients (11 of 21) had minor or no effects from the treatment. There were no complications from the radiosurgery except the development of pituitary insufficiency in 2 of 13 patients who did not undergo previous conventional external irradiation. The remission rates were lower than the results previously reported by us for radiosurgery for Cushing's disease. This may be a result of the predominance in the present study of invasive macroadenomas and single treatments and to the lower radiation doses used in the patients who underwent conventional irradiation previously.(ABSTRACT TRUNCATED AT 250 WORDS)

Acromegaly↗
PubMed1990

CT evaluation of polymorphic reticulosis.

For the understanding of the CT findings of polymorphic reticulosis involving the upper respiratory tract, we reviewed eleven cases of this disease with initial CT study before treatment. CT revealed masses or swelling in the nose or nasal chamber, often with involvement of paranasal sinuses and medial parts of the orbit. In some, nonspecific minimal bony change (either bone destruction or bone sclerosis) was found. These CT findings are not specific. Any large mass in the nose and nasal fossa with little associated bone destruction should, however, raise the differential diagnosis of polymorphic reticulosis.

Adolescent↗
PubMed1990

Prevalence of age-related cataract in Ganzi and Shanghai. The Epidemiological Study Group.

It has been reported that the prevalence of cataract is much higher in plateau than that in plain regions. But the data are incomplete and can not be compared because of different examination methods and different diagnostic criteria. A small group of ophthalmologists was sent to Ganzi, Sichuan Province at the altitude of 3.393 m, and to Qinpu in the suburb of Shanghai which is at the sea level. In Ganzi 3,905 (91.97%) people including 822 Hans and 3,083 Zang and in Qinpu 3,101 (93.20%) were studied. Age-related cataract was diagnosed when there are cortical or nuclear, or mixed opacities; and aphakia due to previous extraction of age-related cataract. Direct method was used to standardize the data. The prevalence of age-related cataract in Ganzi is about 82% higher than that in Qinpu in all age groups; from age 16-60, the prevalence of age-related cataract in Ganzi is about 180% (in Hans) and 160% (in Zangs) higher than that in Qinpu. There is no significant difference in the prevalence of age-related cataract between the ethnic groups in Ganzi. In Ganzi, the sunshine hours per year are 1.28 times that in Qinpu, and the global radiation in Ganzi is 1.47 times that in Qinpu. The higher prevalence of cataract in Ganzi than in Qinpu may be due to the greater exposure to the sunshine on the Tibetan plateau. The differences in prevalence between males and females and between indoor and outdoor work are discussed.

Adolescent↗