the cases included 22 canines and 1 feline that were diagnosed with meningioma between 2006 
 and 2008 .
all were between 8 and 16 years old ( average age of 11 , median age of 11 ) .
nine of the canine cases were golden retrievers , while the 
 other cases included small dogs , such as a chihuahua and a maltese .
their clinical symptoms ranged from only epilepsy to visual defects , 
 depression of postural reflexes with asymmetry or severe ataxia of gait .
computed tomography ( ct ) ( asteion super4 , toshiba medical systems , 
 tochigi , japan ) and digital subtraction angiography examinations were also performed for 
 other diagnostic measurements , and the location of the tumor and its feeding blood vessels 
 were confirmed .
the mri machine was a 0.3 tesla open type ( airis ii comfort , hitachi medical corporation , 
 tokyo , japan ) . in our operating room
, we set a rotary surgical bed and the necessary 
 instruments for the surgery outside of the 5 gauss magnetic field of the mri machine ( fig .
c ) smooth 
 transfer of a patient between the table and mri stage . ) .
this 
 setup allowed us to transfer a patient between the bed and mri stage smoothly .
we were able 
 to use magnetically intolerant instruments and other machines only when the mri was not 
 being used .
mri was 
 performed within a short time with gd - enhanced t1-weighted and 3d gradient echo sequences 
 ( 1.0 mm slice thickness ) .
furthermore , multi planar reconstruction ( mpr ) was applied to the 
 image , and the location of the tumor was confirmed in three dimensions . for craniotomy , a 
 round bar was used . for the removal of the tumor , a bipolar , a surgical microscope ( ome-500 , 

an ultrasonic aspirator ( sonopet , 
 stryker , tokyo , japan ) was applied to stop hemorrhage from the tumor .
the decision to perform surgery was made in consultation with the owners , and informed 
 consent was obtained before all surgeries were performed . before craniotomy , mannitol ( 1 
 g / kg / tid / iv ) , methylprednisolone sodium succinate ( 1530 mg / kg / sid / iv ) and phenobarbital ( 2 

mg / kg / bid / im ) were administered to reduce brain edema and to stabilize the animal .
we 
 performed transfrontal sinus craniotomy for tumors close to the frontal lobe , rostral 
 tentorium craniotomy for partial lobe tumors , zygomatic arch excision craniotomy for 
 temporal lobe tumors , caudal tentorial craniotomy for occipital lobe tumors or a mixture of 
 each based on the best approach determined by the preoperative mri examination .
once we exposed the dura mater , we placed an mri biopsy 24 g needle in the middle of the 
 tumor and performed mri to confirm the location of the tumor ( fig . 2fig .
. the scanned image was displayed on mpr to show the tumor extent in three 
 dimensions .
then , we started the resection surgery under a surgical microscope , referring to 
 the initial mri .
we placed the sonopet ultrasonic aspirator machine in the middle of the 
 tumor to destroy the inner part and released pressure from the entire tumor .
once we created 
 some space between the brain tissue and tumor , we treated blood vessels and confirmed the 
 supplies going to the tumor , and carefully resected them .
we repeated this procedure all 
 around the tumor and finally took out the entire tumor ( fig . 3fig .
b ) an ultrasonic aspirator machine was used to destroy the inner part 
 of the tumor and reduce the pressure .
c ) after creation of some space between the 
 brain tissue and tumor , the blood vessels going to the tumor were cauterized and 
 resected .
d ) the procedure in c was repeated all around the tumor , and the entire 
 tumor was removed . ) .
we took multiple mri with gd - enhanced t1 weighted images during the surgery to 
 check for any residual tumor and for bleeding at any time ( fig .
b ) final mri during surgery . each white 
 arrow shows the remaining tumors .
we transplanted cutaneous muscle to suture back the dura mater and then applied 
 suture glue ( bolheal ; kaketsuken kumamoto , japan ) to prevent any leakage of cerebrospinal 
 fluid .
propofol was 
 given intravenously to calm the patient down and to decrease the brain pressure for 12 hr 
 following the surgery , which was also considered to relieve the stress associated with the 
 operation .
0.5 g / kg / bid / iv ) , methylprednisolone sodium 
 succinate ( 15 mg / kg / sid / iv ) and zonisamide ( 3 mg / kg / bid / po ) for 3 days postoperatively to 
 prevent brain edema .
c ) gd- enhanced t1-weighted image 
 after mpr , transverse image . surgical procedure ( under a surgical microscope ) .
b ) an ultrasonic aspirator machine was used to destroy the inner part 
 of the tumor and reduce the pressure .
c ) after creation of some space between the 
 brain tissue and tumor , the blood vessels going to the tumor were cauterized and 
 resected .
d ) the procedure in c was repeated all around the tumor , and the entire 
 tumor was removed .
twenty - two of the lesions originated from the cerebrum fornix and the arachnoid cells of 
 the falx cerebri , 18 cases were found on the frontal lobe , 2 cases were found on the 
 temporal lobe , 2 cases were found on the parietal lobe , 1 case was found on the tentorium 
 cerebella , and 1 case was found on a brain ventricle ( fig . 5fig .
5.intraventricular meningioma ( mri ) in case 6 . ) . in case 6 , the intraventricular tumor ,
the nutrient vessels from the internal 
 carotid artery were detected by a ct scan ( fig . 

the average length of surgery was 5 hr . we did not have any patient deaths during 
 surgery , and 16 of the 23 cases lived for more than 2 years after the procedure .
we had to monitor the patients closely for 7 days postoperatively , because of the risk of 
 intracranial hypertension .
two patients with widespread brain edema died due to arrhythmia 
 and aspiration pneumonia after surgery .
the rest of the patients lived for more than 7 days 
 without any complications . in case 16 , the patient was 16 years old and had a cerebral 
 hernia .
another 4 cases died within 2 years of gastric dilatation volvulus or other diseases 
 due to their old ages .
none of the patients died from intracranial hypertension caused by 
 recurrence of meningioma within 2 years ( table 
 1table 1.case summary and survival durationscase numberbreedsexage ( years old)affected lobesurvival durations1maltesemale14parietaldied from encephalitis at 1.5 years post - op2mixed breed dogmale12frontal3-year survival3mixed breed dogfemale10cerebellumdied from recurrence at 2 years post - op4mixed breed dogfemale10frontal3-year survival5mixed breed dogmale12frontal2-year
survival15golden retrievermale9frontaldied from gdv at 4 months post - op16labrador retrievermale16frontal8-month survival17labrador retrievermale10frontal2-year survival18german shepherdfemale8frontal3-year survival19shih tzumale9frontal2-year survival20yorkshire terriermale13frontaldied from aspiration pneumonia at 6 months post - op21american cocker spanielfemale11frontaldied from renal diciency at 2 years post - op22chihuahuafemale8frontal2-year survival23american shorthairmale11parietal7-year survival ) .
the longest survival time was 4 years , and this patient is still alive . in 
 case 2 ,
a large recurrent tumor 
 occurred in the dura mater away from the removal site , whereas a small recurrent tumor was 
 found at the removal site ( fig . 7fig .
this patient was doing well after the 
 surgery ; however , epileptic seizure occurred 3 years postoperatively .
mri was 
 performed and showed a recurrent tumor posterior to the removal site . ) . in case 15 , no recurrent tumor was seen for more than 3 years postoperatively , 
 likely because we had performed complete removal of a large portion of the falx cerebri 
 ( fig . 8fig . 8.mri , gd - enhanced t1-weighted image ( coronal section ) in case 15 .
white arrows show the site of tumor formation . no recurrence of tumor 
 was confirmed . ) .
this patient was doing well after the 
 surgery ; however , epileptic seizure occurred 3 years postoperatively .
white arrows show the site of tumor formation . no recurrence of tumor 
 was confirmed .
several cases had cystic meningioma of nauta classification [ 2 , 7 ] type 2 ( case 13 , fig . 9fig .
in addition , the cyst image , dural tail sign and 
 cystic wall extending from the surface of the tumor were confirmed . ) and type 3 ( case 5 , fig . 

d ) gd - enhanced t1-weighted image . the cyst image and 
 high - intensity signal tumor lesion of the mass volume were seen from the basilar 
 portion to cerebral falx .
the cystic wall was not visualized , which led to the 
 determination that the cyst was outside of the tumor . ) . in case 14 , which was type 2 cystic meningioma , we tried to remove the tumor 
 including the cyst wall , as shown on enhanced t1-weighted images and kept resecting tissue 
 until no residue
was observed during mri . in case 5 , we removed a parenchymal tumor in the 
 same way . as a result
, no recurrent cyst was seen on the 6 month follow - up mri for case 5 or 
 the 2 year follow - up mri of case 14 after surgery .
mri , gd - enhanced t1-weighted image ( transverse section ) in case 13 . a high - intensity 
 signal tumor lesion was confirmed . in addition , the cyst image , dural tail sign and 
 cystic wall extending from the surface of the tumor were confirmed .
d ) gd - enhanced t1-weighted image . the cyst image and 
 high - intensity signal tumor lesion of the mass volume were seen from the basilar 
 portion to cerebral falx .
the cystic wall was not visualized , which led to the 
 determination that the cyst was outside of the tumor .
the mris taken during surgery showed a tumorous lesion with a high signal intensity on 
 gd - enhanced t1-weighted images and extensive edema on a t2-weighted image and 
 fluid - attenuated inversion recovery ( flair ) images .
mri provided relatively wide - range 
 images and the anatomical location of the tumor .
especially when a surgical approach 
 around sinus veins was needed , mri was very informative to avoid massive bleeding .
it is 
 possible that artifacts might occur when bleeding is confirmed as a high - intensity signal 
 and could cause unclear tumor images on mri ; however , it was still possible to distinguish 
 these areas by examining the differences of enhancing effects and by microscopic examination 
 ( fig .
the asterisk ( * ) on the 
 white arrowhead shows the sigmoid sinus . ) .
the use of mri scanning during surgery as a navigation system improved our surgical 
 performance and contributed to a prolonged survival time for the patients [ 3 , 6 ] .
mri was able 
 to show the exact location of the tumor before the resection .
performing microsurgery under 
 a surgical microscope was also helpful to obtain good results for canine meningioma , which 
 generally has poorly defined tumor margins .
where the border of 
 the tumor was not identified visibly , multiple mris taken during surgery helped us to 
 confirm the exact location of the tumor and reduce the risk of damaging healthy brain 
 tissue .
additionally , the presence of remnant tumor tissue is generally dependent on the 
 location of the tumor and skills of the surgeons , but mri scans during surgery can allow for 
 better localization of a tumor and therefore more accurate resection .
our techniques can 
 also prevent the rise of a mass effect and intracranial hypertension . however , it was 
 impossible to take mri scans during surgery for confirmation of the site of tumor recurrence 
 on the dura mater and falx cerebri
. therefore , the portion of the dura mater invaded by the 
 tumor needed to be more widely resected , but this resulted in the prevention of tumor 
 recurrence . in case 9 , relapse was confirmed at 6 years post operation .
the tumor developed 
 at the same location and grew to about the same size as the original tumor .
the subtype of 
 this new tumor was diagnosed as a transitional histologic tumor type . in 2006 ,
greco 
 et al . reported that the median survival time of patients with the 
 transitional histologic tumor type of brain meningioma was 1,254 days when using a surgical 
 aspirator . except for that fact that they 
 performed radiation and chemotherapy together as well , their team and our both employed an 
 ultrasonic aspirator for meningioma excision surgery
however , our case 9 patient survived 
 longer , and relapse was slower than in any of their patients as a result .
therefore , we 
 would like to suggest that mri during surgery allowed us more precisely excise the 
 tumor
. the major problems associated with taking mri scans during surgery would be the patient 
 transfer to the mri stage and the mri scanning time . however , our surgical setup allowed us 
 to transfer the patient between the surgical bed and mri stage smoothly with only 2 
 assistants . draping the patient also helped to prevent infections .
gradient echo sequences 
 with mpr took only about 10 min , which did not interfere with the surgery .
we believe that 
 surgeries are not only affected by surgeons . in order to perform multiple mri procedures 
 smoothly during surgery ,
creation of an 
 excellent team with skilled members is necessary to achieve even more accurate treatments 
 and ensure integration of the mri data in surgical planning and performance .
 abstractthe aim of this study was to report the effectiveness of mri scanning during 
 brain meningioma resection surgery in the canine and feline . 
 the subjects were 23 cases 
 from 2006 to 2008 in canines and feline diagnosed with meningioma . 
 all were between 8 and 
 16 years of ages . 
 there were 12 males and 11 females . 
 an appropriate craniotomy was 
 performed for each case according to the initial mri taken to diagnose meningioma prior to 
 the surgery . 
 once the dura mater was exposed , an mri biopsy needle was placed in the tumor 
 as a guide . 
 the first mri sequence during the surgery was performed with this needle to 
 confirm the location of the tumor . 
 this mri image was also processed and displayed by 
 multi planar reconstruction to reveal the tumor extent in three dimensions . 
 a sonopet was 
 applied to the middle of the tumor to destroy the inner part and release pressure from the 
 entire tumor . creating some space between the brain tissue and tumor , we treated blood 
 vessels and carefully resected them . 
 this procedure was repeated until complete removal of 
 the tumor was confirmed by mri . 
 sixteen of the 23 cases survived for more than 2 years 
 postoperatively . 
 the other seven died due to other disorders within 2 years . 
 our method 
 with mri navigation during the surgery improved our surgical performance and contributed 
 to a prolonged survival time for the patients . in order to perform multiple mri procedures 
 smoothly during the surgery , 
 it is necessary to have skillful assistants . 
MATERIALS AND METHODS
RESULTS
DISCUSSION