Volume 49 - Issue 4.pdf - Minimal Invasive Neurosurgery 2006 - MMikulicz

K. Aydin 1

C. Cokluk 1

E. Kuruoglu 1

S. Gelmez 2

B. Diren 2

C. Rakunt 1

F. C

elik 1

Using the Magnetic Resonance Three-Dimensional

Volume Rendering for Tissues Technique in the

Planning of Craniotomy Flaps with Linear Scalp Incision

Abstract

Introduction

Preoperative three-dimensional images with surface venous

anatomy may be used in the planning of a linear scalp incision

and the opening site of the dura mater for protection of surface

veins during surgical dissection, and to ﬁnd the splitting site of

the brain according to the lesion. In 45 patients who had a brain

tumor, linear scalp incision planning was done by regarding the

three-dimensional images derived from post-contrast time-of-

ﬂight (TOF) sequence raw data. The ﬁndings of correspondence

and the quality of routine contrast-enhanced magnetic reso-

nance imaging (MRI) and three-dimensional volume rendering

for tissues (VRT) images were analyzed separately with the

surgical ﬁndings according to a visual grading system. Our

experience revealed that the surgical ﬁndings correlated well

with the three-dimensional VRT images. According to a visual

surgical grading system, a grade III correlation was found in 20

(45 %), grade II in 15 (33 %), grade I in 7 (15 %), and grade 0 in 3

(7 %) patients in our study population. At the end of our research

we conclude that this method is useful in terms of the preopera-

tive determination of brain surface anatomy and may be used in

the determination of the site of a linear scalp incision according

to the localization of an intracranial lesion.

Recent developments in MRI and post-processing techniques

permit the direct and non-invasive depiction of superﬁcial struc-

tures of the brain. At the same time, they allow the visualization

of pathologic tissues and their relationship with nearby neuro-

vascular structures. There are so many imaging methods that

have been presented in the literature to identify cerebral surface

anatomy in relation to intracranial lesions in patients who have

intracranial tumors [1, 2].

In routine practice, cortical and vascular imaging is performed by

speciﬁc sequences based on TOF or phase-contrast (PC) techni-

ques [3–8]. Imaging techniques after contrast medium adminis-

tration have been tried for a better visualization of cortical and

vascular tissues [3, 4, 7, 8]. The present study was carried out in

order to apply a contrast-enhanced imaging technique and a new

post-processing algorithm, namely, the VRT technique for de-

monstrating cortical and venous structures together with a

better depiction of tumor tissue and its relationships.

189

These images may be used in preoperative planning of a linear

scalp incision and the craniotomy location. In this study, we

describe our experience with this technique, and assess the

correlation of the data obtained from this technique with the

surgical observations in 45 patients.

Key words

Three-dimensional images venous anatomy post-contrast

time-of-ﬂight (TOF) sequence data linear scalp incision

intracranial lesion

Afﬁliation

1 Department of Neurosurgery, Medical Faculty, Ondokuzmayıs University, Samsun, Turkey

2 Department of Radiology, Medical Faculty, Ondokuzmayıs University, Samsun, Turkey

Correspondence

Keramettin Aydin, M.D. Department of Neurosurgery Medical Faculty Ondokuzmayıs University

55139 Samsun Turkey Tel.: + 90/362/312/19 19/36 52 int Fax: + 90/362/457/60 41

E-mail: kaydin@omu.edu.tr

Bibliography

Minim Invas Neurosurg 2006; 49: 189–193 r Georg Thieme Verlag KG Stuttgart New York

DOI 10.1055/s-2006-948300

ISSN 0946-7211

Fig. 1AT 2 -weighted axial, and

B T 1 -weighted with contrast coronal

images. T = tumor.

190

Fig. 2Aand B Tumor tissue and its relationship with nearby cortical and vascular structures were well demonstrated by three-dimensional

imaging techniques and surgical observation. T = tumor, SAV = superior anastomotic vein. C The incision site was marked at the workstation.

C = calvarium, T = tumor, I = incision site.

Materials and Method

1.5 Tesla active super-conducting magnet system (Magnetom

Symphony-Quantum, Siemens, Erlangen, Germany).

This study included 45 patients (aged between 26 and 76 years)

who had suffered from a cortical or a subcortical brain tumor

between 2002 and 2004. Before operation, all patients under-

went standard MRI examinations (T 1 -weighted with contrast

and non-contrast axial, coronal, sagittal, and T 2 -weighted axial,

coronal, and sagittal images) (Figs. 1 and 3).

The FOV was planned to include the brain, calvarium and extra-

cranial soft tissues in axial, coronal and sagittal planes in all

patients. We use this sequence primarily as an intracranial

imaging method with no contrast for venous or arterial angio-

graphy in routine practice. The mean acquisition time was about

7 minutes. After scanning, all raw data were transferred to the

workstation (LEONARDO, the syngo post-processing unit, Erlan-

gen, Siemens). Firstly, three-dimensional images were produced

in the unit by using surface-shaded display (SSD). After manual

removal of extracerebral tissues on three-dimensional SSD

images by the crop technique provided by the software, max-

imum intensity projection (MIP) and VRT techniques were ap-

plied on the imaged data. The reconstructions were interactively

Imaging technique

We performed VRT-based, three-dimensional imaging from sui-

table raw data. After injection of 0.1mmol/kg contrast material

(Magnevist, 0.5mmol/mL, Schering, Germany) we planned ﬂash-

three-dimensional TOF sequences (TR/TE: 36/4. 6 FA: 25 slice

thickness: 1.5mm interval: 0mm; matrix: 256384; ﬁeld of

view [FOV]: 150200 cm; number of slabs: 4 partition: 64) in a

Aydin K et al. Using the Magnetic Resonance Three-Dimensional ... Minim Invas Neurosurg 2006; 49: 189–193

Fig. 3AT 1 -weighted with contrast

axial, and B T 1 -weighted coronal images.

T = tumor.

Table 1 Grading of the correlation between three-dimensional

VRT images and surgical observation

morphology and tumor relationships with nearby cortical and

venous structures.

Grades

Description

We used a grading system for assessment of the correlation of

the data obtained from this technique with the surgical observa-

tions. According to this system results were divided into four

grades. These grades are shown in Table 1. Student’s t test was

used for statistical analysis.

Grade 0

There is no correlation between three-dimensional

VRT images and surgical observation.

Grade I

There is some correlation between three-dimensional

VRT images and surgical observation, but this

correlation is not optimal with respect to the

cortical venous system, gyral, sulcal and ﬁssure

formation, and tumor morphology and relationships

with nearby cortical and venous structures.

Results

Grade II

Although the correlation between three-dimensional

VRT images and surgical observation is optimal in the

aspect of lesion location on the brain surface, there is

no complete correlation regarding cortical venous

structures, gyral, sulcal and ﬁssure formation.

Forty-ﬁve patients with intracranial tumors (twenty-ﬁve fe-

males and 20 males, aged between 26 and 76 years) were

operated between 2002 and 2004 after the performance of the

three-dimensional VRT imaging technique. All tumors were

located in cortical and subcortical regions of the brain. Twenty

of themwere meningiomas (45 %), 15 (33%) were metastasis, and

the remainder (22 %) were primary glial tumors.

191

Grade III

There is a complete correlation between three-

dimensional VRT images and surgical observation.

Table 2 Summary of results with respect to the correlation

between three-dimensional VRT images and surgical

observation

Tumor tissue and its relationship with nearby cortical and

vascular structures were well demonstrated by three-dimen-

sional imaging techniques in all patients.

Grades

Results

Grade III correlations were found in 20 (45 %), grade II in 15

(33%), grade I in 7 (15 %), and grade 0 in 3 (7 %) patients in our

study population. Table 2 shows a summary of the results with

respect to the correlation between three-dimensional VRT

images and surgical observations.

Grade 0

Grade I

Grade II

Grade III

We regarded grade 0 and I correlations as poor, and grade II and

III correlations as good results. Good results were clearly better

than poor results. The differences between poor and good results

were statistically signiﬁcant (p < 0.001).

Total

100

post-processed at the workstation and could be viewed from any

chosen angle (Figs. 2, 4 and 5).

Discussion

All data derived frompreoperative routine MRI with contrast and

three-dimensional images were analyzed regarding the depic-

tion of the cortical venous system, cortical formation, tumor

The relationship of tumor tissue with nearby normal cortical and

vascular tissues is an important factor in the planning of a

surgical intervention. Cortical venous structures, for example,

Aydin K et al. Using the Magnetic Resonance Three-Dimensional ... Minim Invas Neurosurg 2006; 49: 189–193

Fig. 4Aand B Tumor tissue and its

relationship with nearby cortical and

vascular structures were well demon-

strated by three-dimensional imaging

techniques and surgical observation.

T = tumor, BV = bridging vein.

tical venous structures may make it easier to approach the lesion

and at the same time can prevent possible cortical venous

damage [1, 2].

192

The T 1 shortening effect of a contrast agent reduces the effect of

spin saturation, and also compensates slow ﬂow and in-plane

ﬂow, which is typical in the distal branch of intracranial vessels,

resulting in better visualization of cortical venous structures. In

this way, both decreasing the ﬂip angle and decreasing TR levels

are possible. Contrast-enhanced magnetic resonance angiogra-

phy (MRA) can be useful in evaluating intracranial vascular

lesions, particularly those with slow ﬂow [7, 8]. There are some

studies in which phase contrast angiography sequences have

been used for the depiction of intracranial vascular structures

in the literature [1, 3, 5].

Fig. 5 The incision site of some case in Fig. 4 was marked at work-

station. T = tumor, BV = bridging vein, I = incision site.

VRT, which was the primary post-processing technique, used for

three-dimensional imaging in this study is a relatively new

technique. Its algorithm is more complex than the other techni-

ques and it requires expensive computation techniques and

software. In this technique, all voxels in the volume are analyzed

under four subgroups.

should be protected as much as possible during the surgical

intervention for the complete removal of a brain lesion to avoid

a devastating complication. Before starting a surgical interven-

tion, knowledge about the location and the relationship of these

structures to brain lesions not only may enhance the orientation

of a surgeon to a surgical ﬁeld but also may facilitate the

planning of a proper linear scalp incision and a small but

sufﬁciently large craniotomy as far distant as possible from

venous structures.

It includes all of the relevant data into the ﬁnal three-dimen-

sional image and overcomes many of the problems seen with

MIP and SSD. Accordingly signal intensity levels, which have

different colors and transparency, can be applied to different

volumes. By using this technique one or more volumes can be

made invisible to demonstrate underlying structures. The rela-

tionship of a volume with other structures can be imaged and

demonstrated. This is a routine and widely using technique like

SSD and MIP, which produces images by the use of preselected

volumes. The primary reasons for using of volume rendering

over MIP and SSD are the improvements of image accuracy and

quality [9,10].

In this study, we mainly hypothesized that three-dimensional

VRT images may show the relationship between tumors and

brain structures such as the cortical venous system, gyral, sulcal

and ﬁssure formation, and tumor morphology. This knowledge

may enhance surgical orientation to a lesion seated in the brain.

Three-dimensional images showing gyri, sulci, ﬁssures and cor-

In 78 % of the cases, the correlation between software images and

direct surgical observation was satisfactorily sufﬁcient. Among

these cases, 45 % of them were grouped into a grade III correla-

tion. In this group, we found that the correlation between soft-

ware images and surgical observation was excellent.

Aydin K et al. Using the Magnetic Resonance Three-Dimensional ... Minim Invas Neurosurg 2006; 49: 189–193

In 22 % of the cases, the correlation between images and direct

observation was insufﬁcient. Among these cases, 15 % of them

showed some correlation between three-dimensional VRT

images and surgical observation, but this correlation is not

optimal with respect to the cortical venous system, gyral, sulcal

and ﬁssure formation, and tumor morphology and relationships

with nearby cortical and venous structures. In 7 % of the cases (3

patients), the correlation was poor and insufﬁcient. But in com-

parison with routine MRI, these data may give some information

about the lesion to enhance the orientation of a surgeon to the

surgical ﬁeld.

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Conclusion

Three-dimensional image generating software programs are

useful in the demonstration of cortical and subcortical lesions

and their anatomical relationship with nearby venous structures,

gyri, sulci, and ﬁssures formation. These data may be used to

localize a linear skin incision on the scalp surface in accordance

to the location of the lesion. At the same time, a small but

sufﬁciently large craniotomy may be done on the cranium in

accord with the lesion and perilesional structures such as drai-

nage veins and sulci. These computer-generated software images

may enhance the surgical orientation to a surgical ﬁeld, and may

also facilitate the protection of venous vessels nearby a lesion.

This imaging technique may be useful in surgical interventions

for cortical and subcortical brain tumors.

References

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technique of surface anatomy MR scanning of the brain: its applica-

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515–518

193

Aydin K et al. Using the Magnetic Resonance Three-Dimensional ... Minim Invas Neurosurg 2006; 49: 189–193

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