Introduction

Gamma Knife Radiosurgery (also known as GKRS) is a treatment that has been thoroughly researched and is proven to be both safe and effective [1]. Modality for patients who have been carefully selected, but despite its high overall efficacy, it carries some risks, including facial nerve paresis, hearing loss, and the progression or recurrence of the tumor [2,3].

In the treatment of vestibular schwannoma, radiosurgery is frequently utilized [4]. The radiosurgery treatment is a non-invasive treatment that provides the tumor with high-dose radiation while reducing the damage to the adjacent, healthy brain tissue [5]. Beams of high-energy X-rays or gamma rays are used to deliver the radiation to the tumor. The goal of the radio surgical treatment for acoustic neuroma is to permanently stop the tumor from growing [6].

In our study the spheroid system was applied to the tumor, in order to better understand the sphericity (φ) concept was applied to the split target volume.

A measure of how closely an irregular Volume's (V) form resembles that of a sphere was given the definition of sphericity [7].

It is possible to compare the Target Volumes (TV) of the various shapes to that of a sphere. Volume, surface area, and the proportions between the orthogonal axes are all taken into consideration. In its theoretical formulation, operational sphericity. Using quality indicators that have already been defined, physicians and physicists evaluate the plans for radio surgical therapy with gamma knife equipment. This review is done by the medical professionals, and these measurements, which include Coverage (C), Selectivity (S), Gradient Index (GI), and Conformance Index (CI) (CI paddick). They are derived using dosage ranges that take into account the volume of the isodose prescribed, the target's volume, the amount of the isodose that is equivalent to fifty percent of the recommended isodose and the point where these volumes overlap [8].

This study's objective was to look into the worldwide dose distribution by making use of the ratio (IV/TV) in the context of radiosurgery planning while also taking into account alternative isodose volumes of varying sizes besides the prescribed isodose. The low doses as well as the dose gradient inside the target volume are also things that this test is supposed to measure. It was attempted to find a correlation between the goal volume and the degree of sphericity of existing indicators. This is significant because utilizing this analysis, we will be able to investigate whether or not it is possible to enhance the evaluation of the plans by making use of the sphericity degree. Consequently, in order to construct this study using the dose distribution that was acquired for the purpose of designing a two-sphere arrangement with a comparable volume; it will be consulted for planning purposes [9].

Materials and Methods

For six months, a cross-sectional study was conducted. .Choosing sixty patients who had been diagnosed with vestibular schwannoma by an oncologist or a neurosurgeon and then having them undergo gamma knife treatment. After patients were diagnosed and referred to the gamma knife treatment, three-dimensional detailed anatomical images of the vestibular schwannomas tumor were acquired using a Magnetic Resonance Imaging (MRI) prototype manufactured by Philips called the Achieva 3 Tesla or 1.5 Tesla. These models were used to acquire the images. The bone and other solid structures of the head are then acquired with the help of Cone Beam Computed Tomography (CBCT), which is mounted on the device known as the gamma knife.in general the MRI using in gamma knife called MRI gamma knife protocol.

Inclusion Criteria:

1. Patients with vestibular schwannomas tumor and underwent a surgery.

2. Patients who refuse removed the vestibular schwannomas surgically.

3. Patients who did not have benefit with linear accelerator.

Exclusion Criteria: All patients with other tumor such as meningioma, Arteriovenous Malformation (AVM), neuroma, acoustic neuroma, and pituitary tumors in gamma knife radiosurgery.

Statistical analyses: The statistical tool known as Statistical Packages for Social Sciences, version 25 (SPSS-25), was used to analyze the data.

Discussion

The mean age of the patients 44.54 ± 11.93 years with range (20-80) years. Gender composition of the patients was 15 (30%) Male and 35 (70%) Female. The female in this study shows more prevalence than male patients. In this study, one tumor was taken vestibular schwannoma only. The prescribed dose for vestibular schwannoma patients was 12 Gy. Which the neurologist chooses depending on the tumor volume, location, and histopathology. The vestibular schwannoma tumor is irregular in shape(10), for this reason can divided The tumor into spheres; the first sphere delineates the regular part of the tumor, and the second sphere is delineated irregular cancer components .The irregular sphere less than regular sphere in size that difference in size give rise to increase the Mean Dose (Gy), Minimum Dose (Gy), Maximum Dose (Gy), and Integral Dose (mJ) for the regular sphere at value according to the readings taken in the table (3.2)chapter three at same the table shown in the results the regular and irregular spheres for vestibular schwannoma dose parameters Significant in Maximum (Gy) and Integral Dose (mJ) when using p–value ≤ 0.05 level (Table 1).

Table 1. Regular and irregular spheres for vestibular schwannoma dose parameters

Sphericity Degree (φ) and evaluation parameters, regression curve was used to estimate the correlation between the overall sphericity degree and, most important the evaluation parameters such as coverage, selectivity, Homogeneity Index (HI), selectivity, Gradient Index (GI), and shot density. The results show that there is a direct correlation between coverage and sphericity degree, selectivity, and gradient index. While an inverse correlation appeared between the sphericity degree, homogeneity index, and shot density.

Coverage (C): A trend line was established in the results (Figure 1) by applying a straight line adjustment to the obtained data. When the sphericity number rises, it indicates that the Coverage value will also rise.

Figure 1: Correlation between the sphericity degree and coverage.

Homogeneity Index: (Figure 2) to create a trend line in the results, a straight line was used to alter the collected data. The correlation between them was (r =0.0387), which shows that the homogeneity value decreases as the sphericity value grows.

Figure 2: Correlation between the sphericity degree and homogeneity index.

Conclusion

The findings of this investigation were presented in, and they offer data that can be used to describe how the dose distribution (IV / TV) behaves in relation to the target volume's degree of sphericity. The newly proposed study of dose distribution that makes use of the sphericity degree is simplest to explain and simplest to compute. Because of this study, a more comprehensive assessment of the dose gradients surrounding the TV and the dose distribution inside and outside the target volume can be performed, resulting in a bigger amount of information a variety of different isodose lines. The sphericity degree is a useful tool when making an objective comparison between two or more treatment plans and determining whether or not it is possible to improve the plan taking low-dose spreading into consideration. As vestibular schwannomas tumors grow larger, they become more spherical, which leads to improved plan quality.