1. Evaluation of metastatic brain lesions by intraoperative ultrasonography (IOUS) Mehdi Abouzari and Mehdi Abdollahzadeh Dr. Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran

2. Introduction Brain metastases are the most common types of intracranial tumor encountered. Brain metastases are the most common types of intracranial tumor encountered. The incidence of cerebral metastasis ranges from 20 to 30% of patients with systemic cancer, with about half being a single metastasis. The incidence of cerebral metastasis ranges from 20 to 30% of patients with systemic cancer, with about half being a single metastasis.

3. Intraoperative Ultrasonography (IOUS) Ultrasonography has been used as an intraoperative diagnostic tool since 1970. Ultrasonography has been used as an intraoperative diagnostic tool since 1970. IOUS is a valuable method supplementing preoperative diagnostic procedures, facilitating the localization of isomorphic tumors, reducing brain traumatization and making possible control of radical removal of the lesions. IOUS is a valuable method supplementing preoperative diagnostic procedures, facilitating the localization of isomorphic tumors, reducing brain traumatization and making possible control of radical removal of the lesions.

4. Materials and Methods Inclusion criteria were: Inclusion criteria were: Single or multiple metastases detected on CT scan and MRI of the brain. Single or multiple metastases detected on CT scan and MRI of the brain. A peripheral location, spherical shape, ring enhancement with prominent peritumoral edema, and multiple lesions, all suggest metastatic disease. A peripheral location, spherical shape, ring enhancement with prominent peritumoral edema, and multiple lesions, all suggest metastatic disease.

5. All lesions were evaluated by using a Tosbee real-time ultrasound scanner. A 3- MHz transducer was used. All lesions were evaluated by using a Tosbee real-time ultrasound scanner. A 3- MHz transducer was used. The tip of the transducer was placed gently on the intact cranial dura and moved in the direction of the sagittal and coronal planes. The tip of the transducer was placed gently on the intact cranial dura and moved in the direction of the sagittal and coronal planes.

6. Imagination parts Tumor location under the craniotomy Tumor location under the craniotomy Margins from the perilesional brain tissue Margins from the perilesional brain tissue Internal configuration and echogenicity Internal configuration and echogenicity Changes in the peritumoral area Changes in the peritumoral area Location of the neuroanatomical structures such as the ventricle, falx, and main arteries to the border of the lesions Location of the neuroanatomical structures such as the ventricle, falx, and main arteries to the border of the lesions

7. Results A total of 50 consecutive patients with metastatic brain lesions were included in this study. A total of 50 consecutive patients with metastatic brain lesions were included in this study. Male/Female: 27/23 Male/Female: 27/23 Mean age: 56.5±24.7 years Mean age: 56.5±24.7 years Range: 29-82 years Range: 29-82 years

8. Source of brain metastasis Lung: 12 (24%) Lung: 12 (24%) Breast: 6 (12%) Breast: 6 (12%) Gastrointestinal tract: 5 (10%) Gastrointestinal tract: 5 (10%) Other: 13 (26%) Other: 13 (26%) Unknown: 14 (28%) Unknown: 14 (28%)

9. IOUS findings The ultrasonographic appearance of malignant cysts was as low echogenic areas. The ultrasonographic appearance of malignant cysts was as low echogenic areas. Free necrotic particles and double density were commonly present in malignant cysts. Free necrotic particles and double density were commonly present in malignant cysts.

10. The solid component surrounding the cysts was thick. The solid component surrounding the cysts was thick. The external surface of solid parts was regular but internal surfaces facing cysts were irregular. The external surface of solid parts was regular but internal surfaces facing cysts were irregular. The most hypoechogenic part was commonly located in the central portion. The most hypoechogenic part was commonly located in the central portion.

11. IOUS characteristics of lesions Single or multiple necrosis with irregular internal wall Single or multiple necrosis with irregular internal wall Single or trabeculated cystic part with very low echogenicity Single or trabeculated cystic part with very low echogenicity Irregular contour with invasive growth pattern Irregular contour with invasive growth pattern Vasogenic edema with poor demarcation line Vasogenic edema with poor demarcation line

12. IOUS of a metastatic lesion The lesions were surrounded by a first, very thin hypoechogenic zone. The second zone was a vasogenic edematous zone. The ultrasonographic appearance of this zone was hyperechogenic and was similar to that of solid tumor parts. The lesions were surrounded by a first, very thin hypoechogenic zone. The second zone was a vasogenic edematous zone. The ultrasonographic appearance of this zone was hyperechogenic and was similar to that of solid tumor parts.

13. Conclusions IOUS is an excellent tool for localization of metastatic brain lesions and for detailed description of their interior. IOUS is an excellent tool for localization of metastatic brain lesions and for detailed description of their interior. The contour of tumors, perilesional changes, the presence of cyst and necrosis and their details are the most important information. The contour of tumors, perilesional changes, the presence of cyst and necrosis and their details are the most important information. Irregular border, necrotic parts, invasive growth pattern, and dense perilesional edema can all be attributed to malignancy. Irregular border, necrotic parts, invasive growth pattern, and dense perilesional edema can all be attributed to malignancy.