I. The texture of pituitary adenoma is one of the important factors affecting the difficulty of surgery Since cushing began to perform pituitary tumor resection by transsphenoidal approach in the early 20th century, transsphenoidal approach has been recognized as the best surgical approach for most pituitary adenomas. In recent years, with the development of surgical microscope, neuroendoscope, neuronavigation equipment and proficiency of surgical operation skills, the total resection rate of transsphenoidal surgery in one group of 302 cases of large (maximum diameter 3-4 cm) and giant (>4 cm) pituitary adenomas was 62.3% and the secondary total resection rate was 22.5% in China.
In our work, we found that the texture of the substantial pituitary adenoma is an important factor affecting the difficulty of surgery, especially for the suprasellar pituitary adenoma of medium size or above with hard texture.
The residual tumor needs to be operated again or stereotactic radiotherapy, which increases the pain and economic burden of patients, and also increases the potential for doctor-patient disputes. It has been documented that radiation therapy has irreversible damage to the pituitary gland and requires lifelong hormone replacement therapy for hypopituitarism. Therefore, total or major resection of pituitary adenomas above medium size should also be pursued in one surgery.
If the tumor is preoperatively estimated to be tough and predominantly suprasellar, craniotomy can be performed directly and eunuch-friendly equipment such as ultrasonic aspirator and electromagnetic knife can be prepared in advance to create conditions for full resection of the tumor. We believe that preoperative MRI can accurately and easily predict the texture of pituitary adenoma, so as to more accurately estimate the difficulty of surgery, better design the surgical approach and prepare the required surgical instruments.
The increase of collagen content is one of the biochemical bases for the decrease of T2WI signal intensity It is usually believed that T1WI signal mainly reflects the anatomical structure and morphology of tissues, while T2wI signal better expresses physiological and biochemical information. The negative correlation between collagen content and T2WI signal intensity has been demonstrated in studies of other tissues such as liver fibrosis and intervertebral disc degeneration. T2WI hyposignal in pituitary adenomas is mainly associated with fibrosis of the tumor, i.e. collagen formation and deposition.
The proportion of fibrotic pituitary adenomas is reported in the literature to be about 5%-13.5%. The slightly higher proportion of such tumors in our group, about 17% (19/112), may be related to the short duration of the study. Intraoperatively, these tumors were found to be tough and required bipolar electrocoagulation cautery or sharp division for resection, and it was difficult to achieve total resection in one operation.
The relationship between preoperative MRI signal characteristics and pituitary adenoma texture has been studied mainly by T/G values and/or tumor/white matter ratio, but it is still controversial as to which index has the absolute advantage. We believe that because pituitary adenomas are more closely related to the adenohypophysis, rich in blood flow, and closer to the gray matter of the brain, it is more realistic to use T/G values to judge signal intensity, and this judgment is the same as that of Koba-yashi et al. In this study, the T/G value was quantified.
So the T: signal of pituitary adenoma can be classified as high signal, equal signal and low signal accordingly using the gray matter around the tumor as a reference. This qualitative analysis is more in line with the actual working situation, because some patients bring their own MRI from outside hospitals to the hospital. Based on the findings of this study, preoperative judgments of tumor texture can be made by the signal characteristics of T: weighted images of pituitary adenomas, i.e., soft texture for high signal, moderate texture for isosignal, and firm texture for low signal.
In this study, cerebrospinal fluid MR values were also measured and T/c values were calculated, mainly for the following reasons: although the same machine was used, the T2-weighted imaging parameters can vary slightly from case to case, and the relatively simple composition of cerebrospinal fluid with uniform signal intensity can be used as a correction standard for signal intensity. the differences in T/c values between the 3 groups were statistically significant, which better indicates that the T2-weighted imaging of MRl signal intensity can predict the texture of pituitary adenomas, and the method is simple, easy to use, and highly accurate, which is worthy of clinical promotion.