gms | German Medical Science

The aim of the study was to evaluate intraoperative high-field MRI in transphenoidal surgery of pituitary macroadenomas in acromegalic patients, regarding the extent of resection and endocrinological remission of acromegaly.

A 1.5 T Magnetom Sonata (Siemens Medical Solutions, Erlangen, Germany) was used for pre- and intraoperative imaging. T1, later in the study T2 weighted sequences were applied before and during surgical resection. Additional T2 weighted HASTE sequences were used for a fast image acquisition and first assessment. The surgeons’ estimate of the extent of tumour removal was documented and compared with the actual extent as evidenced by first intraoperative imaging results. Results of repeated inspections, necessary further resection, and final imaging results were also documented.

From 06/02 to 05/04, 23 patients suffering from acromegaly were operated on pituitary macroadenomas by transphenoidal approach using intraoperative high-field MRI for resection control. In 21 of them, complete tumour removal was considered to be possible. HGH levels in these cases were elevated up to 74.5 ng/ml, IGF1 levels up to 1111 ng/ml. In 5 patients, intraoperative MRI led to further tumour removal, 2 of these met the consensus criteria for endocrinological remission in the 3 months postop control (HGH<1ng/ml, OGTT<1ng/ml, IGF1 normal). In another 2 patients, HGH-levels and OGTT were <2ng/ml, only IGF1 levels were slightly elevated, and in one patient HGH was <5ng/ml, OGTT<2ng/ml, IGF1 elevated. 6 patients met the consensus criteria without any further resection. Intraoperative MRI showed complete tumour removal in 17 patients, partial removal in 3 patients, and suspicious findings in another 3 patients. All patients with suspicious findings on MRI were not normalized endocrinologically.

Intraoperative MRI increased the rate of complete tumour removal and endocrinological normalization from 26% to 34% using the consensus criteria and improved endocrinological outcome in another 3 cases. Regarding the tumour characteristics with high initial HGH-levels, intraoperative MRI can help to achieve endocrinological remission of acromegaly in patients normally considered not to be curable. On the other side, the study showed that considering HGH as tumour marker in acromegaly, intraoperative high-field MRI is not able to detect tumour remnants in every case.