Preparation And Applied Value Of Somatostatin Receptor Imaging Agent In Patients With Meningioma

Meningioma, representing 15%-20% of intracranial neoplasms in adults, is a common tumor. CT or MRI as morphologic imaging becomes first tools to diagnosis meningioma, but they may fail to reflect the density of SSTR2 and meningioma patholgical grading. Octreotide is a somatostatin analogy which has a high affinity to SSTR2. Meningiomas were shown to express somatostatin receptor in nearly 100%. So, 99Tcm-HYNIC-Octreotide may be as a Somatostatin Receptor Scintillography agent to diagnosis meningioma.AIM:The aim of the current study was to evaluate the potential role of 99Tcm-HYNIC-Octreotide as a somatostatin receptor scintillography (SRS) in meningioma, to observe the distribution of 99Tcm-HYNIC-Octreotide, to study the clinical value of SRS in meningioma, expecially the relation between T/NT and the expression intensity of SSTR2. Furthermore, we also study the relation between T/NT and patholgical grading of meningoma. At the same time, SPECT/CT fusion images are applied to improve the value of location and qualitation of meningioma. METHODS:HYNIC-Octreotide was labeled with 99Tcm by a indirect method,the labeling rate was determined with Xinhua I chromatography . The radiochemical property of 99Tcm-HYNIC-OCT were evaluated by Sep Pak Cl8 chromatog- raphy,the cysteine challenge experiment,the serum incubation test and the stability experiment in vitro. 34 patients (including 30 meningiomas, 2 gliomas, 1 chordoma and 1 brain scrofulous gumma confirmed by pathology), were performed the examination of Somatostatin receptor scintillography with SPECT/CT after 4h intravenous injection of 740–925MBq 99Tcm-HYNIC-OCT. Furthermore the relationship between T/NT (the ratio of counts between tumor and corresponding site of opposite side) and its grade of pathology was investigated. Region of interests (ROI) was drew on tumor (T) and corresponding site of opposite side (NT) by two nuclear doctor, the ratio of counts of them (T/NT) were calculated. Pathology Grade of meningioma was according to WHO (2000 year) pathology standard. All the patients's pathological tissue was checked in immunofluorescence in order to observe the express of SSTR2.RESULTS:1. Using stannous tartrate as reductant,HYNIC-Octreotide was successfully labeled by 99Tcm. Labelling efficiency is about 97.8%±0.55% and specific activity is 33.8TBq/mmol;2. The labelling efficiency of 99Tcm-HYNIC-Octreotide was still above 90% when keeping for 4 hours in room temperature;3. The labeling rate of 99Tcm-HYNIC-OCT was 97.8% and free 99Tcm was 1.09% in the cysteine challenge experiment. With the increase of cysteine, free 99Tcm was found to raise slowly, about 23% free 99Tcm was break away from 99Tcm-HYNIC-OCT when the concentration of cysteine was up to 200 mmol/L. There was unobvious combination found between 99Tcm-HYNIC-OCT and serum protein,only 7.09±0.05% combination interactant was found after 4 hours;4. The rate of positive imaging were 100% in all 30 patients with meningiomas. There was a positive correlation between T/NT and pathological grade of meningioma, in other words, the value of T/NT was increased with the raise of pathological grade of meningioma. The value of T/NT in gradeⅠof meningioma was 4.15±1.59,it's 90% confidence interval from 1.53 to 6.77,while in gradeⅡof meningioma it was 9.78±1.72, 90% confidence interval is from 6.95 to 12.61. There was statistical significance difference of uptake between gradeⅠandⅡof meningioma (P<0.05).5. The expression of SSTR2 was seen in all 30 patients. There was a positive correlation between T/NT and level of immunofluorescence in the pathological tissue of meningioma.there were 65% level 1 and 35% level 2 of immunofluorescence in gradeⅠof meningioma, 20% level 2 and 80% level 3 of immunofluorescence in gradeⅡof meningioma.6. Three small meningiomas were found in SPECT imaging but not found in CT imaging, the diameter of them from 2cm to 2.5cm, the fusion imaging of SPECT and CT can clearly loctated their position.CONCLUSION:1. 99Tcm-HYNIC-OCT can be readily prepared,the labeling yields are quite high(>95%),and stable in vivo(vitro);2. The preliminary results indicated that there is a higher specificity to diagnosis meningioma with 99Tcm-HYNIC-OCT imaging. There was a positive correlation between T/NT and pathological grade of meningioma, The preliminarily study demonstrated that 99Tcm-HYNIC-OCT scitigraphy is able to predict the pathological grade through the value of T/NT;3. There was a positive correlation between T/NT and level of immunofluorescence in the pathological tissue of meningioma; which indicated that it may use the value of T/NT to predict the pathological grade of meningioma.4. It is a significance work that SPECT/CT fusion images is applied in MEN,because it can enhance the capability of diagnosis by improving location and quantification of disease.