Intraoperative magnetic resonance imaging during transsphenoidal surgery

OBJECT: The aim of this study was to evaluate whether intraoperative magnetic resonance (MR) imaging can increase the efficacy of transsphenoidal microsurgery, primarily in non-hormone-secreting intra- and suprasellar pituitary macroadenomas. METHODS: Intraoperative imaging was performed using a 0.2-tesla MR imager, which was located in a specially designed operating room. The patient was placed supine on the sliding table of the MR imager, with the head placed near the 5-gauss line. A standard flexible coil was placed around the patient's forehead. Microsurgery was performed using MR-compatible instruments. Image acquisition was started after the sliding table had been moved into the center of the magnet. Coronal and sagittal T1-weighted images each required over 8 minutes to acquire, and T2-weighted images were obtained optionally. To assess the reliability of intraoperative evaluation of tumor resection, the intraoperative findings were compared with those on conventional postoperative 1.5-tesla MR images, which were obtained 2 to 3 months after surgery. Among 44 patients with large intra- and suprasellar pituitary adenomas that were mainly hormonally inactive, intraoperative MR imaging allowed an ultra-early evaluation of tumor resection in 73% of cases; such an evaluation is normally only possible 2 to 3 months after surgery. A second intraoperative examination of 24 patients for suspected tumor remnants led to additional resection in 15 patients (34%). CONCLUSIONS: Intraoperative MR imaging undoubtedly offers the option of a second look within the same surgical procedure, if incomplete tumor resection is suspected. Thus, the rate of procedures during which complete tumor removal is achieved can be improved. Furthermore, additional treatments for those patients in whom tumor removal was incomplete can be planned at an early stage, namely just after surgery.     

Residual anterior pituitary function following transsphenoidal resection of pituitary macroadenomas

A series of 84 patients with pituitary adenomas greater than 1 cm in diameter is presented. Full preoperative and postoperative endocrine evaluations were carried out, and the effects of transsphenoidal surgery on remaining anterior pituitary function were analyzed. Of the patients who had normal anterior pituitary function before surgery, 78% retained normal function after surgery. Thirty-three percent of those patients with pituitary deficits who did not have panhypopituitarism before surgery had improved function after surgery; 33% had worsened function after surgery. None of the patients with panhypopituitarism before surgery regained function after surgery. Transsphenoidal surgery carries an acceptable risk for sacrificing anterior pituitary function, but the risk is greater in patients with larger tumors and preoperatively compromised pituitary function.     

Intraoperative magnetic resonance imaging-guided transsphenoidal surgery for giant pituitary adenomas

Giant pituitary adenomas (GPAs), defined as  ≥40 mm in one extension, present a challenging subgroup of pituitary adenomas in terms of radical tumor removal and complication rates. The potential impact of intraoperative magnetic resonance imaging (iMRI) is investigated in a consecutive series and the results compared to the literature. From November 2004 until February 2005, six (five male) patients were operated for GPAs via an iMRI-guided transsphenoidal approach in the PoleStar™ N20. Clinical, endocrinological, and neuroradiological outcomes (at 3 months and yearly postoperative over 4 years) were assessed. Mean age was 46 years (range, 34–60). All patients presented with preoperative visual field defects, five with pituitary failure. Five adenomas were clinically nonfunctioning, one was producing GH and TSH. Preoperative imaging showed invasion of the cavernous sinus in all and extension to the interventricular foramen in two patients (one with occlusive hydrocephalus). Resection was total in four and subtotal (small cavernous sinus remnants) in two patients, leading to transsphenoidal reoperation in one patient. Visual acuity and fields improved in all six patients. The patient with occlusive hydrocephalus developed a postoperative cerebrospinal fluid leak (subsequently revised), two patients developed temporary, one permanent central diabetes insipidus, and one of them transient hyponatremia. Compared to the preoperative situation, endocrine status in the long-term follow-up (mean, 25 months) remained unchanged in four and worsened in two. Two patients were considered not to require hormone replacement therapy. IMRI supports transsphenoidal resections of GPAs because residual adenoma and related risk structures are easily detected and localized intraoperatively, extending the restricted visual access of the microscope beyond mere surface anatomy to a three-dimensional view. More radical removal of adenomas in a single surgical session combined with low complication rates are accomplished. This may add to a favorable clinical and endocrinological outcome in GPAs.     

Magnetic resonance imaging after transsphenoidal surgery of clinically non-functional pituitary macroadenomas and its impact on detecting residual adenoma

Summary. Summary.   Background and Purpose: In clinically non-functional pituitary macroadenomas, prospective follow-up magnetic resonance imaging (MRI) was conducted after transsphenoidal surgery both to study the changes of the sellar contents at the post-operative site over time and to assess the amount of residual adenoma tissue.   Methods: A total of 50 patients with clinically non-functional pituitary macroadenomas were treated by transsphenoidal tumour resection and were examined by MRI before and directly after surgery (early MR) and 3 months (intermediate MR) and 1 year after surgery (late MR). Changes in the sellar contents over time and the degree of tumour excision were studied on T1-weighted enhanced and unenhanced scans. All patients underwent complete neuro-ophthalmological and endocrinological assessments before and 3 months after surgery. For the interpretation of the post-operative images the results of the endocrinological examinations after surgery were also taken into account.   Results: The maximum size of tumour extension on coronal T1-weighted images ranged from 1.2 cm to 5.0 cm (mean 2.3 cm). Despite tumour resection, early post-operative images still showed a persistent mass in the sella in 83% that was usually caused by post-operative haemorrhage, fluid collection and implanted fat material. However, rapid improvement in visual symptoms was noted in 89%. Changes in the sellar region at the early post-operative site markedly hindered the interpretation of MR images for detecting residual tumour tissue, which was suspected in half of the patients (1 intrasellar, 13 suprasellar, and 11 parasellar). Regression of the post-operative mass in the sella was present 3 months after surgery, resulting in a 50% change in the volume of the coronal sellar extension, which also improved the reliability in interpreting the post-operative MR images. On the intermediate MR images residual tumour tissue was detected in 30% of the patients (4 intrasellar, 2 suprasellar and 9 parasellar). Because the suprasellar mass descended over time, an increasing rate of tumour remnant within the sella was seen 3 months following surgery. Before surgery the pituitary gland was visible superiorly or posterosuperiorly to the macroadenomas in 35 patients. However, at the early post-operative site the remaining gland was only visible in 12 patients. Under the condition that endocrinological function tests confirmed adequate hormonal function, the remaining gland was detectable by MRI in 36 patients 3 months after surgery.   Conclusion: Delayed regression of the sellar contents after transsphenoidal surgery of pituitary macroadenomas was demonstrated by this prospective MR study. Owing to the changes at the post-operative site, it was difficult to interpret early post-operative images and detect residual adenoma tissue. With respect to the delayed regression of the sellar contents, the interpretation of post-operative images for detection of residual adenoma was improved 3 months after surgery. At this time, residual adenoma tissue was found in 30% of clinically non-functional macroadenomas, mostly at the parasellar and, after descent from the suprasellar space, at the intrasellar site.     

Proton magnetic resonance spectroscopy in pituitary macroadenomas: preliminary results

OBJECT: The aim of this study was to correlate proton MR (1H-MR) spectroscopy data with histopathological and surgical findings of proliferation and hemorrhage in pituitary macroadenomas. METHODS: Quantitative 1H-MR spectroscopy was performed on a 1.5-T unit in 37 patients with pituitary macroadenomas. A point-resolved spectroscopy sequence (TR 2000 msec, TE 135 msec) with 128 averages and chemical shift selective pulses for water suppression was used. Voxel dimensions were adapted to ensure that the volume of interest was fully located within the lesion and to obtain optimal homogeneity of the magnetic field. In addition, water-unsuppressed spectra (16 averages) were acquired from the same volume of interest for eddy current correction, absolute quantification of metabolite signals, and determination of full width at half maximum of the unsuppressed water peak (FWHM water). Metabolite concentrations of choline-containing compounds (Cho) were computed using the LCModel program and correlated with MIB-1 as a proliferative cell index from a tissue specimen. RESULTS: In 16 patients harboring macroadenomas without hemorrhage, there was a strong positive linear correlation between metabolite concentrations of Cho and the MIB-1 proliferative cell index (R = 0.819, p < 0.001). The metabolite concentrations of Cho ranged from 1.8 to 5.2 mM, and the FWHM water was 4.4-11.7 Hz. Eleven patients had a hemorrhagic adenoma and showed no assignable metabolite concentration of Cho, and the FWHM water was 13.4-24.4 Hz. In 10 patients the size of the lesion was too small (< 20 mm in 2 directions) for the acquisition of MR spectroscopy data. CONCLUSIONS: Quantitative 1H-MR spectroscopy provided important information on the proliferative potential and hemorrhaging of pituitary macroadenomas. These data may be useful for noninvasive structural monitoring of pituitary macroadenomas. Differences in the FWHM water could be explained by iron ions of hemosiderin, which lead to worsened homogeneity of the magnetic field.     

Application of low-field intraoperative magnetic resonance imaging in transsphenoidal surgery for pituitary adenomas: technical points to improve the visibility of the tumor resection margin

Background

Intraoperative magnetic resonance imaging (iMRI) is proven to be advantageous in transsphenoidal surgery (TSS) for pituitary adenomas. We evaluated the efficacy of low-field iMRI. Also, we described several techniques to enhance the visibility of the tumor resection margin.

Methods

Two hundred twenty-nine patients who underwent TSS using low-field iMRI were analyzed. iMRI was acquired in cases where the tumor removal was thought to meet the surgical goal after the tumor resection cavity had been packed with contrast-soaked cotton pledgets to improve the visibility of the tumor resection margin. Suspicious remnants were localized and explored using updated iMRI-based semi-real-time navigation. A merging technique was adopted for very small tumors. The final outcome was evaluated using postoperative 3-T diagnostic magnetic resonance imaging (MRI).

Results

Among 198 patients in whom total resection was attempted, total resection seemed to have been achieved in 184 patients based on iMRI findings. However, immediate postoperative MRI revealed remnant tumors in 4 out of 184 patients (false-negative rate, 2.2 %). The other 31 patients underwent intended subtotal resection of the tumors. Overall, in 47 patients (20.5 %), the use of iMRI led to further resection. Those patients benefited from the use of iMRI to achieve the planned extent of tumor resection.

Conclusions

iMRI maximizes the extent of resection and minimizes the possibility of unexpected tumor remnants in TSS for pituitary adenomas. It is essential to reduce imaging artifacts and enhance the visibility of the tumor resection margin during the use of low-field iMRI.     

Intraoperative acquisition of three-dimensional imaging for frameless stereotactic guidance during transsphenoidal pituitary surgery using the Arcadis Orbic System

OBJECT: Intraoperative fluoroscopy has long been used for anatomical localization in transsphenoidal pituitary surgery. More recently, frameless stereotaxy has been used to supplement 2D sagittal radiographs with 3D multiplanar reconstructions. Use of Arcadis Orbic allows both conventional fluoroscopic views and multiplanar reconstructions to be acquired intraoperatively without need for preoperative planning studies. The authors report their initial experience using Arcadis Orbic during transsphenoidal pituitary surgery. METHODS: To test the system, the authors placed a dehydrated human skull in a radiolucent head holder, and obtained standard 2D fluoroscopic images of the skull base and sella turcica. Arcadis Orbic was then used with frameless stereotaxy to register 3D multiplanar reconstructed images of skull base anatomy. The authors then used Arcadis Orbic in 26 transsphenoidal pituitary tumor resections and compared image quality, accuracy, and ease-of-use to standard techniques. Results: Arcadis Orbic 2D fluoroscopic images matched or exceeded the quality of images acquired by standard C-arm machines. Arcadis Orbic multiplanar reconstructions provided excellent images of the skull base when compared with preoperative Stealth computed tomography (CT) studies. Intraoperative frameless stereotactic navigation using Arcadis Orbic was highly accurate and more reliable than registering preoperative CT images. CONCLUSIONS: Arcadis Orbic provides excellent quality 2- and 3D images during transsphenoidal pituitary surgery, and intraoperative frameless navigation using these images is highly accurate. Arcadis Orbic is easy to use, even in patients with large body habitus, and image acquisition takes no longer than registration during a frameless stereotactic case. Based upon our preliminary experience, Arcadis Orbic precludes the need for preoperative CT studies in patients with pituitary lesions requiring frameless stereotactic navigation.     

Intraoperative magnetic resonance imaging ablation of hepatic tumors

BACKGROUND: The use of hepatic ablation of tumors for both primary and secondary cancers has continued to increase at a significant rate. The most significant increase in the use of hepatic ablation has come from image-guided techniques with computed axial tomography and ultrasound. Limitations to targeting hepatic lesions by these techniques remain morbid obesity, abnormal hepatic parenchyma, and inability to visualize lesions without the use of intravenous contrast. In contrast, magnetic resonance imaging (MRI) has continued to provide a high contrast of soft tissue-to-lesion conspicuity without the need for intravenous dye. The recent development of open-configuration magnetic resonance scanners--which have allowed improved patient access, near real-time imaging, and more available MRI-compatible equipment--has opened up an entire new area of image-guided surgical and interventional procedures. METHODS: The principles and indications for all types of image-guided hepatic ablations are described. RESULTS: The success and limitations of image-guided ablation techniques. CONCLUSIONS: Image-guided hepatic ablation represents a useful technique in managing hepatic tumors. Intraoperative MRI represents a new technique with initial success that has been limited to European centers. Further evaluation in United States centers has demonstrated intraoperative MRI to be useful for certain hepatic tumors that cannot be adequately visualized by ultrasound or computed axial tomography. A multidisciplinary approach involving a surgical oncologist and interventional radiologist remains integral to the short- and long-term success of image-guided ablation.     

Craniotomy versus transsphenoidal excision of large pituitary tumors: the usefulness of magnetic resonance imaging in guiding the operative approach

Fifteen patients with large pituitary tumors were studied with computed tomography (CT) and magnetic resonance imaging (MRI). CT was performed using General Electric 8800 and 9800 scanners (General Electric Co., Medical Systems Division, Milwaukee, Wisconsin). MRI was performed utilizing a Technicare superconducting scanner (Technicare, Cleveland, Ohio) at 0.5 tesla. Based on the operative findings, the tumors were divided into two groups. Tumors in Group 1 (n = 12) were described by the surgeon as soft or partially necrotic and easily removed by suction and curettage. Tumors in Group 2 (n = 3) were firm and required sharp dissection or the laser for removal. The tumors were divided into four categories based on MRI signal: (a) isointense with surrounding brain on spin echo (SE) 30 and SE 90, (b) increased signal intensity on SE 30 and SE 90, (c) decreased signal intensity on SE 30 and increased signal intensity on SE 90, and (d) isointense signal on SE 30 and increased signal intensity on SE 90. All three of the firm tumors were isointense with brain on MRI appearance. The tumor consistency (firm vs. soft) was not differentiable on CT scan. The transsphenoidal approach is less satisfactory than craniotomy in cases of firm, fibrous pituitary tumors. Based on our preliminary data, if the MRI signal in the tumor is isointense, then the surgeon should be prepared to deal with a fibrous tumor and might elect a transcranial rather than a transsphenoidal approach.     

经蝶窦显微手术切除侵袭海绵窦的垂体腺瘤

目的：探讨经蝶窦显微手术切除侵袭海绵窦的垂体腺瘤的手术适应证和手术技巧。方法：42侵袭海绵窦的垂体腺瘤病例均采用经口-鼻-蝶窦入路，共进行45次手术。术中在C-臂X线机或神经导航监测下尽可能开大侧方式鞍底，显策放大下切开鞍底硬膜。依肿瘤侵袭的方向、通道按不同次序分块切除肿瘤。少量残留的病例加用溴隐亭治疗，溴隐亭治疗无效及部分残留病例加用放射治疗。结果：无手术死亡，近全切除21例，次全切除18例，部分切除3例。术后2-3月复查MRI，影像学肿瘤消失19例，少量残留20例，部分残留3例。结论：该类肿瘤伴蝶鞍扩大、术前MRI检查提示质地软，可经蝶窦手术，采用显微镜手术有助于肿瘤全切除及对鞍隔、颈内动脉等重要结构的保护。     

Intraoperative magnetic resonance imaging for ablation of hepatic tumors

BACKGROUND: The most significant rise in the use of hepatic ablation has come from image-guided techniques with both computed tomography (CT) and ultrasound (US). The recent development of open-configuration magnetic resonance scanners has opened up an entire new area of image-guided surgical and interventional procedures. Thus the aim of this study was to evaluate the use of intraoperative MRI (iMRI) ablation of hepatic tumors performed by surgeons. METHOD: Percutaneous iMRI hepatic ablation was performed from January 2003 to February 2005 for control of either primary or secondary hepatic disease. RESULTS: Eighteen hepatic ablations were performed on 11 patients with a median age of 71 (range: 51-81) years for metastatic colorectal cancer (n = 6), hepatocellular cancer (n = 2), cholangiocarcinoma (n = 2), and metastatic neuroendocrine (n = 1). Median hospital stay was 1 day, with complications occurring in 2 patients. After a median follow up of 18 months, there have been no local ablation recurrences, 5 patients are free of disease, 4 are alive with disease, 1 has died of disease, and 1 has died of other causes. CONCLUSIONS: Image-guided hepatic ablations represent a useful technique in managing hepatic tumors. Intraoperative MRI represents a new technique with initial success that has been limited to European centers. Further evaluation in U.S. centers has demonstrated iMRI to be useful for certain hepatic tumors that cannot be adequately visualized by US or CT.     

右美托咪定对不同类型垂体肿瘤切除术患者血流动力学的影响

目的观察右美托咪定对不同类型垂体肿瘤切除术患者血流动力学的影响。方法回顾分析北京协和医院2013年8月至11月接受经鼻-蝶窦垂体肿瘤切除术的患者60例,分为右美托咪定组(D组)24例,对照组(C组)36例,右美托咪定组患者麻醉诱导后静脉持续泵注右美托咪定0.5μg·kg-1·h-1,直至手术结束;对照组接受常规全身麻醉。进一步分析右美托咪定对垂体无功能腺瘤切除术患者血流动力学的影响。记录麻醉前(术前)、切除垂体腺瘤期间(术中)及在麻醉恢复室苏醒期(术后)的SBP、DBP和HR的最高值(max)与最低值(min);术前、术后WBC、Hb、Plt的变化;术前与术后体温,术中芬太尼用量、手术时间、苏醒时间、住院天数等。结果与C组比较,D组患者术中SBPmax,术后SBPmax、SBPmin均明显降低,HRmax明显减慢(P0.05);垂体无功能腺瘤患者术中SBPmax,术后苏醒期SBPmax、SBPmin、DBPmax、DBPmin明显降低,HRmax明显减慢(P0.05)。术中应用右美托咪定对生长激素腺瘤或库欣病腺瘤患者术中及术后血流动力学指标无明显影响。两组患者术中芬太尼用量、手术时间、苏醒时间、住院天数以及术前术后体温、外周血WBC、Hb与Plt等差异均无统计学意义。结论术中持续输注右美托咪定0.5μg·kg-1·h-1有助于维持术中、术后苏醒期血流动力学平稳,尤其对于垂体无功能腺瘤患者更具有临床意义。