Application of three-tesla magnetic resonance imaging for diagnosis and surgery of sellar lesions

The Party Wall: Redefining the Indications of Transcranial Approaches for Giant Pituitary Adenomas in Endoscopic Era

The evolution of endoscopic trans-sphenoidal surgery raises the question of the role of transcranial surgery for pituitary tumors, particularly with the effectiveness of adjunct irradiation. This narrative review aims to redefine the current indications for the transcranial approaches for giant pituitary adenomas in the endoscopic era. A critical appraisal of the personal series of the senior author (O.A.-M.) was performed to characterize the patient factors and the tumor's pathological anatomy features that endorse a cranial approach. Traditional indications for transcranial approaches include the absent pneumatization of the sphenoid sinus; kissing/ectatic internal carotid arteries; reduced dimensions of the sella; lateral invasion of the cavernous sinus lateral to the carotid artery; dumbbell-shaped tumors caused by severe diaphragm constriction; fibrous/calcified tumor consistency; wide supra-, para-, and retrosellar extension; arterial encasement; brain invasion; coexisting cerebral aneurysms; and separate coexisting pathologies of the sphenoid sinus, especially infections. Residual/recurrent tumors and postoperative pituitary apoplexy after trans-sphenoidal surgery require individualized considerations. Transcranial approaches still have a critical role in giant and complex pituitary adenomas with wide intracranial extension, brain parenchymal involvement, and the encasement of neurovascular structures.

Deep learning-based image reconstruction improves radiologic evaluation of pituitary axis and cavernous sinus invasion in pituitary adenoma

PURPOSE

To compare performance of 1-mm deep learning reconstruction (DLR) with 3-mm routine MRI imaging for the delineation of pituitary axis and identification of cavernous sinus invasion for pituitary macroadenoma.

METHOD

This retrospective study included 104 patients (59.4 ± 13.1 years; 46 women) who underwent an MRI protocol including 1-mm deep learning-reconstructed and 3-mm routine images for evaluating pituitary adenoma between August 2019 and October 2020. Five readers (24, 9, 2 years, and <1 year of experience) assessed the delineation of pituitary axis (gland and stalk) and the presence of cavernous sinus invasion for using a pairwise design. The signal-to-noise ratio (SNR) was measured. Diagnostic performance as well as image preference data were analysed and compared according to the readers' experience using the McNemar test.

RESULTS

For delineation of normal pituitary axis, all readers preferred thin 1-mm DLR MRI over 3-mm MRI (overall superiority, 55.8 %, P <.001), with this preference being greater in the less experienced readers (92.3 % vs. 55.8 % [expert], P <.001). The readers showed higher diagnostic performance for cavernous sinus invasion on 1-mm (AUC, 0.91 and 0.92) than on 3-mm imaging (AUC, 0.87 and 0.88). The SNR of the 1-mm DLR was 1.21-fold higher than that of the routine 3-mm imaging.

CONCLUSION

Deep learning reconstruction-based 1-mm imaging demonstrates improved image quality and better delineation of microstructure in the sellar fossa and is preferred by both radiologists and non-radiologist physicians, especially in less experienced readers.

Improved Detection of Cavernous Sinus Invasion of Pituitary Macroadenomas with Ultra-High-Field 7 T MRI

To compare 7 T magnetic resonance imaging (MRI) of pituitary macroadenomas (PMA) with standard MRI and intraoperative findings regarding tumor detection, localization, size, and extension. Patients with suspected pituitary adenoma underwent pre-operative 1.5 T or 3 T and 7 T MRI; 14 patients with a PMA were included. A qualitative (lesion detection, location, cavernous sinus infiltration) and quantitative (lesion size, depth of cavernous sinus infiltration) analysis of 1.5 T, 3 T and 7 T MRI was performed and compared with intraoperative findings. Both 1.5/3 T and 7 T MRI enabled the detection of all PMAs; lesion size determination was equal. 7 T MRI enables more precise assessments of cavernous sinus infiltration of PMA (n_{correct 7T} = 78.6%, n_{correct 1.5/3T} = 64.3%). Ultra-high-field MRI is a reliable imaging modality for evaluation of PMAs providing exact information on lesion location and size. 7 T MRI yielded more accurate information on cavernous sinus infiltration with better agreement with intraoperative findings than standard MRI.

The value of intraoperative MRI for resection of functional pituitary adenomas-a critical assessment of a consecutive single-center series of 114 cases

This series sought to evaluate the role of intraoperative MRI (iMRI) for resection of functional pituitary adenomas (FPAs). We retrospectively reviewed clinical data of 114 consecutive FPAs with excessive hormone secretion treated with transsphenoidal surgery and iMRI during 01/2010–12/2017. We focused on iMRI findings, extend of resection and postoperative hormonal remission. Variables of incomplete resections and persistent hormone excess were evaluated by binary regression. Patients with FPAs presented with hypercortisolism (n = 23, 20%), acromegaly (n = 56, 49%), and as prolactinomas (n = 35, 31%) resistant to medical treatment. Preoperative MRI showed 81 macroadenomas (71%) and optic system involvement in 41 cases (36%). IMRI was suggestive for residual tumor in 51 cases (45%). Re-inspection of the cavity cleared equivocal findings in 16 cases (14%). Additional tumor was removed in 22 cases (19%). Complete resection was achieved in 95 cases (83%). Postoperative morbidity was low (1.7% revision surgeries, 0.8% permanent diabetes insipidus). Overall hormonal remission-rate was 59% (hypercortisolism 78%, acromegaly 52%, prolactinoma 57%). Supra- and parasellar invasion and preoperative visual impairment were significant predictors for incomplete resections despite use of iMRI. Risk for persistent hormone excess was increased sevenfold after incomplete resections. IMRI enabled reliable identification of tumor remnants during surgery and triggered further resection in a considerable proportion of cases. Nevertheless, tumor size and invasiveness set persistent boundaries to the completeness of resections. The low rate of surgical complications could point at a less invasive iMRI-guided surgical approach while achieving a complete tumor resection was a crucial determinant for hormonal outcome.

T2 hypointense signal discovered incidentally at the posterior edge of the adenohypophysis on MRI: its prevalence and morphology and their relationship to age

PURPOSE

T2 hypointense signal at the posterior edge of the adenohypophysis (T2HSPA) on magnetic resonance imaging (MRI) is incidentally encountered. We aimed to investigate the prevalence and morphology of T2HSPA and their relationship to age.

METHODS

A total of 212 cases between 3 and 88 years old were examined. Sagittal T2-weighted image (T2WI) was evaluated for the presence of T2HSPA, which classified by its morphology into two types (belt-like or nodal). The Wilcoxon rank sum test and chi-square test were used to evaluate the differences between the groups. The T2HSPA was extracted by ImageJ software and measured as a cross-sectional area (CSA) quantitatively by threshold setting. We examined the relationship between CSA of T2HSPA and age, and Spearman's correlation coefficients were used for statistical analysis.

RESULTS

Of the 212 cases, 80 (37.7%) were identified with T2HSPA. The groups with T2HSPA were significantly younger than the groups without it (p = .01). Groups with belt-like T2HSPA were significantly younger than the groups with nodal T2HSPA (p = .01). There was a weak negative correlation between CSA of T2HSPA and age (p = .02).

CONCLUSION

T2HSPAs were incidentally detected in 37.7% of all cases, tended to be more common in younger cases, and their morphology was related to age. They seem to have little clinical significance as they tend to decrease in size with age.

Ultra-High-Field 7 T Magnetic Resonance Imaging Including Dynamic and Static Contrast-Enhanced T1-Weighted Imaging Improves Detection of Secreting Pituitary Microadenomas

OBJECTIVE

A prospective preoperative evaluation of 7 T ultra-high-field magnetic resonance imaging (MRI) in patients with suspected pituitary microadenomas for both adenoma detection and intrasellar localization compared with 3 T MRI was carried out.

MATERIALS AND METHODS

Patients underwent prospective preoperative standardized 3 and 7 T MRI. A distinct qualitative (lesion detection, intrasellar lesion location) and quantitative (lesion diameters, T1/T2 signal intensity ratio of the lesion to normal pituitary gland tissue) analysis was performed, along with an evaluation of image quality (IQ) regarding overall IQ, anatomical parameters, and artifacts; the findings of the qualitative analysis were compared with intraoperative findings and endocrinological outcomes.

RESULTS

Sixteen patients (mean age, 43 ± 16 years; 13 women) with pituitary microadenomas were included. Using 7 T MRI allowed the detection of 15 microadenomas-3 more than 3 T MRI. In addition, 7 T MRI allowed more precise lesion localization with 93.75% (15/16) agreement with intraoperative findings, compared with 75% (12/16) agreement using 3 T MRI. Lesion diameters showed no significant difference between 3 and 7 T MRI. T1 and T2 signal intensity ratio between microadenomas and normal pituitary gland tissue were higher in 7 T MRI than in 3 T MRI. The overall IQ and the IQ of each anatomical parameter of 7 T MRI were rated higher than those of 3 T MRI. No significant differences in susceptibility or head motion artifacts were observed between 3 and 7 T MRI; however, 7 T MRI was more susceptible to pulsation artifacts.

CONCLUSION

Ultra-high-field MRI surpasses 3 T MRI in pituitary microadenoma detection and enables more precise delineation with higher correlation with intraoperative findings. Thus, 7 T sellar imaging is a promising option-especially in previously magnetic resonance-negative patients with endocrinologically confirmed hormone oversecretion-and helps reduce the need for invasive diagnostics.

Deep learning-based thin-section MRI reconstruction improves tumour detection and delineation in pre- and post-treatment pituitary adenoma

Even a tiny functioning pituitary adenoma could cause symptoms; hence, accurate diagnosis and treatment are crucial for management. However, it is difficult to diagnose a small pituitary adenoma using conventional MR sequence. Deep learning-based reconstruction (DLR) using magnetic resonance imaging (MRI) enables high-resolution thin-section imaging with noise reduction. In the present single-institution retrospective study of 201 patients, conducted between August 2019 and October 2020, we compared the performance of 1 mm DLR MRI with that of 3 mm routine MRI, using a combined imaging protocol to detect and delineate pituitary adenoma. Four readers assessed the adenomas in a pairwise fashion, and diagnostic performance and image preferences were compared between inexperienced and experienced readers. The signal-to-noise ratio (SNR) was quantitatively assessed. New detection of adenoma, achieved using 1 mm DLR MRI, was not visualised using 3 mm routine MRI (overall: 6.5% [13/201]). There was no significant difference depending on the experience of the readers in new detections. Readers preferred 1 mm DLR MRI over 3 mm routine MRI (overall superiority 56%) to delineate normal pituitary stalk and gland, with inexperienced readers more preferred 1 mm DLR MRI than experienced readers. The SNR of 1 mm DLR MRI was 1.25-fold higher than that of the 3 mm routine MRI. In conclusion, the 1 mm DLR MRI achieved higher sensitivity in the detection of pituitary adenoma and provided better delineation of normal pituitary gland than 3 mm routine MRI.

Assessment of magnetic resonance imaging criteria for the diagnosis of cavernous sinus invasion by pituitary tumors

Cavernous sinus invasion (CSI) by pituitary tumors is associated with subtotal resection and persistent endocrinopathy. The Knosp classification is a magnetic resonance imaging (MRI) tool used to define CSI in the 2017 World Health Organization Classification. However, alternative criteria may have superior diagnostic performance. This study aimed to assess the diagnostic performance of four MRI criteria, using a combination of endoscopy and day 1 MRI as the reference standard for CSI. A cross-sectional study was conducted including patients treated with endoscopic endonasal transsphenoidal surgery for pituitary macroadenomas, recruited from a tertiary pituitary multidisciplinary center in Sydney, Australia between September 2013, and February 2021. The diagnostic performances of four MRI criteria were assessed: the Knosp criteria, percentage encasement of the internal carotid (PEICA), venous compartment obliteration (VCO), and the Fernandez-Miranda classification. Reference CSI was defined using a combination of intraoperative endoscopy and day 1 MRI. A total of 210 cavernous sinuses (105 patients), were analyzed, (51.7 ± 16.3yrs, 43% female), of which 18% had CSI. CSI was best diagnosed by Knosp ≥ 2 (63% sensitivity and 89% specificity), PEICA ≥ 28% (84% sensitivity and 77% specificity) and VCO of ≥ 3 compartments (65% sensitivity and 89% specificity). CSI was unlikely if any of the following signs were present: Knosp < 1, PEICA < 28%, preservation of the medial or superior compartments or sparing of the superior Fernandez-Miranda compartment (negative predictive value 95%, 95%, 94%, 91% and 92% respectively). In conclusion, alternatives to the Knops criteria including PEICA and VCO can aid CSI diagnosis.

The role of bilateral inferior petrosal sinus sampling in determining the preoperative localization of ACTH-secreting pituitary microadenomas in Cushing's disease: Experience of a tertiary center

INTRODUCTION

Bilateral inferior petrosal sinus sampling (BIPSS) is an important procedure in the diagnostic work-up of Cushing's syndrome (CS). In this study, we investigated the diagnostic performance of BIPSS in detecting the source of adrenocorticotropic hormone (ACTH) secretion in Cushing's disease (CD) without radiological evidence.

METHODS

Thirty-five consecutive patients who underwent BIPSS due to ACTH-dependent CS between 2010 and 2019 in our clinic and subsequently underwent transsphenoidal surgery were included. The indication for BIPSS was biochemically proven ACTH-dependent CS but normal or ≤6 mm pituitary lesion in pituitary magnetic resonance imaging (MRI). Corticotropin releasing hormone (CRH) stimulation was applied to all patients during the BIPSS procedure. BIPSS data, MRI results, pathological findings, and follow-up results were analyzed. The diagnostic performance of BIPSS was calculated.

RESULTS

A total of 35 patients, 6 (17%) males and 29 (83%) females, were included in the study. Pituitary MRI was normal in 12 (34.3%) and revealed lesions ≤ 6 mm in 23 (65.7%) patients. BIPSS lateralized the right side in 13 (37.1%) and left side in 18 (51.4%) patients, while no lateralization was observed in the remaining 4 (11.5%) patients. BIPSS showed lateralization in the same direction with pituitary adenoma in 21 (60%) patients before CRH injection and in 29 (83%) patients after CRH injection (p = 0.034). The sensitivity of the BIPSS procedure was 88%. Accurate localization of the pituitary lesion was more frequent when based on BIPSS results than on MRI (83% vs. 51%, P = 0.005).

CONCLUSION

BIPSS appears to be a valuable and safe diagnostic tool in patients who are diagnosed with CD biochemically but do not have clear radiological evidence of ACTH-producing lesion.

Up-To-Date Magnetic Resonance Imaging Findings for the Diagnosis of Hypothalamic and Pituitary Tumors

Magnetic resonance imaging (MRI) is the preferred imaging technique for the sellar and parasellar regions. In this review article, we report our clinical experience with MRI for hypothalamic and pituitary lesions, such as pituitary adenomas, craniopharyngiomas, Rathke cleft cysts, germinoma, and hypophysitis with reference to the histopathological findings through a review of the literature. Our previous study indicated that three dimensional-spoiled gradient echo sequence is a more suitable sequence for evaluating sellar lesions on postcontrast T1 weighted image (WI). This image demonstrates the defined relationship between the tumor and its surroundings, such as the normal pituitary gland, cavernous sinus, and optic pathway. We demonstrated the characteristic MRI findings of functioning pituitary adenoma. In growth hormone-producing adenoma, signal intensity on T2WI is important to differentiate densely from sparsely granulated somatotroph adenomas. In prolactin-producing pituitary adenomas, distinct hypointense areas in early phase on T2WI, possibly owning to diffuse hemorrhage, indicate pronounced regressions of invasive macroprolactinomas during cabergoline therapy. The two histopathological subtypes, adamantinomatous and squamous papillary craniopharyngioma, differ in genesis. Calcified tumors are mostly adamantinomatous type. On MRI, these lesions have a heterogenous appearance with a solid portion and cystic components. The solid portions and cyst wall enhance heterogeneously. Although cyst fluid of Rathke cleft cysts show variable intensities on MRI, intracystic waxy nodule can be hypointense on T2WI. The enhancing cyst wall may contain the squamous metaplasia. Cystic lesions of the sellar and parasellar areas may be difficult to differentiate on a clinical, imaging, or even histopathological basis.

Guidelines in the management of CNS tumors

INTRODUCTION

Evidence-based, clinical practice guidelines in the management of central nervous system tumors (CNS) continue to be developed and updated through the work of the Joint Section on Tumors of the Congress of Neurological Surgeons (CNS) and the American Association of Neurological Surgeons (AANS).

METHODS

The guidelines are created using the most current and clinically relevant evidence using systematic methodologies, which classify available data and provide recommendations for clinical practice.

CONCLUSION

This update summarizes the Tumor Section Guidelines developed over the last five years for non-functioning pituitary adenomas, low grade gliomas, vestibular schwannomas, and metastatic brain tumors.

Intrasellar cavernous hemangiomas: A case report with a comprehensive review of the literature

Background:

Extra-axial cerebral cavernous hemangiomas particularly those found in the sellar region, are extremely rare. Their clinical manifestations and imaging characteristics can mimic those of a pituitary adenoma thus making preoperative diagnosis difficult. Few cases are reported in the literature. We present a case, along with a comprehensive review of the literature regarding specific aspects of diagnosis and management of all similarly reported rare cases.

Case Description:

We present the clinical, radiological, and operative data of a rare case of a large intrasellar cavernous hemangioma in a 49-year-old female patient presented with headache and diminution of vision, which was diagnosed intraoperatively during an endonasal endoscopic transsphenoidal approach. Subtotal debulking was performed with immediate postoperative clinical improvement. The patient was then referred for radiotherapy and maintained her clinical improvement since then.

Conclusion:

Neurosurgeons should consider this rare pathology in the preoperative differential diagnosis of sellar tumors. Bright hyperintense T2 signal with or without signal voids associated with centripetal delayed contrast enhancement in magnetic resonance imaging images might raise the suspicion which can be further confirmed intraoperatively with frozen sections. Due the reported high vascularity and intraoperative profuse bleeding leading to high operative morbidities, piecemeal subtotal resection followed by radiosurgery may be considered today as the safest and most effective strategy.

Pituitary magnetic resonance imaging vs. bilateral inferior petrosal sinus sampling: comparison between non-invasive and invasive diagnostic techniques for Cushing's disease-a narrative review

Cushing's syndrome is a pathological clinical condition caused by an exposure of elevated cortisol levels over a long period of time. It is therefore essential to establish what the cause of hypercortisolism is. In most cases (about 80%) the pathological process is due to adrenocorticotropic hormone (ACTH), while in a minor part of the cases (about 20%) the cause is represented by a pathology of the adrenal glands and therefore not related to ACTH. Most patients with ACTH dependent Cushing's syndrome have a pituitary microadenoma; in the remaining cases (30%), the high level of cortisol is linked to an ectopic secretion of ACTH. Surgical removal of the pituitary adenoma represents the treatment of choice in Cushing's disease (CD) patients; it is therefore necessary to identify and precisely locate the pituitary tumour responsible for the secretion of ACTH. Adequate diagnostic information is very often, even with magnetic resonance imaging (MRI), and in these cases we rely on bilateral inferior petrosal sinuses sampling (BIPSS). This procedure is considered the gold standard method for the diagnosis, but like any other diagnostic method it is not free from erroneous results such as false positives or false negatives.

A smart switching system to enable automatic tuning and detuning of metamaterial resonators in MRI scans

We present a radio-frequency-activated switching system that can automatically detune a metamaterial resonator to enhance magnetic resonance imaging (MRI) performance. Local sensitivity-enhancing metamaterials typically consist of resonant components, which means that the transmitted radio frequency field is spatially inhomogeneous. The switching system shows for the first time that a metamaterial resonator can be detuned during transmission and tuned during reception using a digital circuit. This allows a resonating system to maintain homogeneous transmit field while maintaining an increased receive sensitivity. As a result, sensitivity can be enhanced without changing the system-provided specific absorption rate (SAR) models. The developed digital circuit consists of inductors sensitive to the transmit radio-frequency pulses, along with diodes acting as switches to control the resonance frequency of the resonator. We first test the automatic resonator detuning on-the-bench, and subsequently evaluate it in a 1.5 T MRI scanner using tissue-mimicking phantoms. The scan results demonstrate that the switching mechanism automatically detunes the resonator in transmit mode, while retaining its sensitivity-enhancing properties (tuned to the Larmor frequency) in receive mode. Since it does not require any connection to the MRI console, the switching system can have broad applications and could be adapted for use with other types of MRI scanners and field-enhancing resonators.

Pituitary Adenomas and Invasiveness from Anatomo-Surgical, Radiological, and Histological Perspectives: A Systematic Literature Review

Invasiveness in pituitary adenomas has been defined and investigated from multiple perspectives, with varying results when its predictive value is considered. A systematic literature review, following PRISMA guidelines, was performed, searching PubMed and Scopus databases with terms that included molecular markers, histological, radiological, anatomical and surgical data on invasiveness of pituitary adenomas. The results showed that differing views are still present for anatomical aspects of the sellar region that are relevant to the concept of invasiveness; radiological and histological diagnoses are still limited, but might improve in the future, especially if they are related to surgical findings, which have become more accurate thanks to the introduction of the endoscope. The aim is to achieve a correct distinction between truly invasive pituitary adenomas from those that, in contrast, present with extension in the parasellar area through natural pathways. At present, diagnosis of invasiveness should be based on a comprehensive analysis of radiological, intra-operative and histological findings.

High-resolution magnetic resonance imaging at 3T of pituitary gland: advantages and pitfalls

Magnetic resonance imaging (MRI) is the primary imaging tool for the evaluation of pituitary gland pathology. In the last decades, MRI with high-field scanners has become widely used in clinical practice, leading to significant improvements in image quality mainly thanks to a superior spatial resolution and signal intensity. Moreover, several advanced functional MRI sequences have been implemented for pituitary imaging, providing valuable information in diagnostic and presurgical planning of pituitary adenomas. Higher field strength presents however some technical pitfalls to be aware of. The purpose of this article is to review the state of the art of high-resolution MRI of the pituitary gland at 3 Tesla (3T), with a particular focus on the main benefits and the possible limitations of higher field imaging.

[Tumors of the sellar region]

METHODICAL ISSUE

The anatomy of the sellar region is complex and tumors of the sellar region are very variable because they arise from the many different tissue types in the sellar region, ranging from benign to life-threatening. Despite this variety, approximately 80% of sellar region tumors are due to the 5 most common lesions: adenomas, meningiomas, aneurysms, astrocytomas and craniopharyngiomas.

STANDARD RADIOLOGICAL METHODS

In addition to clinical and laboratory results, the magnetic resonance imaging (MRI) and computed tomography (CT) results including the exact anatomical position and the proliferation pattern of the lesion are decisive for the diagnosis. The gold standard for diagnostic imaging is multiplanar, thin section, contrast-enhanced MRI with soft tissue contrast. Vessel imaging and CT are complementary modalities in selected cases and often for preoperative planning.

METHODICAL INNOVATIONS

Whereas most sellar region tumors can be well visualized with multiplanar, contrast-enhanced MRI, for very small intrapituitary microadenomas dynamic contrast-enhanced T1-weighted sequences can be necessary. Microadenomas can often only be clearly demarcated from the rest of the pituitary tissue due to the different perfusion pattern. Optimized diffusion-weighted images can also be useful for narrowing down the differential diagnoses of sellar region tumors.

PERFORMANCE AND ACHIEVEMENTS

Tumors of the sellar region can be subdivided in intrahypophysial and extrahypophysial lesions as well as intrinsic skull base lesions. The most common sellar tumors are adenomas of the pituitary gland, which can be subdivided into microadenoma and macroadenoma and into secretory and non-secretory.

PRACTICAL RECOMMENDATIONS

If there is suspicion of a sellar region lesion due to clinical or laboratory results, multiplanar contrast enhanced thin section MRI of the sellar region should be used as the primary imaging modality. The keys to the diagnosis are the precise anatomical location of the lesion and the proliferation pattern. The most common lesions in the sellar region are pituitary gland adenomas, which can be small and often secretory or larger and often non-secretory.

Modern imaging of pituitary adenomas

Decision-making in pituitary disease is critically dependent on high quality imaging of the sella and parasellar region. Magnetic resonance imaging (MRI) is the investigation of choice and, for the majority of patients, combined T1 and T2 weighted sequences provide the information required to allow surgery, radiotherapy (RT) and/or medical therapy to be planned and long-term outcomes to be monitored. However, in some cases standard clinical MR sequences are indeterminate and additional information is needed to help inform the choice of therapy for a pituitary adenoma (PA). This article reviews current recommendations for imaging of PA, examines the potential added value that alternative MR sequences and/or CT can offer, and considers how the use of functional/molecular imaging might allow definitive treatment to be recommended for a subset of patients who would otherwise be deemed unsuitable for (further) surgery and/or RT.

Use of intraoperative intracavitary (direct-contact) ultrasound for resection control in transsphenoidal surgery for pituitary tumors: evaluation of a microsurgical series

BACKGROUND

Perisellar infiltration may be responsible for incomplete removal of pituitary tumors. Since intraoperative visualization of parasellar structures is difficult during transsphenoidal surgery, we are describing the use of intraoperative direct contact ultrasound (IOUS).

METHODS

Within 5 years, in 113 transsphenoidal operations (58 male, 55 female, age 14-81 years, 110 pituitary adenomas (mean diameter 26.6 mm, 69 non-secreting adenomas, 41 secreting adenomas), and 1 of each Rathke's cleft cyst, craniopharyngioma, and xanthogranuloma), IOUS was applied. After wide opening of the sellar floor and removal of the intrasellar tumor portions, a commercially available side fire ultrasound probe is introduced, and in direct contact to the sellar envelope, the perisellar space is scanned perpendicular to the axis of the working channel. We compared the results of IOUS to postoperative MRI after 3-6 months.

RESULTS

Identification of the intracavernous ICA, the anterior optic pathway, and the ACA, was possible, it was safe to operate close to them. In 65 operations (58%), further resection of tumor remnants was performed after IOUS. In this selected series, complete resection of tumors (stated by postoperative MRI after 3-6 months) was achieved in 75 operations (66%) and remission was achieved in 18 operations of secreting adenomas (44%). Compared to MRI after 3 to 6 months, the sensitivity of IOUS was 0.568 and the specificity was 0.907. No complications related to IOUS were seen.

CONCLUSIONS

Visualization of the perisellar compartments by IOUS is easy and fast to perform. It allows the surgeon to identify resectable tumor remnants intraoperatively, which otherwise could be missed.

First Application of 7-T Magnetic Resonance Imaging in Endoscopic Endonasal Surgery of Skull Base Tumors

BACKGROUND

Successful endoscopic endonasal surgery for the resection of skull base tumors is reliant on preoperative imaging to delineate pathology from the surrounding anatomy. The increased signal-to-noise ratio afforded by 7-T MRI can be used to increase spatial and contrast resolution, which may lend itself to improved imaging of the skull base. In this study, we apply a 7-T imaging protocol to patients with skull base tumors and compare the images with clinical standard of care.

METHODS

Images were acquired at 7 T on 11 patients with skull base lesions. Two neuroradiologists evaluated clinical 1.5-, 3-, and 7-T scans for detection of intracavernous cranial nerves and internal carotid artery (ICA) branches. Detection rates were compared. Images were used for surgical planning and uploaded to a neuronavigation platform and used to guide surgery.

RESULTS

Image analysis yielded improved detection rates of cranial nerves and ICA branches at 7 T. The 7-T images were successfully incorporated into preoperative planning and intraoperative neuronavigation.

CONCLUSIONS

Our study represents the first application of 7-T MRI to the full neurosurgical workflow for endoscopic endonasal surgery. We detected higher rates of cranial nerves and ICA branches at 7-T MRI compared with 3- and 1.5-T MRI, and found that integration of 7 T into surgical planning and guidance was feasible. These results suggest a potential for 7-T MRI to reduce surgical complications. Future studies comparing standardized 7-, 3-, and 1.5-T MRI protocols in a larger number of patients are warranted to determine the relative benefit of 7-T MRI for endonasal endoscopic surgical efficacy.

Pituitary magnetic resonance imaging in Cushing's disease

Adrenocorticotropin-secreting pituitary tumor represents about 10 % of pituitary adenomas and at the time of diagnosis most of them are microadenomas. Transsphenoidal surgery is the first-line treatment of Cushing's disease and accurate localization of the tumor within the gland is essential for selectively removing the lesion and preserving normal pituitary function. Magnetic resonance imaging is the best imaging modality for the detection of pituitary tumors, but adrenocorticotropin-secreting pituitary microadenomas are not correctly identified in 30-50 % of cases, because of their size, location, and enhancing characteristics. Several recent studies were performed with the purpose of better localizing the adrenocorticotropin-secreting microadenomas through the use in magnetic resonance imaging of specific sequences, reduced contrast medium dose and high-field technology. Therefore, an improved imaging technique for pituitary disease is mandatory in the suspect of Cushing's disease. The aims of this paper are to present an overview of pituitary magnetic resonance imaging in the diagnosis of Cushing's disease and to provide a magnetic resonance imaging protocol to be followed in case of suspicion adrenocorticotropin-secreting pituitary adenoma.

The value of 3D-FIESTA MRI in detecting non-iatrogenic cerebrospinal fluid rhinorrhoea: correlations with endoscopic endonasal surgery

BACKGROUND

In this study, we investigated the value of three-dimensional (3D) fast-imaging employing steady-state acquisition (FIESTA) magnetic resonance imaging (MRI) in detecting non-iatrogenic cerebrospinal fluid (CSF) rhinorrhoea and compared it with regular MRI and 3D magnetisation prepared rapid acquisition gradient echo (MPRAGE) MRI sequences, as well as high-resolution computed tomography (HRCT) imaging. We also present the endoscopic experiences of such cases.

METHOD

From June 2011 to Feb 2016, 17 patients with non-iatrogenic cerebrospinal fluid rhinorrhoea were included. Seven patients had spontaneous rhinorrhoea, three patients had invasive tumours, and the remaining patients had traumatic aetiologies. All the patients underwent HRCT, regular MRI sequence imaging, 3D-MPRAGE MRI sequence imaging and 3D-FIESTA MRI sequence imaging for the preoperative evaluations of the leakages. For each patient, the CSF fistula site was confirmed by intraoperative neuronavigation and endoscopic findings. Statistical analyses were performed. All patients underwent endoscopic multilayer repair.

RESULTS

The sensitivities of the HRCT, regular MRI (T1 and T2), 3D-MPRAGE and 3D-FIESTA modalities for identifying CSF leakage were 58.8 %, (11.8 % and 29.4 %), 74.7 %, and 88.2 %, respectively. The origins of the leakages included the cribriform plate (18 %), ethmoidal fovea (23 %), lateral recess of the sphenoid (17 %), sellar floor (12 %), ethmoidal roof (12 %), junction of the fovea and cribriform plate (6 %) and the junction of sellar and sphenoidal planum (6 %). Two patients required repair. The first was under local anaesthesia when the nasal packing was removed, and the second underwent repair at the same site a half-year later due to hydrocephalus. Lumbar drainage was performed in all cases. No major complications were encountered.

CONCLUSIONS

The endoscopic endonasal approach is safe and effective for the treatment of CSF rhinorrhoea. The 3D-FIESTA MR modality is superior to 3D-MPRAGE MR and HRCT in the depiction of the CSF fistula site. Due to its non-invasive and reliable properties, 3D-FIESTA MR should be the preferred preoperative examination for the patients with non-iatrogenic CSF rhinorrhoea.

Endoscopic endonasal surgery for nonadenomatous, nonmeningeal pathology involving the cavernous sinus

OBJECTIVE Surgery within the cavernous sinus (CS) remains a controversial topic because of the delicate and complex anatomy. The risk also varies with tumor consistency. Softer tumors such as pituitary adenomas are more likely to be surgically treated, while firm tumors such as meningiomas are often treated with radiosurgery. However, a wide range of pathologies that can involve the CS are amenable to surgery. The authors describe and analyze their results using endonasal endoscopic "medial-to-lateral" approaches for nonadenomatous, nonmeningeal tumors, in relation to the degree of invasion within the CS. METHODS A prospectively acquired database of consecutive endoscopic approaches for tumors with verified intraoperative CS invasion was reviewed. Pituitary adenomas and meningiomas were excluded. Degree of invasion of the CS was classified using the Knosp-Steiner (KS) grading system as well as the percentage of cavernous carotid artery (CCA) encasement. Extent of resection of the entire tumor and of the CS component was assessed by independent neuroradiologists using volumetric measurements of the pre- and postoperative MRI studies. Demographic data and complications were noted. RESULTS Fifteen patients (mean age 51.1 years who received endoscopic surgery between 2007 and 2013 met the selection criteria. There were 11 malignant tumors, including chordoma, chondrosarcoma, hemangiopericytoma, lymphoma, and metastatic cancer, and 4 benign tumors, including 3 cavernous hemangiomas and 1 dermoid. All cases were discussed before treatment in a tumor board. Adjuvant treatment options included chemotherapy and radiotherapy. The mean pre- and postoperative tumor volumes were 12.74 ml and 3.86 ml. Gross-total resection (GTR; ie, resection greater than 95%) was the goal in 13 cases and was achieved in 6 patients (46%) while in addition 5 patients had a greater than 80% resection. Gross-total resection in the CS was accomplished in 55% of the tumors with KS Grades 1-2 and in 16.6% of the tumors with KS grades 3-4, respectively. Likewise, GTR was accomplished in 55% of the tumors with CCA encasement under 75% and in 14.3% of the lesions with CCA encasement over 75%, irrespective of tumor volume and underlying pathology. There were 18 preexisting cranial neuropathies involving cranial nerves III-VI, of which 9 fully resolved, 4 improved, and 3 remained unchanged; 2 of these worsened with tumor recurrence. Surgical complications included 1 transient new cranial nerve VI palsy associated with Horner's syndrome and 1 case of panhypopituitarism. There were no postoperative CSF leaks and no infections. The mean extended follow-up was 34.4 months. CONCLUSIONS Endonasal endoscopic approaches can play a role in the management of nonmeningeal, nonadenomatous tumors invading the CS, either through biopsy, debulking, or GTR. An advantage of this method is the relief of preexisting cranial neuropathies with low risk for new neurological deficit. Extent of resection within the CS varies with KS grade and degree of carotid encasement irrespective of the underlying pathology. The goals of surgery should be clearly established preoperatively in consultation with radiation and medical oncologists.

Application of Ultrahigh Field Magnetic Resonance Imaging in the Treatment of Brain Tumors: A Meta-Analysis

BACKGROUND

Magnetic resonance imaging (MRI) is the imaging modality of choice for the clinical management of brain tumors, and the majority of scanners operate with static magnetic field strengths of 1.5 or 3.0 Tesla (T). During the past decade, ultrahigh field (UHF) MRI has been investigated for its clinical applicability. This meta-analysis evaluates studies pertaining to the application of UHF MRI to patients with brain tumors.

METHODS

The authors performed a systematic review of the literature. Articles relating to application of UHF MRI to brain anatomy and brain tumors with living subjects were included. Studies were grouped into 1 of 3 categories based on area of focus: "Anatomical Structures Involved with Brain Tumors," "Tumor characterization," and "Treatment Monitoring." Comparison studies with extractable outcomes measure data were analyzed for performance of UHF MRI versus clinical field strengths (1.5 T and 3 T).

RESULTS

Twenty-four studies (361 subjects) met inclusion criteria. The field of study was heterogeneous and rigorous statistical analysis was not possible. Overall, 279 patients with brain tumors scanned at UHF MRI have been reported. Of these, glioma and glioblastoma multiforme are the most commonly studied lesions (38.9% and 24.4%, respectively). In comparison studies between UHF MRI and clinical field strengths, 24 of 51 patients had outcome measures that were better with UHF MRI, 17 of 24 were equivalent at both field strengths, and 9 were worse at UHF MRI. The most common causes of a worse performance were susceptibility artifacts and magnetic field inhomogeneities (3 of 9). Imaging of the pituitary gland, pineal gland veins, cranial nerves, and tumor microvasculature were all shown to be feasible.

CONCLUSIONS

UHF MRI shows promise to improve detection and characterization of brain tumors, preoperative planning for neurosurgical resection, and longitudinal monitoring of the effects of radiation and antibody-based therapies. Technical innovations are needed to overcome field inhomogeneity and susceptibility artifacts in certain regions of the skull. Finally, larger studies comparing 1.5 T, 3.0 T, and 7.0 T or greater will determine whether UHF MRI gains acceptance as a clinical standard.

Effective performance of contrast enhanced SPACE imaging in clearly depicting the margin of pituitary adenoma

PURPOSE

The aim of this study is to determine if contrast enhanced (CE) sampling perfection with application-optimized contrasts using different flip-angle evolutions (SPACE) images can provide clearer pituitary adenoma margin than conventional CE T1-weighted spin echo (T1-SE) sequence for cavernous sinus (CS) invasion evaluation.

METHODS

21 healthy volunteers were preformed with SPACE scans before and after administration of gadopentetate dimeglumine at different time points (1, 7 and 13 min). Signal intensity (SI) of regions of interest was plotted in SI/time curves for bilateral CS, pituitary and temporal lobe. 35 patients with pituitary adenoma (≥1 cm) were performed CE T1-SE and CE SPACE scans. Two observers made the visual assessment of the tumor margin delineation and CS invasion evaluation on both SPACE and T1-SE images. Surgical findings were compared with the invasion assessment results.

RESULTS

At 1, 7 and 13 min after enhancement, SI of left CS increased 6.7, 9.5 and 11.2% respectively compared with unenhanced images (all p < 0.05). Right CS increased 7.2, 9.3 and 11.3% (all p < 0.05%). Within pituitary, a decline (6.3%, p < 0.05) of SI was measured at 1 min after enhancement. CE SPACE performed superior to those of CE T1-SE sequence in visual assessment of tumor edge (assessment score, 1.66 ± 0.42 vs. 1.23 ± 0.65, p < 0.05), as well as the specificity (86.8 vs. 66.0%, p < 0.05) and accuracy (85.7 vs. 68.6%, p < 0.05) for CS invasion evaluation.

CONCLUSION

CE SPACE could provide better contrast of pituitary adenoma with surrounding CS and clear demonstration of tumor edge for CS invasion evaluation than conventional CE T1-SE sequence.

High resolution pituitary gland MRI at 7.0 tesla: a clinical evaluation in Cushing's disease

Objective

To evaluate the detection of pituitary lesions at 7.0 T compared to 1.5 T MRI in 16 patients with clinically and biochemically proven Cushing’s disease.

Methods

In seven patients, no lesion was detected on the initial 1.5 T MRI, and in nine patients it was uncertain whether there was a lesion. Firstly, two readers assessed both 1.5 T and 7.0 T MRI examinations unpaired in a random order for the presence of lesions. Consensus reading with a third neuroradiologist was used to define final lesions in all MRIs. Secondly, surgical outcome was evaluated. A comparison was made between the lesions visualized with MRI and the lesions found during surgery in 9/16 patients.

Results

The interobserver agreement for lesion detection was good at 1.5 T MRI (κ = 0.69) and 7.0 T MRI (κ = 0.62). In five patients, both the 1.5 T and 7.0 T MRI enabled visualization of a lesion on the correct side of the pituitary gland. In three patients, 7.0 T MRI detected a lesion on the correct side of the pituitary gland, while no lesion was visible at 1.5 T MRI.

Conclusion

The interobserver agreement of image assessment for 7.0 T MRI in patients with Cushing’s disease was good, and lesions were detected more accurately with 7.0 T MRI.

Key Points

• Interobserver agreement for lesion detection on 1.5 T MRI was good;

• Interobserver agreement for lesion detection on 7.0 T MRI was good;

• 7.0 T enabled confirmation of unclear lesions at 1.5 T;

• 7.0 T enabled visualization of lesions not visible at 1.5 T.

Electronic supplementary material

The online version of this article (doi:10.1007/s00330-015-3809-x) contains supplementary material, which is available to authorized users.

Invasion of the cavernous sinus space in pituitary adenomas: endoscopic verification and its correlation with an MRI-based classification

OBJECT An important prognostic factor for the surgical outcome and recurrence of a pituitary adenoma is its invasiveness into parasellar tissue, particularly into the space of the cavernous sinus (CS). The aims of this study were to reevaluate the existing parasellar classifications using an endoscopic technique and to evaluate the clinical and radiological outcomes associated with each grade. METHODS The authors investigated 137 pituitary macroadenomas classified radiologically at least on one side as Grade 1 or higher (parasellar extension) and correlated the surgical findings using an endoscopic technique, with special reference to the invasiveness of the tumor into the CS. In each case, postoperative MRI was performed to evaluate the gross-total resection (GTR) rate and the rate of endocrinological remission (ER) in functioning adenomas. RESULTS The authors found a 16% rate of CS invasion during surgery for these macroadenomas. Adenomas radiologically classified as Grade 1 were found to be invasive in 1.5%, and the GTR/ER rate was 83%/88%. For Grade 2 adenomas, the rate of invasion was 9.9%, and the GTR/ER rate was 71%/60%. For Grade 3 adenomas, the rate of invasion was 37.9%, and the GTR/ER rate was 75%/33%. When the superior compartment of the CS (Grade 3A) was involved, the authors found a rate of invasion that was lower (p < 0.001) than that when the inferior compartment was involved (Grade 3B). The rate of invasion in Grade 3A adenomas was 26.5% with a GTR/ER rate of 85%/67%, whereas for Grade 3B adenomas, the rate of surgically observed invasion was 70.6% with a GTR/ER rate of 64%/0%. All of the Grade 4 adenomas were invasive, and the GTR/ER rate was 0%. A comparison of microscopic and endoscopic techniques revealed no difference in adenomas with Grade 1 or 4 parasellar extension. In Grade 2 adenomas, however, the CS was found by the endoscopic technique to be invaded in 9.9% and by microscopic evaluation to be invaded in 88% (p < 0.001); in Grade 3 adenomas, the difference was 37.9% versus 86%, respectively (p = 0.002). Grade 4 adenomas had a statistically significant lower rate of GTR than those of all the other grades. In case of ER only, Grade 1 adenomas had a statistically significant higher rate of remission than did Grade 3B and Grade 4 adenomas. CONCLUSIONS The proposed classification proved that with increasing grades, the likelihood of surgically observed invasion rises and the chance of GTR and ER decreases. The direct endoscopic view confirmed the low rate of invasion of Grade 1 adenomas but showed significantly lower rates of invasion in Grade 2 and 3 adenomas than those previously found using the microscopic technique. In cases in which the intracavernous internal carotid artery was encased (Grade 4), all the adenomas were invasive and the GTR/ER rate was 0%/0%. The authors suggest the addition of Grades 3A and 3B to distinguish the strikingly different outcomes of adenomas invading the superior CS compartments and those invading the inferior CS compartments.

Olfactory function and quality of life following microscopic endonasal transsphenoidal pituitary surgery

Olfactory outcomes as well as oronasal postoperative complications of transsphenoidal pituitary surgery have not been well studied. The objective of this study was to investigate nasal symptoms including olfactory function as well as quality of life following transsphenoidal pituitary surgery. The study is designed as a prospective cohort study set in a single tertiary hospital. A total of 53 patients with pituitary adenomas were included. All patients underwent pituitary surgery with the right-sided endonasal transsphenoidal approach. Outcomes were assessed with the Chinese version of the Medical Outcomes Study Short Form-36 (SF-36) to survey patient health, the Chinese version of the 22-item Sinonasal Outcome Test (SNOT-22), and a Toyota and Takagi (T&T) olfactometer. Assessments were carried out before surgery and at 1 week, and 1 and 4 months after surgery. The overall SF-36 scores were significantly lower, but the SNOT-22 scores were higher at 1 week and 1 month postoperatively compared with baseline (all P < 0.001). The results of T&T olfactometer testing showed that there was a significant decline in the ability to detect odors postoperatively, even at 4 months. Multivariate linear regression analysis showed that lower education level, partial tumor removal, and longer duration of surgery were independent risk factors for a higher SNOT-22 score at 1 week after surgery. The findings show that microscopic endonasal transsphenoidal pituitary surgery impairs olfactory function in most patients for at least 4 months after surgery.

Serial 3 T magnetic resonance imaging during cabergoline treatment of macroprolactinomas

OBJECTIVE

Cabergoline is the treatment of choice for prolactin (PRL)-producing pituitary adenomas, because of its efficacy in normalizing PRL levels, and inducing tumor shrinkage. The clinical use of 3 T magnetic resonance imaging (MRI) for neuroimaging has rapidly expanded in recent years. In particular, T2-weighted imaging (T2WI) provides high anatomical and contrast resolution.

PATIENTS AND METHODS

In this study, serial 3 T MRI with T2WI was utilized during cabergoline treatment of 10 patients with macroprolactinomas. Cabergoline was started at a standard weekly dosage and incrementally adjusted on individual posttreatment PRL values.

RESULTS

MRI confirmed tumor shrinkage in all patients during cabergoline treatment. Cabergoline normalized hyperprolactinemia in all but one patient. In six of 10 patients, distinct low-signal-intensity areas were evident throughout the adenomas on T2WI. In four of those six patients, massive low-signal-intensity areas appeared at 1-4 months, after which tumors decreased in size by over 80%. These findings in the early phase of prolactinoma treatment predicted pronounced regression or near-complete disappearance of the tumor. Reduction of T2 intensity possibly reflected dehydration due to diffuse hemorrhage in the adenomas.

CONCLUSION

T2-weighted 3 T MR images are valuable for assessing and monitoring cabergoline treatment of macroprolactinomas.

Physiologic characterization of inflammatory arthritis in a rabbit model with BOLD and DCE MRI at 1.5 Tesla

OBJECTIVE

Our aim was to test the feasibility of blood oxygen level dependent magnetic resonance imaging (BOLD MRI) and dynamic contrast-enhanced (DCE) MRI to monitor periarticular hypoxic/inflammatory changes over time in a juvenile rabbit model of arthritis.

METHODS

We examined arthritic and contralateral nonarthritic knees of 21 juvenile rabbits at baseline and days 1,14, and 28 after induction of arthritis by unilateral intra-articular injection of carrageenin with BOLD and DCE MRI at 1.5 Tesla (T). Nine noninjected rabbits served as controls. Associations between BOLD and DCE-MRI and corresponding intra-articular oxygen pressure (PO2) and blood flow [blood perfusion units (BPU)] (polarographic probes, reference standards) or clinical-histological data were measured by correlation coefficients.

RESULTS

Percentage BOLD MRI change obtained in contralateral knees correlated moderately with BPU on day 0 (r = -0.51, p = 0.02) and excellently on day 28 (r = -0.84, p = 0.03). A moderate correlation was observed between peak enhancement DCE MRI (day 1) and BPU measurements in arthritic knees (r = 0.49, p = 0.04). In acute arthritis, BOLD and DCE MRI highly correlated (r = 0.89, p = 0.04; r = 1.0, p < 0.0001) with histological scores in arthritic knees.

CONCLUSION

The proposed techniques are feasible to perform at 1.5 T, and they hold potential as surrogate measures to monitor hypoxic and inflammatory changes over time in arthritis at higher-strength MRI fields.

KEY POINTS

• BOLD and DCE MRI detect interval perisynovial changes in a rabbit knee • BOLD and DCE MRI act as surrogate markers of physiologic changes in arthritis • BOLD MRI signal represents oxygen extraction compared with intra-articular PO 2 • DCE MRI measurements estimate physiologic periarticular vascular properties • In rabbit knees with acute arthritis, BOLD/DCE MRI highly correlated with histological scores.

High-Field iMRI in transsphenoidal pituitary adenoma surgery with special respect to typical localization of residual tumor

BACKGROUND

Intraoperative high-field magnetic resonance imaging (iMRI) is used as an immediate intraoperative quality control, evaluating the extent of tumor removal during the surgical procedure and allowing us to extend resections in those cases where tumor remnants are documented. The aim of the study was to analyze the typical localization of residual tumor remnants, detected by iMRI during transsphenoidal surgery of pituitary adenomas.

METHODS

We reviewed a series of 72 patients. All patients presented with macroadenomas with or without suprasellar extension. After high-field MRI investigation, we divided the series preoperatively into totally resectable (TR) and non-totally resectable (NTR) tumors. Tumor remnants were documented by iMRI, obtained directly after tumor removal, as well as by intraoperative surgical inspection of the sellar content.

RESULTS

In the TR group, we observed 23 cases suspicious for tumor remnants, located anteriorly, laterally, posteriorly, and suprasellar under descending folds of the diaphragm. Continuing surgery, upon a "second inspection", tumor resection could be completed in all cases.

CONCLUSIONS

Incomplete removal of resectable pituitary adenomas could be avoided in a higher number of cases with the knowledge of the location of the typical remnant tumors. In those cases where it is not possible to achieve a complete resection of adenoma, further treatment can be planned at an earlier stage, without any need to wait for the conventional postoperative MRI scan performed 2 to 3 months after surgery.

Imaging of pituitary pathology

Modern imaging techniques play a vital role in the diagnosis, surveillance, and treatment monitoring of patients with pituitary disease. For its high soft tissue contrast, magnetic resonance (MR) imaging provides detailed information about the localization and extent of a lesion. It is thus, to date, the most important imaging technique for documenting or ruling out structural lesions. It is usually the first and only imaging procedure to be employed in pituitary pathology. While large pituitary adenomas are reliably depicted in standard T1-weighted sequences, small microadenomas, such as in Cushing's disease, may only become visible if repeat studies, sophisticated techniques and high-field scanners are employed. For monitoring treatment effects after surgical procedures, drug applications, or irradiation, follow-up studies with identical parameters should be employed, preferably at the same investigation site. Some space is devoted to intraoperative imaging, which not only allows assessment of how radical tumor resection needs to be during pituitary tumor surgery, but also provides extremely accurate structural data for neuronavigation. Less frequent lesions, such as craniopharyngiomas, meningiomas, germ cell tumors, gliomas, skull base tumors, hypothalamic hamartomas, vascular malformations, inflammatory and developmental lesions and other, even less frequent pathologies should be considered in the differential diagnosis. The particular strength of computed tomography (CT) is the direct depiction of calcification, a weakness of MRI, and the high resolution of bone structures at the skull base. This chapter presents the characteristics of both frequent and less commonly encountered tumoral lesions, with an emphasis on computed tomography and magnetic resonance imaging.

Efficacy of magnetic resonance imaging at 3 T compared with 1.5 T in small pituitary tumors for stereotactic radiosurgery planning

PURPOSE

The objective of this study was to determine the value of high-field magnetic resonance imaging and to clarify the characteristics of each image among three-dimensional gradient echo (3D-GRE), two-dimensional spin echo (2D-SE) and inversion recovery (2D-IR) sequences used as contrast-enhanced T1-weighted images for stereotactic irradiation treatment planning of sellar lesions.

MATERIALS AND METHODS

Pulse sequences of 2D-SE and 3D-spoiled gradient recalled acquisition in the steady state (3D-SPGR) using GRE at 1.5 T and 2D-IR and 3D-fast SPGR (3D-FSPGR) at 3 T after injection of contrast material were acquired for 14 small pituitary tumors. As quantitative methods, signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR) were evaluated using a region-of-interest analysis.

RESULTS

There was no significant difference in SNR between 1.5-T SPGR and 3-T FSPGR, while 3-T IR was superior to 1.5-T SE. The 2D-SE and -IR provided significantly better CNR than 3D-GRE between tumor and normal structures.

CONCLUSIONS

Three Tesla was found to be superior to 1.5 T in distinguishing tumors from the normal sellar structure. Optimal dose planning will utilize each advantage of imaging; 3D-GRE allows high-resolution acquisition and 2D-SE and -IR can offer better tissue contrast.

Magnetic resonance imaging appearance of the medial wall of the cavernous sinus for the assessment of cavernous sinus invasion by pituitary adenomas

PURPOSE

The diagnostic criteria for cavernous sinus invasion (CSI) by pituitary adenomas are still unsatisfactory and controversial. For this reason, the study examined the appearance of the medial wall of the cavernous sinus (MWCS) on proton-density-weighted (PDW) magnetic resonance imaging (MRI) to determine its value for preoperative assessment of CSI.

METHODS

A 3.0-Tesla MRI scanner was used to obtain preoperative PDW images and conventional MRI sequences of 48 consecutive pituitary adenomas, and the MWCS was examined in PDW images to determine the presence of CSI in comparison to surgical findings and three traditional MRI criteria: Knosp grading system (KGS); percentage of encasement of the internal carotid artery (PEICA); and replacement of cavernous sinus compartments (RCSC) by tumors. The value of the MWCS as seen on MRI was compared with that of the Ki-67 labelling index (Ki-67 LI).

RESULTS

CSI images showed that continuity of the MWCS was interrupted and that tumor tissue had infiltrated the cavernous sinus (CS) compartments through the defects. In 96 CSs from 48 patients, the sensitivity of MRI visualization of the MWCS for detection of CSI was 93.3% with a specificity of 93.8%, which was significantly higher than with KGS, PEICA and RCSC (P=0.007, P=0.008 and P=0.056, respectively). Histopathological results showed no significant differences between MRI visualization of the MWCS and the Ki-67 LI.

CONCLUSION

PDW imaging permits adequate visualization of the MWCS and is superior to traditional diagnostic criteria for the detection of CSI, providing accurate preoperative images for intraoperative navigation.

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.

A systematic review of the utility of 1.5 versus 3 Tesla magnetic resonance brain imaging in clinical practice and research

OBJECTIVE

MRI at 3 T is said to be more accurate than 1.5 T MR, but costs and other practical differences mean that it is unclear which to use.

METHODS

We systematically reviewed studies comparing diagnostic accuracy at 3 T with 1.5 T. We searched MEDLINE, EMBASE and other sources from 1 January 2000 to 22 October 2010 for studies comparing diagnostic accuracy at 1.5 and 3 T in human neuroimaging. We extracted data on methodology, quality criteria, technical factors, subjects, signal-to-noise, diagnostic accuracy and errors according to QUADAS and STARD criteria.

RESULTS

Amongst 150 studies (4,500 subjects), most were tiny, compared old 1.5 T with new 3 T technology, and only 22 (15 %) described diagnostic accuracy. The 3 T images were often described as "crisper", but we found little evidence of improved diagnosis. Improvements were limited to research applications [functional MRI (fMRI), spectroscopy, automated lesion detection]. Theoretical doubling of the signal-to-noise ratio was not confirmed, mostly being 25 %. Artefacts were worse and acquisitions took slightly longer at 3 T.

CONCLUSION

Objective evidence to guide MRI purchasing decisions and routine diagnostic use is lacking. Rigorous evaluation accuracy and practicalities of diagnostic imaging technologies should be the routine, as for pharmacological interventions, to improve effectiveness of healthcare.

KEY POINTS

• Higher field strength MRI may improve image quality and diagnostic accuracy. • There are few direct comparisons of 1.5 and 3 T MRI. • Theoretical doubling of the signal-to-noise ratio in practice was only 25 %. • Objective evidence of improved routine clinical diagnosis is lacking. • Other aspects of technology improved images more than field strength.

Advances in pituitary imaging technology and future prospects

There have been substantial advances in pituitary imaging in the last half-century. In particular, magnetic resonance imaging is now established as the imaging modality of choice, providing high quality images of the hypothalamic-pituitary axis and adjacent structures. More recent technological advances, such as the emergence of 3 Tesla MRI, are already being widely incorporated into imaging practice. However, other advanced techniques, including a variety of potential imaging biomarkers, still require further research to evaluate their potential and define their precise role. The recent development of intraoperative MRI appears promising and may have the potential to improve the outcome of pituitary surgery. Modern high quality imaging inevitably leads to the discovery of incidental lesions, including those within the pituitary gland, although it also plays a central role in their subsequent evaluation and management.

Intraoperative multiple-staged resection and tumor tissue identification using frozen sections provide the best result for the accurate localization and complete resection of tumors in Cushing's disease

The treatment of choice in Cushing's disease (CD) is surgical removal; however, most tumors are too small to be detected. The objective was to establish a method to achieve the complete removal of tumors on the basis of the results of high-resolution magnetic resonance imaging (MRI), inferior petrosal sinus sampling (IPSS), and a surgical resection technique using frozen biopsy. Eighteen patients who underwent transsphenoidal surgery from 2004 to 2010 were included. High-resolution MRI and IPSS, multiple-staged resection, and tumor tissue identification in frozen sections (surgical and histological identification, SHI) were performed. All patients achieved surgical remission, as confirmed by 24 h urinary free cortisol excretion tests. Visible microlesions were identified on the initial MRI in 11 patients (61%). The SHI findings agreed with the MRI findings in 10 of the 11 patients (90.9%) and with IPSS lateralization in 6 of the 11 patients (54.5%). In the 7 patients whose lesions were not visible on the initial MRI, only 1 (14.3%) showed an agreement between IPSS and SHI. In 3 of the 7 patients, the microlesions were identified by additional MRI. The rate of concordance with SHI was 77.8% for the overall MRI and 38.9% for IPSS. High-resolution MRI is better than IPSS for localizing corticotroph adenomas. In patients with lesions not visible on the initial MRI, additional MRI should be performed using a different protocol. Although high-resolution MRI is better for localizing tumors, SHI remains an important approach for removing the tumors completely.

Diagnostic usefulness of 3 tesla MRI of the brain for cushing disease in a child

It is sometimes difficult to confirm the location of a microadenoma in Cushing disease. Recently, we experienced an 11-yr-old female case of Cushing disease with hyperprolactinemia. She was referred to our hospital because of decrease of height velocity with body weight gain. On admission, she had typical symptoms of Cushing syndrome. Although no pituitary microadenomas were detected on 1.5 Tesla MRI of the brain, endocrinological examinations including IPS and CS sampling were consistent with Cushing disease with hyperprolactinemia. Oral administration of methyrapone instead of neurosurgery was started after discharge, but subsequent 3 Tesla MRI of the brain clearly demonstrated a 3-mm less-enhanced lesion in the left side of the pituitary gland. Finally, transsphenoidal surgery was performed, and a 3.5-mm left-sided microadenoma was resected. Compared with 1.5 Tesla MRI, 3 Tesla MRI offers the advantage of a higher signal to noise ratio (SNR), which provides higher resolution and proper image quality. Therefore, 3 Tesla MRI is a very useful tool to localize microadenomas in Cushing disease in children as well as in adults. It will be the first choice of radiological examinations in suspected cases of Cushing disease.

Initial experience of 3 Tesla versus conventional field strength magnetic resonance imaging of small functioning pituitary tumours

BACKGROUND

Higher field strength magnetic resonance imaging (MRI) is becoming increasingly available and offers improved image quality; however, the clinical usefulness of this technique for the demonstration of surgically treatable functional pituitary adenomas has not been clearly established.

OBJECTIVE

To determine whether 3 Tesla (3T) MRI improves the detection of ACTH- and GH-secreting microadenomas over conventional imaging at field strengths of up to 1·5 Tesla (1·5T).

DESIGN

Data sets from postgadolinium T1-weighted MRI at 1·5T and 3T were blinded, randomly ordered and assessed for the presence of pituitary tumour by two radiologists. Where possible, lesion signal difference to noise ratio (SDNR) was calculated for quantitative comparison. Imaging diagnoses were correlated with subsequent surgical and histological findings.

PATIENTS

Twenty-four patients (10 men, 14 women) with biochemical evidence of Cushing's disease (19) or acromegaly (5) were identified over a 5-year period.

RESULTS

1·5T MRI gave a clear diagnosis of 12 pituitary tumours, all confirmed at 3T. Four additional definite lesions and one suspicious case were correctly identified at 3T. Histological correlation in 21 cases showed sensitivity improving from 54% with 1·5T to 85% with 3T. Radiologists' subjective image preference favoured 3T in 92%. Quantitative difference between tumour and parenchymal signal was significantly greater at 3T (mean SDNR -7·9 [3T] and -2·8 [1·5T], paired t-test P < 0·05).

CONCLUSIONS

3T MRI appears to offer increased conspicuity and detection of GH- and ACTH-secreting pituitary microadenomas. It is potentially clinically useful when 1·5T imaging is negative or equivocal.

The relationship between MRI invasive features and expression of EMMPRIN, galectin-3, and microvessel density in pituitary adenoma

This study aimed to investigate the relationship between the expression of the molecular markers, extracellular matrix metalloproteinase inducer (EMMPRIN), galectin-3, and microvessel density (MVD) with MRI invasive features in invasive and noninvasive pituitary adenomas. MRI was performed preoperatively in 34 patients with histologically verified pituitary adenomas. The expression of EMMPRIN, galectin-3, and MVD was determined by using immunohistochemical techniques on excised surgical specimen from all patients. Correlative analyses between invasive MRI features and expression of EMMPRIN, galectin-3, and MVD were determined between invasive and noninvasive pituitary adenomas. Among MRI invasive features, adenoma crossing the lateral line (LL) of the internal carotid artery (ICA), percentage of intracavernous ICA encasement by the tumor over 50%, sphenoidal sinus invasion, irregular tumor shape, and bilateral ICA asymmetry correlated with increased expression of EMMPRIN and galectin-3 (P<.05), but tumor cystic necrosis and tumor apoplexy did not correlate with EMMPRIN and galectin-3 expression (P>.05). The invasive MRI features did not correlate with MVD expression. This study demonstrated that EMMPRIN and galectin-3 were associated with aggressiveness and invasion by pituitary adenoma. Furthermore, EMMPRIN and galectin-3 were two potential molecular markers for assessing the invasive potential of pituitary adenoma and may provide useful targets for molecular therapeutic strategy against invasive pituitary adenomas.

Imaging of the pituitary: Recent advances

Pituitary lesions, albeit relatively infrequent, can significantly alter the quality of life. This article highlights the role of advanced imaging modalities in evaluating pituitary-hypothalamic axis lesions. Magnetic resonance imaging (MRI) is the examination of choice for evaluating hypothalamic-pituitary-related endocrine diseases. Advanced MR techniques discussed in this article include dynamic contrast-enhanced MRI, 3T MRI, magnetization transfer (MT) imaging, diffusion-weighted imaging (DWI), proton MR spectroscopy, fluorine-18 fluorodeoxyglucose-positron emission tomography, single-photon emission computed tomography, intraoperative MRI, and intraoperative real-time ultrasonography.

Imaging of the pituitary

In the appropriate clinical setting of pituitary hyperfunction or hypofunction, visual field deficit, or cranial nerve palsy, imaging of the pituitary is necessary. This article reviews the normal appearance of the pituitary and its surroundings, emphasizing magnetic resonance imaging. Typical and variant appearances of pituitary pathology are discussed. Because growth of adenoma into surrounding structures is important to surgical management, cavernous sinus invasion and suprasellar spread as well as adenoma mimics are illustrated. Typical examples of pituitary dysfunction from other entities that secondarily affect the gland, hypophysis, or third ventricle are discussed. Some common errors of interpretation are listed.