Contrast-enhanced 3D-T2-weighted SPACE sequence for MRI detection and localization of adrenocorticotropin (ACTH)-secreting pituitary microadenomas

Advanced Magnetic Resonance Imaging Techniques for Localization of a Small Thyrotropin-Secreting Pituitary Tumor

Thyrotropin (TSH)-secreting pituitary tumors (TSH-omas) are a rare cause of hyperthyroidism. Historically, the majority have been macroadenomas (>1 cm); however, microadenomas (<1 cm) are increasing in frequency. Localization of TSH-secreting microadenomas can be challenging. We report the first case employing advanced pituitary magnetic resonance imaging (MRI) sequences to localize a TSH-secreting microadenoma, leading to successful resection. The patient presented with mild symptoms of hyperthyroidism and biochemistry confirming secondary hyperthyroidism. α-Glycoprotein subunit and sex hormone-binding globulin were elevated; however, cross-linked C-telopeptide of type I collagen was within the reference range. No pathogenic variants in thyroid hormone resistance genes were detected. A triiodothyronine suppression test, thyroid hormone-releasing hormone stimulation test, and short-acting octreotide suppression test were consistent with a TSH-oma. Initial pituitary MRI did not demonstrate a pituitary tumor. However, advanced imaging techniques including coronal T1 3-dimensional volumetric interpolated breath-hold sequence (VIBE) thin-slice scans confirmed a small, right-sided pituitary tumor. Transsphenoidal surgery was performed, and histopathology confirmed a TSH-oma. The patient remains in biochemical remission. TSH-secreting microadenomas are increasing in frequency and localization is likely to become an increasing challenge. Advanced MRI imaging techniques appear beneficial in the localization of TSH-secreting microadenomas.

Preoperative Prediction of Non-functional Pituitary Neuroendocrine Tumors and Posterior Pituitary Tumors Based on MRI Radiomic Features

Compared to non-functional pituitary neuroendocrine tumors (NF-PitNETs), posterior pituitary tumors (PPTs) require more intraoperative protection of the pituitary stalk and hypothalamus, and their perioperative management is more complex than NF-PitNETs. However, they are difficult to be distinguished via magnetic resonance images (MRI) before operation. Based on clinical features and radiological signature extracted from MRI, this study aims to establish a model for distinguishing NF-PitNETs and PPTs. Preoperative MRI of 110 patients with NF-PitNETs and 55 patients with PPTs were retrospectively obtained. Patients were randomly assigned to the training (n = 110) and validation (n = 55) cohorts in a 2:1 ratio. The lest absolute shrinkage and selection operator (LASSO) algorithm was applied to develop a radiomic signature. Afterwards, an individualized predictive model (nomogram) incorporating radiomic signatures and predictive clinical features was developed. The nomogram's performance was evaluated by calibration and decision curve analyses. Five features derived from contrast-enhanced images were selected using the LASSO algorithm. Based on the mentioned methods, the calculation formula of radiomic score was obtained. The constructed nomogram incorporating radiomic signature and predictive clinical features showed a good calibration and outperformed the clinical features for predicting NF-PitNETs and PPTs (area under the curve [AUC]: 0.937 vs. 0.595 in training cohort [p < 0.001]; 0.907 vs. 0.782 in validation cohort [p = 0.03]). The decision curve shows that the individualized predictive model adds more benefit than clinical feature when the threshold probability ranges from 10 to 100%. Individualized predictive model provides a novel noninvasive imaging biomarker and could be conveniently used to distinguish NF-PitNETs and PPTs, which provides a significant reference for preoperative preparation and intraoperative decision-making.

Granulation Patterns of Functional Corticotroph Tumors Correlate with Tumor Size, Proliferative Activity, T2 Intensity-to-White Matter Ratio, and Postsurgical Early Biochemical Remission

Unlike somatotroph tumors, the data on correlates of tumor granulation patterns in functional TPIT lineage pituitary neuroendocrine tumors (corticotroph tumors) have been less uniformly documented in most clinical series. This study evaluated characteristics of 41 well-characterized functional corticotroph tumors consisting of 28 densely granulated corticotroph tumors (DGCTs) and 13 sparsely granulated corticotroph tumors (SGCTs) with respect to preoperative clinical and radiological findings, tumor proliferative activity (including mitotic count and Ki-67 labeling index), and postoperative early biochemical remission rates. The median (interquartile range (IQR)) tumor size was significantly larger in the SGCT group [16.00 (16.00) mm in SGCT vs 8.5 (9.75) mm in DGCT, p = 0.049]. T2-weighted signal intensity and T2 intensity (quantitative) did not yield statistical significance based on tumor granulation; however, the T2 intensity-to-white matter ratio was significantly higher in SGCTs (p = 0.049). The median (IQR) Ki-67 labeling index was 2.00% (IQR 1.00%) in the DGCT group and 4.00% (IQR 7.00%) in the SGCT group (p = 0.043). The mitotic count per 2 mm2 was higher in the SGCT group (p = 0.001). In the multivariate analysis, the sparse granulation pattern (SGCT) remained an independent predictor of a lower probability of early biochemical remission irrespective of the tumor size and proliferative activity (p = 0.012). The current study further supports the impact of tumor granulation pattern as a biologic variable and warrants the detailed histological subtyping of functional corticotroph tumors as indicated in the WHO classification of pituitary neuroendocrine tumors. More importantly, the assessment of the quantitative T2 intensity-to-white matter ratio may serve as a preoperative radiological harbinger of SGCTs.

Neuroimaging of pediatric tumors of the sellar region-A review in light of the 2021 WHO classification of tumors of the central nervous system

Sellar/suprasellar tumors comprise about 10% of all pediatric Central Nervous System (CNS) tumors and include a wide variety of entities, with different cellular origins and distinctive histological and radiological findings, demanding customized neuroimaging protocols for appropriate diagnosis and management. The 5th edition of the World Health Organization (WHO) classification of CNS tumors unprecedently incorporated both histologic and molecular alterations into a common diagnostic framework, with a great impact in tumor classification and grading. Based on the current understanding of the clinical, molecular, and morphological features of CNS neoplasms, there have been additions of new tumor types and modifications of existing ones in the latest WHO tumor classification. In the specific case of sellar/suprasellar tumors, changes include for example separation of adamantinomatous and papillary craniopharyngiomas, now classified as distinct tumor types. Nevertheless, although the current molecular landscape is the fundamental driving force to the new WHO CNS tumor classification, the imaging profile of sellar/suprasellar tumors remains largely unexplored, particularly in the pediatric population. In this review, we aim to provide an essential pathological update to better understand the way sellar/suprasellar tumors are currently classified, with a focus on the pediatric population. Furthermore, we intend to present the neuroimaging features that may assist in the differential diagnosis, surgical planning, adjuvant/neoadjuvant therapy, and follow-up of this group of tumors in children.

MRI for Cushing Disease: A Systematic Review

BACKGROUND

MR imaging is key in the diagnostic work-up of Cushing disease. The sensitivity of MR imaging in Cushing disease is not known nor is the prognostic significance of "MR imaging-negative" disease.

PURPOSE

Our aim was to determine the overall sensitivity and prognostic significance of MR imaging localization of Cushing disease.

DATA SOURCES

We performed a systematic review of the MEDLINE and PubMed databases for cohort studies reporting the sensitivity of MR imaging for the detection of adenomas in Cushing disease.

STUDY SELECTION

This study included 57 studies, comprising 5651 patients.

DATA ANALYSIS

Risk of bias was assessed using the methodological index for non-randomized studies criteria. Meta-analysis of proportions and pooled subgroup analysis were performed.

DATA SYNTHESIS

Overall sensitivity was 73.4% (95% CI, 68.8%-77.7%), and the sensitivity for microadenomas was 70.6% (66.2%-74.6%). There was a trend toward greater sensitivity in more recent studies and with the use of higher-field-strength scanners. Thinner-section acquisitions and gadolinium-enhanced imaging, particularly dynamic sequences, also increased the sensitivity. The use of FLAIR and newer 3D spoiled gradient-echo and FSE sequences, such as spoiled gradient-echo sequences and sampling perfection with application-optimized contrasts by using different flip angle evolutions, may further increase the sensitivity but appear complementary to standard 2D spin-echo sequences. MR imaging detection conferred a 2.63-fold (95% CI, 2.06-3.35-fold) increase in remission for microadenomas compared with MR imaging-negative Cushing disease.

LIMITATIONS

Pooled analysis is limited by heterogeneity among studies. We could not account for variation in image interpretation and tumor characteristics.

CONCLUSIONS

Detection on MR imaging improves the chances of curative resection of adenomas in Cushing disease. The evolution of MR imaging technology has improved the sensitivity for adenoma detection. Given the prognostic importance of MR imaging localization, further effort should be made to improve MR imaging protocols for Cushing disease.

Modern imaging in Cushing's disease

Management of Cushing's disease is informed by dedicated imaging of the sella and parasellar regions. Although magnetic resonance imaging (MRI) remains the investigation of choice, a significant proportion (30-50%) of corticotroph tumours are so small as to render MRI indeterminate or negative when using standard clinical sequences. In this context, alternative MR protocols [e.g. 3D gradient (recalled) echo, with acquisition of volumetric data] may allow detection of tumors that have not been previously visualized. The use of hybrid molecular imaging (e.g. ¹¹C-methionine positron emission tomography coregistered with volumetric MRI) has also been proposed as an additional modality for localizing microadenomas.

The importance of MRI quality and reader's experience for detecting an adenoma in Cushing's disease

OBJECTIVE

In Cushing's disease (CD), detection of an adenoma by MRI is challenging. The aim of this study is to compare real-life MRI in the initial diagnostic workup of CD with high-quality MRI performed in a tertiary center for pituitary diseases.

DESIGN AND METHODS

We retrospectively analyzed 139 patients with CD who underwent primary transsphenoidal surgery (TSS) in our department and had both an MRI conducted at a different institution (external MRI; extMRI) and an MRI conducted at our institution (internal MRI; intMRI). Preoperative interpretation of MRI was performed independently by an external radiologist (extRAD), an internal neuroradiologist (intRAD) and a pituitary surgeon (SURG). Intraoperative detection of an adenoma and endocrinological remission provided proof of the true adenoma localization in 105 patients.

RESULTS

Interpretation of extMRI by extRAD and SURG was concordant in only 64% (89/139) of cases, while 74.1% (103/139) concordance was observed for interpretation of intMRI by intRAD and SURG. Based on extMRI, the true localization of the adenoma was correctly predicted in only 46.7% of the patients by extRAD and in 65.7% by SURG. In contrast, the sensitivity to correctly identify the adenoma on intMRI was 80.0% for intRAD and 94.3% for SURG.

CONCLUSION

Both the quality of MRI and the reader's experience are paramount for detection of microadenomas in CD. Every effort should be made to perform high-quality initial MRI according to current standards and to ensure rating by an expert in pituitary imaging.

Pituitary MRI in Cushing's disease - an update

Pituitary MRI is essential in the diagnosis of ACTH-dependent Cushing's syndrome, but its results are inconsistent. The demonstration of a sellar image compatible with the diagnosis of corticotropinoma varies from 40% to 90%, depending on the centre where the imaging is performed. In fact, the expertise of the neuroradiologist, use of a Tesla 3.0 MRI and choice of sequences are fundamental. The T2 and 3D gradient echo sequences after gadolinium injection are the most informative and today allow the detection of macro- and microadenomas in almost all cases. The diagnosis of numerous picoadenomas (<3-4 mm) is more challenging. The 2D and 3D spin echo or delayed T1 SE or FLAIR sequences after gadolinium can be used as a complement or to confirm a suspicious image. Characterization of corticotropinomas remains problematic. However, the correct assessment of so-called incidentalomas by recognizing artifacts, anatomical variants and frequent Rathke's cleft cysts eliminates around 90% of the incidentalomas that mimic pituitary adenomas, as repetitively reported in the literature. For the time being, there is reason to believe that hybrid imaging combining PET and MRI such as 11C-methionine PET coregistered with volumetric MRI will solve the diagnosis of corticotropinomas in the near future.