Year : 2001 | Volume
: 11 | Issue : 4 | Page : 185--190
Value of dynamic MRI imaging in pituitary adenomas
IK Indrajit, N Chidambaranathan, K Sundar, I Ahmed
Department of Radiology and Imaging, Off Greams Lane, Chennai, 600006, India
I K Indrajit
Apollo Hospital, Dept of Radiology and Imaging, Off Greams Lane, Chennai 600 006
Objectives : MRI has proven to be the best imaging modality in the evaluation of pituitary tumors. Dynamic Imaging is technically a new tool, which has emerged with lot of promise in the evaluation of pituitary adenomas, particularly in accurate delineation of those microadenomas with no contour abnormality and in differentiating residual/recurrent adenoma from surrounding post operative tissue. Dynamic MR imaging is not only useful in the evaluation of pituitary microadenomas but has an equally important role in the assessment of macroadenoma as well. This study analyses and reviews the value of dynamic MR Imaging in pituitary adenomas and postoperative pituitary tumors. Materials and Methods : A prospective MR Study was undertaken in twenty-five consecutive patients with suspected pituitary adenomatous lesions. These patients were subjected to dynamic MR imaging at our Department from Jan 1997 to Dec 1998. The study was performed on a 0.5T super conducting MR imaging system with Fast Spin echo technique. Gadodiamide (0.1 mmol/Kg) was administered over sixty seconds by hand injection. Dynamic coronal images were obtained simultaneously from three different portions of the gland. Fifteen images were obtained from each of the three portions at an interval of twenty to thirty seconds between the images. Result : Dynamic MRI was performed in nineteen patients with microadenoma and six cases of macroadenoma. Dynamic MRI study was of diagnostic value in comparison with routine contrast MRI in eleven of the nineteen patients. Dynamic study did not add to the diagnosis and was merely of confirmatory value in remaining eight patients. Dynamic MRI study was used to identify the optimal time for delineation of the adenomatous tumor, by virtue view of the simultaneous differential contrast enhancement patterns between normal pituitary gland and adenoma. Further the enhancement pattern of the normal pituitary gland, the adenomatous nodule and the optimal delineation were individually assessed. This evaluation revealed the average time in seconds for onset of enhancement and the peak enhancement of normal pituitary gland were 43.1 and 111.9 seconds respectively. In comparison the pituitary adenomatous nodules exhibited an average time of 105.8 seconds for onset of enhancement and 188.1 seconds for peak enhancement. The average time in seconds for optimal tumor delineation was 93.9 seconds. Conclusion : Dynamic MR Imaging has emerged as a technically refined tool in the evaluation of pituitary adenomas. The key questions in evaluation of pituitary adenomas include the presence or absence of a tumor, the number, the location of adenoma nodule, the invasive effects on adjacent structures and the post therapy status of adenoma. Clearly, dynamic MR Imaging is the foremost imaging modality answering these vital questions in patients with pituitary adenomas.
|How to cite this article:|
Indrajit I K, Chidambaranathan N, Sundar K, Ahmed I. Value of dynamic MRI imaging in pituitary adenomas.Indian J Radiol Imaging 2001;11:185-190
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Indrajit I K, Chidambaranathan N, Sundar K, Ahmed I. Value of dynamic MRI imaging in pituitary adenomas. Indian J Radiol Imaging [serial online] 2001 [cited 2020 Feb 22 ];11:185-190
Available from: http://www.ijri.org/text.asp?2001/11/4/185/28399
MRI has proven to be the best imaging modality in the evaluation of pituitary tumors. Dynamic MR Imaging has emerged as a promising tool in the evaluation of pituitary adenomas, particularly in accurate delineation of those microadenomas with no contour abnormality, and in differentiating residual / recurrent adenoma from surrounding post operative tissue ,, . Dynamic MR imaging is not only useful in the evaluation of pituitary microadenomas but has an equally important role in the assessment of macroadenoma as well ,,, .
Dynamic MRI technique captures a temporal phase in which there is a high level of contrast between tumor and the normal pituitary gland. This fleeting moment lasting seconds aids in the optimal delineation of the tumor  .
Material and Methods
In this study, pituitary studies were performed with a 0.5 Tesla machine (Philips T5 Gyroscan, Holland) using a circularly polarized head coil. The criteria for inclusion of the patients in the study included those patients that were clinically referred for pituitary studies with Gadodiamide (Omniscan) for the investigation of possible endocrinopathy, or neurological deficit referable to sellar and parasellar regions, or follow up of previously documented pituitary tumors and had undergone Bromocriptine and / or surgical therapy. Twenty-five patients were evaluated in this study. Eighteen of the twenty-five patients had microadenomas, one patient presented with pituitary hyperplasia and the rest had a macroadenoma [Table 1].
Initially, the study was commenced with a pre-contrast protocol. In this protocol, T1 and T2 spin echo saggital and coronal T1 and T2 weighted images were obtained. These pre-contrast images were utilized primarily to identify the size of the gland, for characterizing the type of adenoma and for selecting the optimal coronal sections while planning the dynamic MRI.
Following the routine scans, dynamic scan menu was initialized and scanning commenced with T1 TSE weighted images obtained in the coronal plane using thin three mm sections. The FOV was maintained at 20-25 cm. Fifteen dynamic sequential images in five fixed sections in the coronal plane over a period of 180 seconds were obtained during slow intravenous injection of IV Gadodiamide.
In all patients, the dose of Gadodiamide was preloaded in a 10 ml syringe and was injected intravenously over a period of fifteen seconds with a 21 gauge butterfly needle placed in the antecubital fossa. Saline flushing with 5 ml was performed before and after injection of intravenous Gadodiamide.
The sequence protocol of 15 dynamic scan of three slices in the coronal plane using a TSE sequence (TR =540 msec: TE = 13 msec ) was strictly applied. The objective was to obtain the most spatially detailed images of the anterior lobe of the pituitary gland in the coronal plane, with the best possible signal noise ratio in the shortest period.
Dynamic MRI study was performed in eighteen cases of microadenoma and six cases of macroadenoma. The sex distribution and details of the type of adenoma are depicted in [Table 1]. This technique was of diagnostic value in comparison with routine contrast MRI in eleven of the eighteen cases of microadenoma. In this group, the routine T1and T2 MRI scans in coronal and sagittal plane were not contributory. Conventional, non-dynamic contrast technique did not reveal the adenomatous nodule clearly. Dynamic MRI study was of immense value since it not merely delineated the tumor but also offered useful information on other important imaging issues such as number of lesions, location of lesions, and relationship with adjacent structures such as cavernous sinus and infundibulum and differential enhancement patterns. The technique was found to be useful particularly in cases of microadenoma with no contour abnormality [Figure 2]a&b [Table 3]. In the remaining seven patients with microadenoma, dynamic study did not add to the diagnosis and was merely of confirmatory value. The morphological appearances of microadenoma are given in [Table 2]. The smallest tumor nodule picked up by this technique in our study was 2 mm in size [Figure 3]a,b.
Further, dynamic MRI study was employed to identify the optimal time for delineation of the adenomatous tumor, in view of the simultaneous differential enhancement patterns, while administering intravenous contrast, between normal pituitary gland and adenomatous nodule [Figure 2]a,b & [Figure 4]. To objectively analyze this differential enhancement pattern the normal pituitary gland, the adenomatous nodule and the optimal delineation were individually assessed. The evaluation of enhancement patterns revealed that the average time in seconds for onset enhancement and the peak enhancement of normal pituitary gland was 43.1 and 111.9 seconds respectively. In comparison, the pituitary adenomatous nodules revealed an average time of 105.8 seconds for onset of enhancement and 188.1 seconds for peak enhancement. The average time in seconds for optimal tumor delineation was 93.9 seconds.
Dynamic MRI revealed pituitary hyperplasia in one patient. The patient had presented with clinical features of suspected adenoma and abnormal endocrine status. However, dynamic MRI showed absence of any adenomatous nodule and enhancement appearances compatible with pituitary hyperplasia [Figure 5]a,b.
Dynamic MRI was performed in six cases of macroadenoma [Table 4]. The utility of dynamic MRI in macroadenoma is twofold, namely the accurate delineation of normal pituitary gland - tumor demarcation and assessment of cavernous sinus involvement, both of which are important from the surgical point of view. In our study, the demarcation between the normal gland and tumor was accurately depicted in three of six patients [Figure 6]a & b. In the remaining three, delineation was not made clearly and was attributed to its large size. The involvement of cavernous sinus was identified in four patients, which was surgically proven [Figure 7]a,b. In the remaining two patients, the adenoma was accurately identified as not invading the cavernous sinus.
Dynamic MRI in pituitary gland has proven to be the best imaging tool in the evaluation of pituitary adenomas. This technique is gaining further importance from the compelling clinical and imaging need for accurately delineating adenomatous nodule from the normal adenohypophysis ,, . Further, in patients with macroadenoma, the accurate information about the location of adenoma and normal pituitary gland is vital to the surgeon, to determine the methods of treatment and the approach during surgery  .
Historically, MRI techniques in pituitary adenomas have witnessed rapid evolution ranging from the onset of non-contrast MRI studies in late 80's to introduction of contrast MRI scans in early nineties. In recent times, it has unfolded further with the introduction of dynamic MRI in mid-nineties. The early non-contrast MRI studies were primarily considered in a comparative role, more so as an alternative imaging modality to CT scan. MRI was found to be superior to CT scan in the evaluation of pituitary adenomas except in the demonstration of the bony sellar erosion and tumor calcification  . The ability of the MRI to detect microadenoma as a focal lesion and the imaging appearance of macroadenoma has been described ,  . Encouraging progress was made during the early 90's in MR technical refinements and in the application of a variety of MRI sequences in pituitary microadenoma  .
Contrast MRI using gadolinium played an important role at the turn of the decade. Its role in detection and characterization of microadenoma has been well described  . Essentially, microadenoma was identified as a focal hypointense lesion showing relative lack of enhancement compared with normal adenohypophysis on post gadolinium scans ,, . Other morphological features such as infundibular displacement, focal gland convexity and sellar floor abnormality were characterized by various authors , ,, . Further, this technique was introduced to evaluate patients with macroadenoma ,  . In patients with macroadenoma, it has been used for delineation of adenomatous tumors from normal pituitary gland and for cavernous sinus invasion ,,,,  . In our study, it was found that the evaluation of macroadenoma by dynamic MRI had more relevance for cavernous sinus invasion than for delineation of adenomatous tumor from normal pituitary gland. This is probably related to the size of the macroadenoma tumors
Dynamic MRI emerged as a new imaging tool in the mid 90's because of evolution of the technical advances and refinements in MR imaging. This technique was equally spurred by stimulating original studies of normal pituitary gland and pituitary adenomas , , , .
Miky et al were the first authors to apply dynamic studies in microadenoma  . Subsequently, Sakomoto et al performed dynamic studies in microadenoma and macroadenoma. Seven to ten images were obtained every 20 to 30 seconds while injecting gadolinium. The earliest contrast enhancement of normal structures was seen in the infundibulum and posterior lobe of pituitary gland at 20 seconds, followed by gradual contrast enhancement of the anterior lobe from the junction of the infundibulum to the peripheral portion of the anterior lobe within 80 seconds after gadolinium injection. The peak enhancement of pituitary adenomas occurred at 60 to 200 seconds usually after the most marked enhancements of the normal pituitary gland  . Yuh et al describe pituitary adenomas that enhance earlier than anterior lobe contrary to the findings of Sakomato. This was attributed to pituitary adenomas having a direct arterial blood supply similar to that of posterior pituitary lobe  . In our study, we did not encounter any case displaying early enhancement of pituitary microadenoma. Tien et al described the expected sequence of enhancement of various portion of the pituitary gland on dynamic MR  . Due to the unique and separate blood supply to the pars nervosa, infundibulum and pars distalis by the inferior hypophyseal artery, superior hypophyseal artery and portal system respectively, enhancement occurs in an expected sequence. This sequence commences with enhancement of the pars nervosa first, followed by the infundibulum and later spreading throughout the pars distalis.
Hayashi et al conducted dynamic study in 14 patients with pituitary adenomas  . In the study, Gadodiamide-DTPA was slowly injected within 90 seconds, providing seven to nine dynamic images during 350 seconds from the start of injection. The study revealed that average time to reach the maximum signal intensity was 170 seconds in adenoma and 156 seconds in normal pituitary gland. The most remarkable contrast between adenoma and normal tissue was obtained from the fourth to eighth images, which occurred between 145 to 300 seconds after the initiation of injection.
In our study, the evaluation of enhancement pattern revealed range 24 to 119 seconds and 72 to 180 seconds for onset and for peak of enhancement of the normal pituitary gland. The average time was 43.1 seconds and 111.9 seconds for onset and for peak of enhancement of the normal pituitary gland. In comparison, the range of time in seconds for onset of enhancement and time for peak enhancement for pituitary adenoma were 52 to 228 seconds and 90 to 256 seconds respectively. The average time was 105.8 seconds and 188.1 seconds for onset and peak of enhancement of the normal pituitary gland. Optimal time range for delineation of pituitary adenoma from normal pituitary gland was derived to be 50 to 139 seconds with the ideal time for delineation at 93.9 seconds.
The key question in evaluation of pituitary adenomas includes the presence or absence of a tumor, the location, the invasive effect on adjacent structure and the post therapy status of adenoma. Dynamic MRI has emerged as a foremost imaging modality answering these crucial questions.
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