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Neurology India, Vol. 59, No. 5, September-October, 2011, pp. 696-699 Original Article 3D volumetry comparison using 3T magnetic resonance imaging between normal and adenoma-containing pituitary glands Ernesto Roldan-Valadez1, Ana Cristina Garcia-Ulloa2, Omar Gonzalez-Gutierrez1, Manuel Martinez-Lopez1 1 Magnetic Resonance Unit, Medica Sur Hospital and Clinic Foundation, Mexico City, Mexico PMID: 22019653 Aims: An in vitro method comparison between geometric volume and 3D volumetry to obtain reference data for pituitary volumes in normal pituitary glands (PGs) and PGs containing adenomas. Design: Prospective, transverse, analytical study. Materials and Methods: Forty-eight subjects underwent brain magnetic resonance imaging (MRI) with 3D sequencing for computer-aided volumetry. PG phantom volumes by both methods were compared. Using the best volumetric method, volumes of normal PGs and PGs with adenoma were compared. Statistical analysis used the Bland-Altman method, t-statistics, effect size and linear regression analysis. Results: Method comparison between 3D volumetry and geometric volume revealed a lower bias and precision for 3D volumetry. A total of 27 patients exhibited normal PGs (mean age, 42.07 ± 16.17 years), although length, height, width, geometric volume and 3D volumetry were greater in women than in men. A total of 21 patients exhibited adenomas (mean age 39.62 ± 10.79 years), and length, height, width, geometric volume and 3D volumetry were greater in men than in women, with significant volumetric differences. Age did not influence pituitary volumes on linear regression analysis. Conclusions: Results from the present study showed that 3D volumetry was more accurate than the geometric method. In addition, the upper normal limits of PGs overlapped with lower volume limits during early stage microadenomas. Keywords: 3D volumetry, Bland-Altman plot, geometric volume, magnetic resonance imaging, pituitary adenoma, pituitary volume Introduction Currently, magnetic resonance imaging (MRI) is the method of choice for pituitary assessment. [1] Pituitary volume (PV) measurements are crucial for diagnosis and for assessing the effectiveness of treatment during follow-up. [2] Although previous studies have reported pituitary gland (PG) measurements for various age groups, the majority of these reports focused on pituitary height (PH). Some reports presented PV data using conventional geometric methods, [3],[4],[5] and several studies reported a normal PV range for some age groups (children and post-menopausal women). [6],[7] The aim of the present study was to obtain reference data for PG volumes from a Latin American population. The traditional geometric volume (GV) method was compared with a three-dimensional (3D) volumetry method, which was based on a computer-assisted algorithm. In addition, normal PG limits were compared with limits observed in early-stage PG adenomas. Materials and Methods The experimental design consisted of a prospective, analytical and transversal design. A total of 48 subjects underwent brain MRI for sellar evaluation between June 2010 and October 2010. Subjects were then assigned to two groups: Group 1 = healthy subjects without clinical evidence of PG lesion; Group 2 = patients with clinical evidence of micro- or macroadenoma (physical exam, high hormone levels documented). Informed consent and approval from the Institution's Ethical Committee were obtained. Conventional evaluations of the PG were performed using a 3.0T HDxt GE Signa scanner (General Electric Healthcare, Milwaukee, WI, USA). All images were acquired using an MRI 8-channel high-resolution brain array coil. The standard clinical sequences consisted of coronal T2-weighted fast spin-echo, axial T2-weighted FLAIR, coronal spin echo T1, sagittal T1 and sagittal T2. Dynamic pituitary evaluation was performed with multiphase sequences. To estimate the 3D volumes, coronal T1 SPGR was used following Gadovist® administration (Bayer Schering Pharma, dose 0.1 mmol/kg). PG diameters consisted of maximum distance in millimeters (mm) between two surfaces using calipers provided with the installed software; pituitary height (PH), pituitary length (PL) and pituitary width (PW) were obtained. GV was obtained by multiplying the three major diameters (PH, PL and PW) by a factor of 0.523 (this factor resulted from the sphere volume equation coefficient and cubic volume calculation: (4/3π)(r3 )/(2r) 3 = 3.1416/6 = 0.52). [8] 3D volumetry was obtained using the Volume Rendering tool from the FuncTool software (version 4.3, GE Medical Systems, Milwaukee, WI, USA). A total of 12 jelly MRI phantoms were previously created to represent normal glands and glands with adenomas; each model was weighed, which was converted to an approximate volume (mm 3 ). Statistical analyses were performed using SPSS software version 17.0 (SPSS, Chicago, IL, USA). Statistical significance was indicated by P <0.05. Data presentation was according to guidelines from the American Psychological Association. [9] Bland-Altman analysis [10] was performed to compare GV and 3D volumetry as well as to determine which results best fit the real volumes. Subsequently, PVs were compared between normal PGs and glands with microadenomas. Normal limits were considered to be mean ± two standard deviations. [11] Kolmogorov-Smirnov and Levene tests, effect size measurements (Cohen's d and effect-size correlation r), Pearson΄s correlation coefficient and regression analysis were also performed. [12] Results Normal PG was detected in 27 subjects (mean age 42.07 ± 16.17 years; range, 16-77 years) and PGs with adenoma were observed in 21 patients (mean age 39.62 ± 10.79 years; range 18-61 years). Although the method comparison between GV and 3D volumetry resulted in an excellent correlation with actual phantom volumes (r = 0.969 and r = 0.998, respectively, P < 0.001), mean differences and confidence limits from 3D volumetry were smaller. Therefore, 3D volumetry was selected to analyze PV (bias and precision fell within criteria cut-offs set a priori). In normal PGs, length, height, width, GV and 3D volumetry were greater in women than in men, but the GV difference only was significant [Table - 1]. For PGs with adenoma, length, height, width, GV and 3D volumetry were larger in men, with significant differences observed in volumes [Table - 2]. Volume comparison between normal PG and adenomas resulted in a non-significant 113% increase in pituitary size [Table - 3]. [Figure - 1] shows an example of a normal PG and a PG with adenoma. Linear regression analyses revealed a strong positive correlation between both methods (r = 0.672 in normal PG and r =0.866 in adenomas, P < 0.001). There was no significant association between 3D volumes and age in normal PGs and in PGs with adenoma (P > 0.05). Discussion It is important to understand the wide range of anatomical variations in the sella region and PG when interpreting MR findings that are suspected to be pathological. [13] The present study demonstrated that 3D volumetry offers a lower bias and higher precision than the geometric method. In addition, the upper normal PG limits overlapped with lower volumes limits in early-stage microadenomas. Results demonstrating larger PG volumes in females were consistent with previous studies. [14] The use of one-dimensional measurements (PH), which are still presented in some specialized neuroradiology textbooks, [15] should be replaced by normative 3D volumetry, which is a new standard for pituitary size measurements. References
Copyright 2011 - Neurology India The following images related to this document are available:Photo images[ni11213f1.jpg] [ni11213t2.jpg] [ni11213t1.jpg] [ni11213t3.jpg] |
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