ABSTRACT
PURPOSE: To investigate the effect of transcytolemmal water exchange on the dynamic contrast-enhanced (DCE) T(1)-weighted MRI of human squamous cell carcinomas of the head and neck (HNSCC). MATERIALS AND METHODS: Nine patients with HNSCC nodal metastasis underwent pretreatment DCE-MRI with a temporal resolution of 2.5 seconds and a spatial resolution of 1 mm x 1 mm x 5 mm at 1.5T. We used two pharmacokinetic models for data analysis: generalized kinetic model (GKM) without considering transcytolemmal water exchange and the shutter-speed model (SSM), based on a two-site exchange model for transcytolemmal water exchange. The results were compared in three subgroups of voxels in the tumor depending on the level of contrast enhancement. RESULTS: SSM was found to be a better fit for more than 75% of pixels of all subjects (P < 0.01) in terms of residual size and Bayesian information criterion (BIC). For all three subgroups based on the contrast enhancement, the median K trans values of SSM were 42% to 55% higher than those of GKM and the median upsilon e values of SSM were 116% to 176% larger than those of GKM. The median K trans and upsilon e of two models were found significantly different (P < 0.01). The median tau i measured by SSM were from 211 to 364 msec. CONCLUSION: The effect of transcytolemmal water exchange is an important factor that needs to be incorporated for adequate modeling of contrast enhancement dynamics measured by MRI of HNSCC.
Subject(s)
Body Water/metabolism , Carcinoma, Squamous Cell/metabolism , Contrast Media/pharmacokinetics , Gadolinium DTPA/pharmacokinetics , Head and Neck Neoplasms/metabolism , Magnetic Resonance Imaging/methods , Bayes Theorem , Chi-Square Distribution , Humans , Lymphatic Metastasis , MovementABSTRACT
BACKGROUND AND PURPOSE: If tumor volumes are to be used for evaluating responses to treatment and long-term outcomes of patients with primary pharyngeal carcinomas, the reproducibility of these measurements must be established. We determined the intraobserver variability of MR imaging-based volume measurements of these cancers and their regional metastases. METHODS: We used an interactive computer program (IDL) that enables the extraction of tumor volumes from 3D MR data to obtain 202 volume measurements in 17 patients with pharyngeal carcinoma (two to five time points each). The primary cancer and largest nodal mass were manually outlined on every T2-weighted image of each MR study. The same neuroradiologist reanalyzed this MR dataset 2-41 weeks later. Measurement error and percentage measurement error (intraobserver variability) were determined. Differences in intraobserver variability between primary lesions and nodes, as well as between stages of treatment were tested with a Wilcoxon rank sum test. RESULTS: The mean and median percentage measurement errors, respectively, were 13% and 12% (range, 0-53%; 95% CI: 10%, 16%) for primary tumors and 9% and 7% (range, 0-37%; 95% CI: 7%, 12%) for nodal metastases. The difference in the percentage measurement error between primary lesions and cervical nodes approached statistical significance (P =.07). Differences in the variation of volume measurements based on the stage of therapy were significant (P =.01). CONCLUSION: Our results suggest that MR imaging-based tumor volumes are reliably reproducible. Such measurements may be important in predicting patient outcome, determining appropriate therapy, and conducting patient follow-up.
