Παρακολούθηση των ασθενών με πρωτοπαθές γαστρικό λέμφωμα με μαγνητική τομογραφία

Abstract

37 consecutive patients (23 men and 14 women) with histologically verified gastric lymphoma were prospectively enrolled and evaluated with an upper abdominal MR scan. Patients' age ranged between 31 to 86 years (median 58,7 years). Clinical and MRI follow-up was conducted every three to twelve months. Informed consent was obtained from all patients. Images were obtained on a superconducting 1.5T MR unit (Philips Gyroscan ACS, The Netherlands) in all patients. Initially, unenhanced fast field-echo T1 weighted axial images on a 256x128 matrix were obtained with respiratory ordered phase-encoding and superior and inferior saturation pulses. The slice thickness was 7-10mm with a 2-3mm interslice gap.T2 TSE images with fat suppression were acquired. Gadopentetate dimeglumine (Magnevist, Schering AG, Germany) or gadodiamide (Omniscan, Nycomed Amersham, England) was administered at a dose of 0.1mmol/kg as a rapid hand-injected bolus, prior to the enhanced images. These consisted ofT1 weighted images (early [1 min] and intermediate [3 min] post gadolinium images). T1 weighed sequence with fat suppression to reduce artifacts and delayed post contrast images (5 min) were also performed. For optimum quality these images were obtained during breath suspension. Patients fasted 6 hours prior to MRI examination. The oral contrast medium administered, was 750 ml 2% oral barium sulphate for the stomach distension and opacification. Patients were instructed to drink 500 ml 30 minutes before the examination and 250ml immediately before the MR examination. The MR studies were evaluated according to their potential to detect the presence of abnormal mural thickening or enhancement. Patients were divided into three categories, according to the imaging pattern of the gastric lymphoma observed: 1. Flat superficial lesions which may produce focal thickening of the gastric wall with or without ulceration, 2. Polypoid pattern with intraluminal protrusion into the gastric lumen, and 3. Diffuse underlying infiltration with longitudinal extension, confined or not to the submucosa and lamina propria. The specific location and extent of the tumor, as well as the possible enlargement of regional lymph nodes were addressed. The results of the MRI examinations were correlated with histopathological findings from endoscopy. Patients were staged according to the Lugano staging system. A total of 72 follow-up MR examinations were performed in 37 patients. Extraserosal invasion was depicted in 2 patients. The signal intensity of gastric MALT lymphoma was intermediate on T1-weighted images, homogeneous in small tumors and heterogeneous in larger masses. After intravenous contrast administration the mucosa enhances intensely, whereas tumor infiltration demonstrates moderate enhancement. Normal gastric wall anatomy is depicted with contrast-enhanced MRI. The mucosal-submucosal layer enhances substantially, while the muscular layers show minimal enhancement. The three-zone appearance of NHL is composed of high-intensity mucosa, intermediate submucosal tumor infiltration and a low-intensity proper muscular layer. When the latter is not visualized, tumor infiltration of the muscular layer has probably occurred. The three-zone appearance may be proved useful in differentiating a submucosal tumor from a mucosal lesion. Enhancement is most intense on images obtained 1-5 minutes after intravenous injection, which reflects the retention of contrast in the interstitial space and increased extracellular fluid that is a feature of tumors or inflammation. Enhanced images enabled us to distinguish between a submucosal neoplastic process from a mucosal one. The optimal sequence, in our study, was T1 contrast-enhanced. An advantage of MRI is that extraserosal extension can be evaluated. A smooth low signal intensity band observed in out-of-phase gradient echo imaging is caused by a signal void caused by a chemical shift artifact and a signal loss caused by a phase cancellation artifact between fat and water. Disruption of the band is detected in extraserosal invasion by neoplastic gastric disease. Even though EUS is effective in evaluating gastric wall pathology it cannot detect pathology around the gastric cavity. Spiral CT in addition to the detection of gastric wall lesions is effective in determining extraluminal disease. The benefits of MRI include multiplanar images which are useful in bypassing the partial volume effect which is unavoidable with axial CT sections, multiple types of parameters, which increase the detection rate of lesions and lack of ionizing radiation, which is an important factor considering that long term follow-up is clearly indicated. In this study, we have shown the potential of MRI in the follow-up of patients with gastric lymphoma.

Έχουν εξεταστεί 37 ασθενείς με διαγνωσμένο γαστρικό λέμφωμα (ηλικίας 31 έως 86 ετών). Η παρακολούθηση των ασθενών γίνεται μετά από κάθε κύκλο θεραπείας (3-12 μήνες). Είκοσι δύο ασθενείς έχουν προσέλθει για επανέλεγχο μετά τον πρώτο κύκλο θεραπείας. Το πρωτόκολλο περιλαμβάνει τη χορήγηση βαρίου per os (2% barium sulphate) για τη διάταση και σκιαγράφηση του στομάχου. Η απεικόνιση γίνεται σε μαγνητικό τομογράφο 1,5Τ και περιλαμβάνει τις ακόλουθες τεχνικές: T1, Τ2, καταστολή λίπους προ και μετά την ενδοφλέβια έγχυση σκιαγραφικού. Επίσης, γίνονται καθυστερημένες λήψεις εικόνων με καταστολή λίπους, μετά την ενδοφλέβια έγχυση παραμαγνητικής σκιογόνου ουσίας. Οι λήψεις γίνονται σε τρία επίπεδα (εγκάρσιο, οβελιαίο και στεφανιαίο επίπεδο). Οι ασθενείς χωρίζονται καταρχάς σε τρεις κατηγορίες: low grade και high grade και ενδιάμεσης κακοήθειας και ταξινομούνται ανάλογα με τον απεικονιστικό τύπο του λεμφώματος: Για περιγραφικούς λόγους ο στόμαχος χωρίστηκε σε θόλο, σώμα και άντρο και έγινε καταγραφή της βλάβης (όπου υφίσταται) βάσει του παραπάνω διαχωρισμού. Επίσης, έγινε μέτρηση του πάχους και του μήκους της αλλοίωσης και σημειώθηκε η ύπαρξη διογκωμένων λεμφαδένων. Η σταδιοποίηση των ασθενών γίνεται βάσει του συστήματος Lugano. Έγινε συσχέτιση των ευρημάτων της μαγνητικής τομογραφίας με τα ιστολογικά αποτελέσματα της ενδοσκόπησης σε διάστημα 3-12 μηνών, μετά τους κύκλους θεραπείας των ασθενών. Αρχικά, η μαγνητική τομογραφία εντόπισε τοιχωματική αλλοίωση του στομάχου σε 31 από τους 37 ασθενείς, 22 με MALT λέμφωμα, 8 με DLCL και 7 με μικτούς όγκους. Σε 6 ασθενείς ο όγκος εξορμάται από το σώμα του στομάχου. Σε 7 ασθενείς η αλλοίωση εντοπίζεται στο θόλο, ενώ σε 5 ασθενείς η εξεργασία εντοπίζεται κυρίως στο πυλωρικό άντρο, ενώ σε 12 ασθενείς συμμετέχει και το πυλωρικό άντρο. Η πιο ευαίσθητη ακολουθία για ανάδειξη βλάβης στο τοίχωμα του στομάχου είναι η Τ1 ακολουθία μετά ενδοφλέβια έγχυση σκιαγραφικού.