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Magnetic resonance imaging (MRI) features of 11 surgically resected pelvic tailgut cysts were analyzed with reference to histopathologic and clinical data. Homogeneity, size, location, signal intensity, appearance and presence of septa and/or nodules and/or peripheral rim and involvement of surrounding structures were studied. Histological examination demonstrated 11 tailgut cysts (TGC), including one infected TGC and one TGC with a component of adenocarcinoma. Lesions (3-8 cm in diameter) were exclusively or partly retrorectal in all cases but one, with an extension down the anal canal in five cases. Lesions were multicystic in all patients but one. On T1-weighted MR images, all cystic lesions contained at least one hyperintense cyst. The peripheral rim of the cystic lesion was regular and non or moderately enhancing in all cases but the two complicated TGC. Nodular peripheral rim and irregular septa were seen in the degenerated TGC. Marked enhancement of the peripheral structures was noted in the two complicated TGC. Pelvic MRI is a valuable tool in the preoperative evaluation of TGC.

RADIOLOGIE ET IMAGERIE MEDICALE : Genito-urinaire - Gyneco-obstetricale - Mammaire - 34-530-A-10

Initial staging of lung cancer is essential to determine the appropriate therapeutic strategy. 18F-FDG PET is currently considered to be the gold standard. 99mTc bisphonate bone scintigraphy has long been indicated to search for bone metastases but it is not know whether this exploration adds further information after an 18F-FDG PET scan. In order to answer this question, two observers unaware of the clinical situation reread PET scans and bone scintigraphies and results compared with other imaging findings. Between February 2001 and March 2004, 39 patients (13F, 26M, 62 +/- 11 yr) underwent 18FFDG PET and bone scintigraphy (mean interval 17 +/- 17 d). When the two explorations agreed for the diagnosis of bone extension, we considered that bone scintigraphy added nothing. When the two explorations were in disagreement, the other imaging examinations, the clinical features and laboratory results during the five-month minimal follow-up were used to establish the reference diagnosis. 18F-FDG PET and bone scintigraphy were in agreement in 29 patients (74%) with positive results in 12 (31%) and negative results in 17 (43%). The two explorations were in disagreement in 10 patients (26%). Among the five disagreement cases with positive bone scintigraphy and no bone anomaly on the 18F-FDG PET, the anomalies were benign and explained by clinical features (3 patients) or were not confirmed by the clinical course and laboratory results (2 patients). Among the 5 cases with a bone anomaly on the 18F FDG PET, no metastasis could be identified during clinical follow-up. Bone scintigraphy does not enable identification of any bone metastases which were not recognized on the PET scan and therefore should not be performed systematically. Using a computed tomography scan with the 18F-FDG PET could further limit the contribution of bone scintigraphy by providing more precision concerning foci identified on the PET scan.

Initial staging of lung cancer is essential to determine the appropriate therapeutic strategy. 18F-FDG PET is currently considered to be the gold standard. 99mTc bisphonate bone scintigraphy has long been indicated to search for bone metastases but it is not know whether this exploration adds further information after an 18F-FDG PET scan. In order to answer this question, two observers unaware of the clinical situation reread PET scans and bone scintigraphies and results compared with other imaging findings. Between February 2001 and March 2004, 39 patients (13F, 26M, 62 +/- 11 yr) underwent 18FFDG PET and bone scintigraphy (mean interval 17 +/- 17 d). When the two explorations agreed for the diagnosis of bone extension, we considered that bone scintigraphy added nothing. When the two explorations were in disagreement, the other imaging examinations, the clinical features and laboratory results during the five-month minimal follow-up were used to establish the reference diagnosis. 18F-FDG PET and bone scintigraphy were in agreement in 29 patients (74%) with positive results in 12 (31%) and negative results in 17 (43%). The two explorations were in disagreement in 10 patients (26%). Among the five disagreement cases with positive bone scintigraphy and no bone anomaly on the 18F-FDG PET, the anomalies were benign and explained by clinical features (3 patients) or were not confirmed by the clinical course and laboratory results (2 patients). Among the 5 cases with a bone anomaly on the 18F FDG PET, no metastasis could be identified during clinical follow-up. Bone scintigraphy does not enable identification of any bone metastases which were not recognized on the PET scan and therefore should not be performed systematically. Using a computed tomography scan with the 18F-FDG PET could further limit the contribution of bone scintigraphy by providing more precision concerning foci identified on the PET scan.

Objectifs Decrire les aspects IRM des hamartomes retrorectaux. Materiels et methodes Etude retrospective a partir de dossiers d’hamartomes retrorectaux entre 2001 et 2006. Dix patients ont eu une IRM pelvienne avec antenne corps (Tl, T2, Tl apres injection de gadolinium). Tous les patients ont ete operes. Les donnees anatomo-pathologiques et bacteriologiques ont ete correlees aux donnees IRM. Resultats Trois hommes et sept femmes, âges de 25 a 67 ans (mediane, 38 ans). Les lesions (2 a 8 cm) etaient retro et laterorectales juste au-dessus du plan des releveurs de l’anus (n = 7) ou dans la fosse ischio-anale (n = 3), toutes au contact du rectum deplace anterolateralement (n = 5). Elles etaient multiloculees ou s’accompagnant de « kystes filles » (n = 9), en hypersignal Tl total ou partiel (n = 7). Une paroi fibreuse reguliere (hyposignal T1/T2 : n = 5, prise de contraste : n = 2) etait presente dans 5 cas. La paroi etait tres epaisse et/ ou irreguliere avec une forte prise de contraste (n = 2) et une infiltra tion de la graisse perilesionnelle (kyste degenere, kyste abcede). Dans un cas, le kyste etait tres heterogene avec des vegetations. Conclusion L’hamartome retrorectal doit etre suspecte devant une lesion multikystique comportant une composante en hypersignal Tl. Certain signes IRM doivent faire evoquer une complication.

A 26-year-old man with a history of major beta-thalassemia was referred to our center for suspicion of femoral bone sepsis. He was treated 12 years ago for femoral bone sepsis that occurred after epiphysis trauma and was scheduled for further surgery. He underwent both F-18 FDG coincidence detection-emission tomography (CDET) and Tc-99m HDP bone scintigraphy in our department. As expected because of beta-thalassemia, bone scintigraphy showed both increased diffuse uptake in all metaphyses and epiphyses and elevated renal activity. FDG-CDET images showed increased diffuse uptake in the bone marrow. The pattern of FDG uptake by the bone marrow in beta-thalassemia should be recognized because of the risk of false positive results.

Objectifs Le but de cette etude retrospective est de decrire et d’illustrer en IRM les lesions kystiques retrorectales. Materiels et methodes Etude retrospective realisee a partir de donnees recueillies sur 5 ans a partir de dossiers d’IRM pelvienne. Resultats Les dossiers recueillis illustrent la variete de la pathologie kystique retrorectale en IRM, dominee par les anomalies kystiques de developpement. Les cas regroupent des kystes retrorectaux (hamartomes retrorectaux, kystes epidermiques retrorectaux, kystes dermoides retrorectaux, kystes inflammatoires) et leur diagnostic differentiel (abces, adenocarcinome mucineux primitif ou recidivant, meningocele a developpement presacre, duplication rectocolique, chordome, schwanomme, GIST). Conclusion L’IRM permet une excellente analyse de la pathologie retrorectale qui est dominee par les anomalies kystiques de developpement.