[Positron emission tomography in the management of cervix cancer patients]

Since its introduction in clinical practice in the 1990's, positron emission tomography (PET), usually with (18)F-fluoro-2-deoxy-D-glucose ((18)F-FDG), has become an important imaging modality in patients with cancer. For cervix carcinoma, FDG-PET is significantly more accurate than computed tomography (CT) and is recommended for loco-regional lymph node and extrapelvic staging. The metabolic dimension of the technique provides additional prognostic information. Ongoing studies now concentrate on more advanced clinical applications, such as the planning of radiotherapy, the response evaluation after the induction of therapy, the early detection of recurrence. Technical innovations, such as PET cameras with better spatial resolution and hybrid positron emission tomography/computed tomography (PET-CT), available now on the whole territory, provide both anatomic and metabolic information in the same procedure. From the point of view of biological metabolism, new radiopharmaceutical probes are being developed. Those hold promise for future refinements in this field. This article reviews the current applications of FDG-PET in patients with cervix cancer.

High-Grade Lymphoma of the Bladder Visualized on PET

F-18 FDG PET is used for the staging of many cancers. One of its limits is the analysis of the pelvis and the urinary tract because of physiological radiotracer excretion. We report a rare case of an 82-year-old woman in whom intravenous administration of diuretics (furosemide) allowed the identification of a primary diffuse large B-cell lymphoma of the bladder wall. This pharmaceutical increases urine flow and, therefore, reduces the concentration of radiotracer in the urinary tract, improving the visualization of pelvic or urinary tumors. Furosemide administration is an easy, safe, and noninvasive method, even in case of renal insufficiency. Newer PET cameras with high-performance crystals allow rapid acquisitions and improve the tolerance of an examination with diuretic injection. The 3-dimensional reconstruction of images in new PET cameras reduces the occurrence of hyperactive bladder artifacts. The present case illustrates the advantages of furosemide in a rare pathologic entity.

Patient set-up using portal images: 2D/2D image registration using mutual information

OBJECTIVE

Conformal radiation therapy requires accurate patient set-up for each fraction delivery. Electronic portal imaging devices allow the acquisition of portal images just before and even during dose delivery. However, the quantitative interpretation of these images in determining and correcting the patient's position remains uncertain, and automated methods are therefore being developed. Such methods must be usable for the different radiation therapy techniques. They must be robust and as automated as possible for use in clinical routines. This work was undertaken to establish the feasibility of 2D/2D registration for portal/portal and portal/simulator images in radiotherapy.

MATERIALS AND METHODS

This paper describes an automated method based on the combination of calibration algorithms and pixel-based registration algorithms. We present experiments with the different imaging techniques, some of which use a phantom with and without a gold standard. Preliminary results obtained using patient data are also presented and discussed.

RESULTS

The results obtained with a phantom demonstrated that this automated method for 2D/2D registration is fast, accurate, and robust, even in the case of blurred images for small treatment fields.

CONCLUSIONS

Mutual information is a feasible method for 2D/2D portal/portal and portal/simulator image registration in radiotherapy.