High-resolution ISAR imaging of maneuvering targets by means of the range instantaneous Doppler technique: modeling and performance analysis.

Very high resolution inverse synthetic aperture radar (ISAR) imaging of maneuvering targets is a complicated task. In fact, the conventional range Doppler (RD) ISAR technique does not work properly when target motions generate terms higher than the first order in the phase of the received signal relative to each scatterer. This effect typically happens when at least one of these situations occur: (1) very high resolution images are required; (2) the target maneuvers; and (3) the target undergoes significant angular motions (roll, pitch, and yaw). A novel ISAR technique, named range instantaneous Doppler (RID), has been proposed for the reconstruction of very high resolution images of maneuvering targets. In this paper, we analytically show that the RID technique works properly when high-resolution ISAR images are required of maneuvering and/or rolling, pitching, and yawing targets; we also quantify the performance improvement of the RID technique with respect to the RD technique. The problem is tackled from an analytical point of view. First, we define a new model of the ISAR received signal that is valid for maneuvering targets, then we derive and compare the analytical expression of the point spread function (PSF) for the two techniques. Furthermore, we perform a statistical analysis to evaluate the improvement of the RID technique versus the RD technique in terms of spatial resolution. Finally, we prove the effectiveness of the RID technique by simulating the imaging process for two different targets: (1) a ship that undergoes roll, pitch and yaw motions and (2) a fast maneuvering airplane.

A new fast method for the reconstruction of 2-D microwave images of rotating objects.

In this paper, the problem of microwave imaging of rotating objects is approached from a digital signal processing point of view. Attention is focused on the reconstruction of the two-dimensional (2-D) image of an object obtained by processing complex samples of the continuous wave (CW) signal return received for different object aspect angles covering a 2pi total variation. The effects of a polar sampling of the Fourier transform (FT) of the target reflectivity function on the impulse response of the imaging system are analyzed. A criterion for the choice of the angular sampling interval in order to control the image blurring is given. Finally, a new and fast digital signal processing method for image reconstruction is proposed. This method reconstructs high resolution images of rotating targets illuminated by a CW electromagnetic signal or by a large bandwidth transmitted signal. This algorithm is suitable for processing wideband received signal of targets observed for a large variation of the viewing angle, so it is very attractive for the reconstruction of very high spatial resolution target images in SAR/ISAR systems. To show the performance of the method we finally present and discuss the results obtained by applying the proposed technique on simulated and experimental data.

[Immediate post-operative enteral nutrition]. / La nutrizione enterale post-operatoria immediata.

Patients with cancer of the upper digestive tract may present with malnutrition, which may cause immunodepression and an increased rate of postoperative complications. In this study we describe the rationale and the feasibility of immediate postoperative enteral nutrition (NEPI) and evaluate its effectiveness for the nutritional support of patients undergoing surgery of the upper digestive tract. We studied 46 patients undergoing the following procedures: total gastrectomy (n = 22); oesophageal resection (n = 12); duodenocephalopancreasectomy (n = 12). NEPI was started on postoperative day 0 with a polymeric diet (calories: 53% as CHO, 22% as proteins, 25% as lipids) aiming at a calorie intake of 25 Kcal/Kg/day by postoperative day 4. It was possible to administer 24 Kcal/kg/day with the enteral diet from the 4th to the 10th postoperative day. Oral intake was resumed on average on postoperative day 13, and the mean hospital stay was 27 +/- 17 days. Tolerance of NEPI was good in most patients: only 5 patients (11%) interrupted the enteral nutrition. The mean postoperative weight loss was 3.7%. The rate of septic complications was 27%; mortality was nil. The surgical procedures caused a transient and reversible acute-phase decrease of nutritional and immunological parameters in the early postoperative period. However the NEPI preserved the nutritional status postoperatively as shown by the lack of significant changes in the nutritional indices at 10-14 days after surgery, as compared with baseline. In summary, we documented that NEPI can be started from postoperative day 0 with good intestinal tolerance, allowing adequate nutritional support, after extensive surgical procedures on the upper digestive tract.

Pre-operative nutritional support and tumour cell kinetics in malnourished patients with gastric cancer.

Stimulation of tumour growth by intensive exogenous nutrient administration could be a major clinical problem when nutritional support is provided in malnourished cancer patients. Nutritional repletion has been clearly shown to stimulate tumour growth in animal models but not in humans. The purpose of this prospective study was to evaluate the effect of pre-operative nutritional support on the proliferative characteristics of gastric tumour cells evaluated by 3H-thymidine (3HT) incorporation and flow cytometry (FCM). Thirty-three malnourished patients with advanced gastric cancer were allocated randomly into two groups receiving different types of nutritional support during the interval between endoscopy and operation: parenteral and/or enteral hyperalimentation (Group 1), and oral alimentation as possible or peripheral fluids (Group 2). In 16 patients with diploid tumours the percentage of 3HT labelled cells and of cells in S+G(2)M phase did not differ between the multiple samples taken from the mucosal surface of the neoplasia. Tumour samples showed higher mean values of cycling cells than the surrounding normal tissue. Both methods (3HT - FCM) demonstrate that tumour cell proliferation is not enhanced following a prolonged period of pre-operative artificial nutrition.