Comparison of L1 and L5 Bands GNSS Signals Acquisition.

Nowadays, civil Global Navigation Satellite System (GNSS) signals are available in both L1 and L5 bands. A receiver does not need to acquire independently the signals in both bands coming from a same satellite, since their carrier Doppler and code delay are closely related. Therefore, the question of which one to acquire first rises naturally. Although the common thought would tell the L1 band signals which are narrowband, an accurate comparison has never been done, and the decision is not as easy as it seems. Indeed, L5 band signals have several advantages such as stronger power, lower carrier Doppler, or a pilot channel, unlike the Global Positioning System (GPS) L1 C/A signal. The goal of this paper is therefore to compare the acquisition of L1 and L5 bands signals (GPS L1 C/A and L5, Galileo E1 and E5a/b) to determine which one is more complex and by which factor, in terms of processing time and memory, considering hardware receivers and the parallel code search. The results show that overall the L5 band signals are more complex to acquire, but it depends strongly on the conditions. The E5 signal is always more complex to acquire than E1, while the L5 signal can have a complexity close to the L1 C/A in some cases. Moreover, precise assistance providing accurate Doppler could significantly reduce the L5 complexity below the L1 complexity.

Standalone GPS L1 C/A Receiver for Lunar Missions.

Global Navigation Satellite Systems (GNSSs) were originally introduced to provide positioning and timing services for terrestrial Earth users. However, space users increasingly rely on GNSS for spacecraft navigation and other science applications at several different altitudes from the Earth surface, in Low Earth Orbit (LEO), Medium Earth Orbit (MEO), Geostationary Earth Orbit (GEO), and feasibility studies have proved that GNSS signals can even be tracked at Moon altitude. Despite this, space remains a challenging operational environment, particularly on the way from the Earth to the Moon, characterized by weaker signals with wider gain variability, larger dynamic ranges resulting in higher Doppler and Doppler rates and critically low satellite signal availability. Following our previous studies, this paper describes the proof of concept "WeakHEO" receiver; a GPS L1 C/A receiver we developed in our laboratory specifically for lunar missions. The paper also assesses the performance of the receiver in two representative portions of an Earth Moon Transfer Orbit (MTO). The receiver was connected to our GNSS Spirent simulator in order to collect real-time hardware-in-the-loop observations, and then processed by the navigation module. This demonstrates the feasibility, using current technology, of effectively exploiting GNSS signals for navigation in a MTO.

Normalized GNSS interference pattern technique for altimetry.

It is well known that reflected signals from Global Navigation Satellite Systems (GNSS) can be used for altimetry applications, such as monitoring of water levels and determining snow height. Due to the interference of these reflected signals and the motion of satellites in space, the signal-to-noise ratio (SNR) measured at the receiver slowly oscillates. The oscillation rate is proportional to the change in the propagation path difference between the direct and reflected signals, which depends on the satellite elevation angle. Assuming a known receiver position, it is possible to compute the distance between the antenna and the surface of reflection from the measured oscillation rate. This technique is usually known as the interference pattern technique (IPT). In this paper, we propose to normalize the measurements in order to derive an alternative model of the SNR variations. From this model, we define a maximum likelihood estimate of the antenna height that reduces the estimation time to a fraction of one period of the SNR variation. We also derive the Cramér-Rao lower bound for the IPT and use it to assess the sensitivity of different parameters to the estimation of the antenna height. Finally, we propose an experimental framework, and we use it to assess our approach with real GPS L1 C/A signals.

[Measurement of tumour response to cancer treatment: morphologic imaging role]. / Evaluation de la réponse thérapeutique en cancérologie: le rôle de l'imagerie morphologique.

New forms of cancer chemotherapy are tested in therapeutic trials (phase I, phase II or phase III) while chemotherapeutic agents whose efficacy has already been demonstrated are used, in routine clinical practice, in the context of protocols. The overall survival rate is the best objective parameter of efficacy of the treatments tested, but this parameter is obtained too late, as the effect on the tumour must be determined as soon as possible in order to institute another treatment if necessary. Tumour response, or objective response, is based on changes in the number and size of measurable primary or secondary tumour "targets". These parameters are obtained more rapidly than survival data, but their reliability is highly dependent on the quality of comparative clinical and especially radiological measurements of tumour targets. Medical imaging plays an essential role in these assessments. The absence of standardized techniques, poor selection of targets and inaccurate measurements can bias the results, particularly those of therapeutic trials. In view of the economic, scientific and patient-related stakes involved, a very rigorous approach is essential, directly implicating the responsibility of radiologists performing assessment examinations. The World Health Organization (WHO) guidelines defining the method of measurement of solid tumours and response criteria are no longer adapted to technical progress in imaging. Recently these guidelines have been updated and a new set of criteria has been proposed by the Response Evaluation Criteria in Solid Tumors (RECIST) Group, taking into account progress in imaging. They remain based on measurement of the size of the target lesion. The use of this single criterion of size to evaluate response to treatment needs to be discussed in the light of new technologies able to provide information on tumour composition, metabolism or neovascularization, modifications of which reflect response to treatment before a reduction in tumour volume can be detected.

Mixed nonseminomatous germ cell tumor presenting as a subcutaneous tissue mass.

Extragonadal germ cell tumors most commonly arise in the midline of the retroperitoneum or the mediastinum. Primary tumors involving the skin are very rare. Only one case of malignant primary germ cell tumor located in the skin has been reported. We present the case of a 44-year-old white man with a primary subcutaneous mixed nonseminomatous germ cell tumor. This man had a long-lasting subcutaneous lump of the breast, which became painful. Surgery revealed 3 juxtaposed nodules. Microscopic examination showed a mixed germ cell tumor with a 90% immature teratoma component and a 10% embryonal carcinoma component. Testicular ultrasound and computed tomography of the chest, abdomen, pelvis, and brain were normal. Serum human chorionic gonadotrophin, beta-human chorionic gonadotrophin, alpha-fetoprotein, and lactate dehydrogenase were within normal ranges. A further surgical excision was performed. The patient is presently alive with no evidence of disease after a follow-up of 7 years. Review of the literature indicates that primary cutaneous extragonadal germ cell tumors usually occur as cutaneous or subcutaneous solitary nodules or as ulcerated lesions. They mainly consist of mature teratomas in children. Only 2 cases have been reported in adults.

Gastrointestinal stromal tumors treated with imatinib: monitoring response with contrast-enhanced sonography.

OBJECTIVE: The purpose of this study was to evaluate contrast-enhanced Doppler sonography with perfusion software as a predictor of early tumor response to imatinib (Glivec) in c-kit-positive gastrointestinal stromal tumors (GISTs). SUBJECTS AND METHODS: Thirty patients (59 tumors) with metastases or a recurrence from a GIST were prospectively included in a single-center imaging trial. Contrast-enhanced Doppler sonography was performed with an Aplio scanner the day before (day-1) starting oral treatment (400 mg) and at days 1, 7, 14, 60, 90, and 6 months, 9 months, and 1 year. The percentage of contrast uptake (Levovist or Sonovue) before treatment and at the different stages of follow-up was evaluated by two radiologists. Digitized quantification was performed using Photoshop software. To define the benchmark standard, all patients were rated as responders or nonresponders at 2 and 6 months by a board consisting of oncologists and radiologists who had all clinical and imaging data at their disposal. Changes in the percentage of contrast uptake at each sonographic examination were compared statistically. RESULTS: A total of 185 examinations were performed. Forty-four lesions in 24 patients were completely evaluated at 2 months, and 29 lesions in 15 patients were completely evaluated at 6 months. Initial contrast uptake at day 1 was predictive of the future response. A strong correlation was found between the decline in tumor contrast uptake at days 7 and 14 and tumor response (p < 10(-4)). CONCLUSION: Contrast-enhanced Doppler sonography is a noninvasive imaging technique that allows the early prediction of tumor response in c-kit-positive GIST treated with Glivec.

To predict progression-free survival and overall survival in metastatic renal cancer treated with sorafenib: pilot study using dynamic contrast-enhanced Doppler ultrasound.

INTRODUCTION: The objective of this study was to evaluate dynamic contrast-enhanced Doppler ultrasound (DCE-US) with perfusion software (Vascular Recognition Imaging) and contrast agent injection as a predictor of tumour response, progression-free survival (PFS) and overall survival (OS). PATIENTS AND METHODS: Thirty patients with a metastatic renal cell carcinoma (RCC) already enrolled in a double-blind randomised study were evaluated. Examinations were performed at baseline, and after 3 and 6 weeks on sorafenib or a placebo in patients with tumour targets that were accessible to DCE-US. RESULTS: A total of 85 examinations were performed, 30 at baseline, 28 at 3 weeks and 27 at 6 weeks. The combination of a decrease in contrast uptake exceeding 10% and stability or a decrease in tumour volume allowed us to discriminate seven good responders and 20 poor responders at 3 weeks. There was a statistically significant difference in PFS (p=10(-4)) and OS (p=10(-4)) between good and poor responders. CONCLUSION: DCE-US is a new noninvasive imaging technique which might be an effective tool for evaluating antiangiogenic drugs in renal cancer.

Prognostic value of angiogenesis evaluated with high-frequency and colour Doppler sonography for preoperative assessment of primary cutaneous melanomas: correlation with recurrence after a 5 year follow-up period.

OBJECTIVE: To study the value of high-frequency sonography (HFS) and colour Doppler sonography (CDS) in evaluating the 5 year metastatic potential of primary cutaneous melanomas (CM). MATERIALS AND METHODS: 111 CM were studied before surgical resection and 107 were depicted on HFS. The maximal HFS thickness was measured and compared with the Breslow thickness. A CDS study was performed in each tumour. RESULTS: HFS thickness ranged from 0.26 to 8.0 mm and Breslow thickness from 0.15 to 8.0 mm. HFS and Breslow thickness correlated strongly (r > 0.93). Intratumour vessels were depicted in 43 of the 107 CM, of which 40 were thicker than 2 mm. The median follow-up was 61 months and 27 patients developed relapses. In the univariate analyses, neovascularization visualized with CDS, sonographic thickness and the Breslow thickness were significantly linked to relapses (p < 0.0001), as were lymph node status and ulceration (p = 0.007 and 0.004). CONCLUSION: Vascularization was observed mainly in thick primary melanoma. A median follow-up of 5 years showed the prognostic value of angiogenesis evaluated by CDS.

Doppler US with perfusion software and contrast medium injection in the early evaluation of radiofrequency in breast cancer recurrences: a prospective phase II study.

INTRODUCTION: The aim of this study was to determine the efficacy of Doppler ultrasonography (US) with perfusion software and contrast agent injection (DUPC) during radiofrequency (RF) treatment of local recurrent breast cancer. MATERIALS AND METHODS: Ten patients were included in this monocentric prospective phase II study. DUPC was performed for each patient the day before treatment and immediately after RF in the operating suite. RF ablation was followed by a total mastectomy. The results of DUPC were compared to the histologic analysis of the operative specimen. RESULTS: Before RF, contrast uptake exceeded 70% in 5 lesions and was less than 50% in 5 lesions. Immediately after RF, no vascularization was detected with DUPC in 9 of the 10 lesions. Contrast uptake attaining 30% was depicted in the remaining lesion. At histologic analysis, complete tumour destruction was confirmed in 7 of the 10 operative specimens. CONCLUSION: In this study, DUPC is highly efficient and better adapted for the confirmation of tumour destruction in tumours that are hypervascularised before RF compared to hypovascularised lesions.

[Interest of color Doppler ultrasonography to evaluate a new anti-angiogenic treatment with thalidomide in metastatic renal cell carcinoma]. / Intérêt de l'échographie-Doppler pour évaluer l'efficacité d'un traitement anti-angiogénique par thalidomide dans le cancer du rein métastatique.

PURPOSE: To assess the effectiveness of Doppler Ultrasonography (DUS) in evaluating the anti-angiogenic effect of thalidomide. MATERIALS AND METHODS: [corrected] Forty patients with metastases of cancer of the kidney were included in a phase II therapeutic trial. Twenty eight had tumor targets which could be evaluated by DUS. Before treatment, the volume was studied in 59 tumors and the vascularity in 54 tumors. During treatment, comparative DUS examinations were performed every 6 weeks. RESULTS: Before treatment, the mean tumor volume was 41 cm3, more than 10 vessels were visible in 57% of them. A correlation was noted between the size of the tumors and the degree of vascularity. A stabilisation of tumor volume correlated with a decrease in the number of vessels and an increase in vascularity preceding an increase in tumor volume were also observed. CONCLUSION: DUS is effective in assessing tumour size and vascularity.

High-frequency sonography and color Doppler in the management of pigmented skin lesions.

We aimed to evaluate high-frequency sonography (HFS) coupled with color Doppler in the management of pigmented skin lesions (PSL). HFS examination was performed in 111 patients with 130 PSL. A color Doppler study was conducted in 107 lesions, to assess intralesional vascularization. Imaging findings were compared with histologic diagnosis. In the case of melanoma, sonographic and histologic maximum thickness measurements were compared. HFS showed 114 of the 130 lesions. Among the detected lesions, HFS alone provided 100% sensitivity and 100% specificity in the distinction of melanoma/nevi from other lesions, and 100% sensitivity and 32% specificity in the distinction of melanomas from nonmelanoma lesions. Sonographic and histologic measurement of melanoma thickness strongly correlated (r > 0.96, p < 0.001). Color Doppler detection of intralesional vessels had a 100% specificity and 34% sensitivity in the distinction of melanomas from other PSL. HFS coupled with color Doppler is a simple, reliable tool for PSL management.

Hepatic focal nodular hyperplasia in children previously treated for a solid tumor. Incidence, risk factors, and outcome.

BACKGROUND: The detection of hepatic nodules, particularly in patients treated for a previous malignancy, raises a diagnostic dilemma. Focal nodular hyperplasia (FNH) of the liver is an uncommon, benign tumor in children and must be differentiated from malignant hepatic lesions. The etiology of FNH is obscure, and its pathogenesis is poorly understood. FNH may be a reaction to localized vascular abnormalities and circulatory disturbances. The goal of the current study was to identify risk factors for the occurrence of FNH in children who had received prior treatment for a malignant tumor. METHODS: The current retrospective study examined 14 cases of FNH in pediatric patients who previously had been treated for a malignancy. Diagnosis was based on clinical and radiologic findings and was proven histologically in four cases. RESULTS: FNH lesions were discovered by chance during routine examination in 78% of patients. The incidence of FNH was particularly high in the current series (0.45%) compared with the incidence in the general pediatric population. High doses of alkylating agents (e.g., busulfan or melphalan), venoocclusive disease, and liver radiotherapy may be responsible for injury to the vascular endothelium and subsequent localized circulatory disturbances. FNH is characterized by the absence of complications after its detection; therefore, only close follow-up is recommended. CONCLUSIONS: FNH appears to be a late complication of an iatrogenic vascular disease in children with a history of malignancy.

Prognostic value of doppler-ultrasonography in hepatic veno-occlusive disease.

BACKGROUND: Currently, the severity of veno-occlusive disease (VOD) is graded retrospectively on the basis of the evolution of clinical and biological criteria. The objective of this study was to describe a noninvasive method capable of predicting the severity of this disease at the time of the diagnosis. METHODS: Seventy-one children who developed VOD after intensive myeloablative therapy with busulfan before hematopoietic stem cell transplantation were included in this study. Sixty-four patients underwent baseline ultrasonography (US) and Doppler examination before transplantation. All patients had posttransplantation US and Doppler examinations at the time of the clinical and biological diagnosis of VOD. Seven US morphological criteria and seven Doppler criteria were studied that yielded three individual scores: a US score, a Doppler score, and a total Doppler ultrasonography (DUS) score. RESULTS: In the univariate analysis, three of 7 US criteria, three of 7 Doppler criteria, and the three scores were correlated with the severity of VOD after transplantation and at the time of the diagnosis. In the multivariate analysis, two US criteria (splenomegaly and ascites) and one Doppler criterion (flow recorded in para-umbilical vein) were correlated with the severity of VOD. The multivariate analysis of the pooled US and Doppler criteria showed that the flow recorded in the para-umbilical vein was the only criterion significantly associated with the grade of VOD (P=0.0001). All patients with a US-Doppler score >9 developed grade 2 or 3 VOD. CONCLUSION: Postgraft US and Doppler examinations have a prognostic significance according to the grade of VOD.

Prognostic value of angiogenesis evaluated with high-frequency and color Doppler sonography for preoperative assessment of melanomas.

OBJECTIVE: The aim of our study was to confirm the value of high-frequency and color Doppler sonography in evaluating the metastatic potential of melanomas. SUBJECTS AND METHODS: Sixty-nine histologically proven melanomas in 67 patients were prospectively studied before surgical resection. A morphologic study was performed with a 20-MHz probe. The maximal thickness of tumors was measured and compared with the Breslow index. A color Doppler sonographic analysis of neovascularization was performed with a 13-MHz probe to depict intratumoral vessels. RESULTS: Of the 69 melanomas, 65 were depicted on sonography. Tumor thickness ranged from 0.26 to 8.0 mm as measured by sonography and from 0.15 to 8.0 mm according to the Breslow index. Sonographic measurements correlated strongly with the Breslow index (r > 0.96). Surgical reexcision was necessary in 33 tumors with a Breslow index exceeding 1 mm, but reexcision could have been avoided in 31 of these cases had the initial surgical planning been based on high-frequency sonographic measurements. Among the 62 patients studied with color Doppler sonography, intratumoral vessels were depicted on color Doppler sonography in 21 melanomas, all of which were thicker than 2 mm. The median follow-up was 40 months. Eleven patients developed metastases, and all except one had a vascularized melanoma. In the univariate analyses, neovascularization visualized with sonography and the Breslow index were both significantly linked to the occurrence of metastases (p < 0.0001). In the multivariate Cox proportional hazards regression analysis, neovascularization was the only significant parameter. CONCLUSION: This study confirms that prognostic value of angiogenesis evaluated with color Doppler sonography could be used to identify melanomas with a high metastatic potential.