An ultra-compact leaky-integrate-and-fire model for building spiking neural networks.

We introduce an ultra-compact electronic circuit that realizes the leaky-integrate-and-fire model of artificial neurons. Our circuit has only three active devices, two transistors and a silicon controlled rectifier (SCR). We demonstrate the implementation of biologically realistic features, such as spike-frequency adaptation, a refractory period and voltage modulation of spiking rate. All characteristic times can be controlled by the resistive parameters of the circuit. We built the circuit with out-of-the-shelf components and demonstrate that our ultra-compact neuron is a modular block that can be associated to build multi-layer deep neural networks. We also argue that our circuit has low power requirements, as it is normally off except during spike generation. Finally, we discuss the ultimate ultra-compact limit, which may be achieved by further replacing the SCR circuit with Mott materials.

Memristive and neuromorphic behavior in a Li(x)CoO2 nanobattery.

The phenomenon of resistive switching (RS), which was initially linked to non-volatile resistive memory applications, has recently also been associated with the concept of memristors, whose adjustable multilevel resistance characteristics open up unforeseen perspectives in cognitive computing. Herein, we demonstrate that the resistance states of Li(x)CoO2 thin film-based metal-insulator-metal (MIM) solid-state cells can be tuned by sequential programming voltage pulses, and that these resistance states are dramatically dependent on the pulses input rate, hence emulating biological synapse plasticity. In addition, we identify the underlying electrochemical processes of RS in our MIM cells, which also reveal a nanobattery-like behavior, leading to the generation of electrical signals that bring an unprecedented new dimension to the connection between memristors and neuromorphic systems. Therefore, these LixCoO2-based MIM devices allow for a combination of possibilities, offering new perspectives of usage in nanoelectronics and bio-inspired neuromorphic circuits.

[Choroidal metastasis from follicular thyroid carcinoma: a rare case]. / Métastase choroïdienne d'un carcinome vésiculaire thyroïdien : un cas rare.

INTRODUCTION: Choroidal metastases are, with melanoma, the most frequent malignant eye neoplasms. Breast carcinoma for women and lung carcinoma for men most commonly metastasize to the eye. We report a rare case of choroidal metastasis from follicular thyroid carcinoma. OBSERVATION: A 75-year-old man, with metastatic follicular thyroid carcinoma, presented a decline in visual acuity of the left eye lasting one month. The best corrected visual acuity was 3/10 in his left eye. Biomicroscopic examination of the anterior segment did not reveal anything abnormal. Funduscopic examination showed an amelanotic choroidal mass located at the posterior pole with serous retinal detachment. Tomoscintigraphy with computed tomography confirmed the thyroid origin by uptake of radioiodine in the choroidal mass. External radiotherapy was then proposed. DISCUSSION: Although it is exceptional, diagnosis of choroidal metastases should be considered in any decline in visual acuity in patients with thyroid cancer. The treatment is difficult because metastases from thyroid cancer are very poorly sensitive to radiotherapy and chemotherapy.

Comparison of seven serum thyroglobulin assays in the follow-up of papillary and follicular thyroid cancer patients.

BACKGROUND: Serum thyroglobulin (Tg) is the marker of differentiated thyroid cancer after initial treatment and TSH stimulation increases its sensitivity for the diagnosis of recurrent disease. AIM: The goal of the study is to compare the diagnostic values of seven methods for serum Tg measurement for detecting recurrent disease both during L-T4 treatment and after TSH stimulation. METHODS: Thyroid cancer patients who had no evidence of persistent disease after initial treatment (total thyroidectomy and radioiodine ablation) were studied at 3 months on L-T4 treatment (Tg1) and then at 9-12 months after withdrawal or recombinant human TSH stimulation (Tg2). Sera with anti-Tg antibodies or with an abnormal recovery test result were excluded from Tg analysis with the corresponding assay. The results of serum Tg determination were compared to the clinical status of the patient at the end of follow-up. RESULTS: Thirty recurrences were detected among 944 patients. A control 131I total body scan had a low sensitivity, a low specificity, and a low clinical impact. Assuming a common cutoff for all Tg assays at 0.9 ng/ml, sensitivity ranged from 19-40% and 68-76% and specificity ranged from 92-97% and 81-91% for Tg 1 and Tg2, respectively. Using assays with a functional sensitivity at 0.2-0.3 ng/ml, sensitivity was 54-63% and specificity was 89% for Tg1. Using the two methods with a lowest functional sensitivity at 0.02 and 0.11 ng/ml resulted in a higher sensitivity for Tg1 (81% and 78%), but at the expense of a loss of specificity (42% and 63%); finally, for these two methods, using an optimized functional sensitivity according to receiver operating characteristic curves at 0.22 and 0.27 ng/ml resulted in a sensitivity at 65% and specificity at 85-87% for Tg1. CONCLUSION: Using an assay with a lower functional sensitivity may give an earlier indication of the presence of Tg in the serum on L-T4 treatment and may be used to study the trend in serum Tg without performing any TSH stimulation. Serum Tg determination obtained after TSH stimulation still permits a more reliable assessment of cure and patient's reassurance.

[Diffuse uptake of brown fat on computed-tomography coupled positron emission tomoscintigraphy (PET-CT) for the exploration of extra-adrenal pheochromocytoma]. / Hyperfixation diffuse de la graisse brune à la tomoscintigraphie par émission de positons couplée à la tomodensitométrie (TEP-TDM) dans l'exploration d'un phéochromocytome extra surrénalien.

We report an observation of strong bilateral uptake on a PET-CT scan compatible with activation of brown adipose tissue in a patient with extra-adrenal pheochromocytoma. A 42-year-old man was hospitalized for hypersudation together with weight loss and palpitations. Heart rate was 120 bpm and fasting blood glucose 1.36 g/l. Endocrine explorations revealed elevated serum chromogranine which reached 517 ng/ml (19-38). The norepinephrine level reached 49.7 nmol/l (<4.00) and urinary norepinephrine and normetanephrine levels reached 13977 nmol/24h (<414) and 32 micromol/24h (0.4-2.5) respectively. The thoraco-abdominal and pelvic scan showed a 6 cm diameter paraaortic hypervascularized mass with an infiltrative lesion of both perirenal area and mediastinal tissue without adenopathies. The abdominal MRI revealed the mass with a low intensity signal in T1 and a slight high intensity signal in T2. MIBG and octreoscan scintigraphies were negative. 18F-DG PET showed intensed uptake in the tumor mass together with intense, diffuse and bilateral uptake above and below the diaphragm. The mass was resected. Histological examination of the surgical specimen confirmed the diagnosis of extra-adrenal pheochromocytoma with an index of 13% cellular proliferation without cell atypia. There was a hypervascularization with small islets of brown adipose tissue in the perirenal fat. Both plasmatic and urinary catecholamines decreased to the normal range after the operation and PET-scan normalized. Bilateral spread of the radiotracer uptake was probably due to brown adipose tissue activation by excessive sympathetic stimulation induced by catecholamines released by the tumor.

Sentinel node biopsy in vulvar malignancies: a preliminary feasibility study.

Sentinel lymph node biopsies (SLNB) were investigated in 8 cases (6 squamous cell carcinomas, 2 melanomas) of vulvar malignancy. The sentinel node was detected by patent blue dye injection (1 case), pre operative lymphoscintigraphy with intra-operative gamma hand-held probe (2 cases), and combined techniques (5 cases). The procedure was successful in all cases but one (1 invasive squamous cell carcinoma) in which there was medial groin recurrence at 6 months. Nodal invasion was observed in only one case and was confined to the sentinel node. No specific morbidity related to the SLNB procedure occurred. SLNB appears to be a feasible and promising technique, however, requiring further evaluation before being considered as a reliable method to spare inguinofemoral lymphadenectomy in early-stage patients free of sentinel node metastasis, or to be substituted in screening elderly clinically node-negative females.

The pitfalls of planar three-phase bone scintigraphy in nontraumatic hip avascular osteonecrosis.

PURPOSE: This study documented the previously reported lower sensitivity of routine planar three-phase bone scintigraphy (BS) performed using a high-resolution parallel-hole collimator compared with MRI to diagnose nontraumatic avascular necrosis of the hip (AVN). METHODS: Six observers reviewed 143 bone scintigrams obtained in patients with nontraumatic hip pain (n = 120) or a control group (n = 23). All patients had a standard radiograph and MRI within 2 months of the BS. Of 280 hips, 148 (53%) were painful on the day of the examination. The osteonecrosis group (AVN) consisted of 93 instances of AVN in 58 patients. Although it departs from the clinical situation, this method evaluated the intrinsic performance of the imaging method. The data were analyzed using a receiver operating characteristic method. RESULTS: For the six observers, the A(z) values were 0.65, 0.67, 0.66, 0.67, 0.73, and 0.79, respectively, and 0.66, 0.71, 0.75, 0.81, 0.81, 0.82, and 0.84 after removing hip diseases other than AVN through data manipulation. Bone marrow edema, as seen on MRI, was the most frequently reported misleading sign in false-positive diagnoses, especially in the early or late phases of the disease. False-negative diagnoses misclassified the scans as "asymptomatic hips" in 28 of 30 cases. Twenty-two of 30 scans appeared normal, but these AVN lesions were small (<25%) and were discovered by chance on MRIs that displayed bilateral involvement associated with radiographic evidence (stage 0 or 1). Thirteen of 20 patients were followed for 3 or more years, and only one worsened. CONCLUSIONS: BS is not indicated to diagnose possible contralateral AVN if the hip is asymptomatic. This study emphasizes the results from the literature; if indicated, a radionuclide hip investigation requires the use of a pin-hole collimator, a SPECT study with scatter correction and iterative reconstruction algorithms, or both.

[Effect of preoperative administration of Lugol's solution on thyroid blood flow in hyperthyroidism]. / Effet de l'administration pré-opératoire du soluté de Lugol sur le débit sanguin thyroïdien dans l'hyperthyroïdie.

A study of 50 patients with hyperthyroidism was conducted to evaluate the effect of preoperative administration of Lugol's iodine solution on thyroid blood flow. Highly significant reductions in diameter, time-averaged velocity, and volume flow of the superior thyroid artery were demonstrated after administration of Lugol's solution. The Duplex ultrasound scanning used in this study is a noninvasive, inexpensive, accurate, and reproducible technique suitable for analysis of thyroid blood flow in hyperthyroidism. On the basis of current ultrasonographic results and low postoperative morbidity in patients, Lugol's solution is well tolerated and may be recommended for use before thyroidectomy, especially for diffuse toxic goiters and Graves disease.

[Hypothyroidism following radiosurgical treatment of cancers of the hypopharynx]. / Hypothyroïdie après traitement radiochirurgical des cancers de l'hypopharynx.

In a series of 224 patients treated between 1980 and 1992 for hypopharyngeal carcinoma by surgery and post postoperative radiotherapy we found an overall 54% incidence of elevated TSH levels. Decreased FT4 levels were associated in about one-third of the patients. When thyroidectomy was performed, 71% of the patients developed thyroid dysfunction. Most TSH abnormalities (45%) occurred within two years of treatment. Nevertheless, long-term followup is indicated since those complications may be delayed. Hormonal replacement therapy is recommended for patients with elevated TSH.

Osteogenic anaplastic carcinoma of the thyroid.

An unusual osteogenic anaplastic carcinoma of the thyroid developed in a 68-year-old man and showed follicular and osteosarcomatous components. Seven months after surgery and 70 mCi 131I treatment, a local tumor recurrence was found and showed an intense uptake of 99mTc-MDP on the bone scan. After a second operation, pathologic and immunostaining analysis revealed no more thyroid carcinoma but only osteosarcomatous cells. Chemotherapy was ineffective and the patient died with diffuse pulmonary metastases 26 months after the diagnosis. The importance of osteogenic sarcomatous differentiation is proven by the bone scan. Osteosarcoma of the thyroid is a rare but well known tumor. Usually these tumors do not contain any cells originating from the thyroid epithelium and only comprise sarcomatous components. Ten cases of undifferentiated carcinoma of thyroid origin with osteogenic component have been reported. These tumors have been recently included in undifferentiated carcinomas in the second edition of the WHO classification. The evolution and pathologic findings favor the hypothesis of a transdifferentiation of the thyroid cell into osteogenic cells.