Noisy fluctuation of heart rate indicates cardiovascular system instability.

Heart rate spontaneously fluctuates despite homeostatic regulatory mechanisms to stabilize it. Harmonic and fractal fluctuations have been described. Non-harmonic non-fractal fluctuation has not been studied because it is usually thought that it is caused by apparatus noise. We hypothesized that this fluctuation looking like apparatus noise (that we call "noisy fluctuation") is linked to challenged blood pressure stabilization and not to apparatus noise. We assessed noisy fluctuation by quantifying the small and fastest beat-to-beat fluctuation of RR-interval by means of spectral analysis (Nyquist power of heart rate variability: nyHRV) after filtering out its fractal component. We observed nyHRV in healthy supine subjects and in patients with vasovagal symptoms. We challenged stabilization of blood pressure by upright posture (by means of a head-up tilt table test). Head-up position on the tilt table dramatically decreased nyHRV (0.128 ± 0.063 vs. 0.004 ± 0.002, p < 0.01) in healthy subjects (n = 12). Head-up position also decreased nyHRV in patients without vasovagal symptoms (n = 24; 0.220 ± 0.058 vs. 0.034 ± 0.015, p < 0.05), but not in patients with vasovagal symptoms during a head-up tilt table test (age and sex paired, 0.103 ± 0.041 vs. 0.122 ± 0.069, not significant). Heart rate variability includes a physiological non-harmonic non-fractal noisy fluctuation. This noisy fluctuation indicates low engagement of regulatory mechanisms because it disappears when the cardiovascular system is challenged (upright posture). It also indicates cardiovascular instability because it does not disappear in upright patients before vasovagal syncope, a transient failure of cardiovascular regulation.

New reconstruction algorithm, distance dependent exact, with reduced statistical α error, dedicated to emission tomography using a collimator with large and long holes.

SPECT (single photon emission computerized tomography) is physically one of the worst medical imaging modalities. Despite a considerable and still increasing medical impact, its spatial resolution (beyond 1 cm) and its sensitivity (less than 10(-4)) are both awful. This situation is mainly due to the use of a thin parallel hole collimator. In addition the application of the unfitted radon-transform worsens the figure.

Parathyroid scintigraphy findings in chronic kidney disease patients with recurrent hyperparathyroidism.

BACKGROUND: Parathyroidectomy (PTX), either subtotal or total with forearm autografting, is a well-established treatment for refractory renal hyperparathyroidism (RHPT). However, 20-30% of patients develop persistent or recurrent disease. Obtaining accurate localization before reoperation is difficult. PATIENTS AND METHODS: The study group comprised 21 consecutive adult patients (18 undergoing haemodialysis and 3 with a renal graft) imaged using (99m)Tc-sestamibi/(123)I subtraction scintigraphy. Of the 21 patients, 12 had undergone one previous PTX and the other 9 between two and four parathyroid operations. All patients had symptoms and signs of severe RHPT. The mean serum PTH level was 1,142 pg/ml. (99m)Tc-Sestamibi and (123)I images were recorded simultaneously. Imaging views comprised a planar view of the neck and mediastinum, followed by a magnified pinhole view over the thyroid bed area. If parathyroid ectopy was detected, SPECT or SPECT-CT was performed. The forearm was imaged in case of autograft. RESULTS: Parathyroid scintigraphy was negative in one patient and positive in the other 20 (sensitivity 95.2%). One patient had uptake corresponding to two unresected parathyroid glands. Recurrence at the site of the partially resected gland or autograft was seen in 11 patients. However, six of them had a second (99m)Tc-sestamibi focus corresponding to a supernumerary parathyroid gland. Seven other patients had a supernumerary parathyroid gland as the sole cause of relapse. Three of the supernumerary glands showed major ectopy (intrathyroidal, low mediastinal, undescended within the vagus nerve). One patient had parathyromatosis with multiple parathyroid nodules scattered over the left side of the neck. Reoperation was possible in 13 patients, with no false-positive findings. CONCLUSION: Many patients referred with the hypothesis of hyperplasia of a subtotally resected parathyroid gland or autograft were found to harbour a supernumerary parathyroid gland missed at the initial surgery.

Uncommon breast tumor attenuation artifact on radionuclide ventriculography.

A 39-year-old woman with locally advanced left breast cancer (T4 N0 M0) underwent equilibrium radionuclide ventriculography for baseline assessment of left ventricular function before neoadjuvant chemotherapy. The left ventricular ejection fraction was 76% at 75 beats per minute, without localized wall motion abnormality. In the best septal left anterior oblique projection, a large photopenic "halo" surrounded the cardiac chambers, mimicking a pericardial effusion. In fact, this aspect resulted from an attenuation artifact by a large left breast tumor, as demonstrated by FDG-PET/CT imaging.

Prognostic value of an increase in the serum thyroglobulin level at the time of the first ablative radioiodine treatment in patients with differentiated thyroid cancer.

PURPOSE: The aim of this study was to assess the prognostic factors for treatment efficacy, and in particular the increase in serum thyroglobulin (Tg) level at the time of the first ablative radioiodine treatment, in patients with differentiated thyroid carcinoma (DTC). METHODS: A retrospective chart review was performed on 407 patients treated for DTC by total thyroidectomy and (131)I ablation between 1995 and 2002, and examined 5-12 months later with diagnostic (131)I whole-body scan and serum Tg measurement after thyroid hormone treatment withdrawal. At the time of the ablative radioiodine treatment, serum Tg level was determined just before (131)I administration (TgD0) and 5 days later (TgD5); Tg variation was expressed as the ratio TgD5/TgD0. At the first post-ablation follow-up examination, unsuccessful ablation was defined by a Tg level > or =2 ng/ml and/or abnormal (131)I uptake. RESULTS: Ablation was unsuccessful in 51 patients. Univariate analysis showed high TgD0 level, low TgD5/TgD0 ratio extrathyroidal invasion, (131)I uptake in the neck (excluding the thyroid bed) during the ablative treatment and distant metastases to be significantly associated with unsuccessful ablation. On logistic multivariate analysis, TgD0 level <5 ng/ml and TgD5/TgD0 ratio > or =20 were independently associated with successful ablation. A receiver operating characteristic curve analysis determined that a TgD5/TgD0 ratio greater than 20 had a 97% positive predictive value for successful ablation. When both TgD0 and TgD5/TgD0 ratio were considered, that is, TgD0 <5 ng/ml or TgD0 > or =5 ng/ml but TgD5/TgD0 ratio >20, ablation was unsuccessful in only 12/301 patients. CONCLUSION: Our data show that the TgD5/TgD0 ratio may be used as a new prognostic indicator of (131)I treatment efficacy in patients with DTC.

Functioning pulmonary metastases of thyroid cancer: does radioiodine influence the prognosis?

Functioning pulmonary metastases are the most common distant lesions of differentiated thyroid cancer. About 50% of patients with such metastases die within 10 years. The impact of iodine-131 therapy is controversial. In this study we examined: (1) the early diagnostic value of post-surgery (131)I ablation for lung invasion and (2) the survival of patients receiving periodic (131)I therapy. Between January 1970 and December 1995 we provided initial treatment for 509 patients with thyroid cancer. Most of them (74%) underwent total thyroidectomy and (131)I ablation. Functioning pulmonary metastases occurred in 20 patients. All these patients received periodic (131)I therapy for as long as (131)I uptake persisted. Additional therapy consisted of lung surgery in three patients and local treatment of bone lesions in four patients. Follow-up data were recorded up to December 2001. Functioning pulmonary metastases occurred late in one patient, and were visible on the post-surgery (131)I therapy scan in the other 19 patients. At diagnosis of lung invasion, 11 patients had negative chest X-ray findings, and serum thyroglobulin levels were not suggestive of metastatic disease in 56% of these cases. One of the 11 patients with negative chest X-ray findings died with a neck recurrence, two have persistent pulmonary (131)I uptake, and the other eight are in apparent remission after receiving an average cumulative (131)I activity of 338 mCi (12.51 GBq). The nine patients with positive chest X-ray findings received an average of 939 mCi (34.74 GBq); two of them died, five are continuing to receive therapy and two are in apparent remission. Overall survival at 10 years is 84%. The average follow-up of the 17 survivors is 12.7 years. These results suggest that patients with functioning pulmonary metastases, even in advanced stages, may survive for many years on (131)I therapy. Early diagnosis, during post-surgery (131)I scanning, of radiologically inapparent metastases is associated with a better prognosis.

Emission tomography with a large-hole collimator (CACAO): a possible new way to improve radionuclide imaging.

This work aims to improve the quality of scintigraphy. It evaluates the use of a large-hole collimator, the Computer Aided Collimation Gamma Camera Project (CACAO), in SPECT. Acquisition data from the same object were simulated for CACAO and for a conventional collimator. Better signal-to-noise ratios were found for CACAO images, whatever the number of emitted photons. This work demonstrates that high-resolution images may be obtained with large-hole collimators. The combination of CACAO and pixilated detectors may further improve radionuclide imaging.

Parathyroid gland radionuclide scanning--methods and indications.

The usefulness of preoperative radionuclide scanning of the parathyroid glands in patients with primary or secondary hyperparathyroidism was long controversial because available techniques were of limited diagnostic efficacy. Technetium-99m-labeled sestamibi (99Tc-sestamibi) is a new radiopharmaceutical agent easily detected by gamma cameras. The first parathyroid imaging studies done with 99Tc-sestamibi about 10 years ago used a double-phase technique to separate thyroid and parathyroid tissue. Although promising, this method was less than ideal, particularly in multiple gland primary hyperparathyroidism and in secondary hyperparathyroidism. For several years, we have been using subtraction between two images acquired simultaneously, one with 99Tc-sestamibi, which binds to thyroid and parathyroid tissue, and the other with 123-iodine, which binds only to thyroid tissue. The remarkable efficacy of this technique in both primary and secondary hyperparathyroidism invites a reappraisal of the place of radionuclide imaging as a preoperative localization procedure done to reduce the need for repeat surgery. The usefulness of this technique in selecting candidates for unilateral surgery among patients with primary hyperparathyroidism is discussed.