Biomedical subjects

A Chatziioannou

Publications and source records attributed to A Chatziioannou.

27 records · Page 2Linked to original sources

PubMed1998

An evaluation of exact and approximate 3-D reconstruction algorithms for a high-resolution, small-animal PET scanner.

MicroPET is a low-cost, high-resolution positron emission tomography (PET) scanner designed for imaging small animals. MicroPET operates exclusively without septa, acquiring fully three-dimensional (3-D) data sets. The performance of the projection-reprojection (3DRP), variable axial rebinning (VARB), single slice rebinning (SSRB), and Fourier rebinning (FORE) methods for reconstruction of microPET data were evaluated. The algorithms were compared with respect to resolution, noise variance, and reconstruction time. Results suggested that the 3DRP algorithm gives the best combination of resolution and noise performance in 9 min of reconstruction time on a Sun UltraSparc I workstation. The FORE algorithm provided the most acceptable accelerated method of reconstruction, giving similar resolution performance with a 10%-20% degradation in noise variance in under 2 min. Significant degradation in the axial resolution was measured with the VARB and SSRB methods, offsetting the decrease in reconstruction time achieved with those methods. In-plane angular mashing of the 3-D data before reconstruction led to a 50% reduction in reconstruction time but also introduced unacceptable tangential blurring artifacts. This thorough evaluation of analytical 3-D reconstruction techniques allowed for optimal selection of a reconstruction method for the diverse range of microPET applications.

Algorithms↗

PubMed1998

Management of renal angiomyolipoma by selective arterial embolization.

4 Patients with renal angiomyolipomas are presented. One of them had tuberous sclerosis with synchronous bilateral tumors. All the patients were symptomatic, 2 of them with retroperitoneal hemorrhage. In all patients selective arterial embolization was performed. Permanent control of the symptoms was successful in 2 patients. In 1 patient temporary resolution of the symptoms was observed, and a second embolization was required. Retroperitoneal bleeding in 1 patient continued and nephrectomy was undertaken.

Adolescent↗

PubMed1997

Oral 18F-fluoro-2-deoxyglucose for primate PET studies without behavioral restraint: demonstration of principle.

We describe a method of orally administering 18F-fluoro-2-deoxyglucose (FDG) for positron emission tomography (PET) scans to determine local cerebral metabolic rates for glucose (LCMRGlc), normalized to that of whole brain, in fully conscious, non-restrained primates. Oral FDG-PET studies were performed in both non-restrained and chaired monkeys, and in one human where results could be compared with traditional intravenous FDG administration. The oral route of FDG administration gave images and whole brain-normalized PET LCMRGlc results comparable to those obtained by the intravenous route. This oral FDG-PET method may provide a useful means by which to obtain measures of LCMRGlcs for brain structures, relative to each other, in non-restrained, non-drugged primates in field and laboratory studies. This method might also have clinical applications for PET studies of children.

Administration, Oral↗

PubMed1987

Green light phototherapy in newborn infants with ABO hemolytic disease.

The efficacy of fluorescent green light phototherapy was compared with that of blue light phototherapy in the treatment of full-term infants with hemolytic disease and jaundice caused by ABO incompatibility. The efficacy of the treatment was expressed as actual (milligrams per hour) and quantum (milligrams per hour per square centimeter per megawatt) efficiency, taking into account the differential emission of energy from the green versus the blue fluorescent tubes. No statistically significant difference in the rate of serum bilirubin photodegradation was found between the two groups after treatment for 84.6 +/- 14.1 hours versus 81.5 +/- 14.2 hours with the green and the blue phototherapy, respectively. These results, coupled with the known effects of the blue light on the genetic apparatus of mammalian cells, support the application of the green light phototherapy for the treatment of neonatal hyperbilirubinemia caused by ABO incompatibility.

Humans↗

PubMedDate not supplied

Complications of lower-extremity outpatient arteriography via low brachial artery.

We retrospectively evaluated low brachial artery puncture for arteriography and its complications as an alternative approach route for bilateral lower extremity run-off. Using the Seldinger technique and catheterization with a sheathless 4-F multiple side-hole pigtail catheter, we performed 2250 low brachial artery punctures in outpatients. The right brachial artery (RBA) was successfully punctured in 2039 patients; the left brachial artery (LBA) in 200. The transfemoral approach was used in 11 patients when catheterizing either of brachial arteries failed. Ten major or moderate complications (2 pseudoaneurysms, 2 thrombosis, 1 dissection and 5 hematomas) were encountered. Surgical intervention was necessary in three cases. There were no transient ischemic attacks. Twenty-one patients suffered temporary loss of radial pulse which returned spontaneously in less than 1 hour. One patient demonstrated prolonged loss of pulse which required heparin. Low brachial artery puncture and catheterization at the antecubital fossa is a very safe and cost-effective alternative to the femoral artery approach for lower extremity intra-arterial arteriography in the hands of experienced operators. The success rate in catheterizing one of the brachial arteries was 99.52% with a low significant complications rate of 0.44%. The transbrachial approach should be used as a standard method for lower extremity IA-DSA in an outpatient setting.

Adolescent↗

PubMedDate not supplied

Acute iliac artery rupture: endovascular treatment.

The authors present 7 patients who suffered iliac artery rupture over a 2 year period. In 5 patients, the rupture was iatrogenic: 4 cases were secondary to balloon angioplasty for iliac artery stenosis and 1 occurred during coronary angioplasty. In the last 2 patients, the rupture was secondary to iliac artery mycotic aneurysm. Direct placement of a stent-graft was performed in all cases, which was dilated until extravasation was controlled. Placement of the stent-graft was successful in all the cases, without any complications. The techniques used, results, and mid-term follow-up are presented. In conclusion, endovascular placement of a stent-graft is a quick, minimally invasive, efficient, and safe method for emergency treatment of acute iliac artery rupture, with satisfactory short- and mid-term results.

Acute Disease↗

PubMedDate not supplied

Imaging and localization of pancreatic insulinomas.

For pancreatic insulinomas, the treatment of choice is surgical excision, which when successful is curative. Intraoperative palpation combined with ultrasonography theoretically depict almost all tumors, however the accuracy of palpation is improved by the preoperative localization. All recent advances in imaging have improved the likelihood for curative surgical resection. Our purpose is to demonstrate the characteristics of all modalities, which may be used in the preoperative localization algorithm.

Algorithms↗

PubMedDate not supplied

Mammography focal spot measurement with a star pattern: techniques to avoid inaccuracies.

The increased emphasis on mammography acceptance testing and quality control make the star pattern test an essential component of the procedure for diagnosing poor resolution due to large focal spots. In this paper procedures for calculating magnification and the correct angle of the star pattern to use are described. The preferred placement of the star pattern in the field and proper exposure technique is also discussed.

Biophysical Phenomena↗

PubMedDate not supplied

Preoperative localization of pancreatic insulinoma by selective intraarterial calcium injection and hepatic venous sampling.

Preoperative localization of insulinomas is desirable by most surgeons. Imaging with ultrasonography, computed tomography, magnetic resonance imaging, nuclear medicine and angiography may fail to demonstrate these small tumors in up to 10%, while a smaller percentage may be missed even after careful surgical exploration and intraoperative ultrasonography. Selective intraarterial injection of calcium with hepatic venous sampling has been reported to be a very accurate technique for preoperative localization of insulinomas. We report such a case where the clinical symptoms were highly suggestive but imaging algorithm failed to reveal any lesion and we review the literature.

Adult↗