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Biomedical subjects

M Paun

Publications and source records attributed to M Paun.

6 recordsLinked to original sources
PubMed2001

Measurement of abdominal aortic aneurysms with three-dimensional ultrasound imaging: preliminary report.

OBJECTIVE: Accurate measurements of abdominal aortic aneurysms (AAAs) are required for surgical planning and monitoring over time. We have examined the feasibility of using a three-dimensional (3-D) ultrasound imaging system to derive quantitative measurements of interest from AAAs. METHODS: A normal aorta, a small AAA, and an AAA repaired with an endovascular stent graft were scanned with a 3-D ultrasound imaging system. For each case, a 3-D surface reconstruction was generated from manual outlines of a sequence of two-dimensional ultrasound images, registered in 3-D space with a magnetic tracking system. The surfaces were resampled in planes perpendicular to the vessel center axis to calculate cross-sectional area and maximum diameter as a function of distance along the length of the aorta. RESULTS: Cross-sectional area and maximum diameter were plotted along the length of the aneurysmal aortas from the renal arteries to the aortic bifurcation. The overall maximum diameter was found for both aneurysms. For the small AAA, the distances of the aneurysm from the renal arteries and the bifurcation were measured. For the repaired AAA, the location of the stent graft relative to the renal arteries was measured. CONCLUSIONS: 3-D surface reconstructions from ultrasound images show promise for quantitatively characterizing the geometry of AAAs both before surgery and after endovascular repair.

Aorta, Abdominal↗
PubMed2000

New ultrasound approaches to dialysis access monitoring.

The failure of dialysis access is a frequent source of morbidity and hospitalization. Traditional methods of graft surveillance include: (1) clinical examination, (2) venous line pressure measurements during dialysis, (3) urea or tracer recirculation measurement, (4) continuous wave (CW) Doppler methods, (5) duplex ultrasonography, and (6) radiograph angiography. All these methods require special training and/or laboratory tests. The purpose of this study was to test a simple continuous-wave Doppler method that could be applied to measure the flow rate in dialysis access every time the patient undergoes dialysis. Twenty dialysis patients, 15 with polytetrafluoroethylene grafts and 5 with arteriovenous fistulae, were studied. Two hundred fifty-three examinations were performed over an 8-month period. Doppler waveforms of the access flow were obtained with the pump on, with the pump off, and with the pump on again. Systolic and diastolic Doppler frequency measurements were made, and the pump-on and pump-off measurements were compared. In an access functioning normally, the Doppler frequencies are higher with the pump off than with the pump on. In 22% of the cases, there were abnormal findings in which the Doppler frequencies were lower with the pump off than with the pump on. This occurs if the needles are incorrectly placed, suggesting that recirculation is occurring. Recirculation also occurs if there is stenosis of the access. Examining the hemodialysis access during each dialysis session with an inexpensive directional Doppler may identify a significant stenosis and improve the efficiency of dialysis by detecting those patients in whom the arterial and venous needles are reversed.

Adult↗
PubMed1991

Duplex scanning for arterial trauma.

Duplex sonography was evaluated as a potential screening examination for arterial trauma in 89 patients with 93 injuries, mostly to the extremities (n = 74) or the cervicothoracic region (n = 17). Among 60 scans performed solely because of wound proximity to nearby vascular structures, 4 (6.7%) were positive. Thirteen of 19 (68%) scans performed for clinical indications were positive. Six of 12 (50%) postoperative studies were abnormal, and each of 4 arterial injuries followed serially remained stable. Four false-negative duplex scans (4.3%) were recorded; no major arterial injuries were missed, and no false-positive studies were noted. Duplex sonography is rapid, noninvasive, inexpensive, and portable. Since it also appears to be reliable in diagnosing and localizing sites of arterial disruption, duplex scanning may be of value in screening patients with trauma for the presence of occult vascular injuries.

Adolescent↗
PubMed1991

Non-invasive vascular tests reliably exclude occult arterial trauma in injured extremities.

We evaluated the ability of noninvasive vascular tests to exclude clinically significant occult arterial damage in injured extremities. In a preliminary study, a Doppler arterial pressure index (API) (the systolic AP in the injured extremity divided by the AP in an uninvolved arm) of less than 0.90 was found to have sensitivity and specificity of 95% and 97%, respectively, for major arterial injury. The negative predictive value for an API greater than 0.90 was 99%. Because these values suggested that noninvasive vascular tests might effectively be substituted for "exclusion" arteriography in patients at risk for silent extremity arterial injuries, we then conducted a trail in which arteriography was performed in extremity trauma victims only when the API was less than 0.90. Among 100 traumatized limbs (84 penetrating, 16 blunt) in 96 consecutive patients, 16 of 17 limbs (94%) with an API less than 0.90 had positive arteriographic findings, and seven underwent arterial reconstruction. Among 83 limbs with an API greater than 0.90, followup (including duplex scanning in 64 limbs) revealed five minor arterial lesions (four pseudoaneurysms, one arteriovenous fistula) but no major injuries. Arteriograms for extremity trauma fell from 14% to 5.2% of all angiographic studies performed (p less than 0.001, Chi-square). These studies suggest that noninvasive vascular tests can reliably exclude major occult arterial damage in injured extremities. Screening for such injuries with Doppler arterial pressure measurements, reserving arteriography for limbs in which the API is less than 0.90, is safe, accurate, and cost effective.

Adolescent↗
PubMed1990

Duplex ultrasonography of the portal vein.

Although the ability of ultrasonography to provide anatomic detail and physiologic information about the arterial system is well established, its applicability for the venous system and the splanchnic circulation has only recently been recognized. We have found duplex scanning, which is non-invasive, rapid, inexpensive, and reproducible, to be highly accurate in (1) establishing or confirming the diagnosis of portal hypertension, (2) demonstrating portal and splenic vein patency and direction of flow, (3) assessing portosystemic shunt patency, and (4) providing novel anatomic and physiologic information regarding the normal and diseased splanchnic venous system. These ultrasonographic techniques also have a significant role to play in the surveillance of patients who have undergone liver transplantation or massive liver resection. To a great extent, ultrasonography may supplant the invasiveness, discomfort, and expense of contrast angiography in the evaluation of many patients with advanced liver disease.

Humans↗