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Biomedical subjects

P Pavone

Publications and source records attributed to P Pavone.

At least 109 records · Page 6Linked to original sources
PubMed1996

[Flow quantification with magnetic resonance: preliminary results with phase contrast technique].

This study investigated the accuracy of phase contrast MRI in blood flow measurements; both in vitro and in vivo studies were carried out. Five normal volunteers (3 women and 2 men, age range: 24 to 30 years) were examined with MR angiography (MRA) and a flow measurement sequence. A 2D phase contrast sequence, with retrospective cardiac gating was also acquired with the following imaging parameters: TR/TE/FA (26/9.3/20 degrees ), field of view 150 mm, matrix 96 x 128; 4 averages. VENC value (cm/s) was chosen according to the examined region. The total acquisition time ranged 3 min 25 sec to 4 min 38 sec. The sequences were acquired on a plane perpendicular to the vessel direction, using MIP-reconstructed MRA images as a scout view. The results are the same as those obtained with other techniques, in the common carotid artery (Vmax = 70.7 cm/s; Vmin = 18.8 cm/sec; flow = 348 ml/min), internal carotid artery (Vmax -54.4 cm/sec; Vmin = 18 cm/sec; flow = 236 ml/min) and vertebral artery (Vmax = 51.7 cm/sec; Vmin = 17.5 cm/sec). The resistance index could always be calculated and exceeded 0.7 in all cases. In conclusion, MRA is an accurate technique for blood flow measurements, in particular with cardiac gating, which permits measurement optimization according to the different cardiac cycles.

Adult↗
PubMed1996

[Biliary-enteric anastomosis: role of cholangiography with magnetic resonance].

Our study was aimed at investigating the role of MR-cholangiography (MRC) in the examination of patients treated with biliary-enteric anastomosis. MRC was performed in 15 patients (8 men and 7 women, mean age: 64.7 years) operated on for biliary-enteric anastomoses (13 hepaticojejunostomies and 2 choledochoduodenostomies) whose symptoms were as follows: persistent jaundice in 4 patients; cholangitis and abnormal liver function tests in 2 patients; associated transient jaundice, epigastric pain, abnormal liver function tests in 2 patients. The remaining 7 patients were asymptomatic and examined during their follow-up. MRC was performed with a non-breath-hold, fat-suppressed 3D turbo spin echo sequence (TR = 3000 msec, TE = 700 msec, ETL = 128) with an acquisition time ranging 4 min 24 sec to 5 min 48 sec. Six patients were subsequently submitted to Percutaneous Transhepatic Cholangiography (PTC) to confirm the diagnosis and to perform a therapeutical procedure. Two patients, submitted to choledochoduodenostomy were examined with ERCP. The remaining seven patients, examined during their surgical follow-up and who presented no major symptoms or dilation of the bile ducts, were not submitted to any invasive procedure. Image quality was graded as good to fair in 12/15 cases (80%) and poor in 3/15 cases (20%). The degree of bile ducts dilation was correctly assessed with complete inter observer agreement in 8/8 patients. MRCP correctly showed: bile ducts irregularities in 2 of 4 patients with cholangitis (k = 0.59), anastomosis stenosis in 8 of 8 patients (k = 0.86), and 5-15 mm stones in 5 of 5 patients (k = 0.95). In conclusion, MRCP is a safe, noninvasive technique in the study of biliary-enteric anastomoses with high accuracy in assessing the cause of jaundice. MRCP images can be used as a guide for subsequent interventional procedures. Its main disadvantages are the lack of functional information and the high cost which limits its its use to the screening of symptomatic patients.

Aged↗
PubMed1996

[Usefulness of the new sequences of magnetic resonance in the study of hepatic hydatidosis].

We investigated the role of new MR Imaging techniques for the diagnosis, characterization and staging of hepatic hydatid disease. We examined 21 patients (30 hydatid cysts), 7 men and 14 women, ranging in age 26 to 74 years, with known hydatid disease. MR examinations were carried out on a 0.5T superconductive magnet (Philips Gyroscan T5, Philips Medical System) with the following imaging protocol: T1w (TR/TE/NEX: 300/10/4) SE, T2w (TR/TE/NEX: 3000/120/6) TSE and fat suppressed (SPIR technique) T2w (TR/TE/NEX: 3000/120/6) sequences. MR Angiography examinations were performed with 2D Time of Flight sequences (TR = 33 ms; TE = 6.9 ms; flip angle = 60 degrees; slice thickness = 4.0 mm with 2.0 mm overlapping; matrix = 256 x 256; number of slices = 45-50; acquisition time = 4 min 19 s), while MR cholangiography was performed with 3D, fat suppressed (SPIR) Turbo Spin-echo (TSE) sequences (TR = 3000 ms, TE = 700 ms, ETL = 12, acq. time = 5 min 48 s). MRI correctly detected all the hydatid cysts on both T1- and T2-weighted images. Characterization was correct in all the cysts larger than 3 cm, where typical signs consistent with hydatid disease were detected. MRA images always showed the inferior vena cava and the splenoportal system. The portal vessels were demonstrated only up to the first branches. In 3 cases an extrinsic compression of the inferior vena cava was diagnosed. MRC, performed in 7 cases, showed normal main bile duct caliber in 6 cases, while in another case, where a cyst ruptured inside the bile ducts, the communication between the cyst and the bile ducts was clearly demonstrated. In conclusion, MR Imaging is a valuable tool in the study of liver hydatid disease. Moreover, the availability of such new MR techniques as MRC and MRA, greatly improves the diagnostic role of MR imaging, especially when studying complications and before surgery.

Adult↗
PubMed1996

[Quantification of mesenteric flow with magnetic resonance imaging before and after a meal: results in healthy volunteers].

Several literature studies showed that total intestinal blood flow approximates superior mesenteric vein flow. Today, new accurate techniques can be used to measure blood flow. We investigated MR capabilities in measuring mesenteric vein flow, to assess total intestinal blood flow. Nine healthy volunteers were examined before and after a meal with a phase-contrast technique to measure blood flow. Flow speed and quantity can be measured positioning a ROI inside the vessel for speed evaluation and around the vessel for flow quantitation. Superior mesenteric blood flow exhibited a three-fold increase after a meal relative to pre-meal values. Cine phase-contrast MRI was a useful tool to measure mesenteric flow in healthy volunteers both before and after a meal and can therefore be suggested for the noninvasive examination of patients with a suspected chronic mesenteric blood supply deficiency.

Adult↗
PubMed1996

[Cholangiography with magnetic resonance in the diagnosis of main common bile duct calculi in candidates to laparoscopic cholecystectomy].

The aim of our work was to investigate Magnetic Resonance Cholangiography (MRC) capabilities in detecting common bile duct (CBD) stones in patients to be submitted to laparoscopic cholecystectomy. MRC was performed as the only preoperative imaging modality in 45 selected patients (16 men and 29 women; age range: 28-72 years, mean age: 54.4 years) before laparoscopic cholecystectomy. MRC images were obtained with 3D Turbo Spin-Echo sequences (TR = 3000 ms, TE = 700 ms, echo train length = 128) with an acquisition time of 5 min 48 sec. Diagnostic confirmation was obtained in all the patients at intraoperative cholangiography. When a stone was detected, it was removed by transcystic or transcholedochal approach. Eighteen of 45 patients (40%) had CBD stones. MRC correctly demonstrated 16 of 18 stones, with 88.9% sensitivity, 100% specificity, 100% positive predictive value, 90% negative predictive value and 95.6% accuracy. Despite the good results we obtained with MRC, this technique cannot be proposed as a screening method to be performed in all the patients candidate to laparoscopic cholecystectomy because of its high cost and of the limited number of MR units available. In conclusion, only selected patients should be submitted to MRC before laparoscopic cholecystectomy.

Adult↗
PubMed1996

[Urography with magnetic resonance: a new method for the study of the renal collecting system in patients without obstructive uropathy].

A new MR technique is proposed to study the renal collecting system and the proximal ureteral portion in patients without obstructive uropathy, using fat-suppressed Turbo Spin Echo sequences, after drug-induced distension of the urinary tract. Nine normal volunteers and 16 patients (11 with renal stones, 1 with bilateral pyeloureteral junction stenosis, 1 with renal ptosis, 1 with ureteral hyperkinesia, 1 with renal tumor and 1 with a symptomatic renal cyst) were submitted to MR-Urography, performed with a 3D non-breath-hold fat-suppressed Turbo SE sequence (TR = 3000 ms, TE = 800 ms, 6 acquisitions, Turbo Factor = 128, Matrix = 128 x 256 or 256 x 256, acquisition time = 5 min 15 sec or 10 min 36 sec) on the coronal plane. With these acquisition parameters, parenchymal signal can be completely suppressed while enhancing fluid signal. These acquisitions were post-processed with the MIP algorithm to obtain very similar images to those of conventional urography. The maximum filling of the renal collecting system was obtained with the i.v. administration of 250 ml saline solution within 2-3 minutes and then the i.v. injection of 20 mg furosemide. The renal collecting system was optimally depicted in all the volunteers and the patients, except for 2 cases because of malfunctioning respiratory gating. Anatomical detailing was really improved after the diuretic administration, especially in the study of the major caliceal systems. To conclude, MR-Urography permits accurate morphological detailing of the renal collecting system also in patients without obstructive uropathy.

Adult↗
PubMed1995

[Restorative proctocolectomy. A morphological-functional study by computed tomography with coronal scans].

Restorative proctocolectomy with ileal pouch has become the surgical treatment of choice for patients with ulcerative colitis and familial polyposis of the colon. Defecography is the radiologic technique commonly used to obtain detailed information on function and morphology of the ileal pouch, but it fails to depict the pelvis. Computed Tomography (CT), with coronal images only was used to examine 10 patients with ulcerative colitis, submitted to restorative proctocolectomy. Coronal CT, yielding a panoramic view of the pelvis, represent an effective alternative technique to defecography. In fact, the two techniques provide comparable information relative to the ileal pouch; coronal CT also depicts the possible thickening of pouch walls and of pelvic fat tissue. Coronal CT also depicts the continence of ileo-anal and ileo-ileal anastomoses and the functional changes of the perineal muscles at rest and during squeezing. Coronal CT images allow easy and clear detection of such major postoperative complications as pelvic inflammation and fistulae (less frequently stenosis or dehiscences of the anastomosis).

Adult↗
PubMed1995

[Pancreatic assessment by magnetic resonance imaging: an improvement in the diagnostic results with new study technics].

Magnetic resonance imaging of the pancreas has been, limited by a series of artifacts with a resulting poor contrast to noise ratio. Nevertheless, technological progress has allowed to reduce not only scanning time but also the number of artifacts, by increasing the number of excitations and matrix size. Moreover, tissue contrast can now be modified. In our study performed on 5 normal volunteers and 20 patients with different pancreatic diseases conditions, fast SE sequences with and without fat suppression were used, with an overall increase in contrast to noise ratio. In all patients MR images allowed the accurate definition of the lesions: in 8 adenocarcinoma patients the lesion could be depicted, including the 2 lesions CT had poorly demonstrated. Also in the 3 patients with endocrine tumors, MRI depicted small tumors which were later confirmed at surgery. This new protocol makes MRI a very sensitive and accurate tool in the study of neoplastic and inflammatory pancreatic diseases thus, MRI is not only a complementary tool to CT but an even better study technique. In particular, its higher contrast to noise ratio allows a dramatic improvement in the depiction of small solid lesions, especially those not altering pancreatic outline. This study proves that MRI, when adequately performed, is a very accurate tool to study, in a very short time, the pancreas and peripancreatic region, yielding much better results than all the other diagnostic imaging modalities.

Acute Disease↗
PubMed1995

[Assessment of renal function using low doses of paramagnetic contrast media].

Dynamic MR techniques with Gd-DTPA bolus administration can be used to study renal perfusion and function. In previous studies, the concentration of Gd-DTPA injected was never lower than 0.1 mmol/kg: as a result, depending on the magnetic susceptibility effect, renal signal intensity reduced in the early phases, right after contrast agent injection. To prevent signal intensity from reducing in the early phases, in our study we used a concentration of 0.05 mmol/kg. Qualitative and quantitative evaluations were performed. Seven healthy subjects and 14 patients with different degrees of renal insufficiency were enrolled in the study. All exams were performed using an 0.5-T magnet (Philips Gyroscan T5, II), with 15 mT/m gradient power. Signal intensity measurements at the cortical, external medullary and internal medullary levels, allowed the drawing of curves typical of each degree of renal insufficiency which correlated well with nuclear medicine (scintigraphy) findings. The qualitative evaluation provided results comparable with scintigraphic findings in all 7 normal subjects, in 3 of 4 cases of moderate renal insufficiency, in all 7 cases of moderate/severe renal insufficiency and in the only case of severe renal insufficiency. To conclude, this trial demonstrates the feasibility of MR studies of renal function, which provide morphological and functional pieces of information. Low concentration Gd-DTPA is decisive to avoid the magnetic susceptibility artifacts observed in previous studies.

Contrast Media↗
PubMed1995

[Magnetic resonance angiography of the intracranial circle using magnetization transfer contrast (MTC)].

Magnetic Resonance Angiography (MRA) is becoming an accurate technique to study vascular conditions, especially when the intracranial circulation is involved. Nevertheless, the contrast-to-noise (C/N) ratio in MRA images is often inadequate to obtain diagnostic images. C/N ratio can be increased by using magnetization transfer contrast (MTC), the technique which allows to reduce the signal from the stationary tissues surrounding vascular structures. To demonstrate the value of MTC, 10 healthy volunteers and 10 patients with different cerebral vascular conditions were examined. All exams were performed using 3D MOTSA (Multiple Overlapping Thin Slab Acquisition) Time of Flight sequences, with and without MTC. A quantitative analysis was carried out in the images with and without MTC, measuring the signal intensity value in the regions of interest at the vascular and stationary structures. A qualitative analysis was also carried out with a double blind study by two independent radiologists. Our results showed that MTC allows to reduce stationary tissues signal intensity, without affecting flowing blood signal intensity. Therefore, the C/N ratio is increased, thus allowing better depiction of smaller peripheral branches. In conclusion, MTC applied to intracranial MRA allows image quality to be markedly improved, with an overall increase in the diagnostic accuracy of this technique.

Cerebrovascular Circulation↗
PubMed1995

[Magnetic resonance cholangiopancreatography. A new method of noninvasive biliopancreatic diagnosis].

Magnetic Resonance cholangiopancreatography (MRCP) is a new noninvasive imaging technique for the visualization of the biliary ducts with cholangiographic images similar to those obtained with ERCP and PTC, but with no contrast agent injection. In this paper, we report on our preliminary experience with a mild-field strength magnet (0.5T) and TSE sequences, acquired with respiratory compensation. The images were compared with ERCP images to compare diagnostic quality. Eighteen patients were examined: the biliary tract was dilated because of chronic pancreatitis in 3 patients, because of choledochal stones in 9, of carcinoma of the pancreatic head in 4, of lymphadenopathy in one patient. A patient submitted to choledochoduodenostomy and waiting for cholecystectomy was also examined. MRCP was performed with a superconductive magnet at 0.5T. Volumetric images on coronal planes were acquired; a T2-weighted TSE sequence (TR = 5000, TE = 244, Nex = 4, ETL = 45; acquisition time = 14 min 10 s) with respiratory compensation was also performed. The images were reconstructed on coronal planes at different angles with the MIP algorithm. All patients were then submitted to ERCP and one to PTC. In all patients, the intrahepatic biliary tracts, hepatic ducts and choledochus were completely demonstrated, with very good image quality in 16 cases and good in 2. The Wirsung duct was always visualized in all the 9 patients with mild to severe dilation. In conclusion, MRCP can be considered a valuable alternative to diagnostic ERCP. Further studies are necessary for better assessment of the potential advantages and pitfalls of this technique.

Adult↗
PubMed1995

[Identification of pancreatic insulinomas. The role of magnetic resonance].

Insulinomas are the most common endocrine tumors of the pancreas. Although their clinical and biochemical diagnosis is extremely accurate, these lesions must be correctly located preoperatively to plan the best possible treatment. Many different noninvasive diagnostic techniques have been proposed, with only partially satisfying results. For many years such non-invasive modalities as arteriography have been considered the most reliable and accurate diagnostic tools. Recently, however, MRI has been proposed for best pancreas imaging, especially for tumor detection, and its results have been excellent especially thanks to its optimal contrast resolution. Fat-suppressed and turbo-spin-echo (TSE) sequences now yield even better results. In our study we examined 21 patients, whose symptoms were typical of insulinoma, using two different 0.5T magnets, one of which with 15 mT/m gradients. We used T1-weighted spin-echo (SE) sequences with and without respiratory compensation, SE ad TSE T2-weighted and fat-suppressed T1-weighted SE sequences. In 16 patients the lesions were correctly diagnosed and located, as confirmed at surgery. In the other 5 patients, MRI failed to locate the insulinomas. Three of these 5 patients were submitted to surgery, during which palpation and intraoperative US findings were also negative for a solid mass. The remaining 2 patients underwent clinical follow-up. Our study demonstrated that MRI, especially with fat-suppressed and T2-weighted TSE sequences, is a very accurate modality to detect pancreatic insulinomas and can therefore be proposed as the only preoperative technique.

Adolescent↗