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Biomedical subjects

P F Hahn

Publications and source records attributed to P F Hahn.

At least 37 records · Page 2Linked to original sources
PubMed1999

Safety profile of ultrasmall superparamagnetic iron oxide ferumoxtran-10: phase II clinical trial data.

The safety data from the phase II clinical trial of ferumoxtran-10, an ultrasmall superparamagnetic iron oxide contrast agent, are presented. One hundred and four patients with focal liver or spleen pathologies underwent ferumoxtran-10-enhanced magnetic resonance (MR) imaging at doses of 0.8, 1.1, and 1.7 mg Fe/kg. Overall, 15% patients reported a total of 33 adverse events, regardless of causality. The adverse events most frequently seen were dyspnea (3.8%), chest pain (2.9%), and rash (2.9%). No serious adverse events were reported during the 48 hour observation period. There were no clinically significant effects on vital signs, physical examination, and laboratory results. Ferumoxtran-10 is a safe and well tolerated MR contrast agent.

Contrast Media↗
PubMed1999

A multisite phase III study of the safety and efficacy of a new manganese chloride-based gastrointestinal contrast agent for MRI of the abdomen and pelvis.

The purpose of this study was to evaluate the safety and efficacy of a manganese chloride-based oral magnetic resonance (MR) contrast agent during a Phase III multisite clinical trial. Two hundred seventeen patients were enrolled who were already scheduled for MRI of the abdomen and/or pelvis. In this group of patients, it was postulated that the use of an oral agent would better allow discrimination of pathology from bowel. Patients with known gastrointestinal pathology including peptic ulcer disease, inflammatory bowel disease, obstruction, or perforation were excluded to minimize confounding variables that could affect the safety assessment. Of these 217 patients, 18 received up to 900 mL of placebo, and 199 patients were given up to 900 mL of a manganese chloride-based oral contrast agent, LumenHance (Bracco Diagnostics, Inc.). Safety was determined by comparing pre- and post-dose physical examinations, vital signs, and laboratory examinations and by documenting adverse events. Efficacy was assessed by unblinded site investigators and two blinded reviewers who compared pre- and post-dose T1- and T2-weighted MRI scans of the abdomen and/or pelvis. In 111 (57%) of the 195 cases evaluated for efficacy by site investigators (unblinded readers), MRI after LumenHance provided additional diagnostic information. Increased information was found by two blinded readers in 52% and 51% of patients, respectively. In 44/195 cases (23%) unblinded readers felt the additional information would have changed patient diagnosis and in 50 patients (26%), it would have changed management and/or therapy. Potential changes in patient diagnosis or management/therapy were seen by the two blinded readers in 8-20% of patients. No clinically significant post-dose laboratory changes were seen. Forty-eight patients (24%) receiving LumenHance and four patients (22%) receiving placebo experienced one or more adverse events. Gastrointestinal tract side effects were most common, seen in 29 (15%) of LumenHance patients and in 3 (17%) of the placebo patients. LumenHance is a safe and efficacious oral gastrointestinal contrast agent for MRI of the abdomen and pelvis.

Abdomen↗
PubMed1999

MR imaging of the liver with Gd-BOPTA: quantitative analysis of T1-weighted images at two different doses.

This study evaluates the efficacy of gadobentate-dimeglumine (Gd-BOPTA) for enhancement of liver signal-to-noise ratio (SNR) and lesion-liver contrast-to-noise ratio (CNR) on T1-weighted spin-echo (SE) and gradient-recalled-echo (GRE) images at two different doses. Fifty patients with known or suspected liver lesions were examined at 1.5 T. T1-weighted SE (TR/TE 300/12 msec) and GRE images (TR/TE80/4.2 msec/flip angle 80 degrees) were obtained before and at 40-80 minutes and 90-120 minutes after administration of 0.05 or 0.1 mmol/kg Gd-BOPTA. Quantitative measurements of tissue signal intensity were performed at each dose. Liver showed significant enhancement after Gd-BOPTA on T1-weighted SE and GRE images (0.05 mmol: P < 0.05; 0.1 mmol: P < 0.001). The dose of 0.1 mmol/kg provided higher liver SNR than 0.05 mmol/kg. Mean liver SNR was higher on GRE than SE images (P < 0.0001). Lesion-liver CNR significantly increased on GRE images after 0.1 mmol (P < 0.05). There was a trend toward superiority of 0.1 mmol over 0.05 mmol/kg. GRE images were superior to SE images for pre- and post Gd-BOPTA lesion-liver CNR (P < 0.05). Our study suggests that Gd-BOPTA provides prolonged enhancement of liver SNR and CNR, that a dose of 0.1 mmol/Kg appears to be superior than 0.05 mmol/Kg, and that GRE techniques should be used in preference over SE techniques.

Adult↗
PubMed1999

Imaging guided biopsy of renal masses: indications, accuracy and impact on clinical management.

PURPOSE: We evaluated the indications, accuracy and impact of image guided biopsy of focal renal masses. MATERIALS AND METHODS: We retrospectively reviewed 79 image guided renal biopsies in 73 patients. Indications, imaging, and histological and clinical features were analyzed. We assumed that nephrectomy, partial nephrectomy or surgical biopsy of suspicious masses would be done when no percutaneous biopsy had been performed. A change in management was defined as surgical to nonsurgical. RESULTS: Clinical management was altered due to results in 32 of the 79 biopsies (41%) in cases managed nonoperatively, including positive and negative biopsies in those followed clinically and with imaging. Of 79 biopsies 49 (62%) were diagnosed positive for malignancy, including 15 (31%) that were not and 34 (69%) that were renal cell carcinoma. The histological diagnosis was negative on 25 biopsies (32%) and positive or negative on 74 (94%). All 5 of the 79 false-negative biopsies (6%) were due to insufficient tissue and involved highly suspicious imaging findings that required further evaluation, such as repeat biopsy or surgery. Renal cell carcinoma was identified in 4 of the 5 cases. In 12 of the 24 patients (50%) with a pre-biopsy history of nonrenal cancer biopsies were diagnostic of nonrenal cancer. No patient had major complications and in 4 small hematomas were treated with observation only. CONCLUSIONS: Image guided renal mass biopsy is safe, reliable and accurate, and it changes clinical management in many cases by avoiding nephrectomy or other surgical options. Radiologists should promote imaging guided biopsy as a potentially useful option for managing suspicious or indeterminate renal masses.

Biopsy, Needle↗
PubMed1999

MR lymphangiography using ultrasmall superparamagnetic iron oxide in patients with primary abdominal and pelvic malignancies: radiographic-pathologic correlation.

OBJECTIVE: The purpose of this study was to administer ultrasmall superparamagnetic iron oxide (USPIO) and compare changes in signal intensity of lymph nodes in patients with primary abdominal and pelvic malignancies. Also, we correlated radiographic with pathologic findings. SUBJECTS AND METHODS: Nineteen patients with proven primary abdominal or pelvic cancer (prostatic [n = 10]; colonic [n = 5]; endometrial [n = 1]; Merkel cell tumor [n = 1]; lymphoma [n = 1]; seminoma [n = 1]) were enrolled as part of our phase II and phase III clinical trials. In these patients, 49 lymph nodes (mean size, 1.4 cm) revealed on CT or MR imaging were evaluated on T1-weighted spin-echo, T2-weighted fast spin-echo, and T2*-weighted gradient-echo MR imaging at 1.5 T 24-36 hr after IV administration of USPIO. Quantitative analyses used measurements of unenhanced and enhanced region-of-interest values in lymph nodes. Qualitative assessment used subjective evaluation and classification of changes in signal intensity. All patients underwent lymph node biopsy or surgical dissection followed by histopathologic correlation. RESULTS: Of the 49 lymph nodes that were evaluated, 20 were benign and 29 were malignant. A decrease in nodal signal intensity on enhanced T2-weighted and T2*-weighted gradient-echo images was seen in 20 benign lymph nodes and two malignant lymph nodes. No appreciable signal change was noted in 27 of the 29 malignant lymph nodes. The mean signal intensity on fast spin-echo T2-weighted images for benign lymph nodes changed from 186.48 (unenhanced) to 73.66 (enhanced). Conversely, mean signal intensity for malignant lymph nodes was relatively unchanged from 191.17 (unenhanced) to 183.18 (enhanced). CONCLUSION: USPIO appears to be a useful MR contrast agent for characterizing benign and malignant lymph nodes based on the enhancement criteria evaluated in our study.

Abdominal Neoplasms↗
PubMed1998

Liver-specific MR imaging contrast agents.

Liver-specific MR imaging contrast agents consist of iron oxide particles or specially designed paramagnetic complexes targeting either the reticulo-endothelial system of the liver or the hepatocytes. These agents enhance the relaxation of water molecules in normal liver tissue and are excluded from abnormal tissue, such as metastases. Relaxation enhancement provides a map of normal liver function, increasing conspicuity of focal abnormalities. Understanding the indications and use of these agents is a central challenge for radiologists practicing liver MR imaging.

Contrast Media↗
PubMed1998

Benign prostatic hyperplasia: US-guided transrectal urethral enlargement with radio frequency--initial results in a canine model.

PURPOSE: To enlarge the prostatic urethra with thermal coagulation with transrectal radio-frequency (RF) application in dogs. MATERIALS AND METHODS: Eight aged dogs underwent RF ablation of periurethral prostatic tissue for 6 minutes. Eighteen-gauge electrodes were placed into the periurethral tissues with a transrectal approach and ultrasound (US) guidance. Prostatic and rectal temperatures were measured during RF application. US, conventional and computed tomographic (CT) retrograde urethrography (RUG), and CT were performed immediately (n = 8) and at 3-96 days (n = 6) after ablation. Histopathologic analysis was performed at sacrifice immediately (n = 2), at 28 days (n = 2), or at 3 months (n = 4) after treatment. RESULTS: All procedures were successful with no complications and were performed in less than 30 minutes. Rectal mucosal temperature did not exceed 38 degrees C. Immediately after treatment, CT and US demonstrated 1.2-cm foci of altered periurethral tissue that corresponded to solid coagulated tissue at histopathologic analysis. By day 3, CT, RUG, and US demonstrated that these foci had begun to cavitate, resulting in enlargement of the urethra. Complete cavitation was demonstrated by day 28. Minimal reduction in the degree of urethral enlargement was noted by day 60, but narrowing, urethral strictures, or fistulas were not observed at 3 months. At histopathologic analysis, focal cavitary enlargement with at least doubling of the urethral diameter and with normal urothelium was noted in all dogs surviving at least 28 days. CONCLUSION: Transrectal RF urethral enlargement is feasible and safe in animals and merits investigation for alleviating urethral obstruction due to benign prostatic hyperplasia.

Animals↗
PubMed1998

Large-volume tissue ablation with radio frequency by using a clustered, internally cooled electrode technique: laboratory and clinical experience in liver metastases.

PURPOSE: To evaluate whether coagulation necrosis achievable with radio-frequency (RF) ablation can be increased by using a cluster of closely spaced electrodes. MATERIALS AND METHODS: RF was applied to ex vivo liver (n = 68), in vivo liver (n = 12), and in vivo muscle (n = 15) by using a cluster array of three separate internally cooled electrodes spaced 0.5 cm apart. The diameter of coagulation necrosis achieved with optimal RF deposition (1,400-2,150 peak mA) for 5-60 minutes of RF application was determined for electrode tip lengths of 1.5-3.0 cm and compared with that obtained by using a single electrode and otherwise similar technique. Ten patients with solitary intrahepatic colorectal metastases were also treated by using cluster electrode RF ablation. RESULTS: In ex vivo liver, simultaneous RF application to electrode clusters for 15, 30, and 45 minutes produced 4.7 cm +/- 0.1, 6.2 cm +/- 0.1, and 7.0 cm +/- 0.2 of coagulation necrosis, respectively. In in vivo liver and muscle, RF applied to electrode clusters for 12 minutes yielded 3.1 cm +/- 0.2 and 7.6 cm +/- 0.4 of coagulation, respectively. RF application to a single electrode produced maximal coagulation of 2.9 cm in ex vivo liver, 1.8 cm in in vivo liver, and 4.3 cm in muscle (P < .01, all tissues). In colorectal metastases, a single 12-15-minute application of RF to an electrode cluster induced 4.5-7.0 cm of coagulation necrosis. CONCLUSION: Simultaneous RF application to a cluster of three closely spaced internally cooled electrodes enables a larger volume of coagulation in ex vivo liver, in vivo tissues, and hepatic colorectal metastases than previously reported.

Animals↗
PubMed1998

Radio-frequency tissue ablation: effect of pharmacologic modulation of blood flow on coagulation diameter.

PURPOSE: To determine whether vasoactive pharmacologic agents can alter radio-frequency (RF)-induced coagulation necrosis by modulating hepatic blood flow. MATERIALS AND METHODS: RF ablation was performed in normal, in vivo porcine liver with 1.5-cm internally cooled electrodes and a standardized RF application (i.e., 500 mA for 10 minutes). Ablation was performed without (n = 9) and with pharmacologic modulation of blood flow with halothane (n = 7), vasopressin (n = 6), or epinephrine (n = 7). Laser Doppler techniques were used to quantify changes in hepatic blood flow. Remote thermometry was also performed. Blood flow was correlated with both induced coagulation necrosis and tissue temperatures. RESULTS: Halothane reduced mean blood flow (+/- SD) to 46.1% +/- 8.5 of normal, and vasopressin increased mean blood flow to 132.7% +/- 13.9. Epinephrine caused increased hepatic blood flow centrally (171.1% +/- 31.7) but not peripherally (102.8% +/- 15.4). Mean coagulation diameter was 1.4 cm +/- 0.3 with vasopressin, 2.2 cm +/- 0.4 with normal blood flow, and 3.2 cm +/- 0.1 with halothane (P < .01). After epinephrine infusion, mean coagulation measured 2.3 cm +/- 0.3 peripherally and 1.4 cm +/- 0.5 centrally (P < .01). A linear correlation between coagulation diameter and blood flow was demonstrated (r2 = 0.78). Temperatures 10 and 15 mm from the electrode correlated with both blood flow and coagulation diameter (r2 = 0.65 and 0.60, respectively). CONCLUSION: The coagulation necrosis achieved for a standardized RF application correlates with relative tissue perfusion. Pharmacologic reduction of blood flow during thermally mediated percutaneous ablation may induce greater coagulation necrosis.

Anesthetics, Inhalation↗
PubMed1998

Performing radiologic gastrostomy or gastrojejunostomy in patients with malignant ascites.

OBJECTIVE: We describe our protocol for performing decompression radiologic gastrostomy and gastrojejunostomy in patients with ascites and small-bowel obstruction. We also assess the technical success rate, the complications, and the morbidity and mortality in 45 patients who underwent radiologic gastrostomy. MATERIALS AND METHODS: Forty-five consecutive patients with ascites associated with metastatic ovarian cancer underwent a radiologic gastrostomy or gastrojejunostomy with gastropexy. Six patients underwent gastrostomy, and 39 patients underwent gastrojejunostomy. Locking catheters were placed using the Seldinger technique after gastropexy in all patients. Paracentesis was performed before gastrostomy or gastrojejunostomy. Additional serial paracenteses were performed after the procedure when reaccumulation of ascites close to the site of gastropexy was detected on follow-up sonography. RESULTS: Forty-five procedures were attempted. The technical success rate was 97.8%. The complication rate was 15.6%. Three major complications (6.7%) and four minor complications (8.9%) occurred. One procedure-related death (2.2%) occurred 16 days after gastrojejunostomy. CONCLUSION: Radiologic gastrostomy and gastrojejunostomy can be performed safely in patients with ascites if the patients undergo paracentesis first and if the reaccumulation of ascites is prevented after tube placement. In patients with ascites, gastropexy plays an important role in preventing pericatheter leakage. Ascites and peritoneal carcinomatosis should not be considered contraindications for radiologic gastrostomy or gastrojejunostomy.

Ascites↗
PubMed1997

MR differentiation of phaeochromocytoma from other adrenal lesions based on qualitative analysis of T2 relaxation times.

AIM: To determine the diagnostic accuracy of MR imaging in differentiating phaeochromocytoma from other adrenal lesions. MATERIALS AND METHODS: Sixty-seven adrenal masses (65 patients) including 17 phaeochromocytomas were imaged using T2-weighted pulse sequences on 0.6 T and 1.5 T GE MR units. The adrenal lesions were qualitatively assessed by three observers and divided into three categories (benign adenomas, malignant lesions and phaeochromocytomas) based on lesion signal intensity relative to liver and cerebrospinal fluid. RESULTS: Eleven phaeochromocytomas (65%) were correctly identified while the remaining six (35%) were misclassified, five as malignant lesions and one as a benign adenoma, because of atypical low signal intensity on T2-weighted MR images. Conversely, six non-phaeochromocytomas (three benign adenomas, two adrenal carcinomas and one metastasis) were wrongly classified as phaeochromocytomas because of very high lesion signal intensity. The sensitivity of MR imaging for diagnosing phaeochromocytoma was 64.7%, specificity 88.0%, positive predictive value 64.7% and negative predictive value 88.0%. CONCLUSION: There is considerable overlap between the MR appearance of phaeochromocytoma and other adrenal lesions. A phaeochromocytoma cannot be excluded on the basis of a lack of high signal intensity on T2-weighted MR imaging.

Adenoma↗
PubMed1997

Liver tumor ablation: real-time monitoring with dynamic CT.

RATIONALE AND OBJECTIVES: To determine whether incomplete contact of ethanol with tumor limits the success of percutaneous ethanol injection therapy. MATERIALS AND METHODS: Percutaneous ethanol injection was performed in seven normal New Zealand white rabbits and 18 rabbits with 1-3-cm liver tumors 10-14 days after percutaneous implantation of suspended tumor cells. A 3-5 mL dose of ethanol was injected at a rate of 0.2 mL/sec either into normal liver remote from large vessels or directly into tumor. During and immediately after injection, axial, 2-mm-thick, contrast material-enhanced computed tomography scans were obtained at reach of three levels every 9 seconds. RESULTS: In normal animals, virtually all injected ethanol tracked to the hepatic capsule. As ethanol was injected into tumors, peripheral tracking, similar to that seen in normal livers, or extratumoral puddling was observed. Ethanol-tumor contact was incomplete in 16 of 18 animals (89%). Histopathologic analysis showed incomplete tumor necrosis. CONCLUSION: In this model of hepatic carcinoma metastasis, the tumor failed to hold sufficient ethanol for successful ablation by means of percutaneous ethanol injection therapy.

Animals↗
PubMed1997

Focal hepatic lesions: effect of three-dimensional wavelet compression on detection at CT.

PURPOSE: To evaluate the effect of three-dimensional, wavelet-based compression on the detection of focal hepatic lesions at computed tomography (CT). MATERIALS AND METHODS: CT images obtained in 69 patients with focal hepatic lesions were studied (35 consecutive cases and 34 cases selected to be difficult on the basis of lesion size or contrast). Image data were compressed by means of a three-dimensional, wavelet-based algorIthm at ratios of 10:1, 15:1, and 20:1. Normal and abnormal sections (on original and compressed images) were reviewed by using an interactive workstation. Four readers rated the presence or absence of a lesion with a five-point scale. RESULTS: At receiver operating characteristic analysis, no statistically significant difference was detected for all cases considered together. Differences approached but did not reach statistical significance for the diagnostic performance of one reader with compressed images (15:1, P = .054; 20:1, P = .051). For the subset of difficult cases, a significant difference was observed with 20:1 compressed images for one reader (P = .026). Diagnostic performance of readers was less certain in normal than in abnormal cases with both original and compressed images (difference was significant for 15:1 [P = .035] and 20:1 [P < .0001] compressed images). CONCLUSION: Three-dimensional wavelet compression is satisfactory at ratios of at least 10:1. Additional studies with a larger sample would help confirm findings with higher ratios.

Cysts↗
PubMed1997

Focal liver lesions: characterization with conventional spin-echo versus fast spin-echo T2-weighted MR imaging.

PURPOSE: To compare prospectively the diagnostic accuracy of T2-weighted conventional spin-echo (SE) and fast SE magnetic resonance (MR) imaging for differentiation of benign (hemangiomas or cysts) from malignant (metastases or hepatocellular carcinoma) liver lesions. MATERIALS AND METHODS: Fifty-three patients with 55 confirmed liver lesions (20 hemangiomas, eight cysts, 22 metastases, four hepatocellular carcinomas, one malignant fibrous histiocytoma) underwent T2-weighted conventional SE (repetition time msec/echo time [TE] msec = 3,100/ 80,160) and fast SE (5,000-5,000/99-104 [effective TE]) MR imaging at 1.5 T. The images were evaluated quantitatively (lesion-liver signal intensity ratio and lesion T2 index [SIlesion TE80/SIlesion TE160, where SI = signal intensity] and qualitatively (blinded reading) by using receiver operating characteristic analysis. RESULTS: Quantitatively, the T2 index (Az = .988) was more accurate than the signal intensity ratio at conventional SE (Az = .920) and fast SE (Az = .910) imaging (P < .05). Qualitatively, there was no statistically significant difference between the blinded reading of conventional SE (Az = .988) and fast SE (Az = .986) images in lesion characterization (benign vs malignant). There was a trend, however, toward superiority of conventional SE imaging for evaluation of "hypervascular" metastases (n = 9). CONCLUSION: With the specific parameters used, conventional SE and fast SE images provide equal accuracy for characterization of focal liver lesions. In patients with hypervascular metastases, double-echo conventional SE images may be preferable.

Adult↗
PubMed1997

Differentiation of liver hemangiomas from metastases and hepatocellular carcinoma at MR imaging enhanced with blood-pool contrast agent Code-7227.

PURPOSE: To evaluate differentiation of liver lesions at magnetic resonance (MR) imaging enhanced with Code-7227. MATERIALS AND METHODS: Thirty-five patients with 38 proved liver lesions (15 hemangiomas, 17 metastases, six hepatocellular carcinomas [HCCs]) underwent T1-weighted gradient-echo and T2-weighted fast-spin-echo MR imaging at 1.5 T before and after intravenous administration of Code-7227 (1.1 mg iron per kilogram of body weight). RESULTS: In hemangiomas, the mean contrast-to-noise ratio on precontrast and postcontrast images, respectively, increased from -4.51 +/- 4.7 (standard deviation) to 5.19 +/- 6.3 on T1-weighted images and decreased from 14.73 +/- 7.4 to 0.64 +/- 5.1 on T2-weighted images. In comparison, metastases remained hypointense to liver on T1-weighted images (from -5.77 +/- 5.9 to -7.8 +/- 6.8) and hyperintense on T2-weighted images (from 8.73 +/- 5.4 to 12.61 +/- 6.1). Although HCC enhanced more than metastases, they also remained hypointense to liver on T1-weighted images (from -4.87 +/- 6.1 to -1.79 +/- 5.7) and hyperintense on T2-weighted images (from 10.12 +/- 7.9 to 8.7 +/- 6.4). The degree of enhancement on T1-weighted images and of signal intensity drop on T2-weighted images were significantly lower in malignant liver masses than in hemangiomas (P < .001). CONCLUSION: Distinctly different enhancement patterns with Code-7227 helped accurate differentiation of liver lesions.

Adult↗