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P F Hahn

Publications and source records attributed to P F Hahn.

At least 55 records · Page 3Linked to original sources
PubMed1997

Adrenal masses: characterization with delayed contrast-enhanced CT.

PURPOSE: To evaluate the use of attenuation measurements from early delayed computed tomographic (CT) scans to differentiate benign from malignant lesions of the adrenal glands. MATERIALS AND METHODS: Forty-four patients (19 men, 25 women; age range, 21-88 years; mean age, 63 years) with 46 adrenal masses underwent dynamic contrast material-enhanced CT and early delayed CT (range, 12-18 minutes; mean delay, 14 minutes) with similar scanning parameters. Each patient also underwent non-contrast-enhanced CT within 3 months of the contrast-enhanced examination. Attenuation of adrenal masses on each type of scan was measured, and receiver operating characteristic analysis was performed. RESULTS: An attenuation threshold of 24 HU was selected; thus, all lesions with attenuation values of 24 HU or less were considered benign. When this threshold was applied to the results, the sensitivity of characterization of adrenal masses on early delayed scans was 96%, and the specificity was 96%. CONCLUSION: Adrenal masses detected with contrast-enhanced CT can be characterized as benign or malignant on early delayed scans of the adrenal glands.

Adrenal Gland Neoplasms↗
PubMed1997

Percutaneous gastrostomy with T-fastener gastropexy: results of 316 consecutive procedures.

PURPOSE: To assess the rates of technical success and complications associated with radiologic gastrostomy or gastrojejunostomy performed with T-fastener gastropexy. MATERIALS AND METHODS: In 316 consecutive patients, radiologic gastrostomy or gastrojejunostomy with T-fastener gastropexy was performed over a 10-year period. Results of the procedures were reviewed. Results of follow-up were available for all patients. RESULTS: Of 316 procedures, 314 were successful (technical success rate, 99.4%). Six (1.9%) major complications occurred; 50% occurred in patients with peritoneal involvement from ovarian carcinoma. Ten (3.2%) minor complications occurred. Four minor complications occurred in patients with ovarian cancer and ascites. The 30-day mortality rate was 3.8% (12 patients) with one procedure-related death (0.3%). CONCLUSION: A T-fastener gastropexy may have a protective role in prevention of leakage of gastric contents into the peritoneum in patients with ascites. Ascites need no longer be considered a contraindication for radiologic gastrostomy. A gastropexy enables routine use of larger gastrostomy tubes and ready replacement of a displaced tube even before the development of a mature tract.

Adult↗
PubMed1997

US-guided thoracentesis: requirement for postprocedure chest radiography in patients who receive mechanical ventilation versus patients who breathe spontaneously.

PURPOSE: To identify a population of patients who may not need chest radiography after diagnostic thoracentesis by assessing and comparing the pneumothorax rates in patients with mechanical ventilation (intubation) versus spontaneously breathing patients (no intubation). MATERIALS AND METHODS: A retrospective review of all radiographs, clinical records, and ultrasound (US) scans obtained in 434 patients who underwent US-guided thoracentesis was performed. Three hundred forty-two patients were not intubated and 92 were intubated. Nine patients were excluded because of preexisting pneumothorax. The size of the effusion, the needle size used, and whether a pneumothorax occurred after the procedure were determined. RESULTS: Results demonstrated that only 10 pneumothoraces occurred (six in intubated and four in nonintubated patients). None of the nonintubated patients with pneumothorax and two of the six intubated patients with pneumothorax needed chest tubes. The difference in the pneumothorax rate between intubated and nonintubated patients was statistically significant (P < .01). CONCLUSION: Spontaneously breathing patients who undergo diagnostic thoracentesis do not need postprocedure chest radiography.

Adolescent↗
PubMed1997

The frequency and significance of adnexal lesions incidentally revealed by CT.

OBJECTIVE: This paper describes the frequency of incidental adnexal findings revealed by routine CT scanning and determines the significance of these lesions in premenopausal and postmenopausal women, particularly in those with an already known malignancy other than ovarian carcinoma. MATERIALS AND METHODS: A computerized search of all radiology reports from 1992 identified 3448 women who underwent abdominopelvic or pelvic CT scans for an indication other than ovarian carcinoma or a known or suspected pelvic mass. Patients were divided into two subgroups: premenopausal and postmenopausal. CT reports were reviewed to identify patients with incidentally discovered adnexal lesions. Imaging characteristics and lesion size were recorded. To determine the significance of the lesions, we also reviewed clinical, radiologic, and histopathologic data. Lesions were judged to be benign on the basis of 12-month clinical follow-up, additional imaging that revealed stability or resolution, or histopathology. Lesions were judged to be malignant on the basis of progression of the lesion on subsequent imaging or histopathology. Lesions were classified as undetermined in patients with a serious or life-threatening illness who consequently underwent no further evaluation of the lesion. RESULTS: An incidental adnexal lesion was revealed by CT scanning in 168 cases (5%). Seventeen of these patients were lost to follow-up. Of the remaining 151 patients, 104 (69%) had incidental adnexal lesions that represented benign disease, 45 (30%) had undetermined lesions, and two (1%) had malignant lesions. In analyzing the two subgroups of patients, we determined that 56 (81%) of 69 premenopausal patients and 48 (59%) of 82 postmenopausal patients had benign adnexal lesions. On the basis of chart review, 67 patients had a known malignancy. Of these patients, 30 (46%) had benign adnexal disease, and 31 (48%) had undetermined findings. Four (6%) were lost to follow up, and the remaining two patients (3%) who were postmenopausal had metastatic disease of the ovaries. No primary ovarian malignancies were discovered incidentally in our study population. CONCLUSION: Our results indicate that in both premenopausal and postmenopausal women a significant proportion of adnexal lesions incidentally revealed on routine CT scanning are benign, even in women with known malignancies other than ovarian carcinoma.

Adnexal Diseases↗
PubMed1997

Arterial versus portal venous helical CT for revealing pancreatic adenocarcinoma: conspicuity of tumor and critical vascular anatomy.

OBJECTIVE: The purpose of this study was to determine the conspicuity of pancreatic adenocarcinoma and surrounding critical pancreatic vascular structures on helical CT scans obtained during the arterial and portal venous phases of enhancement. SUBJECTS AND METHODS: Forty patients with pancreatic adenocarcinomas under-went dual-phase helical CT (3-mm collimation; l-mm overlapping reconstructions; 160 ml contrast medium injected at 4 ml/sec; scan delay: 18 sec for arterial phase, 60 sec for portal venous phase). Tissue enhancement and differences in tumor-to-pancreas contrast were compared. Quantitative evaluation was also done for the aorta, the superior mesenteric artery and vein, and the splenic and portal veins. RESULTS: Tumor conspicuity was significantly greater in the portal venous phase, when the tumor-to-pancreas contrast difference was 54 +/- 31 H, than in the arterial phase, when the difference was 31 +/- 29 H. Enhancement values of critical pancreatic venous structures were significantly greater in the portal venous phase than in the arterial phase. CONCLUSION: Arterial-phase helical CT in patients with pancreatic adenocarcinoma is of limited benefit: lesion conspicuity is suboptimal and depiction of venous anatomy is inferior to the depiction possible with venous-phase helical CT.

Adenocarcinoma↗
PubMed1996

Gadolinium-DTPA enhanced echoplanar MR imaging of the liver: preliminary observations.

This study describes our preliminary experience with dynamic gadopentetate dimeglumine enhanced echoplaner MR imaging (EPI) in fifteen patients with focal liver lesions. Lesion diagnosis was established by histology (n = 3) or typical imaging characteristics (exclusive of the EPI study) combined with clinical follow up (n = 12). Dynamic gadopentetate dimeglumine (0.1 mmol/kg) enhanced MR imaging was performed on a commercially available 1.5 T EPI equipped MR system using a single-excitation fat-suppressed inversion recovery pulse sequence. The choice of an IR sequence allowed nulling of the lesion signal by varying T1 prior to enhancement creating the optimal conditions for qualitative inspection of the enhancement profile. Intershot delay (defined as TR) ranged from 1-5s. Image analysis was performed qualitatively by two radiologists. Benign and malignant lesions displayed temporal enhancement profiles compatible with characteristic findings expected with conventional imaging modalities. Further refinements in our technique and expanded system capabilities will allow dynamic imaging of the entire liver with improved temporal resolution over conventional sequences.

Contrast Media↗
PubMed1996

T2 relaxation times of hypervascular and non-hypervascular liver lesions: do hypervascular lesions mimic haemangiomas on heavily T2-weighted MR images?

AIM: To correlate the T2 relaxation times of liver lesions with their vascularity at angiography and to determine whether hypervascular lesions have similar signal intensity to haemangiomas on heavily T2-weighted MR images. PATIENTS AND METHODS: Thirty-four patients with histologically proven malignant liver lesions had both angiography and T2W (SE 3000/80,160) MR imaging (1.5 T) of the liver. Angiographically, the lesions were hypervascular in 15 and non-hypervascular in 19 patients. Fifteen additional patients with proven haemangioma also had MR imaging during the same time period. The T2 relaxation time of a representative lesion was calculated for each patient and the results compared. RESULTS: The mean T2 time for hypervascular lesions was 76 +/- 21 ms compared with 79 +/- 18 ms for non-hypervascular lesions (P = 0.61). The mean T2 relaxation time for haemangiomas was significantly longer than either group: 147 +/- 46 ms (P = 0.0001). CONCLUSION: The T2 relaxation times of hypervascular and non-hypervascular liver lesions are similar and are significantly shorter than those of haemangiomas. Therefore, hypervascular lesions should not mimic haemangiomas on heavily T2-weighted images.

Carcinoma, Hepatocellular↗
PubMed1996

Mn-DPDP enhanced MR imaging of the liver: analysis of pulse sequence performance.

AIM: To compare liver enhancement and lesion-liver contrast on T1-weighted (T1W) gradient recalled echo (GRE), spin-echo (SE) and fat-suppressed SE (FS-SE) pulse sequences at Manganese-DPDP (Mn-DPDP) enhanced magnetic resonance (MR) imaging of the liver. PATIENTS AND METHODS. Twenty-one patients with known liver lesions were administered 5 mumol/kg of Mn-DPDP. TIW GRE (78/2.3/80 degrees), SE and F-SE (300/12) images were obtained before and 15 min after Mn-DPDP. Signal/noise ratio (SNR) and lesion-liver contrast/noise ratio (CNR) were calculated for each pulse sequence. RESULTS: Liver SNR (n = 21) and lesion-liver CNR (n = 10) increased significantly after Mn-DPDP on all three pulse sequences (P < 0.0001). Liver SNR was highest on the FS-SE and GRE pulse sequences (FS-SE = 43.8, GRE = 38.4, SE = 29.2). Lesion-liver CNR was highest on the FS-SE pulse sequence (FS-SE = -29.3, SE = -23.2, GRE = -19.8), which was significantly higher than the GRE pulse sequence (P < 0.05). CONCLUSION: The T1-weighted fat-suppressed SE (FS-SE) pulse sequence provides highest liver enhancement and lesion-liver contrast and is recommended for Mn-DPDP enhanced MR imaging.

Adult↗
PubMed1996

MR contrast material for vascular enhancement: value of superparamagnetic iron oxide.

OBJECTIVE: The purpose of this study were to quantify abdominal vascular enhancement and to prove the feasibility of iron oxide-enhanced MR angiography in humans using three doses of superparamagnetic iron oxide agent AMI 227. SUBJECTS AND METHODS: Sixteen patients randomly received either 0.8, 1.1, or 1.7 mg Fe/kg of ultrasmall superparamagnetic iron oxide agent AMI 227. T1-weighted breath-hold gradient-echo images were obtained before and 45 min after i.v. administration of AMI 227. Signal intensity was measured in the aorta, the inferior vena cava, the portal vein, and muscle on unenhanced and contrast-enhanced images. Signal-to-noise ratios and enhancement [(SNR after contrast-SNR before contrast) / SNR before contrast] were calculated. Vessels were visually graded before and after administration of AMI 227. RESULTS: All vessels showed statistically significant enhancement 45 min. after administration of AMI 227 by both qualitative and quantitative measures (p < .001). There was no significant increase in noise or signal intensity of muscle after contrast material was administered. The amount of enhancement was not statistically significantly different among the three doses. CONCLUSIONS: AMI 227, which is currently in phase III clinical trials, demonstrates significant vascular enhancement and may prove useful as an MR angiographic contrast agent.

Adult↗
PubMed1995

Percutaneous ethanol injection for the treatment of hepatic tumors: indications, mechanism of action, technique, and efficacy.

Percutaneous injection of ethanol for treatment of hepatic tumors was first described by Sugiura et al. [1] in 1983. To date, reported experience with the procedure has focused mainly on therapy of hepatocellular carcinoma (HCC) [2-15], with little information available regarding its use in treating metastatic liver lesions [16]. Interest in this technique has grown recently as a possible means of treating patients with metastatic liver disease. The purpose of this perspective is to review the indications, mechanism of action, technique, complications, and efficacy of percutaneous ethanol injection for liver tumor treatment.

Carcinoma, Hepatocellular↗
PubMed1995

Blood-pool MR contrast material for detection and characterization of focal hepatic lesions: initial clinical experience with ultrasmall superparamagnetic iron oxide (AMI-227).

OBJECTIVE: AMI-227 is an ultrasmall superparamagnetic iron oxide colloid known to enhance tissue T1 and T2 relaxation rates. Animal studies show that AMI-227 has an estimated blood half-life of more than 200 min. In this study, we evaluated the clinical utility of AMI-227 as an MR contrast agent for detection and characterization of focal hepatic lesions, with MR imaging done while the contrast agent is in the intravascular space (blood-pool phase). SUBJECTS AND METHODS: Twenty-two patients with known or suspected focal hepatic masses underwent T1- and T2-weighted MR imaging of the liver at 1.5 T before and immediately after drip infusion of AMI-227 at doses of 0.8, 1.1, or 1.7 mg Fe/kg. Unenhanced and contrast-enhanced images were analyzed qualitatively (lesion detection and tissue characterization) and quantitatively (lesion-liver contrast-to-noise ratio). RESULTS: AMI-227 enhanced signal in normal liver and blood vessels on T1-weighted images and decreased signal in these tissues on T2-weighted images. Qualitatively and quantitatively, lesion-liver contrast was increased for solid tumors (non-cyst and nonhemangioma) at all three doses (p < .02) on both T1- and T2-weighted images. Differentiation between blood vessels and small lesions was easier on contrast-enhanced images, which allowed increased confidence in excluding lesions. Unique enhancement patterns were noted for hemangiomas, solid tumors, and cysts. CONCLUSION: Initial clinical experience suggests that AMI-227 is a useful contrast agent for detection and characterization of focal hepatic lesions.

Adult↗
PubMed1995

Characterization of adrenal masses (< 5 cm) by use of chemical shift MR imaging: observer performance versus quantitative measures.

OBJECTIVE: The purposes of this study were to evaluate the ability of chemical shift MR imaging to differentiate 1- to 5-cm adrenal adenomas from metastases and to compare subjective interpretation with several different quantitative measures. SUBJECTS AND METHODS: Forty-three patients with 46 proved adrenal lesions (28 adenomas and 18 metastases) had MR imaging with a gradient-echo breath-hold technique and echo time varied to obtain in-phase and out-of-phase images. Qualitative analysis of the MR images was done by three experienced observers, who reported their confidence in diagnosing the benignity versus the malignancy of the adrenal masses on the basis of signal loss on out-of-phase images. Quantitative analysis was performed by calculating the difference in signal intensity between in-phase and out-of-phase images by use of regions of interest (signal intensity index) and by use of adrenal-liver, adrenal-spleen, and adrenal-muscle signal intensity ratios. Results between quantitative and qualitative measures were compared by use of receiver operating characteristic (ROC) analysis. RESULTS: The mean signal intensity was significantly different between adenomas and metastases on out-of-phase images (64 versus 98) (p < .0005) but not in-phase images (130 versus 122) (p = .47). The adrenal-spleen ratio discriminated between adenomas and metastases better than did the adrenal-liver ratio, the adrenal-muscle ratio, or the signal intensity index. No significant difference in interpretation among the three observers was evident (areas under the ROC curves, 0.93, 0.95, and 0.96). The performance of the observers was comparable to the results obtained with the adrenal-spleen ratio measurement (area under the ROC curve, 0.97). CONCLUSION: Experienced observers were able to differentiate adrenal adenomas from metastases just as well as quantitative measures. The adrenal-spleen ratio is the best quantitative means of distinguishing benign from malignant adrenal masses. Chemical shift MR imaging is a good but imperfect discriminator of adrenal adenomas.

Adenoma↗
PubMed1995

Cytopathologic touch preparations (imprints) from core needle biopsies: accuracy compared with that of fine-needle aspirates.

OBJECTIVE: The aim of this study was to evaluate the touch preparation (imprint) cytology method for obtaining rapid interpretations from core material obtained during abdominal percutaneous biopsy. SUBJECTS AND METHODS: For 28 patients undergoing biopsy of abdominal masses, paired slides were prepared for rapid staining by use of smears of standard fine-needle aspirates and by use of a touch preparation of the core material obtained with a semiautomated biopsy gun. The slides were scored in comparison with the final cytopathologic and histopathologic diagnosis. RESULTS: Touch preparation slides were equivalent in diagnostic yield to fine-needle aspirate smears, demonstrating similar cellular features. Touch preparation slides revealed features of tumor architecture not present on smears. CONCLUSION: Touch preparation cytology offers rapid diagnosis from a single core biopsy sample. Carefully performed, the touch preparation method preserves the core material for subsequent permanent fixation and sectioning.

Abdominal Neoplasms↗
PubMed1995

An imaging algorithm for the differential diagnosis of adrenal adenomas and metastases.

OBJECTIVE: The purpose of this study was to develop an algorithm using CT and chemical-shift MR imaging for the characterization of adrenal masses in patients with a primary cancer and no other evidence of metastatic disease. SUBJECTS AND METHODS: Thirty-three patients with 37 adrenal masses (19 metastases, 18 adenomas), all of whom had a known primary cancer, were studied with noncontrast CT and chemical-shift MR imaging (1.5 T). Lesion size and density in Hounsfield units (H) were determined by CT. Adrenal signal intensity normalized to that of spleen was used to calculate adrenal-spleen ratio (ASR), defined as the percentage of signal remaining in the opposed-phase image relative to the in-phase image. Lesions less than or equal to 0 H were classified as benign, lesions greater than 20 H were regarded as malignant, and lesions between 0 and 20 H were regarded as indeterminate. Diagnoses were confirmed by biopsy (for 19 lesions) or by follow-up imaging (for 18 lesions). An imaging algorithm was derived by determining the relative value of CT and MR imaging for diagnosing the lesions. The reimbursement rates for CT-guided biopsy and MR imaging of the abdomen were obtained from Medicare. RESULTS: All 13 lesions of 0 or less H were correctly classified as benign by CT. ASR was less than 70 in 10 of these 13. In another 13 lesions, H was greater than 20; all were malignant and all had an ASR greater than 80. Of 11 CT-indeterminate lesions, four of five adenomas had an ASR less than 70, and four of six metastases had an ASR greater than 80. Two malignant lesions had ASRs between 70 and 80 and were diagnosed by biopsy findings. One CT-indeterminate adenoma had an ASR of 84 and was diagnosed by biopsy findings. The reimbursement rate by Medicare is similar for CT-guided biopsy with pathologic interpretation and for MR imaging of the abdomen. CONCLUSION: An algorithm was developed for diagnosis of adrenal lesions that uses the density reading on noncontrast CT as the first step, with chemical-shift MR imaging for CT-indeterminate lesions. In this algorithm, lesions of 0 H or less may be regarded as benign and further work-up is not required. Lesions with a density greater than 20 H are likely malignant and should be biopsied when the result will influence management. For CT-indeterminate lesions, we recommend chemical-shift MR imaging. An ASR threshold of 70 indicates a benign lesion, and no further workup is required in these patients. Lesions with an ASR greater than 70 should have a biopsy performed, depending on the clinical situation. The above algorithm is cost-effective and reduces the number of biopsies required without reducing the sensitivity of detecting malignant lesions.

Adrenal Cortex↗
PubMed1995

[Echo-planar imaging (EPI) of the abdomen].

The time resolution of echoplanar imaging (EPI) allows the acquisition of images < or = 100 ms, thus eliminating motion-related artifacts of the abdomen. Physical limitations are restrictions in signal-to-noise ratio and spatial resolution. Breath-held acquisitions are recommended to avoid spatial misregistrations and to ensure a defined slice position. Clinical studies have demonstrated the usefulness of EPI for the detection and characterization of focal liver lesions. The development of clinical strategies of EPI for abdominal imaging requires the administration of gastrointestinal contrast agents as in computed tomography. Current clinically approved CT contrast agents appear to be applicable for abdominal EPI because of their long relaxation times.

Abdominal Neoplasms↗
PubMed1994

Failed metallic biliary stents: causes and management of delayed complications.

OBJECTIVE: To describe the incidence, management and long-term outcome of metal stent failure in patients with malignant biliary obstruction. SUBJECTS AND METHODS: Sixty-nine patients received a total of 93 metallic biliary stents for relief of malignant biliary obstruction. Twenty-nine patients had hilar tumours; 40 had common bile duct tumours. RESULTS: Ten of 69 patients (14%) presented with stent occlusion at a mean interval of 4 months after stent insertion. Five of 29 patients (17%) with hilar lesions and five of 40 patients (12%) with common bile duct lesions had stent occlusion. Occlusion was due to tumour overgrowth in eight patients and to occlusion by debris in two. The eight patients with tumour overgrowth were treated with internal/external catheters (5 patients), no therapy (2 patients), and further metal stents (1 patient). These eight patients with tumour overgrowth had a limited lifespan after tumour overgrowth occurred with a mean survival of 2.6 months. The two patients with occlusion due to debris were treated by sweeping the stent with a balloon catheter and these patients survived 26 and 27 months, respectively. CONCLUSION: Adequate peripheral purchase in the biliary tree and overstenting are necessary to prevent tumour overgrowth when stenting hilar lesions. The development of stent occlusion due to tumour overgrowth heralds a limited survival and internal/external catheters are preferred over further metal stents for palliation.

Adult↗
PubMed1994

State-of-the-art MR imaging of the adrenal gland.

The authors discuss the appearances of adrenal diseases characterizable with magnetic resonance (MR) imaging (pheochromocytomas, hemorrhage, cysts, adenomas, myelolipomas, and metastases), new imaging techniques, and differentiation of benign from malignant lesions. Most pheochromocytomas appear markedly hyperintense relative to the liver on T2-weighted images. However, this appearance is not specific, since adrenal metastases and adenomas may have similar features. Occasionally, pheochromocytomas may be iso- or hypointense to the liver on T2-weighted images. One of the new techniques for MR imaging of the adrenal gland, fat suppression, reduces cardiac and respiratory motion-induced artifacts, accentuates small differences in tissue contrast, and eliminates chemical shift artifacts. These advantages far outweigh the disadvantages of inhomogeneity of fat suppression and the fewer sections obtained per acquisition. Differentiation of adrenal metastases from adrenal adenomas with MR imaging is problematic with the use of signal intensity ratios (33% overlap) or T2 calculations. The future of discriminating between adrenal metastases and adenomas may rest with chemical shift MR imaging, which uses in-phase and out-of-phase gradient-echo pulse sequences. This approach relies on the fact that adrenal adenomas contain fat whereas metastases do not. The reported accuracy of chemical shift imaging in differentiating adrenal adenomas from metastases is 96%-100%.

Adrenal Gland Diseases↗