Biomedical subjects

Peter F Hahn

Publications and source records attributed to Peter F Hahn.

67 records · Page 4Linked to original sources

PubMedDate not supplied

Characterization of small liver lesions: Added role of MR after MDCT.

OBJECTIVE: The purpose of this study is to evaluate the added role of magnetic resonance imaging (MR) in characterizing subcentimeter focal liver lesion(s) detected on multidetector row helical computed tomography (MDCT). MATERIALS AND METHODS: A retrospective analysis was performed in 59 noncirrhotic patients with focal subcentimeter liver lesion(s) detected on a 4- or 16-slice MDCT. All patients had a gadolinium enhanced liver MR on 1.5-T systems within 6 weeks after MDCT. Imaging diagnosis was graded on an ordinal scale of 0-5 (0, normal; 1, definitely benign; and 5, definitely malignant). The final diagnosis was established either by histopathology or follow-up imaging for a period of at least 6 months. Receiver operating characteristic analysis was performed to compare the performances of MDCT and MR in characterization of subcentimeter liver lesions. RESULTS: A total of 178 lesions were detected on MDCT in 59 patients. Of these lesions, 129 (72.5%) lesions were benign and the remaining 49 were malignant. The sensitivity, specificity, positive predictive value, and negative predictive value in differentiation of benign from malignant lesions on MDCT were 81.2%, 77.3%, 60.5%, 90.6 % and on MR were 83.3%, 97.5%, 92.1%, and 94.4 %, respectively. Comparative receiver operating characteristic analysis showed an area under curve for MDCT = 0.76 and MR = 0.95 (P < 0.001). CONCLUSIONS: Liver MR has significantly higher accuracy for characterization of subcentimeter focal liver lesions discovered on MDCT.

Adult↗

PubMedDate not supplied

Distinguishing hepatic metastases from hemangiomas: qualitative and quantitative diagnostic performance through dual echo respiratory-triggered fast spin echo magnetic resonance imaging.

OBJECTIVE: To determine the relative value of qualitative (reader opinion) and quantitative (values derived from dual echo T2 fast spin echo [FSE]) measures in distinguishing hepatic metastases from hemangiomas. METHODS: Forty-nine patients with hemangiomas and 23 with metastases were studied with dual echo respiratory-triggered FSE and dynamic 2-dimensional spoiled gradient echo (GRE) imaging. Lesion T2 was estimated from signal intensity ratios on the first and second echoes. Two experienced radiologists independently evaluated groups of images based on 5 separate qualitative measures: first echo FSE, second echo FSE, first and second echo FSE, dynamic GRE, and all images together. RESULTS: The mean calculated T2s were 226 +/- 74 milliseconds for hemangiomas and 105 +/- 22 milliseconds for metastases (P < 0.001). A T2 cutoff of 130 milliseconds distinguished metastases from hemangiomas with a sensitivity of 94%, specificity of 91%, and accuracy of nearly 94%. There was no significant difference between the best quantitative measure and the best qualitative measure for either reader. CONCLUSION: Liver lesion T2 relaxation times calculated from dual echo FSE images provide information useful in discriminating metastases from hemangiomas, as does reader opinion.

Adult↗

PubMedDate not supplied

Comparison of enhancement, image quality, cost, and adverse reactions using 2 different contrast medium concentrations for routine chest CT on 16-slice MDCT.

OBJECTIVE: To evaluate the degree of enhancement and image quality of chest computed tomographic (CT) examinations on 16-slice multidetector CT using low-concentration [300 milligrams of iodine per milliliter (mg I/mL)] and high-concentration (370 mg I/mL) contrast media; to assess the impact on cost and adverse reactions of the use of high-iodine concentration contrast medium. MATERIALS AND METHODS: A total of 100 patients scheduled for routine chest CT examinations were administered nonionic contrast medium of 2 strengths: low-iodine concentration contrast medium (300 mg I/mL) [group A: n = 50; male-female ratio, 28:22; mean age, 58.4 years] and high-iodine concentration contrast medium (370 mg I/mL) (group B: n = 50; male-female ratio, 18:32; mean age, 57.6 years) with a constant amount of iodine (400 mg) injected per kilogram of body weight. Contrast media were injected using a dual injector at 2.5 mL/s followed by a 30-mL saline at 2.5 mL/s. The degree of enhancement was quantified by measuring Hounsfield unit values in different arteries and veins and was also rated on a 5-point scale for qualitative assessment. We also evaluated perivenous contrast-related artifacts. The data were compared using Mann-Whitney U test for both qualitative and quantitative enhancement ratings. A value of less than 0.05 was considered statistically significant. The value was adjusted using Bonferroni correction for statistical significance when multiple comparisons were performed. The difference in cost and the incidence of adverse reactions in both groups were calculated. RESULTS: The mean enhancement values in group B were significantly greater (P < 0.05) than those in group A. The mean Hounsfield units and standard deviation in groups A and B were aorta = 153 +/- 4, 216 +/- 20; pulmonary artery = 147 +/- 10, 208 +/- 20; superior vena cava = 155 +/- 27, 299 +/- 72; and pulmonary vein = 134 +/- 10, 215 +/- 30, respectively. The mean enhancement on a 5-point scale was greater in group B (4.2) than in group A (3.3) (P < 0.01). No significant difference between groups in perivenous artifacts was seen. Up to 5.5% savings in cost resulted from the use of a higher concentration of iodine, with no increase in adverse reactions. CONCLUSIONS: Use of higher-concentration contrast media provides a higher degree of contrast enhancement and image quality for a routine chest CT on a 16-slice multidetector CT. It also contributes to considerable cost savings with no increased risk of adverse reactions compared with low-concentration contrast media.

Adult↗

PubMedDate not supplied

CT-guided transgluteal drainage of deep pelvic abscesses: indications, technique, procedure-related complications, and clinical outcome.

Deep pelvic abscesses may present a unique challenge for percutaneous drainage because of numerous overlying structures, which preclude safe percutaneous access. These structures include the pelvic bones, intestine, bladder, iliac vessels, and gynecologic organs. Use of the transgluteal approach to drain these abscesses can circumvent these obstacles and provide a useful surgical alternative or a temporizing measure. The transgluteal approach requires a thorough understanding of the anatomy of the sciatic foramen region and associated anatomic structures. The ideal approach for transgluteal access is to insert the catheter as close to the sacrum as possible, at the level of the sacrospinous ligament. Transgluteal drainage can be performed with the tandem-trocar technique or the Seldinger technique. Modifications of the procedure are needle aspiration not followed by catheter placement, use of the angled gantry technique, bilateral transgluteal drainage, combined anterior and posterior drainage, and drainage of necrotic pelvic masses. The transgluteal approach is a useful option in pediatric patients. Daily catheter care is essential for successful percutaneous catheter therapy. Although pain has been cited as a common complication of the technique, this complication can be minimized with judicious use of analgesia and a meticulous technique. Other complications are hemorrhage and catheter malposition.

Abdominal Abscess↗

PubMedDate not supplied

Urine leaks and urinomas: diagnosis and imaging-guided intervention.

Urine leaks from the kidney, ureter, bladder, and urethra most commonly result from trauma. Urinomas may be occult initially and may lead to complications such as abscess formation and electrolyte imbalances if not promptly diagnosed and appropriately managed. Radiologists play a key role in diagnosing urine leaks and determining their cause and extent. Contrast material-enhanced computed tomography (CT) with delayed imaging, CT cystography, and retrograde urethrography are the diagnostic imaging studies of choice. Studies such as intravenous pyelography, antegrade and retrograde pyelography, renal scintigraphy, and imaging-guided needle aspiration may play complementary diagnostic roles. In some instances, the role of the radiologist ends with the diagnosis of urine leaks, after which patients are treated conservatively or perhaps surgically. Uncomplicated renal urine leaks, extraperitoneal urinary bladder rupture, and type 1 urethral injuries are generally managed conservatively. Urine leaks that require more extensive, imaging-guided treatment can usually be managed safely and effectively with a combination of percutaneous urinoma drainage catheters, percutaneous nephrostomy catheters, ureteral stents, and bladder drainage. In the appropriate setting, use of these management options may reduce urinoma-related complications and limit or totally eliminate the need for urologic surgery.

Adolescent↗

PubMedDate not supplied

Importance and effects of altered workplace ergonomics in modern radiology suites.

The transition from a film-based to a filmless soft-copy picture archiving and communication system (PACS)-based environment has resulted in improved work flow as well as increased productivity, diagnostic accuracy, and job satisfaction. Adapting to this filmless environment in an efficient manner requires seamless integration of various components such as PACS workstations, the Internet and hospital intranet, speech recognition software, paperless electronic hospital medical records, e-mail, office software, and telecommunications. However, the importance of optimizing workplace ergonomics has received little attention. Factors such as the position of the work chair, workstation table, keyboard, mouse, and monitors, along with monitor refresh rates and ambient room lighting, have become secondary considerations. Paying close attention to the basics of workplace ergonomics can go a long way in increasing productivity and reducing fatigue, thus allowing full realization of the potential benefits of a PACS. Optimization of workplace ergonomics should be considered in the basic design of any modern radiology suite.

Asthenopia↗

PubMedDate not supplied

The inaccessible or undrainable abscess: how to drain it.

Percutaneous abscess drainage is a safe, effective, and widely used technique for the treatment of patients with abdominal or pelvic sepsis. The majority of abdominal and pelvic abscesses afford reasonably straightforward access and are amenable to percutaneous drainage. However, requests are occasionally received for drainage of abscesses or fluid collections that initially appear unsuitable for percutaneous drainage. Factors that render collections seemingly unsuitable for imaging-guided drainage include inaccessibility due to surrounding organs, difficult location, and thickened contents (eg, clotted blood, thick pus). Well-established alternative approaches (eg, transgluteal, transvaginal, transrectal) can be used to facilitate drainage of deep-seated collections that are inaccessible via more traditional routes. Other factors that may improve the accessibility of collections include modifications in patient positioning or in the use of imaging hardware (eg, angling of the computed tomography scanner gantry). Use of these techniques and modifications can allow percutaneous drainage of less accessible intraabdominal abscesses, thus eliminating the need for laparotomy.

Abscess↗

PubMedDate not supplied

MR lymphangiography: imaging strategies to optimize the imaging of lymph nodes with ferumoxtran-10.

Detection of local or regional metastases to lymph nodes is clinically important in virtually any type of primary tumor. Current imaging techniques rely heavily on the size criterion for characterization of nodal disease. However, size can be an ineffective parameter for diagnosis of tumor spread to lymph nodes. Magnetic resonance (MR) imaging performed before and after administration of ferumoxtran-10 is a promising technique for characterization of lymph nodes in patients with various primary tumors. Normal homogeneous uptake of ferumoxtran-10 in nonmetastatic nodes shortens the T2 and T2*, turning these nodes dark, whereas malignant nodes lack uptake and remain hyperintense. To optimize acquisition strategies, the following factors should be considered: the timing of contrast material-enhanced imaging, the section thickness, the imaging plane, and the imaging parameters for T2*-weighted sequences. In addition, MR imaging with ferumoxtran-10 allows presurgical mapping of lymph nodes and quantitative estimation of T2*.

Algorithms↗

PubMedDate not supplied

Imaging diagnosis of cystic pancreatic lesions: pseudocyst versus nonpseudocyst.

Although the clinical, radiologic, and pathologic features of cystic pancreatic lesions are well known, preoperative diagnosis is difficult. Differentiation between a pancreatic pseudocyst and a cystic pancreatic neoplasm is crucial in determining the proper treatment. Careful evaluation of the patient's clinical history is important for accurate diagnosis of a pseudocyst. Clinical scenarios include a pseudocyst developing after acute pancreatitis and a pseudocyst superimposed on chronic pancreatitis. However, a pseudocyst in a patient with no clinical history of pancreatitis poses a diagnostic problem. The differential diagnosis of a neoplastic cystic lesion of the pancreas includes serous cystadenoma, mucinous cystic neoplasms, intraductal papillary mucinous tumor, and solid and papillary epithelial neoplasm. Definitive diagnosis is often possible when the lesion has a typical radiologic appearance, but in many cases characterization with imaging alone is impossible. Thin-section computed tomography with multiplanar reformation, magnetic resonance cholangiopancreatography, and endoscopic ultrasonography have emerged as modalities that can provide additional diagnostic information. Familiarity with the range of imaging appearances and awareness of the diagnostic strengths and limitations of each imaging modality are important for accurate diagnosis and management of cystic pancreatic lesions.

Adult↗

PubMedDate not supplied

Cystic pancreatic lesions: a simple imaging-based classification system for guiding management.

Cystic lesions of the pancreas are increasingly being recognized due to the widespread use of cross-sectional imaging. The initial evaluation of a pancreatic cyst should be directed toward exclusion of a pseudocyst. Patients with pseudocysts generally have a history of acute or chronic pancreatitis, whereas those with cystic tumors most often lack such a history. Several types of cystic lesions are encountered in the pancreas. Because of morphologic overlap at imaging, accurate characterization of these lesions can be difficult. Computed tomography and magnetic resonance imaging are excellent modalities for both initial detection and characterization of cystic pancreatic lesions. An imaging classification system for these lesions has been proposed that is based on the morphologic features of the lesion. This system can be helpful in characterizing lesions, narrowing the differential diagnosis, and making decisions regarding the treatment of affected patients. Endoscopic ultrasonography-guided aspiration and biopsy is useful in cases that are indeterminate at cross-sectional imaging or that require observation.

Algorithms↗

PubMedDate not supplied

Acute epiploic appendagitis and its mimics.

Acute epiploic appendagitis most commonly manifests with acute lower quadrant pain. Its clinical features are similar to those of acute diverticulitis or, less commonly, acute appendicitis. The conditions that may mimic acute epiploic appendagitis at computed tomography (CT) include acute omental infarction, mesenteric panniculitis, fat-containing tumor, and primary and secondary acute inflammatory processes in the large bowel (eg, diverticulitis and appendicitis). Whereas the location of acute epiploic appendagitis is most commonly adjacent to the sigmoid colon, acute omental infarction is typically located in the right lower quadrant and often is mistaken for acute appendicitis. It is important to correctly diagnose acute epiploic appendagitis and acute omental infarction on CT images because these conditions may be mistaken for acute abdomen, and the mistake may lead to unnecessary surgery. The CT features of acute epiploic appendagitis include an oval lesion 1.5-3.5 cm in diameter, with attenuation similar to that of fat and with surrounding inflammatory changes, that abuts the anterior sigmoid colon wall. The CT features of acute omental infarction include a well-circumscribed triangular or oval heterogeneous fatty mass with a whorled pattern of concentric linear fat stranding between the anterior abdominal wall and the transverse or ascending colon. As CT increasingly is used for the evaluation of acute abdomen, radiologists are likely to see acute epiploic appendagitis and its mimics more often. Recognition of these conditions on CT images will allow appropriate management of acute abdominal pain and may help to prevent unnecessary surgery.

Acute Disease↗

PubMedDate not supplied

Imaging of penile neoplasms.

The assessment of penile cancer on the basis of clinical findings alone can often result in inaccurate staging and suboptimal treatment. Imaging of primary penile cancer and metastatic lymphadenopathy can help optimize planning of both primary tumor resection and treatment for lymph node metastases. Magnetic resonance (MR) imaging is the most accurate imaging modality in the assessment of primary penile cancers, which usually manifest as solitary, ill-defined infiltrating tumors that are hypointense on both T1- and T2-weighted MR images. T2-weighted MR imaging allows delineation of the tumor margin and of any extension into the penile shaft. On gadolinium-enhanced T1-weighted images, the tumors enhance to a greater extent than do the corpora cavernosa. In addition, the recently introduced technique known as lymphotrophic nanoparticle-enhanced MR imaging can help identify metastatic lymph node disease. However, further studies will be needed to determine the role of this imaging technique in clinical practice. Computed tomography does not clearly depict the local extension of primary penile cancer; however, it is useful in assessing metastases and postoperative complications.

Humans↗

PubMedDate not supplied

Adult intestinal intussusception: CT appearances and identification of a causative lead point.

The widespread application of computed tomography (CT) in different clinical situations has increased the detection of intussusception, particularly non-lead point intussusception, which tends to be transient. Consequently, determining the clinical significance of intussusception seen at CT poses a diagnostic challenge. Patients with intussusception may or may not be symptomatic, and symptoms can be acute, intermittent, or chronic, making clinical diagnosis difficult. In most cases, radiologists can readily make the correct diagnosis of intestinal intussusception by noting the typical bowel-within-bowel appearance at abdominal CT. However, the CT findings that help differentiate between lead point and non-lead point intussusception have not been well studied. Nevertheless, although there is considerable overlap of CT findings, when a lead mass is seen at CT as a separate and distinct entity vis-à-vis edematous bowel, it can be considered a reliable indicator of a lead point intussusception. Differentiating between lead point and non-lead point intussusception is important in determining the appropriate treatment and has the potential to reduce the prevalence of unnecessary surgery.

Adult↗