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P L Davis

Publications and source records attributed to P L Davis.

At least 37 records · Page 2Linked to original sources
PubMed1994

Digital radiography and conventional imaging of the chest: a comparison of observer performance.

OBJECTIVE: The purpose of this study was to compare observer performance in interpreting high-quality, digitally acquired computed radiographs of the chest displayed on either laser-printed radiographs or a workstation with observer performance in interpreting conventional chest radiographs. SUBJECTS AND METHODS: We performed a receiver-operating-characteristic study in which the presence or absence of five abnormalities was determined by nine experienced radiologists on 310 posteroanterior radiographs of the chest displayed in three forms: conventional radiographs, laser-printed films of digital radiographs, and digital radiographs on a high-resolution workstation. RESULTS: The results of our study suggest that observer performance with laser-printed films of digital radiographs obtained with high-resolution (4K x 5K), high-contrast sensitivity (12 bits) and appropriate exposure is comparable to observer performance with conventional radiographs. Observer performance with digital radiographs displayed on the workstation was found to be significantly lower for abnormalities that contained high-frequency and low-contrast information (e.g., interstitial disease and pneumothorax). CONCLUSION: Computed radiography technology can produce image quality that is adequate for interpreting posteroanterior radiographs of the chest. Observer performance is not as good when radiographs displayed on workstations are used to diagnose specific abnormalities.

Humans↗
PubMed1994

Technologic considerations for breast tumor size assessment.

Breast tumor staging and treatment response is primarily determined by tumor size. Presently there are four techniques to measure breast cancer size: (1) palpations, (2) mammography, (3) ultrasonography, and (4) MR imaging. This article reviews the applications and limitations of each technique and the improvements MR imaging can provide.

Breast Neoplasms↗
PubMed1993

Budd-Chiari syndrome: imaging with pathologic correlation.

We retrospectively evaluated 21 patients with Budd-Chiari syndrome who underwent liver transplant. The pathological findings were correlated with imaging studies that included computed tomography (CT) in all cases, sonography in 20, and magnetic resonance (MR) in 15. Pathological features of Budd-Chiari syndrome in subacute or chronic form, such as parenchymal fibrosis, hemorrhage, and congestion, were found in all resected livers. These occurred usually in conjunction with restricted hepatic veins due to thrombosis or fibrosis with partially recanalized lumen. The status of hepatic veins was correctly assessed and correlated with pathology in 13 of 20 patients who had sonograms, in 12 of 15 patients who had MR, and in nine of 18 patients with contrast-enhanced CT scans. Patency of the inferior vena cava was well seen by all three modalities; parenchymal abnormalities were best visible on CT (19 of 21), while ascites, caudate lobe enlargement and collateral vessels were best detected with MR or CT. We conclude that each imaging modality offers certain values and limitations in the assessment of vascular or parenchymal findings in Budd-Chiari syndrome.

Adolescent↗
PubMed1993

Magnetic resonance imaging can cause focal heating in a nonuniform phantom.

To test if the radiofrequency fields of a magnetic resonance imager could cause focal heating, two cylindrical phantoms were made from a mixture of agar and saline. The first phantom was uniform; the second was nonuniform in that a narrow bridge of agar was produced. Both phantoms were exposed to high levels of radiofrequency power (140 W) at 63 MHz and the temperature rises were measured. In the uniform phantom, the temperature increased as the radius increased. In the bridge phantom, the narrow bridge heated three times greater than at the opposite uniform periphery, and over five times the average of the uniform phantom. This experiment demonstrates that the radiofrequency fields of magnetic resonance imagers can cause focal heating if the exposed object is nonuniform. Since nonuniformity is present in the human body, as the radiofrequency power of magnetic resonance imaging techniques increases, focal heating in patients is a concern.

Hot Temperature↗
PubMed1993

Blood flow in the portal vein: velocity quantitation with phase-contrast MR angiography.

Quantitative phase-contrast magnetic resonance (MR) angiography of the portal vein was prospectively evaluated in 79 fasting patients and 23 healthy volunteers. Images were obtained during a 12-second breath-hold acquisition in the coronal (n = 102) and axial (n = 11) planes. Pathologic correlation was available in 55 of 79 patients and included findings of cholangiocarcinoma, cirrhosis, hepatocellular carcinoma, hepatitis, and metastatic disease. Forty-one patients had correlative Doppler ultrasound (US) findings. MR and US findings correlated as to flow direction in all cases. In nine patients, Doppler US velocity measurements were available and closely correlated with MR findings. A comparison of axial and coronal portal venous phase-contrast measurements in 11 patients revealed no substantial difference with regard to the plane used. Quantitative phase-contrast MR angiography is a simple and rapid technique for the assessment of portal venous patency, flow direction, and flow velocity and, combined with high-resolution conventional MR imaging, may obviate the current use of both computed tomographic and US examinations.

Blood Flow Velocity↗
PubMed1992

MR imaging of hepatocellular carcinoma at 1.5 Tesla.

The authors investigated the magnetic resonance appearance of hepatocellular carcinoma using a 1.5-Tesla magnet. Twenty-four patients with pathologically proven hepatocellular carcinoma had magnetic resonance imaging (MRI) studies, which were retrospectively reviewed. All patients were imaged with at least two of the following techniques: (1) T1-weighted (T1W), (2) T1-weighted with Gd-DTPA enhancement (T1W-E), (3) T2-weighted (T2W), (4) proton density (PD), and (5) gradient-recalled echoes (GRE). T1W images were equal to T2W images for tumor detection using a grading system. T1W images were slightly better than T2W images for the total number of lesions detected. The other pulsing techniques (PD, T1W-E, and GRE) detected fewer lesions. Eight cases of hepatocellular carcinoma (33%) had nonhomogeneous increased signal intensity on both T1W and T2W images. The authors conclude that T1W images are equal to T2W images for detection of hepatocellular carcinoma. The authors also conclude that 33% of hepatocellular carcinomas have an imaging pattern with increased signal intensity on both T1W and T2W images. This pattern is atypical for most other hepatic masses and hence can be used to suggest the mass is hepatocellular carcinoma.

Adolescent↗
PubMed1992

Comparison of function and fixation of small incision circular and oval poly(methyl methacrylate) intraocular lenses.

A prospective study of function and fixation was done on 40 patients implanted with small incision poly(methyl methacrylate), single piece, biconvex intraocular lenses after in situ phacoemulsification cataract extraction via a continuous curvilinear capsulorhexis. A 5.0 mm circular optic (Pharmacia 740 P), 14 mm length lens was compared with an oval 5.0 x 6.0 mm optic (IntraOptics SP18UB), 12.75 mm lens. Twenty patients were implanted with each design and were surveyed three months postsurgery. Satisfactory visual acuity and absence of motor vehicle headlight glare was found in all 40 patients. One glare disability of 35% occurred in a patient with an off-center capsulorhexis that formed a Soemmering's ring partially posterior to a circular optic lens. Fixation was clinically central in all patients. A space between optic and posterior capsule persisted in seven eyes with an oval optic lens and in eight eyes with a circular optic lens. Therefore both designs were associated with a "no space, no cells" situation that should decrease eventual pearl formation. Total Soemmering's rings formed posterior to 9 of 20 circular optic lenses if the capsulorhexis was 5 mm or larger in diameter (only one oval optic lens formed a Soemmering's ring). Compression of the posterior capsule occurred in seven of the nine patients with circular optic lenses and total Soemmering's rings. I conclude that the circular optic design was best implanted via a 5 mm or slightly larger central capsulorhexis to promote both Soemmering's ring formation and posterior capsule compression. Both designs provided satisfactory clinical results.

Cataract Extraction↗
PubMed1991

Hyperintense cirrhotic nodules on MRI.

Descriptions of regenerating nodules of cirrhosis indicate that they are often isointense to liver parenchyma on magnetic resonance imaging (MRI). Regenerating nodules of cirrhosis can occasionally appear hypointense on all MRI sequences due to iron deposition within the nodules. We reviewed 21 cases of pathologically proven mixed or macronodular cirrhosis using MRI. In five patients, nodules appeared as hyperintense to liver parenchyma on short TR/TE images and were isointense on long TR/TE or GRASS images. In another five cases, nodules appeared hypointense on either long TR/TE or GRASS images, and corresponding hypointense nodules were observed on short TR/TE images in one of these patients. Our findings suggest that regenerating nodules of cirrhosis may have a more variable appearance on short TR/TE images.

Carcinoma, Hepatocellular↗
PubMed1991

Evaluation of facial fat distribution using magnetic resonance imaging.

Magnetic resonance imaging (MRI) provides noninvasive images of facial and neck fat for a variety of conditions. It accurately maps the soft tissues pre- and postoperatively, enabling surgeons to precisely and objectively assess results of soft tissue facial contouring and fat transplantation. The risks of MRI are few. It has the potential to provide aesthetic surgeons with a more "scientific" means of comparing various techniques of fat contouring.

Adipose Tissue↗
PubMed1991

Primary CT diagnosis of abdominal masses in a PACS environment.

Whether the display medium--film versus cathode ray tube (CRT)--affects observer performance during interpretation of computed tomographic (CT) images is an important research issue in these times of implementation and growth of picture archiving and communications systems in radiology. The authors performed a multiobserver receiver operating characteristic (ROC) study to determine the performance of radiologists who read abdominal CT studies displayed on film, as well as on a high-resolution workstation (video monitor) that made use of three different display modes. A total of 166 examinations were evaluated by eight radiologists, who recorded their ordinal confidence ratings of the demonstration of presence or absence of abdominal masses. ROC analysis showed small differences in the confidence ratings assigned by individual readers for the detection and interpretation tasks. Results for the group as a whole showed no significant reduction or improvement in observer performance when ratings for any one of the workstation display modes were analyzed. The results of this study demonstrate that current CRT display technology is adequate for enabling the primary detection of abdominal masses with CT examinations.

Abdominal Neoplasms↗
PubMed1990

Attempted murder with pancuronium.

A nurse was accused of attempting to murder her anesthesiologist husband on two occasions by administering to him a neuromuscular blocking agent. In both episodes, urine specimens were obtained from the victim shortly after the suspected assaults. The samples were initially tested fluorometrically using Rose Bengal dye as a pairing agent. Both were presumptively positive for pancuronium. Confirmation of these results was achieved by pairing the drug with potassium iodide, extracting the complex, and submitting the extract to thin-layer chromatography (TLC) cleanup, elution at the appropriate retardation factor (Rf), and, finally, gas chromatography/mass spectrometry (GC/MS) analysis in the selected-ion monitoring mode. The two quaternary amines of pancuronium appear to undergo pyrolytic N-demethylation in the injection port to yield an entity amenable to capillary column gas chromatography. The mass spectrum of the compound consists of a base peak of m/z 322, with additional fragments of 292, 323, 338, and 397 m/z, each of which was monitored. The confirmed positive findings were instrumental in adjudicating the case.

Gas Chromatography-Mass Spectrometry↗
PubMed1989

Indicator dilution time-activity curves demonstrated by rapid magnetic resonance imaging techniques and paramagnetic contrast agent.

Indicator dilution time-activity curves are demonstrated using magnetic resonance imaging (MRI) as the detector and a paramagnetic contrast agent as the indicator. Manganese chloride was injected into a flow phantom. The nuclear magnetic resonance (MR) intensity was measured downstream. Several flow rates were used. The observed MR intensity decreased as the paramagnetic indicator passed through the imaging plane. The qualitative changes of the MR intensity decrease varied in accordance with indicator dilution theory. The equations for gradient refocused echoes, paramagnetic compound relaxation changes, and the indicator dilution analysis were combined and evaluated. Quantitative analysis demonstrates several problems in its implementation.

Chlorides↗
PubMed1989

Peribulbar block for cataract surgery: a prospective double-blind study of two local anesthetics.

We carried out a prospective double-blind study to compare the effectiveness of 2% lidocaine hydrocarbonate (54 patients) and 2% lidocaine hydrochloride plus 0.5% bupivacaine hydrochloride (46 patients) in achieving peribulbar block of the orbit in patients undergoing cataract surgery. A total of 150 IU of hyaluronidase was added to each syringe before injection. Anesthesia was done with a total of 6 mL injected into the periphery of the orbit and a further 3 to 4 mL injected for seventh cranial nerve block. A successful block, defined as akinesis of the globe at 4 minutes after injection, was achieved in 94% of the patients, with no difference between the two groups. Two minor complications (transient lateral rectus paresis and a small retrobulbar hematoma) were observed. We recommend this method of peribulbar block as it has a rapid onset and its use may lead to a reduced occurrence of the central nervous system complications associated with retrobulbar block.

Anesthetics, Local↗