THE QUANTITY OF ETHYLENE PRESENT IN APPLES.
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Journal Article↗
Biomedical subjects
R C Nelson
Publications and source records attributed to R C Nelson.
"Keyhole" method for accelerating imaging of contrast agent uptake.
Magnetic resonance (MR) imaging methods with good spatial and contrast resolution are often too slow to follow the uptake of contrast agents with the desired temporal resolution. Imaging can be accelerated by skipping the acquisition of data normally taken with strong phase-encoding gradients, restricting acquisition to weak-gradient data only. If the usual procedure of substituting zeroes for the missing data is followed, blurring results. Substituting instead reference data taken before or well after contrast agent injection reduces this problem. Volunteer and patient images obtained by using such reference data show that imaging can be usefully accelerated severalfold. Cortical and medullary regions of interest and whole kidney regions were studied, and both gradient- and spin-echo images are shown. The method is believed to be compatible with other acceleration methods such as half-Fourier reconstruction and reading of more than one line of k space per excitation.
Contrast Media↗
MR imaging of silicone gel-filled breast implants in vivo with a method that visualizes silicone selectively.
The lack of an adequately sensitive method for detecting silicone leakage and reported serious complications due to silicone leakage were cited as justification by the U.S. Food and Drug Administration for imposing the current restrictions on silicone gel-filled breast prostheses. The authors report a new magnetic resonance imaging method for visualizing silicone leakage: the silicone-only sequence (SOS). The method uses the conventional STIR (short-inversion-time inversion-recovery) technique combined with a 1331 radio-frequency pulse train widely used for water suppression in spectroscopy. With the SOS, silicone can be imaged while signals from fat and water are suppressed. The authors used the SOS to image phantoms and normal and ruptured silicone gel-filled breast prostheses.
Breast↗
Enhancement effects of a hepatocyte receptor-specific MR contrast agent in an animal model.
The enhancement characteristics of the liver and spleen produced by a hepatocyte-specific magnetic resonance imaging agent, an arabinogalactan-coated ultrasmall superparamagnetic iron oxide derivative, BMS 180550, were evaluated. Both heavily T1- and T2-weighted sequences were used. Imaging was performed in the farm pig model, as a function of contrast agent concentration (5, 10, and 20 mumol of iron per kilogram) and delay (immediate, 0.5, 2.5, 5.0, 7.5, and 9.0 hours) after bolus injection of BMS 180550. BMS 180550 provided excellent contrast enhancement characteristics by producing marked positive enhancement with T1-weighted sequences and marked negative enhancement with T2-weighted sequences. The T1-weighted enhancement immediately after contrast agent injection was of greater magnitude in the spleen (329% +/- 83) than in the liver (66% +/- 16). Postcontrast negative enhancement with T2-weighted sequences was largely hepatocyte specific at 5 and 10 mumol/kg but was also seen within the spleen at 20 mumol/kg. The authors discuss the possible mechanisms that produce these changes and conclude that 10 mumol/kg BMS 180550 is near the optimum dose for maximizing the enhancement properties of this agent with all sequences in the farm pig.
Animals↗
MR of focal liver lesions: comparison of breath-hold and non-breath-hold hybrid RARE and conventional spin-echo T2-weighted pulse sequences.
To compare liver lesion detection rates, tissue signal and noise data, and qualitative parameters for breath-hold (BH) and non-breath-hold (NBH) hybrid rapid acquisition with relaxation enhancement (RARE) and conventional spin-echo (CSE) T2-weighted (CSE-T2) MR sequences, 20 patients were imaged using all three sequences. Lesion detection rates were 73.5% for the CSE-T2 sequence and 81.1% and 88.6% for the BH-RARE and NBH-RARE sequences, respectively (P = .027). Mean lesion-to-liver signal-difference-to-noise ratio for the NBH-RARE sequence was 14.0 +/- 11.5, significantly greater than 9.8 +/- 7.8 obtained for the BH-RARE sequence (P = .050) and 9.0 +/- 6.2 obtained for the CSE-T2 sequence (P = .015). The NBH-RARE sequence demonstrated fewer artifacts and greater overall image quality compared to the CSE-T2 sequence. The NBH-RARE sequence is a useful alternative to the liver signal-difference-to-noise ratio and lesion detection rate and better overall image quality.
Adult↗
Logistic advantages of four-section helical CT in the abdomen and pelvis.
BACKGROUND: Multisection helical computed tomography (CT) has the potential for providing data sets with better section profiles, more anatomic coverage, and shorter breath-holding periods. Our purpose was to quantitate these advantages in a clinical setting when imaging the abdomen and pelvis. METHODS: CT parameters including collimation, timing, z-axis coverage, and milliamperes were gathered retrospectively for the image set of both single-section (GE CT/i with 0.8-s rotation) and four-section (GE QX/i Lightspeed with 0.8-s rotation) helical CT scanners. Data were recorded for the abdomen and pelvis CT (n = 30 each), dual-phase liver CT including the pelvis (n = 15 each), and dual-phase pancreas CT (n = 15 each). RESULTS: The abdominal and pelvic CT averaged 128.4 +/- 5.4 s for single-section scanners (70-s delay, two breath-holds of 21.1 and 17. 7 s with a 19.5-s interscan delay) and 92.2 +/- 2.2 s for the four-section scanner (70-s delay and a 22.2-s breath-hold; p < 0. 0001). For the dual liver and pelvis CT, single-section scanners averaged 119.9 +/- 7.5 s (30-s delay, 15.8-s arterial phase, 20.0-s interscan delay, 21.2-s venous phase, 19.5-s interscan delay, and 14. 2 s for the remaining abdomen and pelvis), whereas the four-section scanner averaged 86.8 +/- 2.5 s (30-s delay, 6.7-s arterial phase, 27.9-s interscan delay, and 21.8-s venous phase including the pelvis; p < 0.0001). For the dual pancreas CT, single-section scanners averaged 86.7 +/- 2.5 s (20-s delay, 28.3-s arterial phase, 17.8-s interscan delay, 21.7-s venous phase), whereas the four-section scanner averaged 78.0 +/- 2.9 s (20-s delay, 9.7-s arterial phase, 30.7-s interscan delay, 13.0-s venous phase; p < 0. 0001). CONCLUSION: CT scanners having four-section technology can reduce overall data acquisition times by 10-30% and total milliamperes by 50-60% depending on the protocol with thinner slice profiles.
Adult↗
The oblique pharyngogram: value in the assessment of dysphagia.
BACKGROUND: To evaluate the diagnostic value of oblique views of the pharynx in patients with dysphagia. METHODS: One hundred thirty-three patients with symptoms referable to the cervical region underwent pharyngoesophography that included views of the pharyngoesophageal junction filmed at three frames per second and spot films of the pharynx obtained in distended frontal, lateral, and both oblique projections. Examination was completed with assessment of the entire esophagus and gastric cardia. RESULTS: The oblique views identified abnormalities not shown on the standard views in 5% of patients. The oblique views proved useful in 12%, where the lower pharynx was obscured in the lateral projection by large shoulders, and in 18% to assess the valleculae when this region was obscured by the occiput and mandible in the frontal projection. In 12%, the oblique views proved useful in demonstrating normal structures when artifacts raised the possibility of lesions on the standard projections. In 10%, poor technique impaired visualization of pharyngeal structures on the standard projections, but repeat swallows in the oblique projections proved adequate to assess these regions. Three (27%) of the 11 cases of cervical esophageal webs were best seen on oblique views, and in another three patients the webs were visible only on oblique views. CONCLUSIONS: Oblique views are of value in the assessment of the pharynx. There will be instances when the standard projections are inadequate, and these alternative views will complement the evaluation of this region. The addition of oblique views will sometimes improve the confidence of the interpretation of normality or assist evaluation of the extent of an abnormality.
Administration, Oral↗
Are hepatic and muscle T2 values different at 0.5 and 1.5 Tesla?
In an effort to determine whether T2 values of liver and muscle change with increasing field strength, 144 abdominal MR examinations were retrospectively evaluated. These patients were evaluated with a dual echo T2-weighted spin-echo sequence. Eighty-two of the examinations were performed at 0.5 Tesla and 72 at 1.5 Tesla (T). Eleven of the patients were evaluated with both MR systems with the same sequences. T2 values were also obtained from a Fe NH4(SO4)2 12H2O phantom. The T2 values of liver decreased from 57.8 +/- 11.3 at 0.5 T to 43.7 +/- 8.3 at 1.5 T. The T2 values of muscle decreased from 44.2 +/- 9 at 0.5 T to 35.4 +/- 7.2 at 1.5 T. Patients who were examined on both systems also demonstrated a decrease in both liver and muscle T2 values. For concentrations in the range of hepatic T2's, the phantom demonstrated a decrease in T2 values from 0.5 to 1.5 T ranging from 20.3 to 23.4%. All the T2 changes were statistically significant (p less than .05). The findings suggest that T2 values may depend on field strength, or may vary due to other hardware-related differences.
Evaluation Studies as Topic↗
Regulatory perspectives and the benzodiazepines.
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Anti-Anxiety Agents↗
Controlled eddy currents: applications to MR imaging.
We describe how the artifact caused by eddy currents generated in free standing copper coils may be controlled and used to advantage in magnetic resonance (MR) imaging. The eddy currents distort the excitation field of the MR imager in the vicinity of the coil; the coils may then be used to reduce the signal intensity of tissues adjacent to them. Two examples of how this signal reduction may be used to advantage are given. In one example a coil was used to eliminate an aliasing artifact by removing the signal from an unwanted object. In another example a coil was placed on the anterior abdominal wall of a subject, thereby reducing the high-intensity signal from subcutaneous fat and the resulting ghosting from respiratory motion.
Abdominal Muscles↗
Helical CT for detecting focal liver lesions in patients with breast carcinoma: comparison of noncontrast phase, hepatic arterial phase, and portal venous phase.
PURPOSE: Our goal was to compare noncontrast phase (NCP), hepatic arterial phase (HAP), and portal venous phase (PVP) helical CT for the detection of focal liver lesions in patients at risk for having metastases from breast carcinoma. METHOD: Eighty-four consecutive CT scans in 80 women with known or suspected liver metastases from breast carcinoma were prospectively evaluated with triple phase helical CT. After NCP, Isovue 300 was administered at 3 ml/s for 40 s, then 2 ml/s for 30 s, with scan delays of 25 s (HAP) and 76 s (PVP), slice thickness of 7 mm, and pitch of 1:1. Two reviewers evaluated each phase for focal liver lesions in a blinded and random fashion followed by side-by-side review for consensus. RESULTS: By consensus, 40 CT scans were normal and 44 CT scans had a total of 105 lesions (46 lesions were graded malignant). PVP detected 39 (85%), HAP 27 (59%), and NCP 28 (61%) malignant lesions. Two malignant lesions were seen only on HAP, 3 only on NCP, and 10 only on PVP. The remainder of lesions were seen on more than one phase. PVP was graded best for detecting lesions in 27 (61%), HAP best in 7 (16%), NCP best in 4 (9%), and PVP equivalent to HAP in 6 (14%) of the 44 cases with lesions. CONCLUSION: In our breast cancer patient population, PVP was superior to NCP and HAP for liver lesion detection. Because no CT scan was converted from negative to positive due to the addition of NCP or HAP, the routine use of these two phases cannot be justified when the clinical concern is the presence or absence of metastases.
Adult↗
Interobserver variability in the interpretation of unenhanced helical CT for the diagnosis of ureteral stone disease.
PURPOSE: The purpose of this study was to analyze interobserver agreement in the interpretation of unenhanced helical CT (UHCT) for the evaluation of ureteral stone disease and obstruction. METHOD: One hundred three UHCT examinations were independently and retrospectively reviewed by five readers including attending radiologists, a radiology resident, and an attending urologist. Examinations were interpreted as positive, negative, or indeterminate for ureteral stone disease and obstruction. The Cohen kappa test was used to measure interobserver agreement. The accuracy of the readers was also assessed. RESULTS: The kappa value ranged from 0.67 to 0.71 among the three attending radiologists and from 0.65 to 0.67 among the radiology attending physicians and radiology resident. Although the urologist tended to agree less well with the other readers (kappa range: 0.33-0.46), there was no statistically significant difference (p < 0.05) in the accuracy among all five readers. The percentage of cases interpreted as indeterminate ranged from 8 to 25% and almost invariably involved difficulty distinguishing phleboliths from minimally obstructing distal ureteral calculi. The percentage of UHCT scans correctly interpreted as positive and correctly interpreted as negative ranged from 73% (n = 27) to 86% (n = 32) and 63% (n = 22) to 86% (n = 30), respectively. CONCLUSION: Interobserver agreement was very good among the radiology attending physicians and resident and moderate with the urologist. The examination is an accurate technique in the evaluation of ureteral stone disease, although limitations exist, particularly in the diagnosis of minimally obstructing distal ureteral calculi.
Abdominal Pain↗
Pancreatic transplantation using portal venous and enteric drainage: the postoperative appearance of a new surgical procedure.
PURPOSE: To review the normal radiologic appearance of pancreatic transplants that use portal venous and enteric drainage, and to review the appearance of a variety of postoperative complications. METHOD: We retrospectively reviewed the computed tomographic (CT) scans, magnetic resonance (MR) images, and ultrasounds of patients who had undergone pancreatic transplantation using portal venous and enteric drainage. RESULTS: At CT, the normal pancreatic transplant appears as a heterogeneous mass composed of pancreatic parenchyma, vessels, and omental wrap. On MR imaging, a normal transplant demonstrates intermediate signal intensity on T1- and T2-weighted sequences. Sonographic evaluation of a normal transplant reveals a hypoechoic gland that contains readily detectable low-resistance arterial and venous Doppler waveforms. Acute postoperative complications include acute rejection, which has a nonspecific radiologic appearance, and transplant pancreatitis, which is often manifested on CT by stranding of the peritransplant fat. Chronic postoperative complications include small bowel obstructions, graft pancreatitis secondary to obstruction of the Roux loop, and chronic rejection. CONCLUSION: Knowledge of the radiologic appearance of the normal pancreatic transplant is required before transplant-related complications can be detected.
Acute Disease↗
Compression CT urography: a comparison with IVU in the opacification of the collecting system and ureters.
OBJECTIVE: The purpose of this study was to evaluate opacification of the collecting system and ureters using compression computed tomography (CT) urography compared with conventional intravenous urography (IVU). MATERIALS AND METHODS: Fifty consecutive patients underwent compression CT urography as part of a dedicated renal CT. A compression belt was applied prior to nephrographic phase imaging. Excretory phase scans were acquired through the kidneys 3 minutes post injection with the compression belt in place. The compression belt was then released, and scans were obtained through the ureters. Three independent readers then scored opacification of the collecting system and ureters on a scale of 0-2 (0 = no opacification, 1 = partial opacification, 2 = full opacification and distension). Fifty consecutive nonmatched IVUs were scored by segment by the same readers. Comparison of the two modalities was made using the Mann-Whitney U test. Interobserver agreement was assessed by the Kappa coefficient. RESULTS: CT demonstrated significantly better opacification (p < or = 0.02) of the upper and lower pole pelvicalyceal systems and midureters bilaterally. There was no difference in opacification of the proximal and distal ureters by CT compared with IVU. The Kappa coefficient was 0.53. CONCLUSIONS: Compression CT urography yields equal or better opacification of the collecting system and ureters when compared with IVU, and shows promise for the routine evaluation of the renal excretory system.
Adult↗
Radiologic manifestations of sclerosing cholangitis with emphasis on MR cholangiopancreatography.
Magnetic resonance cholangiopancreatography (MRCP) is a relatively new, noninvasive cholangiographic technique that is comparable with invasive endoscopic retrograde cholangiopancreatography (ERCP) in the detection and characterization of extrahepatic bile duct abnormalities. The role of MRCP in evaluation of the intrahepatic bile ducts, especially in patients with primary or secondary sclerosing cholangitis, is under investigation. The key cholangiographic features of primary sclerosing cholangitis are randomly distributed annular strictures out of proportion to upstream dilatation. As the fibrosing process worsens, strictures increase and the ducts become obliterated, and the peripheral ducts cannot be visualized to the periphery of the liver at ERCP. In addition, the acute angles formed with the central ducts become more obtuse. With further progression, strictures of the central ducts prevent peripheral ductal opacification at ERCP. Cholangiocarcinoma occurs in 10%-15% of patients with primary sclerosing cholangitis; cholangiographic features that suggest cholangiocarcinoma include irregular high-grade ductal narrowing with shouldered margins, rapid progression of strictures, marked ductal dilatation proximal to strictures, and polypoid lesions. Secondary sclerosing and nonsclerosing processes can mimic primary sclerosing cholangitis at cholangiography. These processes include ascending cholangitis, oriental cholangiohepatitis, acquired immunodeficiency syndrome-related cholangitis, chemotherapy-induced cholangitis, ischemic cholangitis after liver transplantation, eosinophilic cholangitis, and metastases.
Bile Duct Neoplasms↗
MR cholangiopancreatography of bile and pancreatic duct abnormalities with emphasis on the single-shot fast spin-echo technique.
Magnetic resonance cholangiopancreatography (MRCP) is used for noninvasive work-up of patients with pancreaticobiliary disease. MRCP is comparable with invasive endoscopic retrograde cholangiopancreatography (ERCP) for diagnosis of extrahepatic bile duct abnormalities. In patients with choledocholithiasis, calculi appear as dark filling defects within the high-signal-intensity fluid at MRCP. Benign strictures due to sclerosing cholangitis are multifocal and alternate with slight dilatation or normal-caliber bile ducts, producing a beaded appearance. Dilatation of both the pancreatic and bile ducts at MRCP is highly suggestive of a pancreatic head malignancy. Side-branch ectasia is the most prominent and specific feature of chronic pancreatitis. MRCP is more sensitive than ERCP in detection of pancreatic pseudocysts because less than 50% of pseudocysts fill with contrast material. Because the mucin secreted by biliary cystadenomas and cystadenocarcinomas causes filling defects and partial obstruction of contrast material at ERCP, MRCP is potentially more accurate in demonstrating the extent of these tumors. In patients with biliary-enteric anastomoses, MRCP is the imaging modality of choice for the work-up of suspected pancreaticobiliary disease. A potential use of MRCP is the demonstration of aberrant bile duct anatomy before cholecystectomy. MRCP is also accurate in detection of pancreas divisum.
Bile Duct Diseases↗
Protein synthesis, microsomes, and polyribosomes in oral tissues.
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Amino Acids↗
The impact of the addition of naloxone on the use and abuse of pentazocine.
An epidemic of abuse with "T's and blues" began in the late 1970's in which pentazocine-Talwin tablets ("T")--and the antihistamine tripelennamine (known as blues) were crushed, dissolved together, filtered, and injected intravenously. The resulting high was reported to be similar to that of heroin. In 1981, the manufacturer and the Food and Drug Administration met to discuss a possible solution. As a result, 0.5 mg of naloxone hydrochloride, a narcotic antagonist that is pharmacologically inactive at that dose orally but active if administered parenterally, was added to the tablet formulation. The reformulated product, Talwin Nx, was approved for marketing in late 1982 and introduced in the second quarter of 1983. Distribution of Talwin tablets in the United States was discontinued. The Drug Abuse Warning Network (DAWN) of the National Institute of Drug Abuse and IMS America's National Prescription Audit were used to review the use and abuse patterns of pentazocine before and after the naloxone intervention. The number of prescriptions dispensed quarterly for pentazocine products remained fairly stable from 1981 through the first quarter of 1983 and increased after the introduction of Talwin Nx. In contrast, DAWN emergency room and medical examiner mentions decreased after the product reformulation. The rates of both emergency room and medical examiner mentions per million prescriptions were substantially lower in the 2 years following the introduction of Talwin Nx (decreases of 70 percent by emergency rooms and 71 percent by medical examiners), indicating that the product reformulation successfully reduced pentazocine abuse.
Coroners and Medical Examiners↗