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Biomedical subjects

C D Johnson

Publications and source records attributed to C D Johnson.

At least 415 records · Page 23Linked to original sources
PubMedDate not supplied

Abdominal phase-contrast MR angiography: breath-hold versus non-breath-hold techniques.

Breath-hold magnetic resonance (MR) imaging is now replacing many non-breath-hold pulse sequences in the upper abdomen because of faster imaging times and improved image quality. The authors compared non-breath-hold cine phase-contrast (PC) and breath-hold 2D phase-contrast (2DPC) magnetic resonance (MR) angiograms of the main portal vein (MPV) and superior mesenteric artery (SMA) in 12 volunteers. All angiograms were graded in overall image quality, vessel conspicuity, and signal-to-noise ratios (SNR). In the MPV MR angiograms, the breath-hold 2DPC sequence produced better images than the non-breath-hold cine PC sequence as graded by overall image quality (P = .016) and SNR (P = .004). Conversely, in the SMA MR angiograms, the non-breath-hold cine PC sequence produced better images than the breath-hold sequence in terms of overall image quality (P = .008) and SNR (P = .008). By reducing the most significant cause of image artifacts, (ie, using a breath-hold 2DPC sequence to decrease respiratory misregistration of the MPV, and using a cardiac-gated cine PC sequence to minimize pulsatile artifacts of the SMA), one can clearly optimize the quality of MR angiography.

Abdomen↗
PubMedDate not supplied

CT colonography: determination of optimal CT technique using a novel colon phantom.

The aim of this study was to determine the thickest slice at the lowest radiation dose for detection of colon polyps larger than 5mm in diameter at computed tomographic (CT) colonography. A colon phantom containing haustral folds, flexures, and straight segments was constructed of borosilicate. One hundred forty simulated polyps (5, 7, 10, and 12 mm) of various shapes (sessile, flat, and pedunculated) were attached at different colon locations (wall, base of fold, on the fold and fold tip). Polyps were positioned parallel, perpendicular, and oblique to the CT gantry. The air-filled phantom was scanned at different slice thicknesses (1.25-5 mm) and x-ray tube currents (5-308 mA). All polyps were identified in all data sets except one (1.25 mm slice thickness, 5 mA). In this acquisition, image noise reduced polyp visibility, and five of 140 (3%) polyps could not be identified. Unidentified polyps were 5 mm, flat or sessile in shape, located on the colon wall or base of the fold, and oblique or parallel to CT gantry. All tested CT techniques provided optimal polyp detection except settings at 1.25 mm and 5 mAs. Thin collimation (<5 mm) scans may not be necessary to detect clinically significant polyps.

Colon↗
PubMedDate not supplied

Detection of flat lesions in the colon with CT colonography.

BACKGROUND: We investigated whether flat lesions of the colon could be detected on computed tomographic colonography (CTC). METHODS: CTC and conventional colonoscopy were performed on 547 consecutive patients. A subset of 22 polyps was described as flat on colonoscopy (n = 16) or CTC (n = 6) and are the basis of this report. CTC was performed with a standard technique (5-mm collimation, 3-mm reconstruction intervals). Patients were scanned in supine and prone positions. Examinations were randomly assigned and reviewed in a blinded fashion by two of three radiologists. Prospective interpretations were recorded. All patients had conventional colonoscopy, which served as the gold standard. RESULTS: Twenty-two flat lesions ranging from 0.4 to 3.5 cm were histologically classified as adenomatous (n = 8) or hyperplastic (n = 14). The sensitivities for detecting all flat lesions and flat adenomas by each reviewer were 43% and 100%, 65% and 100%, and 15% and 13%, respectively. "Double reading" resulted in detection of 68% of all lesions and 100% of adenomas. Of the seven hyperplastic polyps missed by both reviewers, four were identified retrospectively. CONCLUSION: Flat lesions of the colon represent an important source of false negative CTC examinations. Awareness of their morphology can assist radiologists in finding most of these challenging lesions.

Adenomatous Polyps↗
PubMedDate not supplied

Pancreatic cystic neoplasms: the role and sensitivity of needle aspiration and biopsy.

BACKGROUND: The proper evaluation of patients with pancreatic cystic neoplasms remains controversial. Although computed tomography (CT) and sonography can differentiate the majority of these tumors, needle aspiration and biopsy can be helpful in selected patients. The purpose of this study was to (1) determine the sensitivity of needle aspiration and biopsy of cystic pancreatic neoplasms, (2) assess the complications after needle aspiration and biopsy, and (3) assess the indications for needle aspiration and biopsy by using the radiographic appearance as a guide. METHODS: The histories, imaging studies, and pathologic specimens of 18 patients with serous cystadenoma (10 patients) or mucinous cystic tumor (eight patients) of the pancreas who also underwent CT-guided (n = 16), sonographically guided (n = 3), or intraoperative (n = 4) needle biopsy (n = 23 total biopsies) between 1976 and 1996 were retrospectively reviewed. RESULTS: The histologic diagnosis of the serous subtype was made with needle aspiration and biopsy in five of 10 patients with serous cystadenoma. The histologic diagnosis of the mucinous subtype was made with needle aspiration and biopsy in six of eight patients with mucinous cystic neoplasms. Of the 23 biopsies performed, one patient experienced significant intraperitoneal hemorrhage. Indications for needle biopsy include an atypical cystic mass on diagnostic imaging studies, confirmation of a serous cystadenoma before observation, and confirmation of mucinous cystadenocarcinoma in patients with nonresectable disease. CONCLUSION: Needle biopsy and aspiration is a helpful and safe procedure to aid in the diagnosis of cystic pancreatic neoplasms before surgery.

Aged↗
PubMedDate not supplied

CT demonstration of an adrenal pseudocyst.

The CT and ultrasound findings in a case of an adrenal pseudocyst are reported. The pathology, etiology, usual manifestations, and differential diagnosis of adrenal cysts are discussed.

Adrenal Gland Diseases↗
PubMedDate not supplied

MR angiography in portal hypertension: detection of varices and imaging techniques.

This study was performed to compare time-of-flight MR angiography in detecting varices with conventional portography and endoscopy in patients with chronic liver disease and to compare MR tomographic images with projection angiograms. In eight patients findings on conventional arterial portography (considered the gold standard) were compared with the MR findings. Varices were graded by size and extent on a scale of 0-3. Splenic varices were detected in all patients by MR but were scored larger on portography in 6 (55%) of 11 comparisons. All left gastric varices were identified at MR and were rated within one grade of those seen at portography. All esophageal varices were identified at MR. Among 12 patients with upper endoscopy, MR rated varices significantly (p less than 0.05) larger than endoscopy in 8 (67%) of 12 comparisons. Varices were detected in two patients on MR that were not seen endoscopically. Extraperitoneal varices were identified in six (75%) of eight patients on MR and were only visualized in one patient at portography. Varices were equally well detected using either axial or coronal images. No significant difference existed when tomographic images were compared with projection images. Time-of-flight MR angiography is a valid technique for noninvasive imaging of abdominal varices. Tomographic single slice images are generally as good as projection images except possibly in the demonstration of extraperitoneal varices.

Adult↗
PubMedDate not supplied

MRI of pancreatic islet cell carcinoma.

OBJECTIVE: The purpose of this study is to report the spectrum of MR findings of pancreatic islet cell carcinoma. MATERIALS AND METHODS: The MR scans of 33 patients with islet cell carcinoma were retrospectively reviewed. Magnetic resonance detected the primary tumor in 21 of 27 patients (78%) who had not had prior resection of their primary tumor. Mean tumor diameter was 7.1 cm (range 3.5-13.0 cm). RESULTS: In all patients, the primary tumor on T1-weighted images (TR/TE = 250/15) was of signal intensity equal to or lower than that of the adjacent normal pancreas. The primary tumor on T2-weighted images (TR/TE = 2,000/> or = 100) was of signal intensity the same as or higher than fat in 18 of 21 patients (86%) and had mixed signal intensity in the other 3 (14%). Hepatic metastases were found in 28 of 33 patients (85%). Liver metastases were categorized as "usual" (variably circumscribed, homogeneous lesions of medium signal intensity on T2-weighted images) in 19 of 28 patients (68%), necrotic in 8 of 28 (29%), hemorrhagic in 3 of 28 (11%), and calcified in 1 of 28 (4%). Extrahepatic metastases were found in 18 of 33 patients (55%). CONCLUSION: We conclude that MRI is an excellent modality for the diagnosis and routine follow-up of patients with islet cell carcinoma.

Adenoma, Islet Cell↗
PubMedDate not supplied

Cine phase-contrast MR flow measurements: improved precision using an automated method of vessel detection.

OBJECTIVE: The purpose of this study was to construct a method of vessel edge detection that correctly identifies vessel pixels and to compare the interuser variability of cine phase contrast MR volumetric flow rates obtained with the conventional manual method and an automated method. MATERIALS AND METHODS: The automated method was developed based on a magnitude image threshold value and compared with the manual method in a flow phantom (three users) and in velocity images of the portal vein (five users). The threshold value determined from the magnitude image was applied to a region of interest surrounding the vessel of interest on the magnitude image to construct a vessel edge detection mask m(x,y). The velocity images were then multiplied by the mask m(x,y) and volumetric flow rates determined using the identified vessel pixels. RESULTS: In the flow phantom, flow measurements with the magnitude threshold method had significantly less interuser variability compared with the manual method (p < 0.01) and were within 10% (mean 6.0%) of the actual flow versus 35% (mean 18.6%) with the manual method. Regarding flow measurements in the portal vein of six volunteers, the magnitude threshold method was significantly more precise (p < 0.01) than the manual method with a mean standard deviation between the five users of 40.4 +/- 12.9 ml/min (range 22-60 ml/min) and 110.4 +/- 32.7 ml/min (range 70-155 ml/min), respectively. CONCLUSION: The magnitude threshold method of vessel edge detection developed in this study yields flow measurements that are accurate in the model system and have significantly less interuser variability than the manual method. This method shows promise for improving the precision of cine phase contrast flow measurements.

Adult↗
PubMedDate not supplied

Abdominal manifestations of sarcoidosis in CT studies.

OBJECTIVE: The purpose of this study is to demonstrate the spectrum of abdominal CT findings in patients with tissue proved sarcoidosis, estimate their prevalence, and correlate abdominal findings with stage of thoracic disease. MATERIALS AND METHODS: Between 1987 and 1993, 140 patients with tissue proved sarcoidosis underwent abdominal or chest CT at our institution. After exclusions, 49 patients remained. Abdominal CT was retrospectively reviewed and the findings arrived at by consensus. Chest radiography within 1 month of CT was available for 46 patients. Chest radiography was retrospectively reviewed and stage of thoracic disease arrived at by consensus. RESULTS: Splenic abnormalities consisted of splenomegaly, low density lesions, and punctate calcifications. Hepatic sarcoidosis manifested as hypovascular lesions, hepatomegaly, and punctate calcifications. Lymphatic abnormalities consisted of lymphadenopathy, most commonly between 1 and 2 cm, and an increased number of normal sized lymph nodes. CONCLUSION: Sarcoidosis produces splenic abnormalities in 53% of patients, liver abnormalities in 16%, and lymphatic findings in 43%. No correlation was demonstrated between the abdominal findings and stage of thoracic sarcoidosis.

Female↗
PubMedDate not supplied

Mosaic pattern of hepatocellular carcinoma: histologic basis for a characteristic CT appearance.

PURPOSE: The mosaic pattern is a characteristic CT appearance for hepatocellular carcinoma (HCC). This study was designed to assess the tissue composition responsible for the CT mosaic pattern. METHOD: Gross and whole-mount histologic sections of 10 HCC tumors from eight patients were prepared at identical levels as preoperative CT sections. CT features of the mosaic tumor pattern were spatially registered with the corresponding pathologic sections. RESULTS: CT of mosaic HCC demonstrated enhancing nodules (9/10), low attenuation areas (9/10), and internal septa (3/10). Spatial registration of CT and microscopic sections showed that enhancing tissue was viable tumor in nine of nine. Low attenuation areas were either necrotic (4/9) or of mixed tissue (5/9), including areas of necrosis, fibrosis, and hemorrhage. CONCLUSION: The variable tissue composition of HCC accounts for the mosaic CT pattern. In most patients, enhancing nodules indicate viable tumor cells, and low attenuation areas represent necrosis, fibrosis, or hemorrhage.

Aged↗
PubMedDate not supplied

Feasibility of planar virtual pathology: a new paradigm in volume-rendered CT colonography.

Planar virtual pathology (PVP) is an isometric rendering method for examining the CT colonography dataset, which renders the colon in discrete colonic segments. Ten patients with 36 polyps were evaluated using traditional 2D axial, 2D multiplanar reformatted, and 3D endoluminal images as well as PVP. PVP displayed 13 of 17 (76%) polyps of >1 cm, whereas 11 of 17 (65%) were detected using traditional rendering methods. PVP may be a useful adjunct in detecting additional polyps at CT colonography.

Colonic Polyps↗
PubMedDate not supplied

The dental management of a patient with a cocaine-induced maxillofacial defect: a case report.

There are several dental complications associated with cocaine abuse, including adverse reactions to dental anesthetics, post-operative bleeding, and cellulitis, which can lead to necrosis of orbital, nasal, and palatal bones. Following is a report of the initial treatment rendered to a patient who had destroyed most of her hard palate over a ten-year period of cocaine abuse. There are no classic socio-economic or educational profiles for abusers of cocaine. Drug abuse victims may present as patients in any dental office. Though there are certain classic physiological and psychological symptoms of their condition, they may not display symptoms at all.

Candidiasis, Oral↗
PubMedDate not supplied

Colorectal lesions: evaluation with CT colography.

Computed tomographic (CT) colography is a promising technique for differentiating malignant or premalignant colorectal disease from benign lesions. In this technique, helical CT data are used to produce reformated two-dimensional (2D) CT images and simulated endoscopic images of the colon. Adenomatous polyps 0.7 cm in diameter or larger are easily detected on CT colographic images: A pedunculated polyp is identified by means of its stalk, whereas a sessile polyp appears as a polypoid soft-tissue mass projecting into the air-filled lumen of the colon. However, flat adenomas (lesions raised less than 2 mm from the surface of the colon) are difficult to detect with CT colography. In cases of colorectal cancer, both intraluminal and extraluminal disease can be evaluated with CT colography. Although CT colography does not allow differentiation between hyperplastic and adenomatous polyps, lipomas can be confidently diagnosed because of their fatty attenuation on reformatted 2D images. Pseudolesions that can produce false-positive findings at CT colography include the ileocecal valve, retained stool, retained barium, respiratory artifacts, and a stool-filled diverticulum.

Adenomatous Polyps↗
PubMedDate not supplied

Glutamine-enriched total parenteral nutrition maintains intestinal interleukin-4 and mucosal immunoglobulin A levels.

BACKGROUND: Total parenteral nutrition (TPN) prevents progressive malnutrition but fails to maintain intestinal gut-associated lymphoid tissue (GALT) or established respiratory antiviral or antibacterial mucosal immunity. Our previous work demonstrated that decreases in intestinal immunoglobulin A (IgA) were associated with decreases in Th2-type IgA-stimulating cytokines, interleukin (IL)-4 and IL-10. Because glutamine supplementation of TPN partially preserves respiratory defenses and normalizes GALT, we investigated the ability of parenteral glutamine to normalize respiratory and intestinal IgA levels and measured Th2 cytokines in intestinal homogenates. METHODS: Animals were cannulated and randomly assigned to receive chow (n = 17), TPN (n = 18), or an isonitrogenous, isocaloric TPN solution formulated by removing the appropriate amount of amino acids and replacing them with 2% glutamine (n = 18) for 5 days. Respiratory tract and intestinal washings were obtained for IgA and the intestine homogenized and analyzed for IL-4 and IL-10. RESULTS: TPN decreased intestinal and respiratory IgA in association with decreases in intestinal IL-4 and IL-10 compared with chow-fed animals. Glutamine significantly improved respiratory and intestinal IgA levels, significantly improved IL-4 compared with TPN animals, and maintained IL-10 levels midway between chow-fed and TPN animals. CONCLUSIONS: Glutamine-enriched TPN preserved both extraintestinal and intestinal IgA levels and had a normalizing effect on Th2-type IgA-stimulating cytokines.

Animals↗
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A case report: recognizing factitious injuries secondary to multiple eating disorders.

This report describes the uncommon problem of a female patient diagnosed with an eating disorder, bulimia nervosa, who reported self-mutilating dental factitious behavior. The case presents a serious diagnostic and management problem. Notwithstanding the clinical appearance of the dentition, a thorough medical-dental history was essential for this uncommon diagnosis.

Adolescent↗