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Biomedical subjects

D D Stark

Publications and source records attributed to D D Stark.

At least 145 records · Page 8Linked to original sources
PubMed1983

CT appearance of the normal inferior pulmonary ligament.

The inferior pulmonary ligament, a double layer of pleura that tethers the lower lobe of the lung to the mediastinum, is rarely appreciated on plain radiographs but may be involved in pathologic processes. A linear structure on axial computed tomographic (CT) images of the lung bases corresponds to the inferior pulmonary ligament on cadaver sections. Review of 100 CT studies identified at least one inferior pulmonary ligament in 42%. Its presence and configuration did not correlate with patient age or gender. The anatomy and CT appearance of the ligament are discussed.

Humans↗
PubMed1983

CT and radiographic assessment of tube thoracostomy.

Conventional chest radiography and computed tomography (CT) were used to evaluate tube thoracostomy drainage of pleural empyema in 26 selected patients. Frontal radiographs alone were inadequate in the evaluation of thoracostomy tube placement, as only one of 21 malpositioned tubes was identified; however, when lateral radiographs were also obtained, eight of nine malpositioned tubes were identified. Suboptimal drainage due to malpositioning was demonstrated best by CT in all 21 cases. Prolongation of hospitalization, serious complications, and death correlated with failure of early tube thoracostomy drainage as demonstrated by CT. Routine frontal and lateral chest radiographs are recommended for all patients after thoracostomy tube placement for empyema. For selected patients with empyema, early use of CT to guide tube repositioning or thoracotomy may reduce morbidity and mortality and decrease hospital costs.

Drainage↗
PubMed1983

Radionuclide bone scanning in neuroblastoma: skeletal metastases and primary tumor localization of 99mTc-MDP.

Of 42 radionuclide bone scans in 35 children with neuroblastoma, 21 were abnormal for the presence of skeletal metastases. Of the 21 abnormal scans, 16 were corroborated by positive bone-marrow biopsy or clinical data. The false-negative and false-positive rates for bone scanning were 4.8% and 9.5%, respectively. Calcification of the primary tumor was seen on pretreatment computed tomographic (CT) scans in 24 (89%) of 27 cases, while only 13 (48%) of 27 were detectable by plain radiographs. Uptake of technetium-99m methylene diphosphate (99mTc-MDP) by the primary tumor occurred in 20 of 27 cases, but correlation between tumor uptake and calcification was not statistically significant. All children with markedly elevated urinary vanillylmandelic acid exhibited primary tumor uptake. Survival was not affected independently by primary tumor uptake.

Bone Neoplasms↗
PubMed1983

Parathyroid imaging: comparison of high-resolution CT and high-resolution sonography.

Parathyroid computed tomographic (CT) scanning using a specially designed patient positioning harness, bolus contrast administration, and dynamic scanning significantly improved localization of parathyroid tumors from 45% (19/42) to 76% (35/46) (p less than 0.01) over conventional CT scanning. High-resolution sonography with a 10 MHz transducer localized 65% (57/88) of these tumors. Average tumor size was 15 X 10 X 9 mm. Patients undergoing reoperation for hyperparathyroidism had similarly small tumors localized by CT in 63% (12/19) and high-resolution sonography in 47% (9/19) of cases. High-resolution sonographic equipment suitable for parathyroid imaging is not widely available. Since high-resolution CT is more generally available and more effective, it is recommended as the procedure of choice for localizing cervical parathyroid tumors.

Adenoma↗
PubMed1983

Computed tomography and nuclear magnetic resonance imaging of pancreatic islet cell tumors.

Eleven patients with pancreatic islet cell tumors smaller than 2.5 cm were examined by use of computed tomography (CT) and new scanning protocol. Seven of 11 tumors were localized and CT accurately assessed multiple lesions, retroperitoneal invasion, or liver metastases when present. CT is now the initial imaging procedure of choice for diagnosis and staging of islet cell tumors. Nuclear magnetic resonance can distinguish islet cell tumors from normal retroperitoneal structures and appears to be a promising new pancreatic imaging modality.

Adenoma, Islet Cell↗
PubMed1983

High-resolution ultrasonography and computed tomography of thyroid lesions in patients with hyperparathyroidism.

High-resolution ultrasonography and computed tomography examinations of the thyroid gland were compared with surgical inspection of the thyroid gland at the time of parathyroid surgery in 65 patients with hyperparathyroidism. Twenty-six patients (40%) had one or more nonpalpable thyroid lesions. Thirty benign thyroid lesions averaged 7 mm in size. A 5 mm follicular carcinoma and a 20 mm recurrent medullary carcinoma were also identified. Ultrasonography detected 88% (28/32), computed tomography detected 59% (19/32), and surgical inspection detected 84% (27/32) of the thyroid lesions. Preoperative ultrasonography with a 10 MHz small-parts real-time scanner is suited ideally to complement surgical inspection of the thyroid for delineation of small thyroid lesions in order to determine whether the lesions are solid or cystic and whether they are single or multiple. This information may be important to determine whether biopsy is necessary.

Adult↗
PubMed1982

Biochemical features of urinothorax.

In three patients with obstructive uropathy and retroperitoneal urine collections, rapidly accumulating pleural effusions developed. The diagnosis of urinothorax was confirmed when chemical analysis of pleural fluid disclosed higher creatinine concentrations than found in simultaneously obtained serum samples. Similar determinations made in 71 specimens from control patients with pleural effusions showed that pleural creatinine concentration did not exceed the serum level in other conditions. We conclude that elevated pleural fluid creatinine level is specific for the diagnosis of urinothorax. Low pleural fluid glucose concentration may also be seen in these patients.

Aged↗
PubMed1981

Intrathoracic extension of retroperitoneal urine collections.

Five patients with retroperitoneal urine collections (urinomas) had clinical and radiographic evidence of intrathoracic disease. All five patients rapidly accumulated pleural fluid, documented chemically in three patients to be urine. Two patients developed acute mediastinal widening which rapidly cleared after surgical drainage of the retroperitoneal urinoma. Although rare, thoracic collections of urine should be considered when pleural effusions or mediastinal widening occur in patients with urinary tract obstruction or retroperitoneal urinomas.

Aged↗
PubMedDate not supplied

Diagnosis of fatty liver with MR imaging.

The diagnosis of fatty liver with magnetic resonance (MR) imaging was evaluated in experimental rat models of simple fatty infiltration and fatty liver with hepatocellular injury. T1 and T2 were measured ex vivo and correlated with the histologic degree of fatty infiltration. Enhancement of fatty liver with four different cells-specific contrast agents was studied with ex vivo relaxometry and in vivo MR imaging. Quantitative analysis of conventional and chemical shift MR images was correlated with biochemically determined fat content of the liver. Diet-induced simple fatty infiltration of the liver caused a decrease in T1 of 15%, whereas the T1 of L-ethionine-induced fatty liver with hepatocellular injury increased by 12%. T2 showed a positive correlation with the degree of fatty infiltration in both models. Cell-specific hepatobiliary contrast agents showed the same liver uptake and relaxation enhancement in fatty livers as in normal livers. Conventional T1-weighted images and chemical shift images showed good correlation (r = .83 and .80, respectively) between signal intensity and the degree of fatty infiltration. However, only chemical shift imaging was reliable in the diagnosis of fatty liver.

Acetates↗
PubMedDate not supplied

Enhancement of tumor-liver contrast-to-noise ratio with gadobenate dimeglumine in MR imaging of rats.

The efficacy for tumor detection of the hepatocyte-specific contrast agent gadobenate dimeglumine (gadolinium-BOPTA/Dimeg) was evaluated in four different experimental tumor models in rats. Histologic findings were correlated with quantitative data derived from ex vivo relaxometry and in vivo magnetic resonance (MR) imaging. Noninfiltrating tumors showed maximal enhancement of liver parenchyma 5-10 minutes after contrast agent administration, with a plateau over the next 30 minutes. In contrast, infiltrating tumors, which caused hepatocellular injury and inflammatory changes, delayed maximal enhancement of tumor-free parenchyma by 15-20 minutes. Nonspecific tumor enhancement depended on tumor vascularity and occurred in the early phase after contrast agent administration. Despite differences in specific enhancement of tumor-free parenchyma and nonspecific tumor enhancement, tumor-liver contrast-to-noise ratios increased 96%-248% in all tumor models 30 minutes after intravenous administration of 75 mmol/kg Gd-BOPTA/Dimeg. Gd-BOPTA/Dimeg enhanced tumor conspicuity independently of the histologic characteristics of the tumor.

Animals↗
PubMedDate not supplied

Abdominal imaging.

Explore the source record for details and available documents.

Abdomen↗
PubMedDate not supplied

Evaluation of hepatocyte-specific paramagnetic contrast media for MR imaging of hepatitis.

The hepatocyte-specific paramagnetic magnetic resonance (MR) contrast agents manganese-DPDP [N,N'-dipyridoxylethylenediamine-N,N'-diacetate 5,5'bis-(phosphate)] and gadobenate dimeglumine were used for diagnosing chemically induced hepatitis in rats. Ex vivo liver tissue relaxation times and in vivo MR image signal-to-noise ratios were compared before and after contrast agent administration. Ex vivo relaxometry and in vivo MR imaging showed that Mn-DPDP enhanced normal and diseased livers to the same degree at all time points from 5 to 120 minutes. Gadobenate dimeglumine showed reduced T1 and T2 enhancements in hepatitis relative to those of normal liver, in the early phase (5-30 minutes). However, these effects are offsetting, and as a result, MR imaging failed to allow distinction of diseased from normal livers. This surprising result observed in vivo was in fact predicted by applying the Bloch equation to our ex vivo data. Our results show that detection and quantitation of hepatitis with MR imaging enhanced with paramagnetic cell-specific contrast agents will be more difficult than anticipated.

Acute Disease↗
PubMedDate not supplied

Contrast-enhanced MR imaging of the liver.

Postcontrast images with a 0.1 mmol/kg dose of a gadolinium chelate with extracellular distribution, when acquired dynamically during breath holding, can improve both differential diagnosis and lesion recognition in liver MR imaging. Initial results at 0.3 mmol/kg, compared with 0.1 mmol/kg, suggest a substantial improvement in lesion identification at the high dose, as assessed by using signal intensity difference divided by noise. Of the gadolinium chelates with predominantly renal excretion, only gadoteridol is presently approved in the United States at the high dose, with limited clinical evaluation for liver imaging performed to date. For linear chelates, such as gadopentetate dimeglumine and gadodiamide injection, the degree to which release of free gadolinium ion occurs is a possible issue because of lower in vivo stability (42,43). Preliminary results with hepatobiliary gadolinium chelates and iron particulate agents are favorable with regard to efficacy, although these agents remain in clinical trials.

Animals↗
PubMedDate not supplied

Enhanced tumor detection in the presence of fatty liver disease: cell-specific contrast agents.

It is assumed that hepatobiliary, cell-specific contrast agents will be adversely affected by the presence of diffuse liver disease. The diagnostic efficacy for tumor detection in the presence of fatty liver disease was experimentally studied at contrast-enhanced magnetic resonance (MR) imaging with manganese-DPDP (N,N'-dipyridoxylethylenediamine-N,N'-diacetate 5,5'-bis[phosphate]) and gadobenate dimeglumine (Gd-BOPTA/dimeg) and compared with conventional and chemical shift imaging. Carcinosarcoma was implanted into the liver of rats, and fatty liver was induced with L-ethionine. Without contrast agents, the tumor-fatty liver contrast-to-noise ratio (C/N) was increased on T1-weighted and decreased on T2-weighted MR images relative to tumor-bearing control rats without fatty liver. Chemical shift imaging (phase-contrast method) increased the tumor-fatty liver C/N from 2.3 +/- 1.0 to 6.1 +/- 1.7 (P < .001). Mn-DPDP and Gd-BOPTA/dimeg increased the tumor-fatty liver C/N from -5.4 +/- 1.6 to -11.0 +/- 1.9 and -9.8 +/- 3.4, respectively (P < .001). The hepatobiliary, cell-specific contrast agents were equally effective in both fatty and non-fatty liver and outperformed both chemical shift and conventional MR imaging in detecting liver tumors.

Animals↗
PubMedDate not supplied

Contrast-enhanced MR imaging of diffuse and focal splenic disease with use of magnetic starch microspheres.

The diagnostic value of magnetic starch microspheres (MSM), a new superparamagnetic contrast agent, was studied in experimental models of diffuse and focal splenic disease in rats by means of ex vivo relaxometry and in vivo magnetic resonance (MR) imaging. Owing to small differences in unenhanced T1 and T2 values between diffuse lymphoma and normal spleen, MR imaging failed to distinguish tumor-bearing animals from control animals by signal-to-noise ratios (SNRs) obtained with T1- and T2-weighted spin-echo sequences. One hour after injection of 20 mumol/kg MSM, lymphomatous spleen showed significantly (P < .001) reduced enhancement relative to normal splenic tissue. As a result, animals with diffuse lymphoma (SNR: 10.3 +/- 1.7) could be easily differentiated from control animals (SNR: 5.5 +/- 0.6) on T2-weighted (TR msec/TE msec = 2,000/45) images. In focal splenic disease, MSM produced normal enhancement of nontumorous splenic tissue, whereas relaxation times of tumors were not different before and after contrast agent injection. On T2-weighted images (2,000/45), the tumor-spleen contrast-to-noise ratio increased from 4.8 +/- 1.6 to 21.8 +/- 1.9 (+354%), improving conspicuity of splenic tumors. The results show that MSM-enhanced MR imaging improves the detection of diffuse and focal splenic disease.

Animals↗