Biomedical subjects

N Karstaedt

Publications and source records attributed to N Karstaedt.

At least 19 recordsLinked to original sources

PubMed1999

Noninvasive methods of diagnosing thoracic splenosis.

Thoracic splenosis is a rare condition resulting from concomitant rupture of the spleen and left hemidiaphragm, with autotransplantation of splenic tissue into the left hemithorax. It is usually an incidental finding on chest plain film or computed tomogram and is rarely diagnosed without biopsy or operation. A history of old splenic trauma and findings of left-sided, pleural-based nodules should indicate the diagnosis, which can be confirmed with nuclear medicine studies.

Aged↗

PubMed1991

MR imaging evaluation of endometrial carcinoma: results of an NCI cooperative study.

A prospective study to assess the usefulness of magnetic resonance (MR) imaging in the evaluation of endometrial carcinoma was undertaken by five institutions under the auspices of the National Cancer Institute. Six different MR imagers were used, ranging in magnetic field strength from 0.15 T to 1.5 T. For each unit, appropriate T1- and T2-weighted sequences in the transverse plane and T2-weighted sequences in the sagittal plane were used. Initially, 107 patients were entered in the study, but only 88 fulfilled all the criteria and provide the basis for this study. The abnormality within the endometrial cavity was demonstrated with MR imaging in 81% of the patients. The overall accuracy with MR imaging for staging endometrial carcinoma was 85%. In the evaluation of depth of myometrial invasion for stage I disease, overall accuracy with MR imaging was 74%. The accuracy of MR imaging in assessing tumors confined to endometrium or tumor with superficial myometrial invasion was 89% and decreased to 54% in assessing deep myometrial invasion. The results of this prospective study performed by multiple examiners with vastly different equipment demonstrate the inherent value of MR imaging in the evaluation of this neoplasm.

Adult↗

PubMed1991

Evaluation of a new magnetic resonance imaging method for quantitating adipose tissue areas.

We have developed a new magnetic resonance imaging (MRI) protocol to quantitate intraabdominal and subcutaneous fat and have validated it by comparing measurements of fat areas by MRI with those obtained by computed tomography (CT) in 11 asymptomatic volunteers who all had a single CT and MRI image taken at the level of the umbilicus. The new MRI protocol was based on a water-fat separation method by which the slice selection routines excite water and fat protons in different positions along the slice select direction. This method performed more reliably than earlier methods based on phase differences between water and fat signals. Fat areas measured by MRI exceeded those measured by CT by 8-22 percent, and fat areas and ratios obtained by MRI correlated well with CT (r = 0.98 for areas and, for ratios, r = 0.81). The ratio of intraabdominal/subcutaneous fat measured by MRI in seven males was significantly greater than that in four females. We also compared the new method with a previously published inversion recovery (IR) method in seven additional volunteers. Agreement between the two methods was excellent, and the major differences were technical: the IR protocol produced images that may require custom image processing programs when obtained on some scanners. Comparability of the two methods provides further reassurance of the validity of both. MRI presents an attractive opportunity for directly measuring intraabdominal fat in order to correlate this with metabolic parameters and to visualize changes during weight loss.

Abdomen↗

PubMed1991

Assessment of abdominal fat deposition in female cynomolgus monkeys.

Computed tomography (CT) was used to assess abdominal fat distribution in adult, female cynomolgus macaques (Macaca fascicularis). The technique used was similar to that applied in human beings and allowed intra-abdominal, subcutaneous and total abdominal fat to be quantitated in 1 cm thick sections. Correlations between single scans and the average of scans at several levels ranged from r = 0.96 to r = 1.00, indicating that a single scan is representative of abdominal fat distribution. Significant positive correlations were found between body mass index (BMI) and intra-abdominal fat (r = 0.89), subcutaneous fat (r = 0.91) and total abdominal fat (r = 0.90). As BMI increased, fat was preferentially deposited subcutaneously versus intra-abdominally. A unique fat depot, not previously described, was identified dorso-laterally between the internal abdominal oblique and the transversalis muscle. This fat depot was also positively correlated with BMI (r = 0.79). These results indicate that CT can be used in cynomolgus monkeys to quantitate regional fat deposits and that these monkeys resemble human beings in their abdominal fat patterning.

Adipose Tissue↗

PubMed1990

MRI findings of sciatic endometriosis.

Endometriosis is a rare cause of sciatic mononeuropathy. We report a woman with cyclic, menstruation-related hip pain associated with right leg weakness and sensory loss. Examination and electrodiagnostic studies suggested sciatic nerve dysfunction. Magnetic resonance imaging (MRI) revealed abnormal signal consistent with endometriotic tissue in the region of the right sciatic nerve. The abnormal signal partially regressed after treatment of the endometriosis. This case further illustrates the utility of MRI in the assessment of rare pelvic disorders.

Adult↗

PubMed1990

CT features of renal cell carcinoma with emphasis on relation to tumor size.

Computed tomography (CT) is the current standard for diagnosing and staging renal cell carcinoma (RCC). Although general diagnostic guidelines exist, no large studies to date have delineated the CT features of RCC. We reviewed the CT appearances of 78 pathologically proven RCCs. Of the 61 RCCs larger than 50 mm (78%) there was imaging evidence of extrarenal spread (87%), intratumoral necrosis (61%) and differential growth rates within the tumor (64%). Tumors 50 mm or smaller often had a "benign" appearance with sharp, rounded margins (88%), homogeneous density (65%), and distinct interface with the kidney (82%). The significance of these lesions should not be underestimated. Although RCCs often showed transient marked enhancement after bolus contrast material injection (41%), during the infusion phase 97% were hypodense compared with the kidney regardless of tumor size. Calcifications were visible in 31% of RCCs. Although 22% of RCCs were predominantly cystic, none fulfilled all CT criteria of simple renal cysts.

Adult↗

PubMed1990

Computed tomography versus chest radiography: impact on management of patients with lymphoma.

To assess the influence of computed tomography of the thorax (CTT) in management of patients with lymphoma, we compared results of CTT and chest radiography (CXR) for 42 patients (65 examinations) with Hodgkin's disease (HD) with 48 patients (57 examinations) with non-Hodgkin lymphoma (NHL). Six percent (7/122) of all CTs resulted in major changes in patient management (95% confidence interval = 2-12%). In four patients with HD, influential findings included of additional sites of lymphoma and clarification of x-ray results. In three patients with NHL (5%), management was altered as a result of identification of additional sites of lymphoma on CTT. Eleven percent of CTT examinations clarified equivocal CXR findings in NHL, and management was affected in two of these cases. Our findings suggest that CTT is valuable in clarifying equivocal CXR findings, and in staging or restaging patients for whom the detection of mediastinal adenopathy affect patient treatment.

Hodgkin Disease↗

PubMed1990

Adipose tissue determinations in cadavers--a comparison between cross-sectional planimetry and computed tomography.

The adipose tissue surfaces in 11 slices (+/- 5 cm from the umbilicus) were compared in two cadavers using computed tomography (CT) versus planimetry of band-sawed slices of the corresponding sections. A very close correlation was found with partial correlations of around 0.90. Retroperitoneal fat formed a considerable proportion of the total adipose tissue surface in the slices. The results were similar whether fat was defined as -250 to -50, -190 to -30, or -140 to -40 Hounsfield units. These data indicate that CT measurements agree closely with a direct morphometric method and thus can be used as a 'gold standard' for future development. The fact that fat which is located extraperitoneally, but still intraabdominally, constitutes a significant proportion of the slice surface in the umbilical region indicates that data relating intraabdominal fat measurements to metabolic functions must be interpreted with caution.

Abdomen↗

PubMed1989

Multiple glomus tumors: a role for magnetic resonance imaging in patient evaluation?

Glomus tumors may occur as solitary lesions, or rarely as multiple glomus tumors (MGT). Internal organ involvement in patients with MGT has been reported, but is rare. Magnetic resonance imaging (MRI) has been reported to be useful in evaluating patients with blue rubber bleb nevus syndrome for nongastrointestinal internal organ involvement. Three patients with MGT were evaluated by MRI for both cutaneous and internal involvement. MRI, which is useful in evaluating other vascular lesions, is not useful in the evaluation of patients with multiple glomus tumors. With these results, patients with MGT can be spared the expense of MRI procedure.

Adolescent↗

PubMed1987

Renal sinus histiocytosis.

A 26-year-old woman had an infiltrative renal lesion accompanied by massive regional lymphadenopathy. Biopsy of the renal mass and a coexistent orbital mass revealed identical histologic evidence of sinus histiocytosis. This unusual benign entity is uncommon in the kidney, but radiographically, it may closely simulate an infiltrative renal neoplasm, especially a lymphoma or leukemia or even renal cell carcinoma.

Adult↗

PubMed1986

Tissue contrast enhancement: image reconstruction algorithm and selection of TI in inversion recovery MRI.

It is clearly demonstrated that the proper application of the inversion recovery imaging pulse sequence is dependent on the method of image reconstruction and the selection of TI for optimum tissue contrast. There are two methods of 2DFT image reconstruction of IR sequence time-domain raw data. The first is a modulus-image reconstruction algorithm (contrast-obliterating option), and the second is a phase-correction routine for reconstructing "phase-sensitive" true IR-images. The second option generates proper "in-phase" images, retains proper scale of contrast, but can invert the algebraic sign of image-values under certain conditions. A series of "phase-sensitive" and "modulus" reconstructed brain images, obtained with conventional and optimized new IR pulse sequences, are shown to demonstrate these effects. They illustrate the considerable advantages gained, in practical clinical situations, if one generates "phase-sensitive" true IR-images from IR-sequence raw data at optimum TI for tissue contrast enhancement.

Algorithms↗

PubMed1986

Magnetic resonance imaging of the renal mass.

To compare the effectiveness of magnetic resonance imaging with that of excretory urography, retrograde pyelography, ultrasound, computerized tomography, angiography and venography 34 patients with renal masses, including 25 renal cell carcinomas, were examined on a 0.15 Tesla Picker 1100 magnetic resonance imager with multiple pulse sequences. Pathological proof was available for all cases except renal cysts, for which ultrasound or computerized tomographic findings were accepted. Differentiation of solid from cystic lesions was seen with magnetic resonance imaging, ultrasound and computerized tomography but not excretory urography. Tumor invasion of the renal vein and inferior vena cava was visualized in 7 patients by magnetic resonance imaging, ultrasound, computerized tomography and venography but not by excretory urography. Magnetic resonance T1 contrast scans best characterized renal masses, with good resolution of metastatic lymphadenopathy and renal cysts. Scans showing T2 contrast were best for identification of pseudocapsules in renal carcinoma, venous invasion by tumors and papillary adenocarcinoma. Advantages of magnetic resonance imaging include differentiation of solid masses from benign cystic lesions, and identification of major blood vessels and vascular invasion without administration of contrast medium. Disadvantages of magnetic resonance imaging are long imaging times and motion artifacts. Advances by the manufacturer in solving these problems will strengthen the role of magnetic resonance imaging in renal evaluation.

Angiography↗

PubMed1986

Pancreatitis: an important cause of abdominal symptoms in patients on peritoneal dialysis.

In an eight-month period, four patients in our peritoneal dialysis program developed acute pancreatitis, an incidence significantly higher than that in our hemodialysis program. Diagnosis was difficult since the symptoms of pancreatitis were similar to those of peritoneal dialysis-associated peritonitis. Further difficulties in diagnosis were due to unreliability of serum amylase levels and "routine" ultrasound examinations in suggesting the presence of pancreatitis. Computerized tomography performed in three patients showed enlarged, edematous pancreata with large extrapancreatic fluid collections in all cases. Two patients died, one directly due to complications of pancreatitis. One patient was changed to hemodialysis and showed clinical and radiologic resolution of his pancreatitis. One patient remains on peritoneal dialysis but has now had four attacks of acute pancreatitis. No patient had classic risk factors for development of pancreatitis. Review of patient histories showed no common historical factors except for renal failure itself, peritoneal dialysis, peritonitis, catheter surgery, and hypoproteinemia. It is possible that metabolic abnormalities related to absorption of glucose and buffer from dialysate or absorption of a toxic substance present in dialysate, bags, or tubing can cause pancreatitis in patients on peritoneal dialysis. We feel that a diagnosis of pancreatitis should be considered when peritoneal dialysis patients present with abdominal pain, particularly if peritoneal fluid cultures are negative or if patients with positive cultures do not have prompt resolution of symptoms with appropriate antibiotic therapy.

Abdomen↗

PubMed1986

Paramagnetic macrocyclic complexes as contrast agents for MR imaging: proton nuclear relaxation rate enhancement in aqueous solution and in rat tissues.

Paramagnetic macrocyclic chelates show promise as magnetic resonance (MR) imaging contrast agents due to stability and relaxivity comparable to those of DTPA-type chelates. For the three copper and manganese macrocyclic complexes studied in aqueous solution, T1 and T2 relaxivities ranged from 0.14 to 5.88 mM-1sec-1 at 6.25 MHz. In rats, the intravenous administration of 16 mumol/kg of Mn(cyclam) caused the liver T1 relaxation rate to double at 15 minutes after injection. T1 measurements by pulsed MR imaging and manganese analyses on excised tissue showed that both relaxation rate (1/T1) and manganese content of liver and kidney increase linearly with the dosage of Mn(cyclam). The linear relationship between 1/T1 and manganese content can be considered an "in tissue" relaxivity plot for the agent. The resulting relaxivity is 54 mM-1sec-1 in liver, compared with 3.1 mM-1sec-1 in aqueous solution. Although this work is preliminary, the implication for medical MR imaging applications is that macrocyclic contrast agents can be effective at approximately one-tenth the current typical dose used for gadolinium DTPA.

Animals↗

PubMed1986

MR imaging of the central pulmonary arterial tree in conotruncal malformation.

Successful MR imaging of the central pulmonary arterial tree was performed in four cases of conotruncal malformation and in one case of pulmonary arterial banding. Angiography performed near the time of MR imaging in three cases and 15 years earlier in two other cases did not visualize the central pulmonary arterial tree. Multiplanar imaging was necessary to fully visualize the anatomy of complex congenital defects of the pulmonary arterial tree; the choice of imaging plane varied depending on the portion of the pulmonary artery to be evaluated.

Adult↗

PubMed1985

Pleomorphic carcinoma of the pancreas: computed-tomographic, sonographic, and pathologic findings.

We present a series of eight cases of pleomorphic carcinoma of the pancreas, an uncommon lesion that contains bizarre giant cells and resembles sarcoma histologically. To our knowledge, this entity has not been described in the radiological literature. Clinical symptoms are similar to those of the usual pancreatic ductal cell carcinoma, but at presentation the primary tumor mass is usually large, and widespread metastatic disease is present. The most striking finding is massive lymphadenopathy, which may mimic lymphoma. A combination of clinical history, imaging findings, and results of percutaneous biopsy should lead to the proper diagnosis and may help to differentiate this entity from others that may affect lymph nodes.

Adult↗

PubMed1985

Verification and evaluation of internal flow and motion. True magnetic resonance imaging by the phase gradient modulation method.

We report qualitative and quantitative evaluation and verification studies of the bipolar phase gradient modulation method for true MR imaging of internal flow and motion velocities. Velocity encoding modulations provide speed-of-motion and direction-sensitive images using special phase-sensitive reconstructions. True motion MR imaging does not depend upon subject parameters, T1 or T2, nor upon selective active-volume time-of-flight calculations, nor is it limited strictly to fluid-flow velocities. Conventional MR sequences often induce strong accidental phase gradient modulations that can cause severe artifacts in conventional MR scans and limit the useful sensitivities of true motion MR. Multiple steps of velocity encoding allow resolution of separate elements of the velocity spectrum, and enable suppression of all such phase-artifact difficulties. Some view-to-view phase inconsistencies are intrinsic to the subject being scanned, e.g., strong motion variations during the heart cycle; limitations due to such effects require external modifications in the scanning, such as cardiac gating. Since conventional density information remains in the data, independent of velocity encoding modulations, we suggest a multiple encoding sequence and saving the MR raw data. These evaluations and verifications demonstrate exciting potential in clinical application for the phase gradient modulation method of true flow and motion MR imaging.

Biophysical Phenomena↗

PubMed1985

Simultaneous MR imaging of both breasts using a dedicated receiver coil.

We have designed and built a dedicated magnetic resonance (MR) coil that images both breasts simultaneously with the patient in a prone position, incorporates imaging advantages of surface coils, and benefits from having separate transmitter and receiver coils. This coil is compatible with a 0.15-T (6.3 MHz) resistive-magnet unit. It works as a simple plug-in replacement for the standard receiver coil. The unit's triple-coil structure consists of two outer coils that lie close to the lateral surface of the right and left breast and a central coil positioned between the breasts. A two-chambered box supports the coils. Breast-coil image-reception sensitivity is three to seven times greater than values obtained with a whole-body coil and shows a smooth spatial variation without oscillatory or sharply breaking behaviors. Increased sensitivity for breast tissue allows us, with a given imaging time, to use thinner sections (5 mm thick) than are possible with the whole-body coil. Since the coil is insensitive to organs such as heart and lung, motion artifact is eliminated, and image quality and resolution are further increased. Simultaneous imaging of both breasts allows direct comparison and increases patient throughput.

Breast↗