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Biomedical subjects

D D Stark

Publications and source records attributed to D D Stark.

At least 109 records · Page 6Linked to original sources
PubMed1985

Obstetrical magnetic resonance imaging: fetal anatomy.

Nine patients who were 34-36 weeks pregnant underwent magnetic resonance (MR) imaging. Sagittal images using spin echo technique (TR 2.0 sec, TE 28 msec) were optimal for delineating fetal anatomy. The fetal cardiovascular, pulmonary, and central nervous systems were depicted in all cases. The heart and major vessels were readily seen due to the natural contrast of flowing blood. The intensity of the fluid-filled lungs greatly increased with a longer TR or TE, delimiting thorax from liver. The brain was relatively featureless due to the lack of gray-white matter differentiation. The umbilical cord within the amniotic fluid and its insertion into the placenta and fetus was identified in all cases. MR is a new modality for fetal imaging that offers tissue-characterization information that complements the superior anatomic detail of ultrasound scanning.

Amniotic Fluid↗
PubMed1985

Parathyroid aspiration biopsy under ultrasound guidance in the postoperative hyperparathyroid patient.

A 10-MHz high-resolution dedicated small parts scanner and a static 5-MHz digital scanner were used in the ultrasound (US) examination of 11 patients with hyperparathyroidism who had previously undergone surgery of the parathyroid (eight patients) or thyroid (three patients) gland. Using US localization, aspiration biopsies were performed successfully in nine patients: parathyroid disease was confirmed in seven patients and thyroid lesions in two. Inadequate aspirate was obtained in one patient; in another patient a biopsy was done successfully under CT guidance following a negative US examination. The authors conclude that high-resolution US is an effective tool for guiding the aspiration biopsy of nonpalpable parathyroid tumors in patients who have had neck surgery. They suggest modifications of the US equipment that would simplify the localization procedure.

Adenoma↗
PubMed1985

Intrauterine growth retardation: evaluation by magnetic resonance. Work in progress.

Eleven high risk fetuses between 32 and 37 menstrual weeks gestational age were examined by magnetic resonance (MR) imaging. Serial obstetrical sonograms, birth weights, and serial postnatal examinations were obtained in all subjects. Sagittal MR spin echo images obtained using TR = 0.5 sec and TE = 28 msec were useful for assessing subcutaneous fat. Prospective estimates of fetal fat stores correlated with neonatal outcome better than sonographic measurements of fetal growth parameters or actual birth weight. MR appears to be a safe and useful technique that offers information complementary to obstetrical sonography when IUGR is suspected.

Adipose Tissue↗
PubMed1985

Surface coil MR imaging of abdominal viscera. Part I. Theory, technique, and initial results.

Prototype surface coil magnetic resonance (MR) images were obtained from phantoms and 42 subjects at 0.6 T to assess the feasibility of imaging relatively deep abdominal structures. Surface coil images demonstrated a two- to fourfold improvement in signal-to-noise ratio (SNR) when compared with whole-body coil images with the same resolution elements. This improvement in SNR allowed us to obtain images with thinner sections, higher in-plane resolution, or, alternatively, a decrease in image time. Compared with body images, surface coil images demonstrated greater anatomic detail and reduction in motion artifacts. Despite the limited field of view in very large patients, the use of surface coils improves the diagnostic capability of MR imaging of the abdomen.

Abdomen↗
PubMed1985

Surface coil MR imaging of abdominal viscera. Part II. The adrenal glands.

Magnetic resonance (MR) imaging of the adrenal glands with a prototype surface coil was compared with conventional body coil images in five healthy volunteers and 15 patients with adrenal disease. The spectrum of abnormalities included five nonfunctioning cortical adenomas, of which two were in hyperplastic glands, four adrenal metastases, three pheochromocytomas, a functioning adenoma, a myelolipoma, and a partially calcified, cystic adrenal mass. In both body and surface coil images, anatomic detail was superior on T1-weighted images compared with T2-weighted images obtained with identical imaging time because of decreased motion artifact and superior contrast. In the T1-weighted studies, high-resolution surface coil images showed a threefold improvement in signal-to-noise ratio (SNR) over body coil images, which was manifest by better intrinsic resolution of small adrenal lesions and clearer definition of the extrinsic relationships of large masses to nearby organs. In addition, inferior vena caval invasion by two right adrenal metastases was better demonstrated using the surface coil than body coil MR or computed tomography (CT). Limitations of surface coil imaging include restriction in the field of view to a single gland and additional time required for patient positioning. Since the sensitivity of surface coils diminishes with depth, gains in SNR were limited in large patients with deeper adrenal glands. Despite these limitations, dramatic improvements in SNR and anatomic resolution indicate that surface coil MR imaging will be competitive with CT for examining the adrenal glands.

Adrenal Gland Diseases↗
PubMed1985

Surface coil MR imaging of abdominal viscera. Part III. The pancreas.

Eight healthy volunteers and 11 patients with pancreatic abnormalities were studied using a conventional body coil and a prototype magnetic resonance (MR) surface coil. Final pathologic diagnoses included carcinoma of the head (six), body (one), and tail of the pancreas (two) and chronic pancreatitis (two). In surface coil images of the volunteers, the body and tail of the pancreas was visualized in all cases but one, and the pancreatic duct was seen in five of eight cases. In-plane spatial resolution of 0.9 X 0.9 mm and 5-mm section thickness was obtained. At the same time, pancreatic surface coil images had a twofold improvement in the signal-to-noise ratio (SNR) compared with body coil images. T1-weighted spin-echo images gave greater SNR, reduced motion artifacts, provided superior anatomic detail, and offered more diagnostic information than comparable T2-weighted images. Significant abnormalities detected only by surface coil imaging included a small tumor surrounded by reactive edema and periglandular tumor invasion. This study demonstrates that surface coil imaging of the pancreas not only is feasible but provides an improved method for examining the pancreas by MR.

Adult↗
PubMed1985

Gallbladder bile in cholecystitis: in vitro MR evaluation.

Fifty-three samples of gallbladder bile were obtained at the time of cholecystectomy from patients with the clinical diagnosis of acute or chronic cholecystitis. Five bile samples from patients with clinically normal gallbladders also were obtained. Proton magnetic resonance (MR) relaxation times, protein content, and water content were determined for the bile samples, and the data were grouped according to pathologic diagnosis, which disclosed 11 cases of acute cholecystitis, 41 cases of chronic cholecystitis, and six normal gallbladders. There was no significant difference in the mean T1 and T2 values between the groups with acute and chronic cholecystitis. Patients with chronic cholecystitis were found to have more concentrated bile than those with acute cholecystitis. Protein content varied widely within both groups of patients. We conclude that T1 and T2 relaxation times do not reliably differentiate acute from chronic cholecystitis.

Bile↗
PubMed1985

Pulse sequence optimization for MR imaging using a paramagnetic hepatobiliary contrast agent.

Paramagnetic agents enhance contrast between tissues in magnetic resonance (MR) imaging by altering tissue relaxation times. The effect of these changes on MR image intensity depends in part on the choice of operator-controlled pulse sequence parameters. With the newly described paramagnetic hepatobiliary contrast agent, iron(III) ethylenebis-(2-hydroxyphenylglycine), Fe(EHPG)-, an in vivo experimental analysis of pulse sequence optimization was performed on the rat. We compared the enhancement of the liver divided by background noise, EL/N, of standard inversion-recovery (IR) and spin-echo (SE) T1-weighted pulse sequences and several pulse sequences theoretically predicted to have improved EL/N. Optimization of the echo time (TE = TEmin) gave a substantial (greater than 60%) increase in EL/N over the standard IR and SE pulse sequences. Images obtained with optimized repetition rate and inversion time gave only a slight additional improvement. Within the uncertainties of our relaxation measurements, the measured changes in EL/N with pulse sequence optimization corresponded well with theoretical predictions. With the experimental and theoretical data, the importance of using a short echo time to obtain maximal T1 contrast in contrast-enhanced MR imaging and the relative merits of optimized SE versus IR pulse sequences for contrast-enhanced MR imaging are discussed.

Animals↗
PubMed1985

Pelvimetry by magnetic resonance imaging.

Sagittal and transverse multisection magnetic resonance imaging (MRI) in 10 patients was used to obtain dimensions of the maternal pelvis, determine fetal position, and examine maternal and fetal soft tissues. Dimensions were measured with less than 1% instrument error, and bony landmarks were readily identified. MR pelvimetry is an accurate technique for obtaining traditional pelvimetric measurements without exposure to ionizing radiation. These techniques can be further used to investigate soft-tissue dystocia and obstructed labor.

Dystocia↗
PubMed1985

High-resolution surface-coil imaging of lumbar disk disease.

Seventeen patients with lumbar disk disease were studied using a prototype magnetic resonance (MR) surface coil. The high signal-to-noise ratio achieved with the surface coil permitted increases in spatial resolution to 0.9 X 0.9 mm in-plane resolution with 5 mm slice thickness. The surface coil was also compatible with multiplanar, multiecho imaging techniques. The spatial resolution achieved in this study was nearly equivalent to that achieved by state-of-the-art computed tomographic (CT) scanners, and MR showed a superior range of soft-tissue contrast. One significant limitation of MR was its inability to demonstrate small calcifications. Nevertheless, MR imaging provided diagnostic information comparable to CT or myelography in a completely noninvasive manner. With further technical advances, MR is likely to become the initial procedure of choice for evaluating patients with suspected lumbar disk disease.

Humans↗
PubMed1985

Magnetic resonance imaging of cavernous hemangioma of the liver: tissue-specific characterization.

Twenty-one patients with hepatic hemangioma, five with hepatic cysts, and 25 with primary or metastatic cancer involving the liver were studied by magnetic resonance imaging (MRI). Benign lesions (hemangiomas, cysts) were diagnosed noninvasively by CT, radionuclide studies, and/or sonography and confirmed by follow-up examinations more than 1 year later. Malignant lesions were confirmed by liver biopsy in every case. Identical multisection/multiecho techniques were used in all patients to obtain T1-and T2-weighted spin-echo (SE) and inversion-recovery (IR) images. MRI detected more hemangiomas than any other imaging technique. Of 30 hemangiomas, 25 were spherical or ovoid with a homogeneous appearance and smooth, well defined margins. Cancer tended to have a heterogeneous appearance and poorly defined margins. On T2-weighted SE images obtained with 2000 msec TR and 60, 120, or 180 msec TE, hemangiomas had significantly greater contrast-to-noise ratios (C/N) than liver cancer (p less than 0.001). The SE 2000/120 sequence provided the single most useful image for distinguishing hemangiomas from cancers. When morphologic criteria are used in conjunction with measured C/N, MRI correctly distinguished cavernous hemangiomas from liver cancer with 90% sensitivity, 92% specificity, and an overall accuracy of 90%. Cysts had a low signal intensity on SE 500/30 images and could often be distinguished from hemangiomas and cancers that were nearly isointense relative to liver. IR images were sensitive for lesion detection but provided no tissue-specific information. The data indicate that T2-weighted SE imaging may become the procedure of choice for distinguishing cavernous hemangioma from liver cancer.

Adenoma, Islet Cell↗
PubMed1985

Magnetic resonance imaging of fetal anomalies in utero: early experience.

Five cases of fetal dysmorphology were examined with high-resolution sonography and magnetic resonance imaging (MRI). Postpartum confirmation was available in all cases. The high contrast resolution of MRI resulted in clear depiction of the abnormalities, particularly dilated fluid-filled structures, whereas the real-time capability and spatial resolution of sonography permitted better appreciation of anatomic detail. While sonography will remain the primary imaging method for pregnancy, MRI appears to be a promising complementary technique in difficult cases.

Female↗
PubMed1985

Chemical shift imaging of bone marrow: preliminary experience.

A phase-contrast method of chemical shift imaging was used to evaluate bone marrow in normal volunteers and in patients with metabolic, inflammatory, traumatic, and neoplastic disorders. Five normal volunteers were examined in order to obtain preliminary data on normal patterns of signal intensity in hematopoietic and fatty marrow using both conventional magnetic resonance imaging and proton chemical shift imaging. Normally, hematopoietic marrow yields low signal intensity on phase-contrast images; pathologic conditions affecting hematopoietic marrow typically result in increased signal intensity due to either accumulated lipid or water. Because of its high fat content, yellow marrow normally yields high signal intensity on phase-contrast images, whereas abnormal conditions usually result in decreased phase-contrast signal intensity due to increased tissue water. Proton chemical shift imaging is likely to be a valuable supplement to standard magnetic resonance imaging techniques in the study of bone marrow in vivo.

Adult↗
PubMed1985

Cardiac magnetic resonance imaging: the Massachusetts General Hospital experience.

The combination of gated cardiac imaging with the magnetic resonance parameters of flow void and tissue characterization forms the basis for a powerful noninvasive technique for imaging the cardiovascular system. Images constructed in planes orthogonal to the axis of the heart allow cardiac structures to be reproducibly detected in serial studies and measured. The data acquisition techniques used at Massachusetts General Hospital are presented, along with examples of their application in a variety of cardiac diseases. Future prospects are illustrated with flow-encoded images and with surface coil techniques.

Aorta↗
PubMed1984

Primary cystic arthrosis of the hip.

Subchondral cysts can mimic the radiographic features of intra-osseous ganglia or a variety of neoplastic processes. This case demonstrates the development of a massive subarticular cyst in the supra-acetabular bone. The unique pathogenesis of subchondral cysts is illustrated by the evolution of radiographic features that may be useful in planning treatment.

Bone Cysts↗
PubMed1984

Radiographic assessment of venous catheter position in children: value of the lateral view.

Frontal chest radiographs can be misleading in the evaluation of central venous catheter placement. Lateral chest radiographs were obtained, in addition to the standard frontal radiographs, in 25 young children. In five (20%) of the children, the catheters were found to be malpositioned, and the frontal radiograph showed evidence of the abnormality in all five. The lateral radiographs also showed evidence of the abnormality in all five children; however, in three of the five, the lateral radiographs provided additional, more specific, diagnostic information. The lateral chest radiographs also demonstrated satisfactory catheter positioning in three other children in whom the frontal radiographs suggested abnormal positioning. Accurate assessment of catheter position was possible in all patients using both frontal and lateral chest radiographs. Injection of contrast material was not necessary to locate malpositioned catheters. Lateral radiographs are recommended whenever an abnormal catheter position is suspected clinically or from findings on the routine frontal radiograph.

Catheterization↗
PubMed1984

Computed tomography of malignant carcinoid disease.

Twenty-two patients with malignant carcinoid syndrome were evaluated with CT, the largest series to date. A mass representing the primary tumor or local adenopathy was identified in four patients, appearing as a homogeneous mass involving mesentery and bowel. In two other patients the primary was not identifiable by barium series, angiography, CT, or laparotomy. In the remaining 16 patients who were scanned after resection of the primary four had mesenteric thickening and five had adenopathy. Malignant ascites was present in seven of 21 patients. All hepatic metastases were hypodense on the precontrast study. The effect of contrast administration on lesion detectability was variable, obscuring at least one or more metastases in eight of 21 scans. We recommend noncontrast scans of the liver in patients in whom the number and size of metastases are critical to therapy.

Contrast Media↗