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Biomedical subjects

H Hricak

Publications and source records attributed to H Hricak.

At least 145 records · Page 8Linked to original sources
PubMed1991

MR imaging of the seminal vesicles.

MR imaging (0.35 and 1.50 T) was used to assess the appearance of the seminal vesicles. The size and signal intensity of normal seminal vesicles vary with the age of the subject. In general, on T2-weighted images, the signal intensity of normal seminal vesicles is lower than that of fat in prepubertal children, similar to or higher than that of fat in adults, and similar to or lower than that of fat in patients older than 70 years of age. Endocrine and radiation therapy will influence the size and signal intensity of the seminal vesicles. The purpose of the essay is to illustrate the spectrum of seminal vesicle disease, including congenital anomalies, inflammation, and neoplastic disease. Although MR imaging is helpful in depicting seminal vesicle abnormalities, it does not allow differentiation of benign from malignant disease, distinction of hemorrhage due to tumor invasion from postbiopsy changes, or distinguishing between glandular obstruction due to tumor infiltration and mechanical compression.

Genital Diseases, Male↗
PubMed1991

Magnetic resonance imaging of renal calculi: an in vitro study.

Extracorporeal shock wave lithotripsy (ESWL) has been established as a standard method of urinary stone treatment. Poor fragmentation with an increased rate of complications has been noticed with certain calculi types (calcium oxalate monohydrate and cystine). In devising appropriate pre-operative strategies, it would be useful to know the calculi composition. We have investigated the in vitro utility of using magnetic resonance imaging (MRI) in analyzing urinary calculi. Our in vitro analysis found no difference in signal characteristics between calculi of varying composition. The absence of signal can be understood from a molecular basis. We conclude that MRI will not offer any assistance in characterizing the composition of urinary calculi.

Humans↗
PubMed1991

Role of imaging in the evaluation of pelvic cancer.

The last 15 years have witnessed dramatic advances in the detection, assessment, and management of cancer. Progress is due to increased knowledge of the basic biology of cancer, oncogenes, and immunologic mechanisms controlling cancer; a better understanding of the disease and its diagnosis and management; and improved imaging technology. Diagnostic imaging has been revolutionized by the development of microcomputers and television instrumentation, and by technological advances producing better ultrasound transducers, x-ray detectors, and more homogeneous magnetic fields, as well as more precise magnetic coils and better software. At the time that we have come to understand more about cancer prognostic variables, imaging has developed to offer a unique display of a number of morphologic factors such as tumor size, location, depth of invasion, lymph node status, presence of metastases, and overall stage of disease. Just as accurate knowledge of prognostic variables is essential for designing optimal treatment protocols, it is fundamental in rendering a useful radiology report. Because "the first treatment should be the best possible since it has the greatest chance for curing the patient," an assessment of the full extent of cancer prior to the initiation of treatment is mandatory. Two elements in the clinical setting contribute to the ability to capitalize on these advances and breakthroughs: continuing education about progress in the field of oncology, and a motivated team of treatment specialists. This combination of application of new knowledge and technological advances and team work will promote the necessary environment for the conquest for cancer.

Female↗
PubMed1991

Varicoceles. Radiologic diagnosis and treatment.

The association of clinically apparent varicoceles with male subfertility and infertility has been noted in the urology literature since the late nineteenth century, and surgical ligation of varicoceles has been considered appropriate therapy in an attempt to improve semen quality and increase fertility for the past 40 years. It has been established by several authors cited herein that varicocele size does not predict prognosis after ligation reliably. Because subclinical varicoceles may affect testicular function and histologic characteristics adversely and because age at time of therapy may affect probability of successful enhancement of fertility, the interest of radiologists and urologists has been directed toward diagnosis and treatment of both clinically obvious and clinically occult varicoceles, particularly in young adult men or adolescent boys. Testicular growth after varicocele ligation in adolescent boys also suggests a benefit from early intervention. Sonographic evidence of a varicocele must be correlated with analysis of semen for sperm density, motility, and morphology, as not all patients with varicoceles are infertile. Although surgical therapy is standard for varicocele occlusion, fairly extensive evidence exists to show that percutaneous transvenous occlusion of varicoceles is feasible, safe, and effective, particularly in the setting of varicocele recurrence after conventional surgical treatment.

Embolization, Therapeutic↗
PubMed1990

MR imaging of bladder neoplasms: correlation with pathologic staging.

This retrospective study describes the accuracy of magnetic resonance (MR) imaging in determination of local disease extent in 34 examinations performed for evaluation of primary or recurrent bladder carcinoma. The 34 examinations were carried out in 29 patients (17 men, 12 women, aged 34-89 years). All studies were followed within 30 days by surgical and pathologic evaluation. Images were interpreted by two radiologists unaware of clinical or pathologic findings. MR imaging staging conformed to the TNM system of the International Union Against Cancer (IUAC). Pathologic evaluation showed bladder neoplasms in all cases; three patients' pathologic specimens contained two or more histologic types of tumors. MR imaging staging of the depth of tumor invasion was correct in 85% of examinations. Sensitivity of MR imaging for detection of deep muscle invasion was 97%, specificity 83%, and accuracy 94%. Sensitivity of MR imaging for detection of extravesical tumor extension was 95%, specificity 100%, and accuracy 97%. Sensitivity for detection of pelvic lymph node metastases was 50%, specificity 100%, and accuracy 82%. Our population included many patients with locally advanced disease. This pattern reflects standards of clinical practice by which superficial lesions are staged and resected endoscopically, and deeply invasive tumors are imaged prior to radical surgery.

Adult↗
PubMed1990

MR imaging of the uterus: low-signal-intensity abnormalities of the endometrium and endometrial cavity.

T2-weighted magnetic resonance (MR) images showing focal areas of low signal intensity involving the endometrium or endometrial cavity were analyzed retrospectively in 28 women. The causes of the hypointense foci were disclosed histologically in 25 patients and by follow-up MR examinations in the other 3. The low signal intensity foci were due to submucosal leiomyoma (11 patients), blood clot (7 patients), endometrial carcinoma (4 patients), early intrauterine pregnancy (3 patients), retained products of conception (2 patients), and endometrial hamartoma (1 patient). The correct diagnosis was made on the basis of MR findings alone in 9 of the 11 submucosal leiomyomas. MR findings were nonspecific in the remainder of the cases. The results indicate that, on MR images, hypointense foci within the endometrium or endometrial cavity can arise from a variety of causes. Often, a specific diagnosis is not possible, and correlation with clinical history is essential.

Abortion, Therapeutic↗
PubMed1990

Cervical incompetence: preliminary evaluation with MR imaging.

The ability of magnetic resonance (MR) imaging to demonstrate cervical incompetence in nonpregnant women was investigated in a prospective study of 41 volunteers referred in random order. These included 20 patients with normal cervices, 11 with cervical incompetence of traumatic or congenital origin, and 10 with clinically small cervices due to in utero diethylstilbestrol (DES) exposure. On MR images of the normal patients, cervical length was 33.0 mm +/- 1.0 (mean +/- standard error of the mean) and the width of the internal cervical os was 3.3 mm +/- 0.1. In patients with cervical incompetence, the cervical length did not significantly differ from those in the normal group. However, the internal cervical os was significantly wider (4.5 mm +/- 0.3, P less than .001), and localized irregularity of the endocervical canal was demonstrated in two patients. The MR appearance of the cervical stroma varied from normal, uniformly low signal intensity (n = 4) to uniformly (n = 3) or partially (n = 4) medium-to-high signal intensity on T2-weighted images. In the patients with in utero DES exposure, the mean length of the cervical canal (22.9 mm +/- 1.7) was significantly shorter than that of the normal group. The width of the internal cervical os and the MR signal intensity of the cervical stroma were normal. In summary, MR findings of a cervical length shorter than 3.1 mm (95% confidence limit), an internal cervical os wider than 4.2 mm (95% confidence limit), or abnormal signal intensity in the cervical stroma are highly suggestive of incompetent cervix and should assist in planning further therapeutic decisions.

Cervix Uteri↗
PubMed1990

Obstructive nephropathy: evaluation with dynamic Gd-DTPA-enhanced MR imaging.

The potential of dynamic gadolinium diethylenetriaminepentaacetic acid (DTPA)-enhanced magnetic resonance (MR) imaging for the examination of obstructive nephropathy was analyzed in 27 subjects (five healthy subjects, seven patients with dilated nonobstructed kidneys, six patients with acute obstruction, and nine patients with chronic obstruction) with use of a 1.5-T magnet. Morphologic findings were compared with quantitative analysis of temporal changes in signal intensity. Dynamic postcontrast images of the normal kidney demonstrated four phases of enhancement; cortical enhancement phase, early tubular phase, ductal phase, and excretory phase. The pattern of enhancement in dilated nonobstructed kidneys was similar to that in normal kidneys. In acutely obstructed kidneys, cortical enhancement was similar to that in normal kidneys (17% increase), but medullary enhancement was higher than normal, resulting in diminished corticomedullary differentiation. The early tubular phase was prolonged (until 2.5 minutes after injection), with delayed appearance of the ductal and excretory phases. In chronically obstructed kidneys, the increase in cortical intensity was less than that in normal kidneys (13% increase). The early tubular phase was prolonged, and the ductal phase was diminished or absent.

Acute Disease↗
PubMed1990

Postirradiation changes in the pelvis: assessment with MR imaging.

Magnetic resonance (MR) imaging features of pelvic radiation change were assessed in 51 patients and were correlated with tumor and critical tissue radiation dose, time after treatment, and clinical symptoms. The severity of MR tissue changes was graded. Radiation tissue toxicity increased significantly when the dose exceeded 4,500 cGy, with the incidence of marked bladder and rectal changes rising from 8% to 51% and from 24% to 48%, respectively. Similar dose-related changes were seen in other pelvic organs. All grades of tissue change were seen in the bladder and rectum regardless of the time from start of therapy. All patients who exhibited clinical grade 2 or 3 bladder and rectal changes showed moderate or severe changes on MR images. In asymptomatic patients, minimal MR changes were seen in the bladder (47%) and in the rectum (33%). The accuracy of MR imaging in differentiating between radiation damage and residual/recurrent tumor varied with the primary tumor site, being excellent for recurrent cervical cancer and less so for rectal carcinoma.

Adult↗
PubMed1990

Müllerian duct anomalies: MR imaging evaluation.

Twenty-nine patients underwent magnetic resonance (MR) imaging for investigation of müllerian duct anomalies (MDAs). The anomalies evaluated were uterine agenesis (n = 2), uterine hypoplasia (n = 5), unicornuate uterus (n = 5), uterus didelphys (n = 5), bicornuate uterus (n = 10), and septate uterus (n = 2). The MR imaging interpretation was correlated with results of laparotomy (n = 18), hysterosalpingography (HSG) (n = 5), laparoscopy (n = 2), hysteroscopy (n = 1), HSG and laparotomy (n = 2), and HSG and laparoscopy (n = 1). MR imaging enabled correct classification of the anomaly in each patient and identification of coincidental gynecologic disease in 10 patients (34%). MR imaging results influenced clinical treatment in six (24%) of 25 patients referred prospectively. Of particular value was the ability to characterize septal tissue (myometrium versus fibrous tissue), identify the patients in whom the septum of bicornuate uteri had both fibrous and myometrial components, and establish that suspected adnexal lesions were actually components of obstructed MDAs.

Adult↗
PubMed1990

In vivo human testicular function assessed with P-31 MR spectroscopy.

The clinical feasibility of assessing testicular metabolic integrity with phosphorus-31 magnetic resonance (MR) spectroscopy was investigated in six healthy volunteers and 23 patients with azoospermia. MR spectroscopic findings were compared with sperm count and motility in all patients and with findings at testicular biopsy in 23 patients. Significant differences (P less than .05) were found between the P-31 spectra of normal and azoospermic testicles in the following peak area ratios: phosphomonoester (PM)/beta-adenosine triphosphate, PM/phosphodiester, and inorganic phosphate/PM. In the patients with azoospermia, there were significant differences in these same peak area ratios between patients with primary testicular failure and those with chronic tubular obstruction. Although the differences between these two groups were statistically significant, there was a large overlap in numbers, and therefore a study with a larger patient population will be required. P-31 MR spectroscopy is a sensitive tool for assessment of testicular metabolic integrity and differentiation of normal testicles from those with markedly decreased spermatogenesis.

Humans↗
PubMed1990

Fat-saturation MR imaging of the upper abdomen.

The fat-saturation (fatsat) MR technique decreases the signal intensity of fat, thereby enhancing the definition of upper abdominal organs and reducing artifacts while maintaining the T1 and T2 information available on spin-echo sequences. To evaluate the potential of fatsat in examining the abdomen, we conducted a prospective study involving 30 subjects, including four normal volunteers, 18 patients investigated for liver disease, and eight patients studied for miscellaneous abdominal disease. Short TR, 300-600/15-20 (TR/TE), and long TR, 2000-2500/20-30, 70-80, spin-echo images with and without fatsat were compared. The images were evaluated both qualitatively and quantitatively. Qualitative assessment was made with receiver-operating-characteristic (ROC) curve analysis of the confidence level of observers to detect the presence of disease, comparing fatsat with standard spin-echo sequences. ROC analysis showed greater interpreter confidence and accuracy for fatsat sequences than for standard spin-echo sequences. The measured signal-difference-to-noise (SD/N) ratio comparing upper abdominal organs with surrounding tissue revealed the highest values for short TR/TE regular spin echo, followed by short TR/TE fatsat. The highest SD/N ratio for hepatic masses was with long TR/TE fatsat followed by short TR/TE fatsat. The results of this study suggest that the fatsat technique may improve abdominal MR imaging.

Abdomen↗
PubMed1989

Androgen sensitivity of rat prostate carcinoma studied by 31P NMR spectroscopy, 1H MR imaging, and 23Na MR imaging.

31P NMR spectroscopy, 1H magnetic resonance (MR) imaging, and 23Na MR imaging were used to study the biochemical difference between nine hormone-sensitive and six hormone-resistant rat prostate cancers and to follow bioenergetic and morphologic changes subsequent to androgen deprivation in the hormone-sensitive model. Neither 1H nor 23Na MR image characteristics were useful in distinguishing androgen-sensitive from androgen-resistant prostate cancer nor in identifying androgen deprivation. 31P NMR spectroscopy did detect bioenergetic differences between the hormone-sensitive and hormone-resistant tumors. Baseline spectra showed a significantly higher PCr/ATP ratio (mean 0.86 +/- 0.09 SEM) for hormone-sensitive tumors than for hormone-resistant tumors (mean 0.26 +/- 0.07 SEM). By 3 days after androgen deprivation (orchiectomy (castration], PCr/ATP ratios had decreased noticeably; by 1 week, the decrease was statistically significant and remained so for the rest of the study (3 weeks). It appears that 31P NMR spectroscopy is useful in detecting androgen sensitivity of prostatic carcinoma.

Androgens↗
PubMed1989

Assessment of male infertility: correlation between results of semen analysis and phosphorus-31 magnetic resonance spectroscopy.

To evaluate the usefulness of phosphorus-31 magnetic resonance spectroscopy (31P-MRS) in assessing male infertility, we compared it with conventional semen analysis. Specimens were obtained from otherwise healthy patient groups as follows: group A, 7 fertile control subjects; group B, 12 azoospermic men after vasectomy; and group C, 11 patients presenting for infertility evaluation. Correlations between established semen analysis parameters and the 31P-MRS-derived ratio of glycerylphosphorylcholine to total phosphate (GPC/TP) were investigated. Group A controls had a mean GPC/TC ratio of 0.10 +/- 0.05, which was the same as that of group C. With the exception of significantly lowered motility and normal morphology in group C (p less than 0.001 and 0.05, respectively) semen analysis parameters in these two groups were similar. In contrast, the GPC/TP ratio in group B (0.05 +/- 0.04) was significantly different from the control (p less than 0.05), which appropriately reflected complete vasal occlusion. The results suggest that a significant portion of seminal GPC is derived from epididymal secretion and that 31P-MRS is useful for monitoring the GPC/TP levels when assessing epididymal function and male infertility.

Glycerylphosphorylcholine↗
PubMed1989

Rapid, contrast-enhanced, diuretic magnetic resonance imaging of unilateral partial ureteral obstruction. An experimental study in micropigs.

The value of rapid, contrast-enhanced, diuretic magnetic resonance (MR) imaging (using ferrioxamine B and furosemide) in demonstrating partial unilateral ureteral obstruction and the potential of such MR imaging in differentiating obstructive from nonobstructive hydronephrosis was assessed in six micropigs. MR imaging (0.35 Tesla, partial-flip technique with repetition time [TR] of 125 milliseconds, echo-delay time [TE] of 20 milliseconds, and flip angle of 70 degrees) was performed before, and at 5, 12, and 19 days after partial ureteral obstruction. Additionally, MR images were acquired 5, 12, and 19 days after release of obstruction. The diuretic was injected 10 minutes after the contrast medium. MR findings were correlated with results from nuclear scintigraphy (99mTc-DMSA uptake). MR images provided good morphologic detail from which renal size, parenchymal thickness, and degree of hydronephrosis could be determined. Contrast medium allowed assessment of cortical uptake and urinary excretion. The course of cortical signal enhancement best characterized the difference between obstructive and nonobstructive hydronephrosis. Normal kidneys and kidneys with nonobstructive hydronephrosis showed progressive decrease in cortical signal enhancement (-11.7% within 40 minutes) after furosemide injection. The kidneys with obstructive hydronephrosis demonstrated a plateau of signal enhancement without decrease (-0.7% within 40 minutes). These results demonstrate the utility of rapid contrast-enhancing, diuretic MR imaging in differentiating obstructive from nonobstructive hydronephrosis.

Animals↗
PubMed1989

Noncontrast and contrast enhanced MR imaging in the evaluation of partial ureteral obstruction: an experimental study in the micropig.

Twelve Yucatan micropigs (3 controls; 3 sham-operated; 6 with unilateral obstruction) were studied to assess the value of noncontrast and contrast-enhanced (Gadolinium-DTPA) magnetic resonance (MR) imaging in the evaluation of partial ureteral obstruction. MR findings were correlated with findings of quantitative (Tc-99m-DMSA) scintigraphy, and histology. On noncontrast T1-weighted images, the normal porcine kidney demonstrated good corticomedullary contrast (CMC = 16.8% +/- 5.0). Five minutes after administration of Gd-DTPA, there was enhancement of the renal cortex (+24.4% and medulla (+46.2%), and CMC was no longer discernible. Enhancement of the urine within the collecting system (+119.1%) was also observed. The obstructed kidneys demonstrated marked thinning of the renal parenchyma and decreased signal intensity on noncontrast T1- and T2-weighted images (P less than 0.01). Urine in the dilated collecting system did not differ significantly from urine in controls except in the three animals with urinary tract infection (P less than 0.05). Five minutes following injection of Gd-DTPA, there was enhancement of the renal parenchyma in all kidneys. Excretion was seen in three pigs and no excretion in two. Thus, useful information can be obtained in partial ureteral obstruction from both pre-contrast and Gd-DTPA-enhanced MR images of the kidney.

Animals↗
PubMed1989

Phosphorus-31 MRS of the kidney.

Phosphorus-31 (31P) magnetic resonance spectroscopy of the kidneys promises to provide metabolic information leading to better assessment of renal physiology. However, the problems of studying the metabolism of the heterogeneous renal architecture by precisely localizing the origin of the signal obtained from small voxels and eliminating motion artifacts have not been solved as yet. The normal 31P MRS spectra show a characteristic fingerprint of six peaks including phosphomonoesters, phosphodiesters, inorganic phosphorus, and gamma, alpha, beta adenosine triphosphate (ATP). Renal failure, regardless of its etiology and mechanism of inducement (hypoxia, ischemia, acidosis, or obstruction) produces a loss of ATP with a progressive increase of inorganic phosphorus and a decline in intracellular pH. The severity of renal failure correlates with the severity of the metabolic disturbance. The potential use of 31P MRS in the assessment of renal viability has been applied to the study of renal preservation methods and prediction of renal function following transplantation.

Adenosine Triphosphate↗