Biomedical subjects

H Hricak

Publications and source records attributed to H Hricak.

At least 163 records · Page 9Linked to original sources

PubMed1989

Phosphorus-31 MRS of human testicular function and viability.

The current clinical use of magnetic resonance spectroscopy (MRS) is explored with attention to testicular function and pathology. Magnetic resonance spectroscopy provides insights into metabolic processes that are occurring in vivo. Information on these processes were, until now, only obtained through the use of invasive procedures such as biopsy, with the attendant undesired side effects. Phosphorus-31 (31P) MRS of the testes can provide unique metabolic information noninvasively and may provide clinicians with an alternative to the invasive procedures. The practical applicability of 31P MRS to the study of human infertility and testicular pathologies is described in some very preliminary studies.

Adenosine Triphosphate↗

PubMed1989

Radiation-induced uterine changes: MR imaging.

To assess the capability of magnetic resonance (MR) imaging to demonstrate postirradiation changes in the uterus, MR studies of 23 patients who had undergone radiation therapy were retrospectively examined and compared with those of 30 patients who had not undergone radiation therapy. MR findings were correlated with posthysterectomy histologic findings. In premenopausal women, radiation therapy induced (a) a decrease in uterine size demonstrable as early as 3 months after therapy ended; (b) a decrease in signal intensity of the myometrium on T2-predominant MR images, reflecting a significant decrease in T2 relaxation time, demonstrable as early as 1 month after therapy; (c) a decrease in thickness and signal intensity of the endometrium demonstrable on T2-predominant images 6 months after therapy; and (d) loss of uterine zonal anatomy as early as 3 months after therapy. In postmenopausal women, irradiation did not significantly alter the MR imaging appearance of the uterus. These postirradiation MR changes in both the premenopausal and postmenopausal uteri appeared similar to the changes ordinarily seen on MR images of the nonirradiated postmenopausal uterus.

Adult↗

PubMed1989

Pelvic endometriosis: MR imaging.

The value of magnetic resonance (MR) imaging at 0.35 T in detecting, characterizing, and staging pelvic endometriosis was prospectively investigated in 30 consecutive women in whom this disease was clinically suspected. MR findings were correlated with the results of laparoscopy (13 women) and laparotomy (17 women). Surgical examination revealed a normal pelvis in five patients and endometriosis in 25. Three of the five normal cases and 16 of the 25 cases of endometriosis were correctly identified with MR imaging (sensitivity, 64%; specificity, 60%; accuracy, 63%). MR imaging demonstrated seven of eight endometriomas but only 14 of 29 adhesions and only six of 45 endometrial implants. While MR imaging demonstrated endometriomas, ovarian adhesions, and extraperitoneal endometrial implants, it could not accurately depict extraovarian endometrial adhesions and intraperitoneal endometrial implants. In addition, MR imaging findings did not correlate with the surgically determined severity of the disease. These limitations indicate that MR imaging cannot be used as the primary modality in the detection, characterization, and staging of endometriosis; laparoscopy remains the procedure of choice.

Adult↗

PubMed1989

Malignant versus nonmalignant retroperitoneal fibrosis: differentiation with MR imaging.

To evaluate the features on magnetic resonance (MR) images of malignant and nonmalignant retroperitoneal fibrosis (RPF) and to assess the usefulness of MR imaging in differentiating the two conditions, MR studies of nine patients with malignant RPF were retrospectively examined and compared with those of eight patients with nonmalignant RPF. Morphologic findings at MR imaging were similar for both conditions. The lesions were, however, heterogeneous in six of the nine patients with malignant RPF and homogeneous in all eight patients with nonmalignant RPF. On T2-predominant images, malignant RPF showed high signal intensity, while nonmalignant RPF showed low signal intensity. On T2-predominant images, signal intensity and T2 were significantly higher in malignant RPF than in nonmalignant RPF. Differentiation between malignant and nonmalignant RPF appears feasible and depends on tissue contrast rather than on morphologic characteristics.

Adult↗

PubMed1989

P-31 MR spectroscopy in assessing testicular torsion: rat model.

To develop phosphorus-31 magnetic resonance (MR) spectroscopy as an indicator of testicular viability, unilateral 720 degrees torsion of the spermatic cord was performed in 11 Copenhagen rats. In six of 11 rats, detorsion was done 1 hour later. The authors used special surface coils to obtain P-31 MR spectra (at 2 T) from both tests, then correlated MR findings with those from gross morphologic and histologic examination. In the normal testis, P-31 MR spectra had prominent phosphomonoester (PME) and adenosinetriphosphate (ATP) peaks. Testicular torsion dramatically reduced ATP to almost undetectable levels and significantly decreased the PME/Pi at 1 hour (1.18 +/- 0.22) in nine rats. In two rats, however, no spectral changes were present. Of the six rats in which detorsion was performed, three showed immediate regeneration of ATP and a normal PME/Pi (2.87 +/- 0.06) 3 hours later; testicles in the other three rats did not recover (PME/Pi = 0.72 +/- 0.01). Because gross morphologic observations and histologic findings prior to detorsion were unable to differentiate viable from nonviable tests, these preliminary data suggest P-31 MR spectroscopy may help clinicians diagnose testicular torsion and assess testicular viability.

Animals↗

PubMed1989

Prosthetic testicle: appearance at MR imaging.

The appearance of testicular prostheses on magnetic resonance (MR) images was studied in six patients with seven silicone implants: two with a fluid consistency and five that were solid. On T1-weighted images, both types of prosthesis demonstrated homogeneous low signal intensity; on T2-weighted images, the fluid implants had a uniformly low signal intensity, and the solid implants had a uniformly high signal intensity. Both prostheses created a chemical shift artifact on all imaging sequences owing to the difference in chemical composition of the prostheses and the surrounding tissue.

Adolescent↗

PubMed1989

MR appearance of the liver after partial hepatectomy.

To define the MR appearance of the liver after partial hepatectomy, we reviewed retrospectively 61 MR examinations performed on 25 patients 10 days to 48 months after surgery. Twenty-seven partial hepatectomies performed in the 25 patients included right lobectomy in 11, trisegmentectomy in two, left lobectomy in five, and wedge resection in nine. By using vascular landmarks, demonstration of the falciform ligament, and the presence of surgical clips, we correctly identified the type of partial hepatectomy in 21 of the 25 patients. The signal intensity of the resection margin was similar to that of the remaining parenchyma in 16 of 18 patients and was poorly defined and had a higher signal intensity (T2-weighted image) in the remaining two. Liver regeneration was observed on serial MR scans 2-16 months after surgery. Findings related to chemotherapy, including periportal changes and inhomogeneous appearance of the liver, were shown in six of eight patients. Tumor recurrence was present in nine patients, either intrahepatic (seven patients) or at the resection margin (two patients), and was consistently identified with MR imaging. The ability of MR imaging to produce images without artifacts from surgical clips is helpful in displaying the MR appearance of the liver after partial hepatectomy. Anatomic landmarks, findings related to chemotherapy, and tumor recurrence were shown well.

Adolescent↗

PubMed1989

Mixed müllerian sarcoma of the uterus: MR imaging findings.

MR images of seven patients with histologically documented mixed müllerian sarcoma were analyzed retrospectively to determine whether the scans showed findings that could suggest the diagnosis. Spin-echo T1- and T2-weighted sagittal and transverse images from either a 0.35- or a 1.5-T unit were available for each patient. MR image analysis included evaluation of tumor signal intensity on T1 and T2 images; tumor location, size, and extent; depth of myometrial invasion; and presence of pelvic metastases. In all seven patients, MR images showed a large endometrial mass deeply invading the myometrium or beyond. In addition, MR images showed intraperitoneal (two patients) and ovarian (one patient) metastases. Although the massiveness of the tumors on initial presentation may suggest the diagnosis of mixed müllerian sarcoma, the MR imaging findings are nonspecific and mimic invasive endometrial carcinoma.

Aged↗

PubMed1989

Current status of MR imaging of the female pelvis.

Magnetic resonance imaging (MRI) has become an important diagnostic method for the study of the female pelvis. It provides a noninvasive means of evaluating uterine zonal anatomy and can reflect the variable appearance of the female genital tract in response to different hormonal stimuli. It is considered a problem-solving technique for evaluating benign uterine and adnexal masses and is the primary imaging modality for staging endometrial, cervical, and vaginal carcinoma. It is also valuable in the assessment of vaginal agenesis and congenital uterine anomalies by providing information needed in surgical management. The role of MRI has not yet been established in the evaluation of ovarian carcinoma.

Female↗

PubMed1989

Gynecologic tumor imaging.

Anatomy of the female pelvis is superbly delineated by MRI due to excellent soft tissue contrast. In patients with infertility, MRI is the best technique to evaluate suspected myomata. Since tumors are directly visualized, MRI can be an effective technique for staging cervical, uterine, and vaginal malignancies.

Female↗

PubMed1988

Advances in imaging.

The introduction of sonography, x-ray computed tomography, magnetic resonance imaging (MRI), and magnetic resonance spectroscopy (MRS) have enhanced the radiologist's ability to delineate and stage neoplasms in all parts of the human body. Images of excellent quality can be generated within a reasonable time frame and with minimal biologic risk. All of the more sophisticated imaging modalities are costly and none can, isolated from clinical data, provide histologic diagnoses. Within the next few years it is anticipated that the speed of magnetic resonance image acquisition will increase and that contrast agents for MRI will be brought into clinical use. Evaluation of cost-effectiveness will continue and new diagnostic algorithms can be expected to evolve.

Diagnostic Imaging↗

PubMed1988

Pelvic lipomatosis: diagnosis and characterization by magnetic resonance imaging.

While the number of reported cases of pelvic lipomatosis has been relatively small, this entity's prevalence is probably underestimated. Disease progression can cause hydroureteronephrosis and renal failure, and clinical follow-up is mandated after diagnosis. Diagnosis is based on detection of characteristic findings in conventional radiographs and computed tomographic (CT) images. We report here the magnetic resonance imaging (MRI) features of pelvic lipomatosis in 5 male patients, 2 of whom ultimately required placement of a ureteral stent to alleviate mechanical obstruction. Multiplanar MRI not only allows diagnostic confirmation comparable to that possible with CT but also provides delineation of cephalad displacement of the bladder base, elongation of the bladder neck and posterior urethra, and elevation of the prostate gland. The MR images show characteristic medial and superior displacement of the seminal vesicles and show fatty tissue separating the prostate gland from the rectum. The noninvasive nature and low biological risk of MRI are desirable features, particularly when serial evaluation of pelvic anatomic distortion is necessary.

Adult↗

PubMed1988

Use of an agonistic analog of gonadotropin-releasing hormone (nafarelin) to treat leiomyomas: assessment by magnetic resonance imaging.

The purposes of this study were to investigate the effect of a superactive agonistic analog of gonadotropin-releasing hormone, nafarelin, on uterine leiomyomas and to assess the use of magnetic resonance imaging in monitoring uterine and myoma size. Eleven women with uterine leiomyomas were treated with 800 micrograms of nafarelin per day for 6 months. Serum gonadotropin and estradiol concentrations were suppressed during treatment. The mean +/- SEM serum luteinizing hormone level decreased from 11.1 +/- 1.4 to 5.6 +/- 0.42 mlU/ml and follicle-stimulating hormone from 9.5 +/- 0.66 to 7.5 +/- 0.72 mlU/ml by 3 months of treatment (p less than 0.01). The estradiol level decreased from a pretreatment follicular phase mean +/- SEM of 43 +/- 8.3 to 19.8 +/- 3.1 (p less than 0.05) and 14.8 +/- 2.2 pg/ml (p less than 0.01) at 3 and 6 months of treatment, respectively. Mean pretreatment androgen levels (testosterone, androstenedione, and dehydroepiandrosterone sulfate) were low in these women and did not change significantly during treatment. Ten women had magnetic resonance imaging, which provided excellent resolution of individual uterine myomas. As assessed by magnetic resonance imaging, the largest myoma decreased in size in nine of 10 women; the mean decrease was 46% +/- 9%. Uterine volume decreased in all 10 patients; the mean decrease was 57% +/- 7%. In several women myomas reenlarged after discontinuance of nafarelin treatment. Posttreatment myomectomy was carried out in four women; there was minimal blood loss and no surgical complications. These data indicate that suppression of ovarian estrogen production with nafarelin is associated with a decrease in uterine myoma size in many women but that myomas may regrow with reinstitution of ovarian function. Magnetic resonance imaging is an excellent method by which to monitor treatment as changes in the size of the uterus, as well as individual myomas, can be assessed. The optimal use of gonadotropin-releasing hormone analogs may be in perimenopausal women or as presurgical treatment to decrease uterine and myoma size to facilitate myomectomy.

Adult↗

PubMed1988

Invasive cervical carcinoma: comparison of MR imaging and surgical findings.

The accuracy of magnetic resonance (MR) imaging in staging invasive carcinoma of the cervix was determined retrospectively in 57 consecutive patients in whom the extent of disease was surgically confirmed. MR images were analyzed for (a) location and size of the primary tumor; (b) tumor extension to the uterine corpus, vagina, parametria, pelvic sidewall, bladder, or rectum; and (c) pelvic lymphadenopathy. The accuracy of MR imaging in determination of tumor location was 91% and for determination of tumor size within 0.5 cm, 70%. Its accuracy was 93% for vaginal extension and 88% for parametrial extension. Pelvic sidewall, bladder, and rectal involvement were accurately excluded in all patients, but the positive predictive values were 75%, 67%, and 100%, respectively. Overall, the accuracy of MR imaging in staging was 81%. MR imaging is valuable because it can accurately demonstrate tumor location, tumor size, degree of stromal penetration, and lower uterine segment involvement. It is also valuable for ruling out parametrial, pelvic sidewall, bladder, and rectal involvement.

Adult↗

PubMed1988

Detection and staging of renal neoplasms: a reassessment of MR imaging.

The use of magnetic resonance (MR) imaging in the detection and staging of renal neoplasms was investigated in 104 patients with 106 renal cell carcinomas confirmed at surgery or autopsy. Overall, MR imaging demonstrated 101 of 106 lesions (95%), including all 93 tumors that were larger than 3 cm in diameter but only eight of the 13 smaller tumors (62%). MR imaging enabled accurate staging of 82% of all detected lesions but led to the understaging of nine lesions and the overstaging of nine. At present, MR imaging cannot be used as a screening modality for renal tumors. However, its negative predictive values of 98% and 99%, respectively, for the evaluation of tumor vascular extension and tumor spread to adjacent structures makes it an excellent staging modality that should be used when the CT findings are equivocal. MR imaging is not accurate in indicating bowel and mesentery involvement, but rapid technical advances and the introduction of bowel contrast medium may improve this present limitation.

Adult↗

PubMed1988

Imaging the testis: comparison between MR imaging and US.

The potential role of magnetic resonance (MR) imaging in the diagnosis and local staging of testicular tumors was evaluated in 23 patients who subsequently underwent surgery or biopsy. Findings at MR imaging were compared with those at ultrasonography (US) and were correlated with the surgical-histologic findings. At surgery, three patients were found to have extratesticular and 20 patients intratesticular abnormalities. This distinction had been correctly made with both imaging modalities, but US did not demonstrate the intratesticular abnormality in four patients with diffuse infiltrating tumors. Neither modality allowed differentiation of benign from malignant disorders. When local tumor staging was analyzed in 11 patients, the accuracy of both modalities was disappointing (true-positive findings with MR imaging in seven patients and with US in five). At present, US remains the primary imaging modality for testicular disease. MR imaging should be employed when findings at physical examination and US are discrepant and considered when diffuse infiltrative disease is suspected.

Humans↗

PubMed1988

Müllerian duct cyst: diagnosis with MR imaging.

The value of magnetic resonance (MR) imaging in diagnosing clinically suspected müllerian duct cysts was assessed in six patients. MR imaging correctly demonstrated the abnormality to be intraprostatic, consistent with the diagnosis of müllerian duct cysts in four patients, and allowed the diagnosis to be excluded in the other two. The demonstration of prostatic zonal anatomy, the ability to obtain direct images in all three orthogonal planes, and a large field of view make MR imaging valuable in the study of suspected müllerian duct cysts.

Adolescent↗

PubMed1988

Complete and partial ureteral obstruction: evaluation of renal effects with P-31 MR spectroscopy and Tc-DMSA scintigraphy.

Phosphorus-31 magnetic resonance (MR) spectroscopy was used to study the effects of partial and complete ureteral obstruction on the porcine kidney; results were compared with renal tubular function as determined with technetium-99m dimercaptosuccinic acid (DMSA) scintigraphy. Twenty-seven pigs were used: nine as sham-operated controls, six with partial ureteral obstruction, and 12 with complete ureteral obstruction. P-31 MR spectra and Tc-DMSA scintiscans were obtained weekly over 3 weeks. Partial obstruction caused no significant change in P-31 MR spectra, whereas Tc-DMSA scintiscans showed a 74% decrease in tubular function by the end of 3 weeks. Complete obstruction caused a 43% reduction in the mean adenosine triphosphate (ATP) to inorganic phosphate (Pi) ratio, which paralleled the 96% decrease in Tc-DMSA uptake over 3 weeks. The difference in ATP/Pi ratios between control and completely obstructed kidneys was significant (P less than .01) at 2 and 3 weeks after ligation. These results indicate that radionuclide Tc-99m DMSA uptake is very sensitive to the pathophysiologic changes in renal tubular function, while the organ average cellular bioenergetic state (ATP/Pi) is not as strongly affected.

Adenosine Triphosphate↗