E. Scott Pretorius

Liver tumor characterization: Comparison between liver-specific gadoxetic acid disodium-enhanced MRI and biphasic CT - A multicenter trial

Objective: In our multi center trial we compared the potentials of biphasic contrast-enhanced computed tomography (CT) and a novel tissue-specific magnetic resonance imaging (MRI) contrast agent gadoxetic acid disodium in liver lesion characterization. Methods: A total of 176 patients with 252 liver lesions were analyzed. There were 104 malignant and 148 benign lesions. High-field strength (1.0 T or 1.5 T) MR systems with T1-and T2-weighted sequences were used with and without fat suppression. After gadoxetic acid disodium injection, dynamic imaging and hepatocyte phase MR imaging were performed. Biphasic with 150 mg I/kg of body weight (100-200 mL) spiral CT was also performed. Image reading consisted of on-site (by study investigators) and fully blinded off-site (by E.S.P; C.R; and A.S) evaluations. The classification (benign or malignant) and characterization (lesion type) outcomes of both techniques were assessed. All imaging results were verified against a standard of reference. Results: Both on-site and off-site evaluations demonstrated increases in the lesion classification accuracy with gadoxetic acid disodium-enhanced MRI when compared with spiral CT. This improvement was also shown for characterization. Gadoxetic acid disodium was well tolerated. Conclusions: Gadoxetic acid disodium offers a safe and diagnostically powerful tool for the evaluation of patients with focal liver lesions with a reliable assessment of lesion classification and characterization.

Magnetic resonance imaging to determine the distribution of a vaginal gel: before, during, and after both simulated and real intercourse

Abstract To provide effective contraception and protection against sexually transmitted disease, vaginal gels should maximally cover the cervical os and the vaginal epithelium before, during and after intercourse. To non-invasively monitor the intravaginal distribution of an applied intravaginal gel, we performed high-resolution magnetic resonance imaging (MRI) of the female pelvis before, during and after both real and simulated sexual intercourse. We sought to determine whether simulated intercourse with a plastic phallus could be used as a surrogate for real intercourse for such experiments. Dilute gadolinium chelate solution was mixed with Gynol-II gel and introduced intravaginally to volunteer female human subjects using a conventional applicator. MRI was performed at 1.5 Tesla with a surface coil. Imaging of the female pelvis was performed: (1) immediately after insertion of the gel; (2) during real intercourse with a male partner (2 subjects) or simulated intercourse with a plastic phallus (4 subjects); and (3) after completion of real or simulated intercourse. Subjects were studied after application of both 3 mL and 5 mL of vaginal gel. Measurements of gel thickness covering the vaginal mucosa were made digitally using electronic calipers. The bolus of gel is initially located in the upper vaginal canal, superior to the urogenital diaphragm. Both real and simulated intercourse dramatically increases the spread of gel to the lower vagina. The cervix appears to be adequately covered with gel both before and after intercourse. Increasing the volume of the gel increases initial vaginal mucosal coverage but also increases leakage from the introitus. No statistically significant differences in vaginal mucosal coverage were found between patients having undergone real vs. simulated intercourse, or on post-intercourse scans of 3 mL versus 5 mL. MRI is a sensitive, reproducible means of tracking the spread of intravaginal medications.

CT of hemorrhagic complications of anticoagulant therapy.

Anticoagulant therapy is commonly used in patients at risk for, or known to have, thromboembolic disease. Although complications of therapy are uncommon in most patients, in others it may result in complications with substantial morbidity and occasionally may be life threatening. This essay reviews the role of anticoagulant therapy and defines the potential complications that may occur in the chest, abdomen, musculoskeletal system, and CNS. Specific pitfalls in diagnosis as well as complications of the bleeding process are discussed and illustrated. The role of CT scanning in the diagnosis and triage of these patients is clearly defined through select cases and clinical dilemmas.

Wegener's Granulomatosis: CT Evolution of Pulmonary Parenchymal Findings in Treated Disease

OBJECTIVE To determine the computed tomography (CT) evolution of various pulmonary manifestations of Wegeners Granulomatosis (WG) following appropriate pharmacologic treatment of the disease. METHODS Eleven patients with WG were identified, each of whom had had at least two CT examinations. CTs were reviewed retrospectively to identify pulmonary lesions of WG. Lesions were categorized as nodules, cavities, lobar atelectasis, pulmonary bands, or infiltrates. To determine the evolution of each individual lesion following pharmacologic treatment, the authors compared the lesions at presentation to their appearances on follow-up CT examinations. RESULTS A total of 112 lesions were identified (nodules = 70, cavities = 25, lobar atelectasis = 7, pulmonary bands = 6, infiltrates = 4). The mean time interval between CT examinations was 34 weeks (range: 3-248 weeks). Treated nodules tended to become smaller (33/70, 47%), to resolve (14/70, 20%), or to remain unchanged (8/70, 11%). However, the nodules became larger or cavitated in a substantial minority of cases (13/70, 19% and 2/70, 3%, respectively). Although more than half of the treated cavities became smaller (13/25, 52%) or resolved (1/25, 4%), many evolved into nodules (6/25, 24%) or enlarged (5/25, 20%). All cases of lobar atelectasis (14/14, 100%) and transpulmonary bands (6/6, 100%) were unchanged at follow-up. All infiltrates were either resolved (3/4, 75%) or substantially improved (1/4, 25%). CONCLUSION WG has a wide spectrum of pulmonary manifestations. Nodules, cavities, and infiltrates are among the most common lesions seen on CT. Although these findings tend to improve with treatment, mixed responses are not uncommon. Lobar atelectasis and transpulmonary bands tend not to improve, even with the occurrence of clinical disease remission.

Use of MRI to determine the in vivo position of a silicone vaginal barrier contraceptive device.

This study was performed to determine the location of a silicone rubber vaginal barrier contraceptive device, the Leas Shield, in vivo. Two women, one parous and one nulligravid, were enrolled in the study. Surface coil, multiplanar Magnetic Resonance Imaging (MRI) was performed immediately following insertion of the contraceptive device, and was repeated following 35-40 min of normal ambulation by the participant.The contraceptive device was markedly hypointense to pelvic structures on both T1 and T2 weighted images. Its position within the vagina and relationship to the cervix were readily identifiable on MR images. The device was located in the upper vagina and completely covered the cervix in both patients. The valve appeared closed, and there was no apparent pressure on the urethra. The position was not altered by ambulation. In conclusion, MRI was a reproducible and rapid means for noninvasively determining the intravaginal location and orientation of a barrier contraceptive device. After insertion, the Leas Shield occupies the upper vagina and completely covers the cervix.

Continuous arterial spin-labeling perfusion magnetic resonance imaging of the human testis1

RATIONALE AND OBJECTIVES The purpose of this study was to determine if continuous arterial spin-labeling perfusion magnetic resonance imaging could be used to detect testicular perfusion in human subjects. MATERIALS AND METHODS Continuous arterial spin-labeling magnetic resonance perfusion imaging was performed in seven normal male volunteers and in one patient with a painful scrotum following vasectomy. RESULTS Normal testicular blood flow was demonstrated in 14 of 14 normal testes in seven volunteers, as well as in two normally perfused testes in the post-vasectomy patient. A change in the steady state magnetization was observed in all of the normally perfused testes of the seven volunteers. CONCLUSION It is possible to detect blood flow to the normally perfused testes using noninvasive spin-labeling perfusion magnetic resonance imaging. This modality could potentially, in future investigations, be used to image patients with suspected testicular torsion and resultant testicular ischemia.

Magnetic Resonance Imaging in Kidney Cancer

Magnetic resonance imaging is a powerful and versatile tool for single-modality evaluation of potential renal malignancies. A well-planned and executed high-field MR imaging examination can simultaneously detect and characterize a renal neoplasm. Multiphasic post-contrast imaging can generate MRA/MRV/MRU data sets with which, after post-processing, the radiologist can characterize the renal vasculature and stage the tumor. Magnetic resonance imaging also has an important role to play in helping clinicians to select the proper therapy for a renal tumor and in evaluating the patient following therapy. Ongoing advances in MR imaging, including the development of new pulse sequences, the increased availability of whole-body 3-T scanners, and the growing practicality of parallel imaging techniques will likely expand the role of MR imaging in imaging patients with known or suspected renal malignancies.

Magnetic resonance imaging to determine the distribution of a vaginal gel: before, during and after both simulated and real intercourse

To provide effective contraception and protection against sexually transmitted disease, vaginal gels should maximally cover the cervical os and the vaginal epithelium before, during and after intercourse. To non-invasively monitor the intravaginal distribution of an applied intravaginal gel, we performed high-resolution magnetic resonance imaging (MRI) of the female pelvis before, during and after both real and simulated sexual intercourse. We sought to determine whether simulated intercourse with a plastic phallus could be used as a surrogate for real intercourse for such experiments. Dilute gadolinium chelate solution was mixed with Gynol-II gel and introduced intravaginally to volunteer female human subjects using a conventional applicator. MRI was performed at 1.5 Tesla with a surface coil. Imaging of the female pelvis was performed: (1) immediately after insertion of the gel; (2) during real intercourse with a male partner (2 subjects) or simulated intercourse with a plastic phallus (4 subjects); and (3) after completion of real or simulated intercourse. Subjects were studied after application of both 3 mL and 5 mL of vaginal gel. Measurements of gel thickness covering the vaginal mucosa were made digitally using electronic calipers. The bolus of gel is initially located in the upper vaginal canal, superior to the urogenital diaphragm. Both real and simulated intercourse dramatically increases the spread of gel to the lower vagina. The cervix appears to be adequately covered with gel both before and after intercourse. Increasing the volume of the gel increases initial vaginal mucosal coverage but also increases leakage from the introitus. No statistically significant differences in vaginal mucosal coverage were found between patients having undergone real vs. simulated intercourse, or on post-intercourse scans of 3 mL versus 5 mL. MRI is a sensitive, reproducible means of tracking the spread of intravaginal medications.