Dynamic spin-echo MRI of liver cancer using Gadolinium-DTPA: animal investigation

An animal model of liver cancer was used to demonstrate that with a fast MRI technique, Gadolinium-DTPA increases tumor-liver contrast. A spin-echo pulse sequence with short repetition (TR) and echo-delay (TE) times (TR 250/TE 15/Excitations 1) has a scan time of 0.6 min, which allows early dynamic postcontrast infusion imaging. This is necessary to capture peak compartmental differences when an extracellular contrast agent such as Gadolinium-DTPA is used. This short TR/short TE pulse sequence also increases T1-dependent tissue contrast over the traditional (inversion recovery or spin echo) T1-weighted pulse sequences. Our studies suggest a significant potential for improved detection of liver metastases with Gadolinium-DTPA-enhanced liver MRI.     

Childhood Malignant Thymoma: Clinical, Therapeutic, and Immunohistochemical Considerations

Malignant thymomas are among the least common mediastinal tumors in the pediatric age group. Thymomas are considered malignant on the basis of macroscopic and microscopic invasiveness. As only 20 well-documented cases involving children have been reported in the literature, the pattern of responsiveness to therapy and the value of prognostic signs is obscure. Two cases of malignant pediatric thymomas are reported with pathognomonic histoimmunological features of aggressive thymoma. One was cured, with a follow-up of 70 months, and one died while on therapy. Analysis of the histological features and the immunoperoxidase staining displays the complexity of pediatric thymomas and the inability to prognosticate the outcome, respectively.     

Quantitation of T2′ anisotropic effects on magnetic resonance bone mineral density measurement

In this paper, the authors quantitate the anisotropy of susceptibility effects in an uniaxial trabecular bone model and show its relevance to clinical MR bone mineral density measurements. A physical model is described that quantitates the anisotropic MR behavior of uniaxial trabecular bone. To test the model, a phantom of parallel polyethylene filaments was scanned every 15° between 0° and 90° with respect to the system's main magnetic field (B₀). The distal radial metaphysis of a healthy female volunteer was scanned in orthogonal projections. The signal from each phantom image and each radial image was separated in a pixel-wise fashion into R₂ and R₂′ maps. As predicted, R₂′ relaxation showed anisotropic behavior and changed according to sin² (?), confirming that columnar structures parallel with B₀ will cause no MR susceptibility effects. Scans of the distal radius showed that R₂′ relaxation was twice as great with the forearm perpendicular to B₀ as when it was parallel to it, demonstrating different contributions from struts and columns. For both phantom and radial bone scans, R₂ relaxation was isotropic and did not change with object orientation.     

Time after excision and temperature alter ex vivo tissue relaxation time measurements

Previously unreported effects of tissue storage were recently observed in the authors' experimental magnetic resonance (MR) studies. To evaluate the effect of elapsed time after excision and storage temperature on tissue relaxation time measurements, tissue samples from the liver, pancreas, kidney, testis, spleen, and brain were obtained in rats. T1 and T2 were first measured within 5 minutes of excision, and between subsequent measurements, tubes were kept in a water bath at 40°C, at room temperature (28°C), or in an ice bath (4°C). Cellular and organellar integrity was assessed with electron microscopy and correlated with the MR findings. At 40°C (20-MHz spectrometer), the T1 of liver decreased from 280 msec ± 8 to 212 msec ± 10 during the first 60 minutes; the T1 of pancreas decreased from 276 msec ± 3 to 208 msec ± 2. Other tissues showed less than a 5% decrease in T1. T2 changes were smaller than T1 changes in all tissues. Electron microscopy of pancreatic acinar cells showed postmortem changes in mitochondria evolving over the first 60 minutes after death. Manganese loading experiments implicated mitochondrial manganese stores in the observed enhanced postmortem decrease in T1. This study calls into question reported relaxation time data for liver and pancreas. MR studies of excised tissues must account for time and temperature to prevent systematic experimental errors.     

Prolactin release induced by opiate agonists, effect of glucocorticoid pretreatment in intact and adrenalectomized rats

Cortisol administered at a dose of 25 mg/kg 24 h before measurements decreased the prolactin secretion induced by intraventricularly given opioids (dynorphin, beta-endorphin, Met-enkephalin or D-Met-Pro-enkephalinamide). The effect of cortisol was depressed by actinomycin D pretreatment. The cortisol-induced inhibition of the action of morphine was facilitated in adrenalectomized animals; measuring the effects of increasing doses of cortisol a maximal inhibition was obtained at a dose of 5 mg/kg. The opioid-induced corticosterone secretion was not affected 24 h after a single administration of cortisol. The present results show that the cortisol-induced inhibition of opioid-induced prolactin secretion is dependent on protein synthesis and independent of changes in drug metabolism, and of the type of opiate receptor preferentially affected by the opiate agonists employed.     

MR imaging of focal splenic tumors

This study was undertaken to define the MR appearance of splenic tumors in 16 cancer patients with focal splenic lesions; 50 volunteers and liver cancer patients without splenic abnormalities served as controls. In 14 patients with focal splenic lesions, differences between splenic and lesion signal intensities permitted detection of splenic lesions on MR images, either because of cystic or necrotic areas lengthening T2 within the tumor, because of T1 shortening from tumor-associated hemorrhage, or because of T2 shortening of surrounding spleen in two cases of suspected transfusional iron overload. In one spleen, a lesion appeared isointense on both T1- and T2-weighted pulse sequences and was detected only by gross splenic deformity. In one other case, CT defined splenic metastases not visible on MR images. Measurements of signal intensity of normal spleens and tumor are so similar that spin-echo MR imaging can underestimate the size and extent of focal splenic disease or may miss lesions entirely. We conclude that MR imaging is a less sensitive technique for detecting focal lesions of the spleen than for detecting focal hepatic lesions.     

Posterior chamber intraocular lens implantation in the absence of posterior capsular support

Because of the high incidence and great variety of complications associated with anterior chamber intraocular lenses, we have developed a technique for the implantation of a posterior chamber intraocular lens in the absence of posterior capsular support. The posterior chamber IOL is placed in the ciliary sulcus by suturing the superior haptic to the iris and the inferior haptic to the sclera at the ciliary sulcus. We have used this technique successfully in both complicated extracapsular surgery and secondary intraocular lens implantation.     

Use of the biceps femoris following failed inferior gluteal flap transfer. Case report.

Considering the high recurrence rate of pressure ulceration in paraplegic patients, flap procedures to reconstruct a defect should not be at the expense of another possible future flap. The posterior thigh fasciocutaneous flap is useful for the coverage of ischial and trochanteric pressure sores; the biceps femoris musculocutaneous flap is a useful choice for deep ischial defects. However, the cutaneous portions of these two flaps is nearly identical. The previous transfer of the biceps flap excludes the further use of the posterior thigh flap. In contrast, use of the posterior thigh flap still permits the employment of a biceps V-Y advancement flap. Even if the donor site of the previous posterior thigh flap must be skin-grafted, the graft will remain viable on its muscular bed and function as the cutaneous portion of the flap; thus stable coverage is provided, despite previous use of 'first line' flaps. We demonstrate how careful planning of the stages of flap procedures can allow the most economic use of donor areas in this difficult patient group.     

Long-term results and complications of preoperative radiation in the treatment of rectal cancer

A retrospective study of 149 patients with rectal cancer diagnosed between 1972 and 1979 was undertaken to compare survival, disease-free survival, recurrence sites, and long-term complications of 40 patients who received 4000 to 4500 rads of preoperative adjuvant radiotherapy (radiation group) with those of 109 patients treated by resection alone (control group). After a mean follow-up of 84 months and 99 months, respectively, survival of the irradiated patients was significantly better than that of controls (68% versus 52%, p less than 0.05). Disease-free survival of those patients rendered free of disease by treatment was also superior for the irradiated group (84% versus 57%, p less than 0.005). Local recurrence without signs of distant metastases developed only one-third as often in irradiated patients (6% versus 18%). Distant metastases, alone or in combination with local recurrence, were also less common after radiation (12% versus 27%). Second primary tumors developed in 15% and 10% of the respective groups, a difference that was not statistically significant. When we consider the survival benefit of preoperative radiation therapy, long-term complications were relatively mild. Delayed healing of the perineum was noted in two irradiated patients. Persistent diarrhea was severe enough to warrant treatment in only one case, and one patient required a colostomy for intestinal obstruction from pelvic fibrosis.