Use of intraoperative parathyroid hormone measurement does not improve success of bilateral neck exploration for hyperparathyroidism.

HYPOTHESIS: Use of intraoperative measurement of intact parathyroid hormone (iPTH) to confirm complete excision of hyperfunctioning parathyroid tissue does not improve overall operative success rates. DESIGN: Case series of patients undergoing parathyroidectomy with or without intraoperative iPTH measurement. SETTING: University teaching hospital. PATIENTS AND INTERVENTIONS: Fifty patients undergoing parathyroidectomy before our institution of intraoperative iPTH sampling in March 1999 (group 1) were compared with 50 patients undergoing parathyroidectomy after this technique was adopted (group 2). Overall, 100 patients underwent operation between December 1996 and May 2000. Serum calcium and iPTH levels were measured at 1- and 3-month intervals. Intraoperative frozen sections and operative times were also analyzed. RESULTS: Mean preoperative calcium levels were 2.85 and 2.82 mmol/L (11.4 and 11.3 mg/dL) in groups 1 and 2, respectively. One-month postoperative calcium values were identical in both groups at 2.35 mmol/L (9.4 mg/dL) (group 1 SD = 0.18 [0.74], group 2 SD = 0.20 [0.82]). At 1 month, all but 1 patient in group 1 had normalized calcium values (2% failure rate), while 3 patients in group 2 (6%) remained hypercalcemic. All 3 patients in group 2 had intraoperative iPTH levels that returned to normal. There was a significant difference in the number of intraoperative frozen sections between groups, with a mean (SD) of 3.4 (1.7) in group 1 and 2.0 (1.6) in group 2 (P<.01). There was no significant difference in operative times between groups. CONCLUSIONS: Use of intraoperative iPTH sampling did not significantly affect the overall success of parathyroidectomy, as determined by postoperative normocalcemia. There was, however, a significant decrease in the number of frozen sections sent at operation.

Normalization of intraoperative parathyroid hormone does not predict normal postoperative parathyroid hormone levels.

BACKGROUND: Intraoperative intact parathyroid hormone (iPTH) is being used to confirm complete excision of hyperfunctioning parathyroid tissue. It is uncertain whether normalization of intraoperative iPTH levels accurately predicts long-term postoperative iPTH values. METHODS: Fifty-two consecutive patients with primary or secondary hyperparathyroidism underwent parathyroidectomy with measurement of intraoperative iPTH. Ten patients were excluded due to incomplete laboratory follow-up. Follow-up serum calcium and iPTH levels were measured at 1- and 3-month intervals. RESULTS: Before operation, the mean serum iPTH level was 249 pg/mL (SD=208) and mean serum calcium level was 11.4 +/- 0.9 mg/dL (+/- SD). In all but 4 patients, final intraoperative iPTH levels normalized to less than 67 +/- 41 pg/mL (mean, 35 pg/mL). One week after operation, serum calcium levels had returned to normal (mean, 9.4 +/- 1.1 pg/mL), which directly correlated with the final intraoperative serum iPTH values (Pearson correlation, r = -.434; P <.01). By 1 month, all but 2 patients were normocalcemic (mean, 9.4 +/- 0.9 pg/mL) with a mean iPTH level of 74.8 +/- 82 pg/mL. There was no correlation between final intraoperative and postoperative serum iPTH values (r =.099; P <.533). Both patients with persistent hypercalcemia at 1 month had appropriate intraoperative decreases in iPTH values. CONCLUSIONS: Intraoperative serum iPTH levels significantly correlate with postoperative serum calcium levels but not with postoperative serum iPTH levels. There was a 4.8% failure rate in the correction of postoperative serum calcium levels and a 29% failure rate in the normalization of postoperative serum iPTH levels.

Renal perfusion: pharmacologic changes depicted with power Doppler US in an animal model.

PURPOSE: To evaluate the ability of power Doppler ultrasonography to depict changes in renal perfusion after pharmacologic manipulations. MATERIALS AND METHODS: Six domestic swine were intubated and anesthetized. The right renal artery was catheterized for injection of epinephrine (100 micrograms) and papaverine (2 mg/kg). Intraarterial blood pressure, heart rate, and oxygen saturation were measured continuously. Longitudinal images of the kidney were obtained, and the power Doppler color map was analyzed subjectively and by computer at baseline and at the time of maximum drug effect. RESULTS: Epinephrine produced vasoconstriction with a diminished power Doppler color map and a decrease in both subjective and computer scores. After papaverine-induced vasodilatation, the power Doppler map was enhanced, as reflected by increased subjective and computer scores. CONCLUSION: The power Doppler color map reflects anticipated changes in renal perfusion after alterations in blood flow by vasoactive drugs.

Blood back flow into angiographic catheters.

PURPOSE: Because of a potential impact on thrombus formation, this study determines the degree of blood back flow into catheters filled with different fluids. MATERIALS AND METHODS: Catheters filled with saline or non-ionic or ionic contrast medium were placed in pulsatile circulating human blood in vitro. Catheter orientation was varied, and blood back flow was recorded. RESULTS: When the leading end of the catheter was angled downward, blood back flow into a contrast material-filled catheter was far greater than that into a saline-filled catheter (7.0 vs 0.5 cm). Conversely, when the leading end of the catheter was horizontal, blood back flow was much greater when the catheter contained saline versus contrast media (3.6 vs 0.4 cm). Ionicity of contrast material did not affect back flow. CONCLUSION: Back flow of blood into a catheter can be considerable and is dependent on the type of fluid within the catheter and orientation of the leading end of the catheter. Angiographic techniques adjusted to these findings are important to maintain patient safety.

Interaction of manganese-mesoporphyrin with oleic acid vesicles.

We investigated the interaction between manganese(III)mesoporphyrin (MnMeso), a metalloporphyrin, and liposome membranes containing oleic acid (OA; cis-9-octadecenoic acid). MnMeso associates preferentially with OA but minimally with egg phosphatidylcholine (EPC). Using small unilamellar vesicles, we characterized the MnMeso-OA binding at neutral pH. Our data suggest that MnMeso binds to the OA bilayer with Kd = 6.8 x 10(-4) M; the binding stoichiometry of MnMeso-OA was 1:3.4. This OA-MnMeso interaction was analyzed further for changes in the T1 relaxation property of MnMeso. OA increased the T1 of MnMeso significantly more than did EPC, suggesting that the OA-MnMeso interaction was stronger than that of PC-MnMeso. The side-chain specificity of the OA interaction with this porphyrin derivative was further supported in an experiment with manganese mesotetra(4-sulfonatophenyl)porphine, which lacks hydrophobic side chains for OA interaction. The association of MnMeso with the OA membrane was proposed according to the structure of MnMeso and OA and further verified using electron microscopy. A strong association of MnMeso with OA, an absorption enhancer of the gastrointestinal tract, may be useful for delivery of MnMeso as an oral contrast agent for magnetic resonance imaging.

Intravenous manganese-mesoporphyrin as a magnetic resonance imaging contrast agent: an experimental model using VX-2 carcinoma in rabbits.

RATIONALE AND OBJECTIVES: We investigated the potential of manganese (III) mesoporphyrin (Mn-mesoporphyrin) as a hepatobiliary contrast agent for magnetic resonance (MR) imaging in rabbits given VX-2 carcinoma liver implants. METHODS: Rabbits given VX-2 carcinoma liver implants (n = 8) were imaged before and after the intravenous (i.v.) administration of 0.04 mmol/kg Mn-mesoporphyrin. MR images were correlated with gross-specimen cross-sections. The distribution of Mn in various tissues following i.v. administration of 0.04 mmol/kg Mn-mesoporphyrin was determined using atomic absorption analysis. A standard panel of serum chemistries was followed over 7 days in six rabbits following this same dose of Mn-mesoporphyrin and compared with chemistries from two control rabbits. RESULTS: I.v. administration of 0.04 mmol/kg (25 mg/kg) Mn-mesoporphyrin resulted in improvement of tumor-to-liver contrast, with enhancement of normal liver (99.7 +/- 14.7%) and the gallbladder (442 +/- 116%), but not VX-2 tumor tissue (14.8 +/- 13.9%), (n = 8, p = .05). Analysis of tissue Mn levels 100 min after i.v. Mn-mesoporphyrin injection demonstrated preferential distribution of Mn to normal liver tissue (57.8 +/- 15.3 micrograms Mn/g) compared with VX-2 tumor (4.28 +/- 1.48 micrograms Mn/g). No significant change was found in the serum chemistries of six normal rabbits over a 7-day period after the i.v. administration of 0.04 mmol/kg Mn-mesoporphyrin. CONCLUSION: I.v. Mn-mesoporphyrin improved lesion-to-liver contrast because of preferential distribution of Mn-mesoporphyrin to normal liver parenchyma and bile.

MR assessment of radiation-induced blood-brain barrier permeability changes in rat glioma model.

PURPOSE: To assess the potential of a T1-weighted, gadolinium-enhanced MR technique for quantifying radiation-induced changes of blood-brain barrier permeability in a model of stereotactically implanted intracerebral gliomas in rats. METHODS: We calculated the gadolinium blood-to-tissue transport coefficient for gadopentetate dimeglumine from signal intensities in sequential MR images in nine control animals that were not irradiated and in five and three animals that had received 2500 cGy and 1500 cGy whole-brain irradiation, respectively, at 2 days before imaging. RESULTS: The average blood-to-tissue transport coefficient values were 9.76 mL.kg-1.min-1 in the control group, 23.41 mL.kg-1.min-1 in the 2500 cGy group, and 25.63 mL.kg-1.min-1 in the 1500-cGy group. Blood-to-tissue transport coefficients were significantly higher after irradiation, indicating increased radiation-induced blood-brain barrier permeability. Similar increased blood-brain barrier leakiness in brain tumors after high-dose irradiation has been shown by previous nuclear medicine studies using quantitative autoradiography. CONCLUSION: Contrast-enhanced dynamic MR of brain gliomas is a sensitive method to document radiation-induced blood-brain barrier breakdown. Quantitative gadolinium-enhanced MR may become a useful tool for the management of patients with brain tumors undergoing radiation therapy.

Animal model of portal hypertension with observations regarding the relationship between portal flow and pressure.

RATIONALE AND OBJECTIVES: The feasibility of producing acute portal hypertension in a porcine model was evaluated to test the relationship between portosystemic shunt flow and portal pressure. METHODS: Percutaneous transhepatic cannulation of the portal vein and cutdown of a systemic vein was accomplished in anesthetized pigs. The portal system was subsequently embolized with polyvinyl alcohol (Ivalon) particles. Portosystemic shunting was performed with the assistance of a centrifugal pump. RESULTS: Portal hypertension could be routinely produced, and portosystemic shunting was successfully studied in three of four animals. Linear changes in shunt flow led to exponential pressure changes. CONCLUSIONS: This animal model provides a representation of acute portal hypertension that provides useful data regarding the compliance of the portal system and illustrates the pressure/flow relationship.

Temperature-dependent ultrasound color flow Doppler imaging in the study of a VX2 tumor in rabbits: preliminary findings.

Neovascularity in a VX2 carcinoma in rabbit liver was detectable, using an ultrasonic color Doppler flow imager. Intraportal infusion of heated saline increased the fractional area of color flow Doppler signals by at least 5% and as much as 30%, within and surrounding the tumors of all six rabbits studied. The effect of the fluid load was an increase in fractional area of color flow Doppler signals by 5 to 20% and was determined by the measurements following infusion and return to baseline temperature. The largest increment in color Doppler signal was observed in peritumoral vessels (10-40%). In contrast, the fractional area of color-coded pixels within the tumor was only slightly higher or lower (5-10%) at the peak temperature than at the baseline measurements. The temperature within the tumors was as much as 1 degree lower than parenchymal tissue in all animals measured. This was presumably due to the portal vein blood supply to normal tissue and predominantly hepatic artery supply to the pathological tissue. High velocities and persistent bidirectional flow were observed within the tumors only at the peak temperatures (> 43.5 degrees C). This experiment suggests that thermal stress may enhance tumor detectability by color Doppler imaging. Further development of a quantitative analysis method for color Doppler studies is needed.

In vivo evaluation of iophendylate-cyanoacrylate mixtures.

Cyanoacrylate glue is a rapidly polymerizing agent used for vascular embolization. Polymerization occurs when the glue comes into contact with ions in the blood or on the vascular endothelium. Mixing iophendylate with cyanoacrylate causes slowing of polymerization, allowing flow-directed embolization into the nidus of an arteriovenous malformation (AVM) or the central neovascularity of a tumor or hemangioma. The authors attempted to define the relationship between the iophendylate-glue ratio and polymerization time with an in vivo swine model. In this model, glue setup occurred much more rapidly than predicted on the basis of in vitro studies. This appeared to be due to glue polymerizing on the endothelium at vessel bifurcations and at areas of acute angulation or marked vessel narrowing. On the basis of these data, the authors substantially increased the iophendylate-glue ratio in their most recent AVM embolization procedures and achieved nidus occlusion in each case. With use of the authors' guidelines, it is possible to achieve optimal distal flow-directed embolization with cyanoacrylate.

Hepatic contrast-enhancing properties of manganese-mesoporphyrin and manganese-TPPS4. A comparative magnetic resonance imaging study in rats.

OBJECTIVES: Manganese (III) mesoporphyrin (Mn-mesoporphyrin), a synthetic and stable complex, was investigated for its hepatic magnetic resonance imaging (MRI) properties and compared with manganese tetrakis-(4 sulfonatophenyl) porphyrin (Mn-TPPS4). METHODS: Liver abscesses (n = 10) and tumors (n = 14) were induced in rats. These rats then underwent MRI at 2.0 T. Animals received one of the two contrast agents, and measurement of lesion enhancement was performed. RESULTS: At an intravenous dose of 0.035 mmol/kg, Mn-mesoporphyrin caused significant enhancement of normal liver parenchyma and increased the lesion-to-liver contrast in both the models of heptic liver abscess and metastatic liver disease. Mn-TTPS4 at an intravenous dose of 0.04 mmol/kg typically enhanced both lesion and normal liver parenchyma and therefore did not improve the lesion-to-liver contrast. CONCLUSIONS: The hepatotrophic properties of Mn-mesoporphyrin indicate its potential as an intravenous contrast agent for liver imaging.

A reservoir model for repeated CSF access in the rabbit.

A simple, reliable and inexpensive subcutaneously implanted reservoir-catheter system method was developed for repeated sterile access to the rabbit brain ventricular system. The system provides an avenue for the repeated intrathecal administration of drugs and for the withdrawal of cerebrospinal fluid (CSF). Reservoirs were subcutaneously implanted under the scalp and connected to tubing inserted into the cisterna magna or the lateral ventricle. The systems successfully functioned in 38 of 41 animals (12 with cisternal magna catheters and 29 with lateral ventricle catheters), for up to 12 weeks following implantation. Patency of the systems were documented with X-rays and radiopaque injected contrast medium.

Organ ablation by fluid emboli. An experimental study comparing two solidifying liquids.

Embolization for ablation of organs and tumor infarction requires uniform permanent occlusion of the distal vasculature. This is best accomplished through the use of solidifying liquids. The study on 15 dogs reported here compares the degree of peripheral vascular embolization and its relation to tissue infarction both acutely and chronically following embolization of the renal arteries with two solidifying liquids, a low viscosity silicone and the occlusion gel Ethibloc. Silicone produced quite uniform distal distribution including 50 to 80% (mean 66%) of renal glomeruli, whereas Ethibloc occluded more proximally and reached only 10 to 50% (mean 22%) of all glomeruli. After three months complete cortical infarction of all nine kidneys embolized with silicone was found, whereas two of the three kidneys embolized with Ethibloc retained nests of viable glomeruli. Balloon occlusion of the entire renal artery inflow during embolization prevented distal venous emboli whereas partial inflow occlusion allowed systemic venous embolization. It is concluded that due to its more uniform distal penetration low viscosity silicone is a more suitable embolization agent than Ethibloc for organ ablation. Total arterial inflow occlusion during embolization effectively prevents systemic venous embolization.

The radiology research technologists: who are they?

Over the years, radiology research has expanded its application due to the tremendous advances in imaging technology and the expanding role of the radiologist in the care and management of the patient. This paper is intended to provide insight into the activities and role of the radiologic technologist in radiology research today.

A reproducible canine model of nonocclusive mesenteric ischemia.

A technique for producing a reliable, clinically applicable, and highly reproducible canine model of nonocclusive mesenteric ischemia was developed. Following left thoracotomy in 10 dogs, a 1 mm diameter soft polyethylene tube was inserted into the pericardial space via a small puncture site. This tube was sealed in place with cyanoacrylate tissue adhesive. A solution of 10% Dextran 40 in saline was infused into the pericardial space until a 50% reduction (as monitored by electromagnetic flowmeter) in superior mesenteric artery flow (SMAQ) was obtained. Without additional intrapericardial infusion of the Dextran solution, SMAQ was reduced 51 +/- 4% to 54 +/- 3% of control values during a 60 minute post-tamponade observation period. During the same time. Cardiac output was depressed between 40 +/- 8% and 54 +/- 3%, and right atrial pressure remained elevated between 164 +/- 15% and 171 +/- 15%. Systemic arterial pressure initially dropped 28 +/- 5% but compensated to within 11 +/- 5% of pre-tamponade level at 60 minutes. The stability of this model is well suited for evaluating new experimental diagnostic and therapeutic procedures.

A simple method to measure mesenteric arteriovenous shunt flow during arteriography.

A quantitative method for external detection of mesenteric arteriovenous shunts was developed. 99mTc-Human Serum Albumin Microspheres (15--30 microns) were injected into the superior mesenteric artery of dogs through an angiographic catheter, followed by external scintillation counting of the liver activity, which represented the shunted spheres. Thereafter, 99mTc-sulfur colloid was injected identically and the liver activity counted again. The liver net count after sulfur colloid represented a 100% shunt, when a correction factor for the actual liver uptake was applied. The a shunt rate was calculated. Eleven animal studies were performed and shunt rates similar to previous in vitro determinations were obtained. This method is suitable for clinical investigation and can conveniently be applied to mesenteric arteriography.