Tumor necrosis factor gene polymorphism and septic shock in surgical infection

OBJECTIVES

To evaluate the relationship of the genotype distribution of the tumor necrosis factor (TNF)-alpha polymorphism with regard to the plasma TNF-alpha concentration and the development of septic shock as well as mortality of infected patients in a surgical intensive care unit (SICU).

DESIGN

A total of 112 postoperative critically ill infected patients were prospectively enrolled.

SETTING

SICU of a tertiary university-affiliated medical center.

PATIENTS

Patients who were consecutively admitted to the SICU because of surgical infection with sepsis.

INTERVENTION

Blood sampling.

MEASUREMENTS AND MAIN RESULTS

Blood sample was obtained 24 hrs after intensive care unit (ICU) admission or within 2 hrs after the onset of septic shock to determine the plasma TNF-alpha level and to analyze the genotype of the biallelic polymorphism of the TNF-alpha.

RESULTS

The allele frequency of the TNF2 in our infected ICU patients was 12%. Forty-two (37.5%) patients admitted fulfilled the criteria of septic shock during their ICU stay. Patients carrying the TNF2 allele were not more likely to develop septic shock, nor did they have a higher mortality rate. In the patients with septic shock, those carrying the TNF2 allele had a significantly higher mortality rate than those with the homozygous TNF1 genotype (92% vs. 62%, p < .05). In those who developed septic shock, the TNF2 allele was significantly associated with higher TNF levels.

CONCLUSION

In patients admitted to SICU with surgical infection, the frequency of TNF2 allele was higher than in the general population. SICU patients with TNF2 allele did not show a higher incidence of developing septic shock, nor was there a higher baseline TNF-alpha level after infection. However, once septic shock had developed, the mortality rate was higher in those patients carrying the TNF2 allele.

Ultrasonographic findings and differentiation of benign and malignant focal splenic lesions

The purpose of this study was to analyse the sonographic findings of focal splenic lesions with an attempt to differentiate benign lesions from malignancies. The sonographic findings of 53 cases of verified focal splenic lesions, excluding post-traumatic haematomas and phleboliths, were retrospectively analysed. Of the 53 cases, 30 cases (57%) were benign and 23 cases (43%) were malignant. The malignancies included lymphoma (n=13), metastases (n=10); while the benign lesions included cysts (n=17), infarcts (n=3), and abscesses (n=5), and one case each of haemangioma, hamartoma, spontaneous rupture, tuberculosis, and lymphangioma. Significant differences were noted between the benign and malignant groups with respect to the presence of solitary lesions (p<0.0001), anechoic mass (p<0. 0001), lesions with highly echogenic foci due to gas or calcification (p = 0.0303), hyperechoic/mixed echoic lesions (p<0. 0001), presence of extrasplenic abdominal masses (p<0.0001), and nodules with the target sign (p<0.0001). Solitary lesions, anechoic mass, and lesions with highly echogenic foci due to gas or calcification each had a positive predictive value of 85%, 100%, and 100%, respectively, for the lesions to be benign. The multifocal/diffuse lesions, presence of extrasplenic abdominal masses, hyperechoic/mixed echoic lesions, and nodules with the target sign each had a positive predictive value of 70%, 100%, 70%, and 100%, respectively, for the lesions to be malignant. In summary, focal lesions with anechoic pattern or echogenic foci due to gas or calcification are suggestive signs of benign process. The sonographic observations of multifocal or diffuse solid lesions, especially those associated with target sign or extrasplenic abdominal masses are suggestive of malignancy.

Chest wall thickness measurements of the LLNL phantom for small area germanium detector counting

The Lawrence Livermore National Laboratory (LLNL) phantom was developed to calibrate lung counting systems that are used to estimate plutonium and other low energy photon emitting radionuclides deposited in the lung. Originally, low energy photon counting systems consisted of sodium iodide or phoswich detectors, but they have been largely replaced by smaller germanium detector arrays. The average chest wall thicknesses of the LLNL phantom's torso plate and its overlay plates provided by the manufacturer refer to the regions covered by phoswich detectors; however, germanium detectors are of a different size and are placed in different locations on the phantom's torso plate. Previous work has shown that the manufacturer's data were not applicable for large area germanium detectors. The lung counting system at the Korea Atomic Energy Institute (KAERI) is a small area germanium detector array. Although the detectors are placed within the phoswich circles, only about 25% of the area is covered by the detectors. The LLNL phantom at KAERI has been examined to determine if the manufacturer's data are valid or if new chest wall thickness values must be determined. This paper presents chest wall thickness data for the LLNL phantom with and without its B-series overlay plates at 17 keV, 60 keV, 200 keV, and 1,500 keV and shows that these values are different from the manufacturer's values.

Morphology-based three-dimensional interpolation

In many medical applications, the number of available two-dimensional (2-D) images is always insufficient. Therefore, the three-dimensional (3-D) reconstruction must be accomplished by appropriate interpolation methods to fill gaps between available image slices. In this paper, we propose a morphology-based algorithm to interpolate the missing data. The proposed algorithm consists of several steps. First, the object or hole contours are extracted using conventional image-processing techniques. Second, the object or hole matching issue is evaluated. Prior to interpolation, the centroids of the objects are aligned. Next, we employ a dilation operator to transform digital images into distance maps and we correct the distance maps if required. Finally, we utilize an erosion operator to accomplish the interpolation. Furthermore, if multiple objects or holes are interpolated, we blend them together to complete the algorithm. We experimentally evaluate the proposed method against various synthesized cases reported in the literature. Experimental results show that the proposed method is able to handle general object interpolation effectively.

Detection of iatrogenic cardiac tamponade by transesophageal echocardiography during vena cava filter procedure

PURPOSE

To present a patient who developed cardiac tamponade during insertion of an inferior vena cava (IVC) filter. Intraoperative transesophageal echocardiography (TEE) was used as a means to diagnose the cardiac tamponade and to facilitate guiding of pericardiocentesis.

CLINICAL FEATURES

A 45-yr-old man with protein S deficiency complicated by repeated attacks of deep vein thrombosis and pulmonary thromboembolism was scheduled for insertion of an IVC filter. He had history of chronic renal insufficiency, heart failure, and cerebral infarction with mild left hemiparesis. Current medication included diltiazem (30 mg, I tab tid ), prednisolone (5 mg, 2 tabs qd ), and warfarin (2.5 mg daily). Preoperative transthoracic echocardiography demonstrated bilateral pleural effusions, moderate mitral regurgitation and tricuspid regurgitation, left atrial appendage thrombus and severe generalized hypokinesia of left ventricle. Nuclear medicine examination by (99)Tc showed ejection fractions of left ventricle and right ventricle as 20% and 22%, respectively. Under the impression of protein S deficiency with multiple attacks of thromboembolism and failure of anticoagulant therapy, he was arranged for the procedure of vena caval filter insertion. Unfortunately, iatrogenic cardiac tamponade occurred during the course of the procedure with rapid hemodynamic deterioration. Because of the expedient of routine monitoring of cardiac condition with TEE, a prompt diagnosis was made. We successfully improved the patient's hemodynamic status after transthoracic echo-guided pericardiocentesis.

CONCLUSION

Intraoperative TEE is recommended to be used routinely in patients undergoing vena cava filter procedures. The availability of echocardiographic monitoring in the operation room allows the confirmation of the diagnosis and facilitation pericardiocentesis.

Cerebral blood volume and blood flow at varying arterial carbon dioxide tension levels in rabbits during propofol anesthesia

There are little data on the effects of propofol on cerebral blood volume (CBV). We studied the effects of changes in PaCO(2) on CBV and cerebral blood flow (CBF) during propofol anesthesia in eight New Zealand white rabbits. We also investigated the effects of propofol over time on CBV and CBF during normocapnia (control group). At normocapnia, the mean (+/- SD) CBV and CBF values were 2.41 +/- 0.68 mL/100 g and 56 +/- 28 mL/100 g/min, respectively,. When PaCO(2) was reduced from 41 to 27 mm Hg, no significant change in either CBV or CBF was observed (P > 0.10). However, increasing PaCO(2) from 41 to 58 mm Hg resulted in a 30% increase in CBV (3.08 +/- 0.86 mL/100 g, P < 0.05) and a 91% increase in CBF (97 +/- 39 mL/100 g/min, P < 0.01). In the control group, there were no significant changes in CBV and CBF (P > 0.10) during 2 h of propofol anesthesia. These results indicate that, during propofol anesthesia, cerebrovascular reactivity of blood flow and blood volume is maintained during hypercapnia but is markedly diminished during hypocapnia.

IMPLICATIONS

During propofol anesthesia in rabbits with normal brains, a reduction in the arterial carbon dioxide level may not always be accompanied by a reduction in brain blood flow and blood volume.

Nephrotic syndrome in a bone marrow transplant recipient without chronic graft-versus-host disease

A 5-year-old girl developed severe proteinuria and microscopic hematuria 17 months after allogeneic bone marrow transplantation (BMT) for chronic myeloid leukemia. These nephrotic symptoms occurred during cyclosporin tapering, in the absence of other signs of chronic graft-versus-host disease (GVHD). A renal biopsy revealed focal segmental glomerulosclerosis. After methylprednisolone therapy, the proteinuria gradually decreased. The altered or disordered immune regulation that occurred after BMT may have resulted in the development of nephrotic syndrome.

Treatment of complicated hepatolithiasis with intrahepatic biliary stricture by ductal dilatation and stenting: long-term results

A group of 190 cases of hepatolithiasis with postoperative residual stones located proximal to the stricture sites were managed with the aim of complete clearance of stones and relief of bile stasis to decrease the potential risk of recurrence. All procedures were performed through a T-tube track with gradual dilatation and stent placement through the stricture sites, creating a channel that allows cholangioscopy and electrohydraulic lithotripsy. Complete clearance of intrahepatic duct (IHD) stones was achieved in 88.4% of cases. Multiple sharply angulated IHD strictures in right-sided hepatolithiasis constituted a major cause of failure. Recurrent stone formation and repeated cholangitis, subsequent drainage, and liver resection are associated with high mortality rates particularly if there is late development of a cholangiocarcinoma. We concluded that postoperative ductal dilatation and stenting through the T-tube track combined with endoscopic electrohydraulic lithotripsy is effective and safe for managing complicated hepatolithiasis. Persistent irreversible aneurysmal dilatation of IHD and atrophic change of the affected hepatic lobe at follow-up were ominous signs of recurrence and cholangiocarcinoma development. Early drainage with stone extraction combined with surgical intervention can prevent subsequent morbidity and mortality.

Successful management of massive blood loss to extremely low hemoglobin in an elderly woman receiving spinal surgery

Blood transfusion is absolutely indicated in acute anemia when the hemoglobin concentration falls below 6 g/dL. Sometimes it challenges the anesthesiologists if the blood intended for urgent transfusion is not readily or quickly available. In this case report, we describe an 81-year-old lady who accidentally sustained acute anemia after spinal surgery with the hemoglobin concentration falling to 1.4 g/dL. During the long wait for the process of cross-matching tests and delivery of blood from the blood bank in the city remote from the hospital, we could do nothing but administer crystalloid and colloid solutions to maintain the circulatory volume to prevent low cardiac output. Epinephrine was given when systolic blood pressure fell below 70 mmHg. Central venous pressure and arterial blood pressure were monitored to guide all the treatment. Fortunately, patient fully recovered on postoperative day 3 without any adverse events.

Effects of glucose-free maintenance solution on plasma glucose during anesthesia in patients undergoing long neurologic surgery

BACKGROUND

Using glucose-free solution as fluid maintenance is widely advocated during neurosurgery because of concerns about hyperglycemia aggravating cerebral ischemia. This study evaluated the alterations in plasma glucose concentrations in both adult and pediatric patients undergoing lengthy neurologic surgery, during which they were given glucose-free solutions.

METHODS

This study included 154 patients (ASA class II, aged 3 months-75 years) undergoing elective neurosurgical procedures. They were divided into two groups: group A (15-75 years-of-age) and group P (3 months-14 years-of-age). Groups A (n = 126) and P (n = 28) were further divided into five subgroups, respectively, based on the duration of surgery: 5, 6, 7, 8 and 9 hours. Anesthesia was maintained with isoflurane, fentanyl and vecuronium. Blood sampling was undertaken every hour throughout surgery.

RESULTS

Adult patients differed significantly in body weight (61.5 +/- 10.9 vs 25.6 +/- 14.9 kg), age (58.9 +/- 15.7 vs 7.5 +/- 4.3 years), use of preoperative beta-blocking agents (33/126 vs 1/28) and the need for blood transfusion (58/126 vs 24/28). Neither group had elevated glucose levels. Compared with pediatric patients, the incidence of intraoperative hypoglycemia was statistically higher in adult patients, with a rate that peaked in the eighth (25.9%, group A vs 0% group P) and ninth hours (27.3%, group A vs 0% group P) of surgery. There were no differences in glucose concentrations at other points in time.

CONCLUSIONS

In contrast to pediatric patients, intraoperative hypoglycemia occurred more often in adult patients during prolonged neurosurgical procedures when glucose-free solution was used for fluid maintenance. Therefore, frequent determination of plasma glucose concentrations is mandatory, especially in patients undergoing long-lasting neurosurgical anesthesia.

Dynamic contrast enhanced CT measurement of blood flow during interstitial laser photocoagulation: comparison with an Arrhenius damage model

One effect of heating during interstitial laser photocoagulation (ILP) is to directly destroy the tumour vasculature resulting in a loss of viable blood supply. Therefore, blood flow measured during and after treatment can be a useful indicator of tissue thermal damage. In this study, the effect of ILP treatment on rabbit thigh tumours was investigated by measuring blood flow changes using dynamic contrast enhanced computed tomography (CT). The CT measured changes in blood flow of treated tumour tissue were fitted to an Arrhenius model assuming first order rate kinetics. Our results show that changes in blood flow of tumour tissue distant from surrounding normal tissue are well described by an Arrhenius model. By contrast, the temperature profile of tumour tissue adjacent to normal tissue must be modified to account for heat dissipation by the latter. Finally, the Arrhenius parameters derived in the study are similar to those derived by heating tumour tissue to a lower temperature (<47 degrees C) than the current study. In conclusion, CT can be used to monitor blood flow changes during ILP and these measurements are related to the thermal damage predicted by the Arrhenius model.

Effect of milrinone on postbypass pulmonary hypertension in children after tetralogy of Fallot repair

BACKGROUND

Postbypass pulmonary hypertension in surgical correction of tetralogy of Fallot (TOF) is a risk for right ventricular failure. Effective management remains a major challenge. Milrinone is a new drug with a unique mechanism of "inodilation", which offers both inotropic and vasodilatory effects. We attempted to determine if application of milrinone could improve cardiopulmonary dysfunction in children after TOF repair.

METHODS

We studied 10 children with postbypass pulmonary hypertension after TOF repair within six months. Heart rate, systolic pulmonary arterial pressure (PAP), systolic arterial blood pressure (SBP), pulmonary capillary wedge pressure and PAP/SBP ratio were recorded. Standard cardiopulmonary bypass (CPB) was performed. After CPB, if PAP/SBP was more than 0.5, pulmonary hypertension was suspected and milrinone was administered with a loading dose of 20 micrograms/kg followed by continuous infusion of 0.2 microgram/kg/minute. Hemodynamics were compared before and after administration of milrinone to evaluate its effect.

RESULTS

significant reduction in PAP/SBP ratio within 15 minutes was found after administration of milrinone. The effect persisted for 24 hours during continuous infusion of milrinone. No remarkable adverse effect was noted in the study.

CONCLUSIONS

We conclude that milrinone is effective in the management of pulmonary hypertension following CPB in children who underwent TOF repair.

Differential expression of receptor tyrosine kinases and Shc in fetal and adult rat fibroblasts: toward defining scarless versus scarring fibroblast phenotypes

The remarkable ability of the fetus to heal early gestation skin wounds without scarring remains poorly understood. Taking advantage of recent advances in signal transduction, the tyrosine phosphorylation patterns of fetal rat fibroblasts, representing the scarless cutaneous repair phenotype, and adult rat fibroblasts, representing scarforming phenotype, were examined whether there were inherent differences in cellular signaling. Specifically, correlation of the phosphorylation patterns with the expression levels of the signaling molecules that transmit information from the plasma membrane receptor to the nucleus was sought. By using three different cell lines of explanted fibroblasts from gestational day 13 fetal rat skin (n = 24) and 1-month-old postnatal adult rat skin (n = 3), immunoblotting was performed to compare tyrosine phosphorylation patterns. The results revealed five major protein bands of interest in fetal rat fibroblasts, but not in the adult rat fibroblasts. These phosphorylated protein bands are of interest because of their possible role in wound repair and may have the potential to regulate cellular responses to the extracellular matrix and their secondary signaling molecules. It was hypothesized that these bands represented receptor tyrosine kinases, epidermal growth factor receptor, and discoidin domain receptor 1, and their downstream adaptor protein Shc that binds receptor tyrosine kinases to transduce signals intracellularly. Furthermore, elevated expression of platelet-derived growth factor receptor-beta in adult compared with fetal fibroblasts was demonstrated, suggesting that decreased expression of certain growth factors may also be important for the scarless phenomenon to occur.

Pseudomonas cepacia induced septic shock after propofol--a case report

We report a healthy young female who developed septic shock and multiple organ failure soon after receiving a cosmetic surgery for augmentation of breasts under general anesthesia. Blood cultures yielded the growth of pseudomonas cepacia. We describe the clinical course and investigate the causes of the septic shock. Contamination of propofol, the intravenous anesthetic agent, was suspected.

A CT method to measure hemodynamics in brain tumors: validation and application of cerebral blood flow maps

BACKGROUND AND PURPOSE

CT is an imaging technique that is routinely used for evaluating brain tumors. Nonetheless, imaging often cannot show the distinction between radiation necrosis and neoplastic growth among patients with recurrent symptoms after radiation therapy. In such cases, a diagnostic tool that provides perfusion measurements with high anatomic detail would show the separation between necrotic areas, which are characterized by low perfusion, from neoplastic areas, which are characterized by elevated CBF. We attempted to validate a dynamic contrast-enhanced CT method for the measurement of regional CBF in brain tumors, and to apply this method by creating CBF maps.

METHODS

We studied nine New Zealand White rabbits with implanted brain tumors. We obtained dynamic CT measurements of CBF, cerebral blood volume (CBV), and permeability surface (PS) from the tumor, peritumor, and contralateral normal tissue regions. In all nine rabbits (two studies per rabbit), we compared CT-derived CBF values with those simultaneously obtained by the standard of reference ex vivo microsphere technique. Using CT, we examined three rabbits to assess the variability of repeated CBF and CBV measurements; we examined the other six to evaluate regional CBF reactivity to arterial carbon dioxide tensions. Finally, CT CBF maps were obtained from a rabbit with a brain tumor during normocapnia and hypocapnia.

RESULTS

We found a significant linear correlation (r = 0.847) between the regional CT-and microsphere-derived CBF values, with a slope not significantly different from unity (0.99+/-0.03, P>.01). The mean difference between regional CBF measurements obtained using both methods did not significantly deviate from zero (P>.10). During normocapnia, tumor had significantly higher CBF, CBV, and PS values (P<.05) than did peritumor and normal tissues. The variability in CT-derived CBF and CBV measurements in the repeated studies was 13% and 7%, respectively. CT revealed no significantly different CBF CO2 reactivity from that determined by the microsphere method (P>.10). The CBF map of tumor regions during normocapnia showed much higher flow than normal regions manifested, and this difference was reduced on the hypocapnia CBF map.

CONCLUSION

The dynamic CT method presented herein provides absolute CBF measurements in brain tumors that are accurate and precise. Preliminary CBF maps derived with this method demonstrate their potential for depicting areas of different blood flow within tumors and surrounding tissue, indicating its possible use in the clinical setting.

Effect of oral clonidine premedication on perioperative hemodynamic response and postoperative analgesic requirement for patients undergoing laparoscopic cholecystectomy

BACKGROUND

To investigate the clinical efficacy of oral clonidine premedication in anesthesia and analgesia in patients undergoing laparoscopic cholecystectomy (LC).

METHODS

One hundred and ten patients, scheduled for elective laparoscopic cholecystectomy, were recruited for the prospective, randomized, single-blind, comparative study. They were randomly allotted to either of the placebo or clonidine group. Patients of the placebo group (n = 65) were premedicated with oral antacid (alugel hydroxide 300 mg), while those in the clonidine group (n = 45) were premedicated with oral clonidine 150 micrograms prior to anesthesia. The premedication was given 60 to 90 min before the anticipated time of induction of anesthesia. Normocapnia was maintained throughout the perioperative period. Mass spectrometer was used to assess the inspired and expiratory concentrations of isoflurane, the anesthetic used for maintenance of anesthesia. Postoperative pain intensity, sedation scores, adverse events, time to the first dose of postoperative analgesic and cumulative analgesic requirement in 24 hours were recorded. Data were expressed as mean +/- SD.

RESULTS

Patients in the clonidine group displayed greater hemodynamic stability perioperatively and the isoflurane requirement was also reduced (30% less). The postoperative analgesic requirement was less (1.5 +/- 1.3 vs. 2.2 +/- 1.3 dose, P < 0.05) and the time for the first dose of analgesic was prolonged (411 +/- 565 vs. 264 +/- 441 min) in comparison with the placebo group but no statistic difference was found.

CONCLUSIONS

Oral clonidine premedication helped to provide perioperative hemodynamic stability, spared the use of isoflurane and reduced the requirement of postoperative analgesia so as to smoother the way to recovery in patients undergoing LC.

Combined spinal-epidural anesthesia for cesarean section in a patient with Takayasu's disease

We describe a successful episode of anesthesia management in a parturient affected with Takayasu's disease who underwent elective cesarean section under combined spinal-epidural anesthesia. Takayasu's disease is characterized by chronic occlusive inflammation of the arteries (panarteritis) of unknown origin that usually involves the aorta and its main branches. Progression of the disease may be marked by aneurysmal dilation of the affected arteries and may lead to a fatal outcome, usually from cerebral ischemia or heart failure. The impact of pregnancy on Takayasu's disease is unclear, but worsening of ischemic symptoms, cardiac failure, aggravation of hypertension and cerebral hemorrhage have been reported in sufferers who are in the later stages of pregnancy. Nonetheless, anesthesia management of a parturient with advanced Takayasu's disease presents a challenge to anesthetists.

Transesophageal three-dimensional echocardiographic assessment of anomalous coronary arteries

We describe the usefulness of transesophageal three-dimensional echocardiography in the evaluation of anomalously arising coronary arteries in four adult patients recently studied by us.

Postoperative right atrial and pulmonary embolism after prolonged spinal surgery

Perioperative pulmonary thromboembolism can proceed rapidly with grave prognosis, in which immediate or accurate diagnosis and management is not easy. According to the literatures, patients receiving spinal surgery are at relatively lower risk of developing thromboembolism. We would like to present a case of postoperative pulmonary thromboembolism which developed after a prolonged lumbar spinal surgery. Tachycardia and unstable hemodynamics were noted postoperatively. Pulmonary and right atrial thrombi were disclosed by transesophageal echocardiography. Although cardiotomy and thrombectomy were immediately performed, the patient finally died 3 days after the operation. The pathogenesis of venous thromboembolism (VTE) in the surgical patients, the risk factors which predispose a patient to VTE, diagnosis, and treatment as well as the prophylactic measures of VTE are herein reviewed and discussed.

Estimating kinetic parameters from dynamic contrast-enhanced T(1)-weighted MRI of a diffusable tracer: standardized quantities and symbols

We describe a standard set of quantity names and symbols related to the estimation of kinetic parameters from dynamic contrast-enhanced T(1)-weighted magnetic resonance imaging data, using diffusable agents such as gadopentetate dimeglumine (Gd-DTPA). These include a) the volume transfer constant K(trans) (min(-1)); b) the volume of extravascular extracellular space (EES) per unit volume of tissue v(e) (0 < v(e) < 1); and c) the flux rate constant between EES and plasma k(ep) (min(-1)). The rate constant is the ratio of the transfer constant to the EES (k(ep) = K(trans)/v(e)). Under flow-limited conditions K(trans) equals the blood plasma flow per unit volume of tissue; under permeability-limited conditions K(trans) equals the permeability surface area product per unit volume of tissue. We relate these quantities to previously published work from our groups; our future publications will refer to these standardized terms, and we propose that these be adopted as international standards.

Estimating kinetic parameters from dynamic contrast-enhanced T(1)-weighted MRI of a diffusable tracer: standardized quantities and symbols

We describe a standard set of quantity names and symbols related to the estimation of kinetic parameters from dynamic contrast-enhanced T(1)-weighted magnetic resonance imaging data, using diffusable agents such as gadopentetate dimeglumine (Gd-DTPA). These include a) the volume transfer constant K(trans) (min(-1)); b) the volume of extravascular extracellular space (EES) per unit volume of tissue v(e) (0 < v(e) < 1); and c) the flux rate constant between EES and plasma k(ep) (min(-1)). The rate constant is the ratio of the transfer constant to the EES (k(ep) = K(trans)/v(e)). Under flow-limited conditions K(trans) equals the blood plasma flow per unit volume of tissue; under permeability-limited conditions K(trans) equals the permeability surface area product per unit volume of tissue. We relate these quantities to previously published work from our groups; our future publications will refer to these standardized terms, and we propose that these be adopted as international standards.

Estimating kinetic parameters from dynamic contrast-enhanced T(1)-weighted MRI of a diffusable tracer: standardized quantities and symbols

We describe a standard set of quantity names and symbols related to the estimation of kinetic parameters from dynamic contrast-enhanced T(1)-weighted magnetic resonance imaging data, using diffusable agents such as gadopentetate dimeglumine (Gd-DTPA). These include a) the volume transfer constant K(trans) (min(-1)); b) the volume of extravascular extracellular space (EES) per unit volume of tissue v(e) (0 < v(e) < 1); and c) the flux rate constant between EES and plasma k(ep) (min(-1)). The rate constant is the ratio of the transfer constant to the EES (k(ep) = K(trans)/v(e)). Under flow-limited conditions K(trans) equals the blood plasma flow per unit volume of tissue; under permeability-limited conditions K(trans) equals the permeability surface area product per unit volume of tissue. We relate these quantities to previously published work from our groups; our future publications will refer to these standardized terms, and we propose that these be adopted as international standards.