Hypoxemia after Implantation of a Permanent Pacemaker

We describe a case in which the patient developed profound, intermittent hypoxemia after implantation of a permanent pacemaker and subsequently after revision of its leads. Cardiac catheterization demonstrated right-to-left shunting at the level of the atria in the presence of a patent foramen ovale that required closure, resulting in the resolution of symptoms. Our report highlights the fact that the presence of a patent foramen ovale with intermittent right-to-left shunting should be considered in a differential diagnosis of hypoxemia after implantation of heart rhythm devices.

Right-to-left interatrial shunt with hypoxemia caused by a right atrial thrombus

A right-to-left shunt in the presence of normal pulmonary artery pressure is an unusual cause of hypoxemia in an adult who has a patent foramen ovale. We report a rare case of such a shunt-the result of a right atrial thrombus that formed in a hypercoagulable patient after placement of an indwelling central venous catheter for chemotherapy. In order to ascertain the nature of the right atrial mass and to decrease the risk of systemic embolization, the thrombus was surgically removed with the patient on cardiopulmonary bypass.

Molecular imaging of tumor metabolism and apoptosis

Increased metabolism has been found to be one of the most prominent features of malignant tumors. This property led to the development of tracers for the assessment of glucose metabolism and amino acid transport and their application for tumor diagnosis and staging. Prominent examples are fluorodeoxyglucose, methionine and tyrosine analogs, which have found broad clinical application. Since quantitative procedures are available, these techniques can also be used for therapy monitoring. Another approach may be based on the noninvasive detection of apoptosis with tracers for phosphatidyl-serine presentation and/or caspase activation as surrogate markers for therapeutic efficacy. Finally, the evaluation of hypoxia with nitroimidazoles may be a valuable tool for prognosis and therapy planning.

Use of an inspiratory impedance threshold valve during chest compressions without assisted ventilation may result in hypoxaemia

INTRODUCTION

Although the concept of intermittent airway occlusion with the inspiratory impedance threshold valve (ITV) is a well-recognised strategy for improving efficiency of cardiopulmonary resuscitation (CPR), little is known about possible pulmonary side effects.

METHODS

After a baseline chest CT-scan, 24 pigs with beating hearts undergoing apnoeic oxygenation received an injection of a contrast medium and were then assigned randomly to either active compression-decompression CPR with ITV (ACD ITV CPR), ACD CPR alone, or standard-CPR with ITV (standard-ITV CPR), or standard-CPR alone. After a maximum of 5 min of chest compressions or if oxygen saturation dropped below 70%, the experiment was stopped, haemodynamic variables and blood gas values were measured, and another CT-scan was performed; all animals underwent a 30 min recovery-period and a third subsequent CT-scan.

RESULTS

At baseline arterial oxygen saturation by pulse oxymetry was 99% in all four groups; in both the ACD ITV CPR and the standard-ITV CPR groups, arterial oxygen saturation dropped below 70% within 126+/-9s, whereas chest compressions in all ACD CPR and standard-CPR pigs were performed over 5 min (P<0.001). Before stopping chest compressions arterial oxygen pressure decreased in the ACD ITV CPR group from 426+/-96 to 42+/-8 mmHg while it decreased in the ACD CPR group only from 415+/-116 to 197+/-127 mmHg (P<0.001 between groups); in the standard-ITV CPR group arterial oxygen partial pressure decreased from 427+/-109 to 34+/-5 mmHg while oxygen partial pressure decreased only from 467+/-44 to 144+/-98 mmHg in the standard-CPR group (P<0.004 between groups). After the second CT scan arterial oxygen partial pressure decreased further to 19+/-2 mmHg in the ACD ITV CPR versus 210+/-41 mmHg in the ACD CPR group; to 20+/-2 mmHg in the standard-ITV CPR versus 148+/-33 mmHg in the standard-CPR group. Lung-density values (Hounsfield units) were significantly higher in the ACD ITV CPR versus ACD CPR group (-134+/-54 versus -330+/-77) and standard-ITV CPR versus standard-CPR group (-98+/-50 versus -387+/-42). After a 30 min recovery-period, there were no significant differences in arterial oxygen partial pressure (ACD ITV CPR 275+/-110 mmHg versus ACD CPR 379+/-111 mmHg and standard-ITV CPR 265+/-138 mmHg versus standard CPR 367+/-55 mmHg). Furthermore, there were no differences in lung density values between groups after 30 min of recovery.

CONCLUSION

In this animal model with a beating heart, intermittent airway obstruction through an ITV combined with apnoeic oxygenation and without active ventilation resulted in hypoxaemia due to transiently impaired lung function.

FDG--a marker of tumour hypoxia? A comparison with [18F]fluoromisonidazole and pO2-polarography in metastatic head and neck cancer

PURPOSE

Experimental data suggest that the accumulation of [(18)F]fluorodeoxyglucose (FDG) in malignant tumours is related to regional hypoxia. The aim of this study was to evaluate the clinical potential of FDG positron emission tomography (PET) to assess tumour hypoxia in comparison with [(18)F]fluoromisonidazole (FMISO) PET and pO(2)-polarography.

METHODS

Twenty-four patients with head and neck malignancies underwent FDG PET, FMISO PET, and pO(2)-polarography within 1 week. Parameters of pO(2)-polarography were the relative frequency of pO(2) readings <or=2.5 mmHg, <or=5 mmHg and <or=10 mmHg, respectively, as well as the mean and median pO(2).

RESULTS

We observed a moderate correlation of the maximum standardised uptake value (SUV) of FDG with the tumour to blood ratio of FMISO at 2 h (R=0.53, p<0.05). However, SUV of FDG was similar in hypoxic and normoxic tumours as defined by pO(2)-polarography (6.9+/-3.2 vs 6.2+/-3.0, NS), and the FDG uptake was not correlated with the results of pO(2)-polarography. The retention of FMISO was significantly higher in hypoxic tumours than in normoxic tumours (tumour to muscle ratio at 2 h: 1.8+/-0.4 vs 1.4+/-0.1, p<0.05), and the FMISO tumour to muscle ratio showed a strong correlation with the frequency of pO(2) readings <or=5 mmHg (R=0.80, p<0.001).

CONCLUSION

These results support the hypothesis that tumour hypoxia has an effect on glucose metabolism. However, other factors affecting FDG uptake may be more predominant in chronic hypoxia, and thus FDG PET cannot reliably differentiate hypoxic from normoxic tumours.

Monitoring the effect of mild hyperthermia on tumour hypoxia by Cu-ATSM PET scanning

PURPOSE

Mild hyperthermia can improve tumour oxygenation and enhance radiosensitivity. Imaging the hypoxic fraction of a tumour can guide hyperthermia treatment planning and facilitate treatment optimization. 64Cu-ATSM (Copper-diacetyl-bis(N4-methylthiosemicarbazone)) is a positron emitting compound that has been demonstrated to have rapid uptake and selective retention in hypoxic cells and has been used for imaging human and animal tumours. The purpose of the present report is to establish methodology that will allow one to use Cu-ATSM PET scanning to detect the impact of hyperthermia on tumour physiology in as little time as possible.

MATERIALS AND METHODS

EMT6 tumours (mouse mammary carcinoma) were implanted into the subcutaneous tissue of both thighs of 10 BALB/c mice (one heated, one control tumour per animal). The target thermal dose was 41.5 degrees C x 45 min. Without interrupting heating, 64Cu-ATSM (mean activity 1.8 mCi) was then injected and serial PET scans were obtained. In a sub-group of four animals, a low administered activity (approximately 0.3 mCi) 64Cu-ATSM scan was also conducted before heating to permit a direct comparison of the effects of hyperthermia on the same tumours. In another sub-group of five animals, a low activity (approximately 0.3 mCi) 64Cu-PTSM (pyruvaldehyde-bis(N*-methylthiosemicarbazone)) scan was conducted before heating, to confirm a posited correlation between perfusion and early 64Cu-ATSM uptake.

RESULTS

This study corrected for perfusion differences by dividing tumour uptake by the average early (first minute) uptake ('self-normalized uptake'). The 10 heated tumours showed a significantly (p = 0.007) lower self-normalized uptake than control tumours by 2 min. For the four mice with low activity Cu-ATSM scans performed before hyperthermia, the tumours to be heated demonstrated self-normalized uptake consistent with the unheated control tumours and which departed significantly (p < or = 0.02) from their post-hyperthermia scans by 5 min. Comparisons between scans and needle electrode surveys were performed in an additional four animals with eight tumours. For technical reasons electrode surveys were done after the end of hyperthermia-and, therefore, these animals also had comparison scans taken after hyperthermia. Reduced self-normalized uptake on scans was associated with increased pO2 on electrode surveys. These data also suggested a substantial degradation of the effect on tumour hypoxia by approximately 15-45 min after the end of mild hyperthermia.

CONCLUSION

Short imaging times of approximately 5 min with modest (approximately 4-10) numbers of mice can discriminate the effects of mild hyperthermia on tumour physiology. The long-term objective is to use this tool to identify as short and mild a hyperthermia session as possible.

Cardiopulmonary function after recovery from swimming-induced pulmonary edema

OBJECTIVE

This study aimed to compare cardiopulmonary function in patients with a history of swimming-induced pulmonary edema (SIPE) with controls by measuring pulmonary function tests, oxygen consumption with exercise, and the pulmonary arterial pressure response to hypoxemia.

DESIGN

Case control study.

SETTING

Tertiary Military Medical Center.

PATIENTS

US Navy Special Warfare members who had previously suffered SIPE.

INTERVENTIONS

Measurement of pulmonary function tests, cardiopulmonary exercise test, pulmonary artery pressure by echocardiography at rest on room air and with hypoxia.

MAIN OUTCOME MEASUREMENTS

Pulmonary function testing, carbon monoxide diffusing capacity, maximal oxygen consumption, and pulmonary arterial pressure response to hypoxemia.

RESULTS

Subjects who previously had SIPE did not demonstrate differences in pulmonary function tests, carbon monoxide diffusing capacity, maximal oxygen consumption, or pulmonary arterial pressure response to hypoxemia.

CONCLUSIONS

Subjects with a history of SIPE do not have abnormal pulmonary function tests, abnormal exercise capacity, or abnormal pulmonary arterial pressure response to hypoxemia when tested in dry conditions.

Mechanism of hypoxemia in acute lung injury evaluated by multidetector-row CT

RATIONALE AND OBJECTIVES

Hypoxic pulmonary vasoconstriction (HPV) is a homeostatic mechanism causing pulmonary arterial constriction in response to local hypoxia, redistributing blood flow to lung regions with better oxygenation and ventilation. We present the use of computed tomographic (CT) volume and perfusion imaging to show differences in the mechanisms of hypoxemia from alterations in blood flow distribution within different animal models of acute lung injury (ALI).

MATERIALS AND METHODS

Three anesthetized, instrumented, and ventilated sheep were studied, two with induced ALI and one with native pneumonia. One subject was injured by using intravenous infusion of lipopolysaccharide (LPS), and the other, by repetitive saline lavage. Subjects were imaged using multidetector-row CT (MDCT) before and after injury. Lung volume scans were gated to the respiratory cycle. Contrast injection perfusion images were electrocardiogram gated. Computer-based image analysis quantified regional blood flow and total lung, air, and tissue volumes.

RESULTS

Total lung air fraction was decreased in both ALI models. In lavage injury, there was a decrease in perfusion to dependent poorly aerated regions, with perfusion shifting to nondependent regions. Conversely, LPS injury greatly increased perfusion to dependent poorly aerated regions. In the subject with pneumonia, decreasing fraction of inspired oxygen redistributed blood flow into the injured regions.

CONCLUSIONS

MDCT techniques can be used to investigate regional lung perfusion and lung volume distributions to explain physiological mechanisms in ALI. Our findings suggest that after lavage injury, blood flow is redistributed, consistent with preserved HPV and resulting in better oxygenation despite greater lung volume loss compared with LPS injury. In native pneumonia, HPV inactivation can be localized to the injured regions.

[Prospect of hypoxia imaging of nuclear medicine in tumors]

Tumor tissue hypoxia is taken as an important biologic character of malignant tumors, it could reduce the therapeutic efficacy of radiotherapy and chemotherapy. Presenting a noninvasive approach in detecting hypoxic state in tumors, hypoxia imaging of nuclear medicine can be used in the differential diagnosis, prognosis evaluation and guiding therapy of malignant tumors.

Spectrum of radiopharmaceuticals in nuclear oncology

A major field of interest in nuclear medicine is in vivo tumor characterization and measurement of biological processes at cellular and molecular levels by means of positron emission tomography (PET) or single photon emission computed tomography (SPECT). Functional imaging with radiopharmaceuticals represents a useful noninvasive tool to evaluate the biological status of the tumor and its progression. The properties of radiopharmaceuticals are exploited for initial staging of cancer, assessment of recurrent or residual disease and, more recently, considerable progress has been made in the field of the evaluation of tumor response to treatment. PET and SPECT can both detect changes in tumor activity caused by therapy or disease progression before any detectable change in tumor volume. Measurement of tumor response to therapy using PET and SPECT is the subject of intense investigations because it may result in individualization of treatment and may have a prognostic value for long-term outcome. This review focuses on the various methods used to monitor anticancer therapy with a variety of clinically approved or investigational tracers. We summarize the mechanisms of radiopharmaceutical uptake based on certain physiological activities affected by treatment: proliferation, apoptosis, hypoxia, angiogenesis and multidrug resistance (MDR).

Modulation of intratumoral hypoxia by the epidermal growth factor receptor inhibitor gefitinib detected using small animal PET imaging

Blockade of signaling through the epidermal growth factor receptor (EGFR) tyrosine kinase by inhibitors such as gefitinib (Iressa) can inhibit tumor angiogenesis and enhance responses to ionizing radiation. In this study, the ability of gefitinib to modulate intratumoral oxygenation was evaluated in human EGFR-expressing A431 squamous cell carcinoma xenografts using in vivo small animal positron emission tomography (PET) imaging with the hypoxia marker [(18)F]fluoroazomycin arabinoside (FAZA) and by the immunohistochemical detection of hypoxia-induced adducts of the 2-nitroimidazole, pimonidazole. Serial noninvasive PET imaging of A431 xenografts showed a significant reduction in FAZA uptake following treatment with 75 mg/kg/d of gefitinib [tumor to background ratio, 6.1 +/- 1.0 (pretreatment) versus 2.3 +/- 0.6 (posttreatment); P = 0.0004]. Similarly, ex vivo quantitation of FAZA uptake showed significantly reduced FAZA uptake in established A431 xenografts treated with gefitinib compared with vehicle control (tumor to blood ratio for controls versus gefitinib, 8.0 +/- 3.0 versus 2.7 +/- 0.8; P = 0.007; or tumor to muscle ratio controls versus gefitinib, 8.6 +/- 2.8 versus 2.6 +/- 1.0; P = 0.002). The effect of gefitinib treatment seemed to be independent of tumor size. In addition, gefitinib treatment reduced pimonidazole-binding in A431 xenografts measured after 5 and 8 days of gefitinib treatment compared with baseline and with tumors treated with vehicle alone. A strong correlation was observed between pimonidazole binding and FAZA uptake. Together, these findings show that gefitinib reduces intratumoral hypoxia.

Prolonged ECMO support for virus-induced cardiorespiratory failure early after cardiac surgery

Extracorporeal membrane oxygenation (ECMO) after cardiac surgery is a rescue for life-threatening respiratory or circulatory failure. Although ECMO support for short periods (<10 days) represents an effective means of respiratory and cardiac support, treatment for longer periods remains controversial. We describe successful long-term use of ECMO support (48 days) for acquired virus-induced respiratory failure complicated by circulatory collapse following heart surgery.

Validation of 18F-fluoro-4-thia-palmitate as a PET probe for myocardial fatty acid oxidation: effects of hypoxia and composition of exogenous fatty acids

Fatty acid oxidation (FAO) is the predominant energy-producing pathway in the healthy heart. Abnormalities in FAO are associated with many ischemic and nonischemic disease states. The aim of the present study was to further validate 16-[(18)F]-fluoro-4-thia-palmitate ((18)F-FTP) as a metabolically trapped FAO probe in the isolated perfused rat heart model by examining both the effects of hypoxia and the effects of changes in exogenous fatty acid availability.

METHODS

Hearts were excised from Sprague-Dawley rats and perfused in the Langendorff mode with Krebs-Henseleit solution under the following conditions: palmitate at 0.4 mmol/L with 95% oxygen, palmitate at 0.4 mmol/L with 35% oxygen, palmitate at 0.2 mmol/L plus oleate at 0.2 mmol/L with 95% oxygen, and palmitate at 0.2 mmol/L plus oleate at 0.2 mmol/L with 35% oxygen. Hearts were paced at 270 beats per minute, and the rate of left ventricular pressure change (LV dP/dt) was monitored. (18)F-FTP in the perfusion medium was administered for 20 min, and this step was followed by a 20-min washout period without tracer in the perfusion medium. (18)F kinetics in the whole heart were monitored externally, and the time-activity curves were analyzed to determine the fractional trapping rate for (18)F-FTP (FTR(FTP)). A "lumped constant" (LC) was defined as the ratio of FTR(FTP) to the fractional rate of oxidation of fatty acid in the perfusion medium.

RESULTS

The kinetic data for (18)F-FTP demonstrated metabolic trapping of (18)F radioactivity that was insensitive to changes in the mixture of fatty acids in the perfusion medium but that was sensitive to the inhibition of mitochondrial FAO by hypoxia. LV dP/dt was reduced 47%-67% in hypoxic hearts relative to hearts with normal oxygenation (controls). FAO rates for palmitate and oleate were similar in group 3 (palmitate alone) and group 4 (palmitate and oleate). FAO was decreased 70%-76% with hypoxia, whereas FTR(FTP) was reduced 86%-88%, demonstrating hypersensitivity of a change in (18)F-FTP retention to FAO inhibition by oxygen deprivation. The (18)F-FTP LC was approximately 2 in myocardium with normal oxygenation and fell to 1.0-1.2 in hypoxic myocardium.

CONCLUSION

The results confirm (18)F-FTP to be a metabolically trapped palmitate analog that is capable of indicating rates of myocardial oxidation of exogenous long-chain fatty acids. The heterogeneous nature of fatty acids in plasma does not alter the quantitative analysis of (18)F-FTP kinetics. However, the decreased LC value in hypoxic myocardium suggests the need to develop an understanding of the relationship of (18)F-FTP processing to natural fatty acids at key limiting transport and metabolism processes, analogous to previous studies examining the LC values for radiolabeled deoxyglucose tracers used to estimate the glucose metabolic rate.

Right and left ventricular adaptation to hypoxia: a tissue Doppler imaging study

Hypoxia has been reported to alter left ventricular (LV) diastolic function, but associated changes in right ventricular (RV) systolic and diastolic function remain incompletely documented. We used echocardiography and tissue Doppler imaging to investigate the effects on RV and LV function of 90 min of hypoxic breathing (fraction of inspired O2 of 0.12) compared with those of dobutamine to reproduce the same heart rate effects without change in pulmonary vascular tone in 25 healthy volunteers. Hypoxia and dobutamine increased cardiac output and tricuspid regurgitation velocity. Hypoxia and dobutamine increased LV ejection fraction, isovolumic contraction wave velocity (ICV), acceleration (ICA), and systolic ejection wave velocity (S) at the mitral annulus, indicating increased LV systolic function. Dobutamine had similar effects on RV indexes of systolic function. Hypoxia did not change RV area shortening fraction, tricuspid annular plane systolic excursion, ICV, ICA, and S at the tricuspid annulus. Regional longitudinal wall motion analysis revealed that S, systolic strain, and strain rate were not affected by hypoxia and increased by dobutamine on the RV free wall and interventricular septum but increased by both dobutamine and hypoxia on the LV lateral wall. Hypoxia increased the isovolumic relaxation time related to RR interval (IRT/RR) at both annuli, delayed the onset of the E wave at the tricuspid annulus, and decreased the mitral and tricuspid inflow and annuli E/A ratio. We conclude that hypoxia in normal subjects is associated with altered diastolic function of both ventricles, improved LV systolic function, and preserved RV systolic function.

Assessing regional hypoxia in human renal tumours using 18F-fluoromisonidazole positron emission tomography

OBJECTIVE

To assess renal tumours for hypoxic regions using 18F-fluoromisonidazole (18F-FMISO) positron emission tomography (PET), a recognized noninvasive method for detecting hypoxia in tumours, as renal cell carcinoma (RCC) can be potentially cured with nephrectomy but recurrence develops in most patients, who then respond poorly to treatments such as chemotherapy, and hypoxia is known to confer resistance to radiotherapy and chemotherapy in many solid tumours.

PATIENTS AND METHODS

In all, 17 patients had 18F-FMISO PET scans before nephrectomy for presumed RCC. Specimens were examined histologically, and immunohistochemistry was used to compare the microvessel density (MVD) as an indicator of angiogenesis in the tumour and normal parenchyma, in 15 patients. Tumour oxygenation was measured invasively in three patients using a polarographic oxygen sensor probe.

RESULTS

Of the 15 patients with histological results, 11 had RCC and four had other tumours. Although there was a trend there was no statistically significant (P = 0.14) difference in the maximum standardized uptake value (SUV(max)) when comparing the region of the kidney involved with RCC; the mean (95% confidence interval) SUV(max) in the tumours was 1.3 (0.15), whilst that in the normal contralateral kidney was 1.1 (0.22). The MVD was greater in RCC, at 13.7 (3.1) mean vessels per high-power field than in normal tissue, at 6.9 (1.9). Hypoxia as measured polarographically was detected in three RCCs (median pO2 9.6 mmHg) compared to normal parenchyma at 37.6 mmHg.

CONCLUSIONS

Although 18F-FMISO scans showed significant uptake in other solid tumours, there was only mild 18F-FMISO uptake in the present RCCs. The invasive measurements indicated that there was hypoxia in RCC, but the median pO2 did not fall below 9.5 mmHg. Further direct studies of renal tumour oxygenation combined with therapies directed towards hypoxia may allow a better understanding of the relationship between 18F-FMISO results and the biological significance of hypoxia in RCC.

Platypnea-orthodeoxia associated with a fenestrated atrial septal aneurysm: case report

BACKGROUND

Platypnea-orthodeoxia describes the condition of combined dyspnea and hypoxia respectively, whilst in the upright position, which improves in the recumbent position.

CASE REPORT

We present a case of platypnea-orthodeoxia due to a fenestrated atrial septal defect associated with an atrial septal aneurysm. Due to the fenestrated nature of the atrial septal defect, surgical rather than percutaneous correction was performed.

CONCLUSION

A high index of suspicion is required to diagnose the syndrome of platypnea-orthodeoxia. Careful echocardiographic evaluation is required to identify the syndrome, and to determine suitability for percutaneous repair.

Normal angiogram in acute coronary syndromes: the underestimated role of alternative substrates of myocardial ischemia

The study is aimed at evaluating the real incidence of normal coronary arteries and the role of alternative substrates of myocardial ischemia in patients with acute coronary syndrome (ACS) but with no coronary artery disease (CAD) in a real world secondary care public hospital. The medical records of 941 patients undergoing coronary arteriography for ACS within 48 h of onset between January 1st 2000 and November 1st 2003 were critically reviewed. In 70 patients (7.4%, 35 males, mean age 60 +/- 17.2 years) no CAD was documented. Alternative substrates of acute myocardial ischemia included coronary artery anomalies (7 patients, 10%), coronary spasm (10 patients, 14.3%), spontaneous coronary dissection (2 patients, 2.8%), paradoxical embolism through a patent foramen ovale (4 patients, 5.7%), embolism from left atrium or calcified aortic valve (4 patients, 5.7%), imbalance between oxygen demand and supply (20 patients, 28.5%), mitral valve prolapse (11 patients, 15.7%). No alternative substrates were found in 12 patients (17.1%). Patients with no CAD are more frequently female and younger. Absence of CAD is an uncommon finding in patients undergoing coronary artery angiography for ACS.

Noninvasive measurement of isovolumetric contraction time during hypoxemia and acidemia: Fetal lamb validation as an index of cardiac contractility

OBJECTIVES

The objectives of this study are firstly to clarify how the Doppler isovolumetric contraction time (ICT) is influenced by arterial oxygen pressure (PaO2) or pH, and secondly to confirm the relationship between the Doppler ICT and myocardial contractility during hypoxemia and/or acidemia in the fetal lamb.

MATERIAL AND METHODS

In 12 pregnant ewes, fetal hypoxemia and acidemia were induced by giving ewes a variable mixture of gases for 120 min. The chronological change of fetal PaO2, pH, Doppler ICT and maximum first derivative of the left ventricular pressure waveform (Max dp/dt) was recorded every 30 min.

RESULTS

Doppler ICT and PaO2 had no significant regression. On the other hand, Doppler ICT and pH demonstrated a significant negative regression. Moreover, one critical given pH point was indicated with statistical significance at 7.20 and the prolongation of the Doppler ICT was found more markedly in the range below the pH of 7.20 compared with the range above 7.20. A significant negative linear regression was found between the Doppler ICT and the Max dp/dt.

CONCLUSION

The measurement of Doppler ICT enables us to predict severe acidosis and a decrease of myocardial contractility in the fetus.

[Development of [18F]FRP-170 injection for imaging hypoxia by PET]

A novel [18F]FRP-170 injection for imaging hypoxia by PET was developed for clinical use. The preparation was based on the simple on-column basic-hydrolysis and the whole procedure was automated by detecting He flow change for transferring and evaporating liquids. [18F]FRP-170 was prepared in around 15-20% decay-corrected radiochemical yield within 60 min and stable in saline for more than 6 hr. Radiochemical purity was over 99% and specific activity at EOS was 40-60 GBq/micromol. The radiation-absorbed dose to the whole body was estimated to be 1.0 mSv/185 MBq. The [18F]FRP-170 injection proved to be suitable for clinical use without acute toxicity or mutagenicity.

Platypnea-orthodeoxia induced by fenestrated atrial septal aneurysm

Platypnea-orthodeoxia is a peculiar syndrome characterized by a right-to-left shunt, which occurs in the upright position. The diagnosis is made by contrast transesophageal echocardiography, paying attention to include contrast visualization in the orthostatic decubitus. The association of this syndrome with a fenestrated atrial septal aneurysm is rare and probably underlies a peculiar and also rare mechanism of shunting in presence of normal pulmonary pressure. We report of a case of a 58-year-old man with a fenestrated atrial septal aneurysm and platypnea-orthodeoxia syndrome treated by surgical closure of the atrial defect.

Advances in positron emission tomographic imaging of lung cancer

Positron emission tomography (PET) with [18F]fluorodeoxyglucose (FDG) has been established as a useful tool in the management of patients with non-small cell lung cancer and promises to be as valuable in the clinical management of other cancers. PET imaging with FDG allows the assessment of tumor glucose metabolism in vivo; however, a number of other PET tracers are being used in oncologic research to assess changes in other cellular processes associated with malignant transformation of the cell. [11C]-Labeled methionine and choline are being used to assess changes in cell membrane synthesis; however, small studies have not shown the added information from these tracers to be clinically useful. DNA synthesis can be assessed by measuring the uptake of the thymidine analog 3'-deoxy-3'-[18F]fluorothymidine, which may be more specific for evaluating malignancy without the problem of false-positive results from inflammatory lesions, as seen with FDG. Tumor hypoxia imaging with copper-labeled diacetyl-bis(N(4)-methylthiosemicarbazone) or [18F]fluoromisonidazole may provide a better method of predicting which tumors will respond best to conventional therapy. The role of PET will continue to evolve with further clinical studies using these and other new tracers.