Combined CT venography and pulmonary angiography: how much venous enhancement is routinely obtained?

OBJECTIVE: Combined CT venography and helical pulmonary angiography is a new diagnostic test that permits radiologists to check both the pulmonary arteries for embolism and the deep veins of the abdomen, pelvis, and legs for thrombosis in a single examination. The purpose of this study was to determine the degree of venous enhancement routinely obtained using this combined CT examination. MATERIALS AND METHODS: We identified all patients at a single institution who, during a 29-month period, had symptoms suggestive of pulmonary embolism and who underwent CT venography and helical pulmonary angiography. The examinations were performed after the patients received a rapid (3--5 mL/sec) IV injection of 150 mL of nonionic contrast medium (240 mg I/mL). CT venography of the abdomen, pelvis, and lower extremities was performed as follows: Beginning 3 min after the start of contrast medium infusion for helical CT pulmonary angiography, 1-cm axial images obtained at 5-cm intervals were acquired from an area ranging from the diaphragm to the calves. Patients who had evidence of deep venous thrombosis on CT scans were excluded from further analysis. The venous portions of the remaining 429 examinations were retrospectively reviewed at a CT console or workstation by one of two radiologists, and Hounsfield unit measurements were recorded from the inferior vena cava as well as from the right and left external or internal iliac, common femoral, superficial femoral, and popliteal veins. A single Hounsfield unit measurement was obtained from the center of each vessel using a region of interest that was approximately half the diameter of the vessel. Mean Hounsfield unit measurements were then calculated for these venous stations. RESULTS: Mean Hounsfield unit measurements at the inferior vena cava and at the right and left external or internal iliac veins were 97, 95, and 95 H, respectively. Mean measurements at the common femoral veins were 95 H for both the right and left; the mean measurements at the superficial femoral veins were 91 H for both the right and left, and those at the popliteal veins were 97 H for the right and 94 H for the left. CONCLUSION: CT venography of the abdomen, pelvis, and lower extremities begun 3 min after the start of contrast medium infusion for helical CT pulmonary angiography routinely produced high mean levels of venous enhancement.

A simple and efficient approach for the synthesis of fluorinated and nonfluorinated octaethylporphyrin-based benzochlorins with variable lipophilicity, their in vivo tumor uptake, and the preliminary in vitro photosensitizing efficacy.

Starting from commercially available Ni(II)octaethylporphyrin (OEP), an efficient approach for the preparation of a series of fluorinated and nonfluorinated benzochlorins with variable lipophicity has been developed. Their spectroscopic properties, preliminary in vitro photosensitizing efficacy, and tumor selectivity were determined. Our methodology provides a facile approach for the preparation of the free-base and the related Zn(II) benzochlorins containing alkyl and alkyl ether side chains with variable carbon units. For the preparation of benzochlorins containing alkyl groups attached to the exocyclic phenyl ring, the Ni(II) meso-(2-formylvinyl)octaethyl porphyrin 2 was reacted with various reagents such as (trifluoromethyl)trimethylsilane (TMS-CF3) or the Grignard reagents of various fluorinated or nonfluorinated alkyl halides. The corresponding intermediates 3, 6a-6e, and 8 obtained via intramolecular cyclization under acidic conditions afforded the related benzochlorins 5, 7a-d, and 9 in good yields except for 7e which was obtained in poor yield (11.4%). The alcohol 10 obtained by reacting porphyrin 2 with ethynylmagnesium chloride did not produce the expected acetylenic benzochlorin; instead the corresponding acetyl derivative 11 was obtained as a major product, which under appropriate reaction conditions was converted into a series of alkyl ether derivatives 13a-13d. To obtain a benzochlorin bearing an ester functionality (15), porphyrin 2 was first reacted with ethyl acetate/LDA and the intermediate alcohol 14 was then cyclized with sulfuric acid. Unlike most of the natural and synthetic chlorins, the Zn(II) complexes of the benzochlorin analogues exhibited a significant bathochromic shift ( approximately 10 nm) in the electronic absorption spectra, and the long wavelength absorptions were observed in the range 671-677 nm (epsilon: 43270-50360). For investigating the in vitro efficacy of these analogues, Molt-4 cells were used. At a concentration of 2.5 microM, and a light dose of 4 J/cm2, all benzochlorins produced significant photosensitizing efficacy. The tumor (RIF) and muscle uptake in C3H mice of these photosensitizers was determined by in vivo reflectance spectroscopy. These results indicate that in this series increasing the length of the alkyl or alkyl ether carbon chains at the fused phenyl ring system produced a significant increase in tumor uptake.

Deep venous thrombosis with suspected pulmonary embolism: detection with combined CT venography and pulmonary angiography.

PURPOSE: To determine the frequency and location of deep venous thrombosis at computed tomographic (CT) venography after CT pulmonary angiography in a large series of patients clinically suspected of having pulmonary embolism and to compare the accuracy of CT venography with lower-extremity venous sonography. MATERIALS AND METHODS: Venous phase images were acquired from the diaphragm to the upper calves after completion of CT pulmonary angiography in 650 patients (373 women, 277 men; age range, 18-99 years; mean age, 63 years) to determine the presence and location of deep venous thrombosis. Results of CT venography were compared with those of bilateral lower-extremity venous sonography in 308 patients. RESULTS: A total of 116 patients had pulmonary embolism and/or deep venous thrombosis, including 27 patients with pulmonary embolism alone, 31 patients with deep venous thrombosis alone, and 58 patients with both. Among 89 patients with deep venous thrombosis, thrombosis was bilateral in 26, involved the abdominal or pelvic veins in 11, and was isolated to the abdominal or pelvic veins in four. In patients in whom sonographic correlation was available, CT venography had a sensitivity of 97% and a specificity of 100% for femoropopliteal deep venous thrombosis. CONCLUSION: Combined CT venography and pulmonary angiography can accurately depict the femoropopliteal deep veins, permitting concurrent testing for venous thrombosis and pulmonary embolism. CT venography also defines pelvic or abdominal thrombus, which was seen in 17% of patients with deep venous thrombosis.

Perinephric xanthogranulomatosis: CT diagnosis and confirmation by CT-guided percutaneous biopsy.

Xanthogranulomatosis is an idiopathic, rare process in which lipid-laden histiocytes may deposit in various locations in the body, which if systemic is called Erdheim-Chester disease. A rare case of isolated retroperitoneal, bilateral perinephric xanthogranulomatosis is reported. The diagnosis was suspected on cross-sectional imaging and was confirmed by CT-guided percutaneous core biopsy.

Extra-thoracic findings on the venous phase of combined computed tomographic venography and pulmonary angiography.

A growing consensus is that pulmonary embolism and thrombosis represent different aspects of the same disease, and a single study that accurately defines both pulmonary emboli and deep venous thrombosis would be a desirable examination. The purpose of this pictorial review is to demonstrate the extra-thoracic findings on the venous phase of such a study, which combines computed tomographic venography and pulmonary angiography.

Combined CT venography and pulmonary angiography in suspected thromboembolic disease: diagnostic accuracy for deep venous evaluation.

OBJECTIVE: Combined CT venography and pulmonary angiography is a new diagnostic test that evaluates both pulmonary embolism and deep venous thrombosis (DVT) in a single study. Our purpose was to compare the CT venous findings with lower extremity venous sonography. SUBJECTS AND METHODS: Seventy-one consecutive patients with suspected pulmonary embolism underwent helical CT pulmonary angiography during rapid i.v. infusion of contrast medium. Axial scans at 5-cm intervals from the patient's upper calves to the diaphragm were generated 3.5 min after the beginning of contrast medium injection. CT venous phase images were interpreted prospectively and compared with subsequent bilateral lower extremity venous sonography performed within 12 hr. RESULTS: DVT was revealed by CT venous phase images in 19 patients, 12 of whom also had pulmonary embolism. CT and sonographic findings correlated exactly in the femoropopliteal deep venous system, where most pulmonary emboli originate. CT venous phase images also revealed pelvic extension of DVT in six patients and isolated vena cava thrombus in one patient. CONCLUSION: CT venous phase imaging at the time of CT pulmonary angiography is comparable with venous sonography in the evaluation of femoropopliteal DVT. The iliac veins and vena cava, vessels poorly shown on sonography but sometimes the source of significant pulmonary emboli, are also depicted by CT venography.

Effect of substituents in directing the formation of benzochlorins and isobacteriochlorins in porphyrin and chlorin systems.

[formula: see text] A first synthesis of free-base fluorinated benzochlorins by acid-catalyzed cyclization of 20-(2-trisiloxy-trifluoromethylvinyl)octaethylporphyrin++ + is achieved. Under similar reaction conditions, the purpurin-18-N-hexylimide analogues produced the corresponding fluorinated and nonfluorinated ethylidene-substituted isobacteriochlorins and fluorinated chlorin, respectively. The structure of the porphyrin based fluorinated benzochlorin was also confirmed by X-ray analysis.

Experimentally produced pulmonary arterial occlusion in the dog: identification with pertechnegas inhalation.

Pertechnegas, a variant of technegas, is a fine, dry aerosol formed when technetium-99m pertechnetate is vaporized in a technegas generator under appropriate conditions. After inhalation, the aerosol is deposited almost entirely on the surfaces of terminal respiratory structures. Unlike technegas, however, pertechnegas crosses the alveolar-capillary membrane and leaves the lung through the pulmonary circulation. To demonstrate prolonged retention of pertechnegas in regions of lung supplied by an occluded pulmonary artery, 12 pulmonary arterial occlusions were experimentally produced in two dogs. After inhalation of pertechnegas, a transient focus of increased pulmonary radioactivity was seen in 11 occlusions; 10 of these 11 foci were easily confirmed by means of subsequent perfusion scintigraphy. All 11 foci of retained pertechnegas corresponded to the location of the non-perfused lung. Thus, it is possible to identify ischemic lung with focal retention of pertechnegas (a finding that indicates preserved ventilation but diminished perfusion) by use of a single examination.

Imaging of the human torso using cone-beam transmission CT implemented on a rotating gamma camera.

Radionuclide transmission CT generated on a rotating gamma camera can improve SPECT imaging by providing attenuation maps for attenuation compensation and for anatomical correlation. This paper demonstrates the feasibility and high quality of cone-beam transmission CT (CB-CT) of human subjects, in comparison to conventional parallel-ray CT, and evaluates some possible imaging protocols. Two CB-CT implementation modes, with a cone-beam collimator and without any collimator, were evaluated. Three human subjects of different dimensions were imaged. For the two smaller subjects, the CB-CT images were dramatically superior, in terms of noise and resolution, to those obtained with a parallel-ray geometry. The image noise was less by a factor of 6. CB-CT linear attenuation coefficients were found to be in close agreement with published values for various tissues. For the largest subject, image truncation produced a ring artifact at the edge, but inside the artifact, the image quality was still very good. Cone-beam images obtained without any collimator were acceptable, but photon scatter degraded the image contrast.

Thrombus imaging: a comparison of radiolabeled GC4 and T2G1s fibrin-specific monoclonal antibodies.

Radioimmunoimaging of experimentally-induced canine thrombi has previously been achieved with iodine-131- and indium-111-labeled (131I and 111In) anti-fibrin T2G1s monoclonal antibody (MAb). We now compare T2G1s to another anti-fibrin MAb, designated GC4, for imaging fresh and aged canine thrombi. GC4 is specific for a neoepitope exposed on fibrin later in the thrombolytic process after plasmin digestion. Femoral venous thrombi were induced in six groups of dogs, each containing three dogs. In two groups, the MAbs were compared when the thrombi were 3-hr or 3-days old at the time of injection, and the dogs were killed at 48 hr. In thrombi 3-hr-old, the GC4/T2G1s concentration ratio averaged 0.53 compared to 1.9 in 3-day-old thrombi. Two groups of dogs with thrombi 1- or 3-days-old were heparinized before MAb injection and were killed at 24 hr. The heparinized dogs with thrombi 1- or 3-days-old had GC4/T2G1s mean ratios of 2.3 and 2.9, respectively. In the unheparinized groups, the corresponding ratios were 1.1 and 1.9. GC4 may be more useful for clinical thrombus imaging than T2G1s because spontaneous venous thrombi are usually several days old at the time of presentation and patients are often heparinized immediately.

Monoclonal antibodies and thromboembolism.

For many years intensive efforts to reliably image thrombi by radionuclide techniques have been unrewarding. Recently, however, monoclonal antibodies to platelet cell-surface antigens and to fibrin polymer have emerged as potent thrombus imaging agents in experimental animals. In Britain antiplatelet antibody has been successful in clinical trials, as has antifibrin in the United States. It is to be hoped that radiolabeled antibody technology will evolve to the point where it can detect thrombi anywhere, including the lungs and brain. The relative efficacy of radionuclide thrombus detection and Doppler ultrasonography is currently undefined.

Immunoreactivity of 111In and 131I fibrin-specific monoclonal antibody used for thrombus imaging.

Immunoreactivity of radiolabeled F(ab')2 fragment of anti-fibrin T2G1s monoclonal antibody was determined by affinity chromatography using fibrin-coated Sepharose. This preparation is useful for thrombus detection in vivo by gamma camera imaging, provided a high percentage of immunoreactivity is retained after labeling. For 111In labeling, DTPA/F(ab')2 molar ratios were varied from 1000 to 6600/1, with little effect on immunoreactivity. Immunoreactivity of the F(ab')2 fragment, labeled with imaging doses of 131I and 111In, remained high and ranged from 81% to 89%. Equilibrium binding analysis determined the affinity constants of 111In- or 125I-labeled T2G1s and its F(ab')2 and Fab fragments, to be equivalent (Kd approximately 3 X 10(-8) M). This suggests that only one binding domain of T2G1s binds to fibrin even though there are two antigenic sites/mol of fibrin.

Thrombus imaging with indium-111 and iodine-131-labeled fibrin-specific monoclonal antibody and its F(ab')2 and Fab fragments.

We have previously reported successful imaging of fresh (2-4 hr old) and aged (1-5 days old) canine thrombi with 131I-labeled intact monoclonal antibody (MAb) specific for fibrin. We now report thrombus imaging with 131I-labeled F(ab')2 and Fab and 111In-labeled intact MAb, F(ab')2, and Fab. Indium-111-labeled F(ab')2 proved to be the best imaging agent due to less nonspecific binding in the liver than whole IgG. Image quality was improved by the higher administered dose permissible with 111In and its better physical characteristics for imaging, compared to 131I. Immunofluorescence of fresh human histologic sections showed intact MAb and F(ab')2 binding to thrombi, pulmonary emboli, and atherosclerotic plaques, strengthening the feasibility of clinical thrombus imaging.

Clearance of aerosolized 99mTc-diethylenetriaminepentacetate before and after smoke inhalation.

The pulmonary clearance of aerosolized 99mTc-diethylenetriaminepentacetate (DTPA) was studied in mongrel dogs immediately after exposure to wood smoke to see if a sensitive, objective way of assessing the degree of pulmonary injury might be found. Animals were studied in four groups as follows: control, following five minutes, two minutes, and 15 seconds of smoke exposure. Chest roentgenograms and 133Xe scans were taken before and after smoke exposure. The DTPA clearance was more sensitive in detecting injury than either of these imaging techniques. The DTPA clearance rates increased in a dose responsive way following smoke inhalation: 2.4 percent and 12.1 percent excreted per minute for control animals and those exposed to five minutes of smoke, respectively. Seven patients in a clinical trial of DTPA following smoke exposure are described; their DTPA clearance rates were all normal, although five were active cigarette smokers. Despite encouraging results in animal experiments, DTPA clearance studies may be of little practical value in the clinical setting of acute inhalation injury.

Imaging fresh venous thrombi in the dog with I-131 and In-111 labeled fibrin-specific monoclonal antibody and F(ab')2 fragments.

The authors report success in imaging thrombi using labeled monoclonal antibody or antibody fragments. An In-111 labeled antibody fragment appears to be the best imaging agent studied to date.