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Biomedical subjects

M V Marx

Publications and source records attributed to M V Marx.

At least 19 recordsLinked to original sources
PubMed1999

Severe skin reactions from interventional fluoroscopy: case report and review of the literature.

Some patients with certain preexisting health conditions may be at elevated risk for unusually intense radiation-induced skin reactions and late tissue damage from high-dose interventional procedures. The authors present a case report of a patient with mixed connective tissue disease and non-insulin-dependent diabetes mellitus who developed an unusual complication after placement of a transjugular intrahepatic portosystemic shunt. On the basis of a review of the literature, the following experiences may help identify patients at increased risk: previous high-dose procedures, connective tissue disease, diabetes mellitus, and homozygosity for ataxia telangiectasia.

Diabetes Mellitus, Type 2↗
PubMed1998

Gadolinium-enhanced magnetic resonance venography of the portal venous system prior to transjugular intrahepatic portosystemic shunts and liver transplantation. Original investigation.

RATIONALE AND OBJECTIVES: The accuracy of gadolinium-enhanced magnetic resonance venography (GdMRV) in identifying visceral venous abnormalities was assessed in patients before they underwent transjugular intrahepatic portosystemic shunt (TIPS) or orthotopic liver transplantation (OLT). METHODS: Twenty-seven patients with portal hypertension underwent GdMRV and transcatheter venography prior to OLT or TIPS. The gadolinium dose was 0.5 mL/kg (0.25 mmol/kg), administered by rapid hand injection. Coronal 3D spoiled gradient-echo GdMRV was performed in a single breath-hold. Four blinded reviewers retrospectively evaluated coronal maximum intensity projection (MIP) images, while two reviewers evaluated the MIPs and multiplanar reconstructions. Abnormalities that could affect transjugular intrahepatic portosystemic shunt or transplantation were noted and compared with the results of corresponding catheter venograms read by a separate blinded reviewer. RESULTS: Abnormalities were identified by GdMRV with a sensitivity and specificity of 83% and 97% for the right hepatic vein, 86% and 100% for the main portal vein (MPV), 42% and 99% for the right portal vein, 54% and 94% for the left portal vein, 61% and 96% for the superior mesenteric vein, and 74% and 91% for the splenic vein. Varices and shunts were correctly identified with a sensitivity of 96%. Multiplanar reconstruction increased MPV sensitivity to 100%. CONCLUSION: Vascular abnormalities that affect TIPS and OLT can be identified by GdMRV. Multiplanar reconstruction increased the accuracy to 100% for the MPV.

Catheterization, Central Venous↗
PubMed1997

A phase I trial of hepatic arterial bromodeoxyuridine and conformal radiation therapy for patients with primary hepatobiliary cancers or colorectal liver metastases.

PURPOSE: We have previously found that conformal radiation therapy (RT) and hepatic arterial fluorodeoxyuridine was associated with durable responses and long-term survival for patients treated for nondiffuse primary hepatobiliary tumors and colorectal liver metastases. Further improvements in hepatic control may result from the addition of selective radiosensitization using bromodeoxyuridine (BrdU) infused through the hepatic artery (HA) concurrently with RT. This is a Phase I study of escalating doses of HA BrdU combined with our standard hepatic RT. METHODS AND MATERIALS: Patients with unresectable primary hepatobiliary cancer or colorectal liver metastases were treated with concurrent HA BrdU and conformal RT (1.5 Gy per fraction, twice a day). Three-dimensional treatment planning was used to define both the target and normal liver volumes. The total dose of RT (24, 48, or 66 Gy) was determined by the fractional volume of normal liver excluded from the high dose volume. HA BrdU was escalated in standard Phase I fashion with at least three patients receiving each combination of RT dose and BrdU dose. The starting dose of HA BrdU was 10 mg/kg/day, with two potential escalations to a maximum of 25 mg/kg/day (the maximum tolerable dose of HA BrdU when given alone on this same schedule). Grade > or = 3 toxicity was considered dose limiting. Patients receiving 24 Gy had one cycle of HA BrdU, while those receiving either 48 or 66 Gy had two cycles. Patients were followed for toxicity, complications, and response (when evaluable). RESULTS: A total of 41 patients (18 with colorectal liver metastases, 16 with cholangiocarcinoma and 7 with hepatoma) were treated. Five patients were removed from the protocol (three had HA catheter complications, one developed atrial fibrillation, and one was removed due to recurrent Grade 4 toxicity), although all five are included for toxicity purposes. Dose-limiting toxicity was primarily thrombocytopenia and there was no obvious relationship with the RT dose. Only 2 of 17 cycles given at 25 mg/kg/day had Grade > or = 3 toxicity. Complications developed in four patients, including one patient with radiation-induced liver disease. Response rates were not improved compared to our previous experience. CONCLUSIONS: The appropriate dose of HA BrdU for Phase II evaluation is 25 mg/kg/day. Neither the hepatic parenchyma nor the gastrointestinal mucosa appeared to be sensitized by this method of BrdU administration. It is anticipated that these, or still newer methods of therapy, can improve treatment results in the near future.

Adult↗
PubMed1997

The dissected aorta: part III. Anatomy and radiologic diagnosis of branch-vessel compromise.

PURPOSE: To determine the anatomic, hemodynamic, and radiologic characteristics of branch-vessel compromise in patients with aortic dissection. MATERIALS AND METHODS: Sixty-two patients with aortic dissection were evaluated with aortography (n = 62), intravascular ultrasound (US) (n = 35), and manometry (n = 56). Branch-vessel compromise with ischemia was suspected in 40 of these patients. Radiologic and manometric findings were correlated with clinical findings of ischemia. Femoral artery pulse strength was correlated with access from the respective femoral artery to the true and false lumina of the dissected aorta. RESULTS: Twenty-six of 40 patients suspected of having ischemia had angiographic evidence of branch-vessel compromise, and intravascular US helped identify two types of branch-vessel compromise in them: static (dissection intersected and narrowed the vessel origin) and dynamic (dissection spared the vessel origin, but the dissection flap appeared to compress the true lumen at or above the origin and covered the origin). False-lumen pressure in classic dissections exceeded (n = 16) or equaled (n = 30) true-lumen pressure. Branch vessels that arose exclusively from the false lumen were well perfused. Findings of a dissection flap oriented concave toward the false lumen were 91% sensitive and 72% specific for a true-lumen pressure deficit. CONCLUSION: Intravascular US and manometric findings clarify the mechanisms of branch-vessel compromise after aortic dissection and provide a rational guide for percutaneous treatment.

Adolescent↗
PubMed1996

The use of intra-arterial urokinase in the management of hand ischemia secondary to palmar and digital arterial occlusion.

Impending gangrene of the hand or digits secondary to palmar or digital artery occlusion can be a devastating complication of upper extremity thromboembolic or atheroembolic disease. Over the past 7 years, 9 patients with severe unilateral hand ischemia and impending tissue loss secondary to distal forearm, palmar arch, and digital artery occlusion were managed with intra-arterial urokinase (UK) infusion. The etiology of the ischemia was thromboembolism in 3 patients, atheroembolism in 2, and traumatic ulnar artery occlusion ("hypothenar hammer syndrome") in the remaining 4 patients. Initial high-dose UK was administered in 3 patients (240,000 U per hour for 2 hours) and all 9 patients were maintained on 80,000 to 120,000 U per hour until clot lysis occurred or until a minimum dose of 600,000 U had been given without clinical improvement. Following UK therapy, the 3 patients with thromboemboli had angiographic demonstration of clot lysis as well as complete resolution of ischemia. The 2 patients with atheroemboli showed no angiographic or clinical improvement, and both required surgical intervention. Angiographic improvement was demonstrated in only 1 patient with traumatic ulnar artery occlusion, although 3 of the 4 patients were clinically improved. A pericatheter thrombosis due to insufficient heparinization and a subcutaneous abscess at the femoral artery puncture site were the only complications of UK infusion. No hemorrhagic complications occurred and no adverse effects of lytic therapy were documented in patients who subsequently required surgery. UK is an effective treatment for recent thromboembolism, because it lyses unorganized thrombi. It is ineffective for treatment of organized thrombi or atheroemboli. Because the etiology of acute hand ischemia is not always obvious at the time of presentation, a trial of UK infusion is warranted, because it is relatively safe and its use may obviate the need for complex microsurgical reconstruction.

Acute Disease↗
PubMed1996

Early placement of prophylactic vena caval filters in injured patients at high risk for pulmonary embolism.

OBJECTIVE: Pulmonary embolism (PE) is a major problem in patients with multiple injuries. We present our experience with early placement of prophylactic vena caval filters (VCFs). DESIGN: Prospective study group with historical control. MATERIALS AND METHODS: From March 1993 to December 1993, VCFs were placed in 40 consecutive patients with three or more risk factors for PE and had demographic, physiologic, venous thromboembolic prophylaxis, and outcome data collected prospectively (VCF group). They were compared to 80 injured patients admitted between November 1991 and February 1993 who survived > 48 hours and who were matched with the VCF group for mechanism of injury and risk factors for PE (NO VCF group). MEASUREMENTS AND MAIN RESULTS: VCF placement affected a significant reduction in the incidence of PE (2.5% vs. 17%) and a clinical reduction in PE-related mortality. Embolic trapping was suggested by a 10% incidence of documented vena caval thrombi and although two patients developed significant venous stasis disease, no other VCF-related morbidity was noted. CONCLUSIONS: In spite of long-term morbidity, early prophylactic VCF placement is safe and should be considered in the prophylaxis of PE in the high-risk injured patients. This intervention may be effective in eliminating PE as a major cause of posttrauma morbidity and mortality.

Adult↗
PubMed1996

Three-dimensional gadolinium-enhanced MR angiography of the thoracic aorta.

OBJECTIVE: Our objective was to evaluate image quality and preliminary clinical experience with three-dimensional gadolinium-enhanced MR angiography of the thoracic aorta. SUBJECTS AND METHODS: Ninety patients with suspected thoracic aorta pathology underwent 97 MR examinations at 1.5 T with a 4-min, three-dimensional spoiled gradient-echo techniques. Gadolinium infusion was timed for maximum arterial contrast during acquisition of the central portion of K-space. No ECG gating or breath-holding was used. All MR examinations were evaluated retrospectively for intravascular signal-to-noise ratio (SNR). In 30 of the 90 patients, results from surgery (n = 11), angiography (n = 12), or both (n = 7) were available. Four radiologists who were unaware of the angiographic or surgical findings assessed each of these 30 examinations for three types of pathology: dissection, coarctation, or aneurysm. The observers also assessed aortic branch vessel patency and vascular anomalies in the 19 patients who had angiographic correlation. RESULTS: Image quality (determined as SNR) was highest in the aortic arch, upper descending thoracic aorta, and upper abdominal aorta. We saw a small reduction in the SNR in the ascending aorta and lower descending thoracic aorta (p < .0001), attributable to cardiac and respiratory motion. Image quality was not affected by slow flow. MR imaging correctly diagnosed pathology in all 30 patients with angiographic or surgical correlation, including eight dissections, three coarctations, and 10 aneurysms. The type of the dissection was correctly determined in all eight patients. Stenoses of major branch vessel origins were detected with a sensitivity of 90% (95% bayesian confidence interval, 99-63%) and a specificity of 96% (95% bayesian confidence interval, 99-89%) in the 19 patients with angiographic correlation. Five vascular anomalies, including an aberrant right subclavian artery, a bovine arch, and three accessory renal arteries, were correctly identified. CONCLUSION: Three-dimensional gadolinium-enhanced MR angiography has the potential to accurately diagnose aortic dissection, coarctation, and aneurysm. It does not require ECG gating or breath-holding and thereby extends the diagnostic utility of MR imaging for the thoracic aorta.

Adolescent↗
PubMed1995

Gadolinium-enhanced magnetic resonance angiography of abdominal aortic aneurysms.

PURPOSE: The objective of this study was to assess the usefulness of gadolinum-enhanced magnetic resonance angiography (MRA) for defining anatomic features relevant to performing aortic surgery for aneurysmal disease. METHODS: Anatomic data defined by MRA, including abdominal aortic aneurysm (AAA) size and character, as well as the status of the celiac, mesenteric, renal, and iliac arteries, were correlated with angiography, ultrasonography, computed tomography, or operative data in 43 patients. Five MRA sequences were obtained in an hour-long examination optimized for aortoiliac, splanchnic, and renal artery imaging at 1.5 T in a body coil. Four of the sequences were performed during or after infusion of gadolinium to improve image quality. RESULTS: MRA correctly defined the maximum aneurysm diameter, as well as its proximal and distal extent in all patients. MRA detected 33 of 35 significant stenoses among 153 splanchnic, renal, or iliac branches examined (sensitivity = 94% and specificity = 98%). MRA did not resolve the degree of aortic branch stenotic disease sufficiently to precisely grade its severity. MRA did not reliably define the status of the inferior mesenteric artery, lumbar arteries or internal iliac arteries. One ruptured AAA and one inflammatory AAA were correctly diagnosed by MRA. No patient had a contrast reaction or contrast-induced renal toxicity related to administration of gadolinium. CONCLUSION: Gadolinium-enhanced MRA of AAA provides appropriate, essential anatomic information for aortic reconstructive surgery in a 1-hour examination devoid of contrast-related renal toxicity or catheterization-related complications attending conventional arteriography.

Adult↗
PubMed1995

A real-time, flat-panel, amorphous silicon, digital x-ray imager.

As part of the development necessary for implementing a fully digital radiology department, the authors have investigated thin-film photodiodes and transistors for use in new photoelectronic imaging devices. One such device, a large-area, flat-panel, amorphous silicon imaging array, has been developed and is currently being tested. The array has a format of 512 x 560 pixels, a pixel-to-pixel pitch of 450 microns, and an area of 230 x 252 mm2, making it the largest self-scanning, solid-state imaging array developed to date. The array is used in conjunction with an overlying x-ray converter. Although specifically designed for megavoltage imaging, the device can produce high-quality, low spatial resolution, diagnostic x-ray images. Qualitative comparisons of array images of anthropomorphic head, chest, and pelvic phantoms and a spatial resolution pattern suggest that much of the information content of the film images at low spatial resolution is present in the corresponding array images. Current trends in the development of large-area, flat-panel imaging technology hold the promise of higher resolution arrays in the near future.

Humans↗
PubMed1995

Positional variation in the Whitaker test.

PURPOSE: To describe positional variation in the outcome of the Whitaker test. MATERIALS AND METHODS: The authors retrospectively reviewed the cases of six patients in whom the pressure gradient during Whitaker testing varied by at least 10 cm of water and changed from normal ( < or = 13 cm of water) to abnormal ( > 13 cm of water) when patients were placed in different positions. RESULTS: Four patients had obstruction only in nonstandard positions. All had intermittent symptoms, and three had ureteral kinks at fluoroscopy. Two patients with ileal conduits had abnormal results in the standard position but normal results at repositioning related to compression of the conduits (seen as conduit distention at fluoroscopy). All six had undergone urinary tract surgery. Gradient differences with positional change ranged from 10 to > 38 cm of water. CONCLUSIONS: Whitaker testing in different positions may help identify intermittent obstructions that might otherwise go undetected or prevent inappropriate diagnosis of obstruction. Intermittent or unexplained symptoms, tortuous ureters, malpositioned kidneys, or previous surgery are indications for provocative positional testing.

Adult↗
PubMed1995

Breath-hold gadolinium-enhanced MR angiography of the abdominal aorta and its major branches.

PURPOSE: To develop and evaluate a sequence for breath-hold three-dimensional gadolinium-enhanced magnetic resonance (MR) angiography of the abdominal aorta. MATERIALS AND METHODS: In 63 patients, the abdominal aorta and its branches were imaged for 29, 43, or 58 seconds with breath holding. A fast spoiled gradient-echo sequence was used at 1.5 T during infusion of 42 mL of a gadolinium chelate. Correlation with conventional angiography was performed in 19 patients. MR image quality (signal-to-"total" noise ratio [S/N*]) with breath holding was compared with that with free breathing (104 patients). RESULTS: With breath-hold gadolinium-enhanced MR angiography, renal, celiac, and superior mesenteric artery occlusive disease was graded appropriately in 15 of 19 patients, and 10 of 11 accessory renal arteries were depicted correctly. Renal artery branches were visualized in 86 of 95 kidneys on breath-hold images compared with only 84 of 236 kidneys with free breathing (P < .001). Distal renal artery S/N* was 3.1 with breath holding and 2.1 with free breathing (P < .001). CONCLUSION: Breath holding statistically significantly improves three-dimensional gadolinium-enhanced MR angiography of the renal, celiac, and superior mesenteric arteries.

Adult↗
PubMed1994

The estimation of occupational effective dose in diagnostic radiology with two dosimeters.

Annual effective dose limits have been proposed by national and international radiation protection committees. Radiation protection agencies must decide upon a method of converting the radiation dose measured from dosimeters to an estimate of effective dose. A proposed method for the estimation of effective dose from the radiation dose to two dosimeters is presented. Correction factors are applied to an over-apron collar dose and an under-apron dose to estimate the effective dose. Correction factors are suggested for two cases, both with and without a thyroid shield. Effective dose may be estimated by the under-apron dose plus 6% of the over-collar dose if a thyroid shield is not worn or plus 2% of the over-collar dose if a thyroid shield is worn. This method provides a reasonable estimate of effective dose that is independent of lead apron thickness and accounts for the use of a thyroid shield.

Fluoroscopy↗
PubMed1993

Interventional radiologists: occupational radiation doses and risks.

Interventional radiologists receive nonuniform occupational radiation doses, with relatively high doses to the head and extremities and low doses to the trunk, which is protected by a lead apron. Twenty-eight interventional radiologists from 17 institutions wore thermoluminescent dosimeters over their collars and under their aprons for a 2-month period. The estimated annual radiation dose was converted to effective dose as suggested by the International Commission on Radiological Protection. Effective dose is used to relate the risk associated with nonuniform dose to that associated with an equivalent uniform whole-body dose. The mean annual effective dose was 3.16 mSv (316 mrem), with a range of 0.37-10.1 mSv. The mean annual effective dose is approximately equal to the mean natural background dose of 3 mSv per year from radon and other natural sources and is only 6% of the National Council on Radiation Protection and Measurements' recommended effective dose equivalent limit of 50 mSv per year. The annual radiation risk of fatal cancer would be less than one per 10,000 for almost the entire career of an interventional radiologist.

Humans↗
PubMed1992

Design and testing of a high-flow autoperfusion catheter: an experimental study.

An autoperfusion catheter is similar to an angioplasty balloon catheter with side holes in the guide-wire lumen proximal to the balloon. When the balloon of the autoperfusion catheter is deployed and inflated in an artery, the guide wire is removed, and the hub of the guide-wire lumen is capped. The catheter then allows passive distal perfusion by using ambient pressure to drive blood into the guide-wire lumen, through the balloon, and out the end hole. This article discusses the requirements and constraints of a high-flow autoperfusion catheter, summarizes attempts to modify standard angioplasty catheters for use as an autoperfusion catheter, and describes the design and testing of a custom autoperfusion catheter capable of delivering approximately 3 mL/sec at physiologic pressures. In a model of canine acute renal artery occlusion lasting 90 minutes, the custom autoperfusion catheter provided marked protection from acute tubular necrosis compared with conventional percutaneous transluminal angioplasty catheters. The authors conclude that the high-flow autoperfusion catheter may be useful as a temporary stent in cases of rupture, dissection, or penetrating wounds involving large arteries.

Angioplasty, Balloon↗
PubMed1992

Occupational radiation exposure to interventional radiologists: a prospective study.

This study investigates the occupational radiation dose to interventional radiologists and the operator-controlled factors that may affect dose. Thirty interventional radiologists wore radiation badges over and under lead aprons for 2 months and answered a questionnaire. The relationships between dose and caseload, case mix, experience, optional fluoroscopy features, lead apron type, and additional lead shielding were evaluated. Mean projected yearly dose (PYD) over lead was 49.1 mSv (1 mSv = 100 mrem) but was 66.6 mSv for persons performing 1,000 or more cases per year (P = .027). Mean PYD under lead was 0.9 mSv but was 1.3 mSv for persons with 0.5-mm lead coverage and 0.4 mSv for those with 1.0-mm lead coverage (P = .002). No other significant correlation was found. Conclusions are that caseload and apron thickness are the primary determinants of total body dose, that over-lead dose is high enough to warrant additional lead shielding for the head and neck, and that a double-thickness apron lowers under-lead dose by two-thirds. The large difference between under-lead and over-lead doses suggests that use of a collar badge alone for monitoring purposes is not predictive of total-body effective dose for this group of radiation workers.

Adult↗