Biomedical subjects
Publications and source records attributed to A F Jacobson.
Hypertension secondary to an activated renin-angiotensin system without renal artery stenosis can be detected by angiotensin-converting enzyme (ACE) inhibitor renography. Two cases of renin-mediated hypertension without major or branch vessel stenosis supplying the kidney with parenchymatous disease were discovered by ACE inhibitor renography.
Secondary analysis of existing data offers many advantages to the nurse researcher. Data from large-scale studies may be reanalyzed and refined by secondary analysts with a fresh perspective, thus enhancing the original study's contribution to scientific knowledge. High-quality data can be obtained for comparatively little expenditure of time and money. The secondary analyst, however, must exercise care in evaluating and analyzing a data set to maximize the internal and external validity of the reanalysis. Because the secondary analyst's lack of involvement in data collection procedures may decrease insight into the original study's limitations, vigilant skepticism should accompany all phases of the research process in secondary data analysis, just as it should in all other research. Miller (1982) advised, "Begin by assuming the worst and seek out the same kinds of information about sample selection procedures, sample size, response rates, field procedures, and coding conventions that you would insist on if you were collecting your own data" (p. 722). By systematically evaluating potential data sets according to rigorous predetermined criteria, the nurse researcher can minimize the possible pitfalls inherent in secondary analysis. On the other hand, investigators who use secondary sources appropriately can make significant contributions to nursing science at less cost than that engendered by traditional research methods.
With hepatobiliary scintigraphy and sonography, we prospectively studied the occurrence of new hepatobiliary abnormalities in 18 patients before, and from 1 to 103 days after, bone marrow transplantation (BMT). Prior to BMT, all patients had normal hepatic uptake and visualization of the gallbladder by 60 min on scintigraphy, and no sludge, stones, or other abnormalities on sonography. After BMT, 16 patients (89%) developed new scintigraphic and/or sonographic hepatobiliary abnormalities. Fifteen patients had impaired liver uptake of mebrofenin, while 11 developed gallbladder uptake of mebrofenin, while 11 developed gallbladder sludge and/or stones, and 10 had gallbladder nonvisualization at 60 min. Nevertheless, no patient developed clinical or laboratory evidence of acute cholecystitis. New hepatobiliary abnormalities are more common during the first months post-BMT than clinically suspected, probably reflecting the combined effects of hepatotoxic chemoradiation therapy, graft-versus-host disease, and prolonged administration of parenteral alimentation. Evidence of acute cholecystitis is generally not found.
A 67-yr-old male status post right pneumonectomy for non-small cell lung cancer who later developed an open right bronchial stump underwent a ventilation-perfusion lung scan because of episodes of recurrent dyspnea suspected to be due to pulmonary embolism. Xenon-133 ventilation images showed both rapid entry into and later washout of activity from the air-filled portion of the right thoracic cavity. A wide-open bronchial stump, documented both at bronchoscopy and later autopsy, allowed the xenon gas to freely wash out from the thoracic cavity, resulting in a different imaging pattern than for a typical bronchopleural fistula, which is usually characterized by prolonged trapping of radioactive gas within the pleural space.
The skeletal distribution of red marrow-containing sites with a decreased uptake of indium-111-labelled leucocytes was examined as part of a retrospective review of 128 consecutive scans in 113 patients. The prevalence of photopenic defects was determined for sites of suspected osteomyelitis and for other skeletal locations included as part of limited or total-body surveys. Of 52 sites suspected of osteomyelitis based upon radiological and clinical data, 21 (40%) demonstrated a decreased leucocyte uptake. The prevalence of photopenia ranged from 79% (11/14) in the spine and 63% (5/8) in the pelvis to 25% (4/16) in the proximal femur and 0% elsewhere in the extremities (0/9) and in the skull (0/3). Fourteen of these 21 defects (67%) were due to active (n = 9) or healed (n = 5) osteomyelitis/discitis. All sites of active osteomyelitis showed destructive changes on correlative radiographs and were associated with infectious processes of more than 1 months duration. Thirty-seven photopenic defects were observed as incidental findings. The prevalence of photopenia as an incidental finding ranged from 0% in the skull, neck and chest to 3%-4% in the thoracolumbar spine and pelvis and 14% in the femoral heads, the latter reflecting primarily bilateral loss of femoral head marrow. No incidentally found photopenic defect reflected active osteomyelitis. At sites in the spine and pelvis with radiologic evidence of bone destruction suggestive of osteomyelitis, an absence of normal red marrow uptake of labelled leucocytes often reflects a variant presentation for active chronic infection. In contrast, incidental photopenia is uncommon at all skeletal sites except the femoral heads, and should not raise concern over unsuspected active osteomyelitis.
Twenty-one bone marrow transplantation (BMT) patients were studied prospectively to determine the prevalence of sonographic hepatobiliary abnormalities and to determine if these abnormalities were associated with hepatic venocclusive disease (VOD). Baseline US was performed in all patients prior to chemoradiation therapy, with follow-up ultrasound (US) examinations at the time of BMT and 14 days and 28 days after BMT. Sonograms were reviewed for the presence of ascites, gallbladder wall thickening, hepatosplenomegaly, hepatofugal flow, hepatic vein compression, increased periportal echogenicity, and increased hepatic echotexture. The baseline scans showed 13 of 21 patients (62%) with abnormalities prior to BMT. Within 2 weeks after BMT, serial US showed interval development of hepatomegaly in five patients (three with VOD and two without), gallbladder wall thickening in one (with VOD), hepatic vein compression in two (both with VOD), hepatofugal flow in one (without VOD), and ascites in one (with VOD). US scans obtained 4 weeks after BMT in 15 of the 21 patients showed even fewer new abnormalities. No sonographic finding was strongly associated with VOD.
Changes in regional ejection fraction (rEF) of the interventricular septum following coronary artery bypass graft (CABG) surgery were examined using first-pass radionuclide ventriculography (RNVG) in patients without objective evidence of postoperative myocardial infarction (MI). One hundred and one patients had pre- (mean 6.3 days) and early postoperative (mean 8.7 days) RNVGs, and 60 of these patients had follow-up studies at 14-39 months (mean 27 months) postsurgery. Early post-CABG, mean rEF in the proximal septum was unchanged from the preoperative value (35.3%), with almost equal numbers of patients showing increased (n = 36), unchanged (n = 33) or decreased (n = 32) rEFs. In the distal septum, mean rEF increased from 47.1 to 50.7%, with more than twice as many patients having increased (n = 44) as decreased (n = 20) rEF. At late follow-up, proximal septum rEF in individual patients tended to revert to the presurgery baseline, with 72% (13/18) of regions with early decrease improved and 61% (14/23) of those with early improvement decreased. In the distal septum, rEF was less than early post-CABG in 76% (19/25) of patients with early improvement, while being improved in 27% (3/11) of those with early decrease in rEF. In the absence of MI, changes in rEF in the proximal septum early post-CABG tend to resolve over time. While global changes in cardiac systolic motion are the probable cause of many new post-CABG septal abnormalities, persistent septal dysfunction probably reflects effects of permanent damage as a result of the operative procedure.
The effects of region of interest (ROI) selection and correction for Compton-scattered photons using a buildup factor on radionuclide left ventricular volumes calculated by the Links method were compared in 19 humans with contrast ventriculography and in phantoms. Three different methods of ROI selection were compared: a manual ROI, a second derivative ROI and a 50% count-threshold ROI. In phantoms without Compton scatter correction, volumes were overestimated by 30% (manual ROI), 20% (derivative ROI) and 1% (count threshold ROI). In subjects, results without Compton scatter correction were similar with overestimates of 50% (manual ROI) and 20% (derivative ROI) and an underestimate by 3% (count threshold method). Correction for Compton-scattered photons with the use of a phantom-derived buildup factor resulted in improved accuracy for the manual ROI (+15%) and the derivative ROI (0%). A 50% count threshold ROI following interpolative background subtraction allows the accurate calculation of cardiac volumes without the need for scatter correction, while a second derivative ROI method requires a correction for Compton scatter with the use of a buildup factor.
The prognostic significance of the results of late imaging in patients with early negative 99mTc-labeled red blood cell (RBC) gastrointestinal (GI) bleeding studies was examined in a retrospective review of studies performed on 48 patients. Twenty-two studies showed intraluminal accumulation of labeled RBCs only on late images acquired from 3-24 hr following RBC injection. Patients with late positive studies had larger transfusion requirements than those with negative late images (mean total units transfused: 7.3 versus 3.5 (p less than 0.05); mean units transfused following scan commencement: 4.5 versus 2.0 (p less than 0.005)). Patients with late positive studies more frequently required angiography (3/22 versus 0/26) and surgery (5/22 versus 2/26). Sites of bleeding were more commonly identified in the stomach or small bowel in patients with late positive studies, while colon bleeding sources were more commonly found in those with late negative studies. The location of intraluminal blood on late images did not reliably discriminate upper from lower tract hemorrhage. In patients with early negative GI bleeding studies, results of later imaging provide objective evidence of the presence or absence of continued intermittent hemorrhage, and suggest both the region of bowel responsible and the relative risk for requiring further invasive procedures.
Differential renal blood flow and parenchymal mass were compared in 50 pairs of scintigraphic studies performed on 44 patients. Background corrected total kidney counts were determined between 1 to 2 minutes following injection of I-123 or I-131 orthoiodohippurate (OIH), and at 1 to 2.5 hours after injection of Tc-99m glucoheptonate (GHA). The OIH and GHA differentials agreed within 5% in 36 studies (72%). When the OIH differentials were symmetric (45% to 55% in each kidney), agreement with the GHA results was complete (17 out of 17). By comparison, 42% (14 out of 33) of studies with asymmetric OIH differentials had a greater than 5% disparity from the GHA split function. Serum creatinine was elevated at the time of 9 out of 14 studies (64%) with OIH/GHA disagreement and 18 out of 36 studies (50%) with OIH/GHA agreement. Of the 14 studies with disparate OIH/GHA differentials, the GHA differential was more symmetric in 10 (71%). When different scinitigraphic measures of differential renal flow and parenchymal mass disagree, this is most likely due to the effects of asymmetric renal impairment rather than to those of global renal dysfunction.
Left ventricular internal cavity dimensions (LVID) were determined from radionuclide ventriculographic (RNVG) studies using a spatial calibration algorithm and visually defined edges and were compared to the results from two-dimensional echocardiography. Routine clinical cases were used with no additional views and no attenuation or scatter correction. In an initial set of 21 patients, mean RNVG LVID was 5.7 +/- 1.1 (mean +/- 1 S.D.) cm compared to 5.3 +/- 1.0 cm for echocardiography. In a prospective validation of the regression equations derived in the initial set of patients, regression-corrected RNVG results were within 5 mm of those determined echocardiographically in 18/22 patients and the mean LVID values were the same. Quantitative estimation of LVID by RNVG is simple, rapid, and reproducible. Systematic overestimation of dimensions compared to echocardiography can be corrected using a regression equation.
A Tc-99m glucoheptonate renal flow study performed in a patient with chronic renal insufficiency and worsening congestive heart failure demonstrated evidence of massive tricuspid regurgitation, with activity appearing in a markedly dilated inferior vena cava within 4 seconds of the tracer bolus entering the right ventricle. Autopsy subsequently confirmed the scintigraphic findings, demonstrating an incompetent tricuspid valve secondary to immobilization of the posterior leaflet as a result of adhesions from a longstanding right ventricular pacemaker wire.
In a series of 62 male patients undergoing exercise TI-201 SPECT myocardial scintigraphy, planar 45 degrees LAO images were acquired before (2-5 minutes postinjection, P1) and after (35 minutes postinjection, P2) the initial SPECT study in order to identify those patients with redistribution during the first 30 minutes after exercise. Consensus interpretation by four readers identified early redistribution (between P1 and P2) in 11 patients (18%), rated major (change of greater than 1.5 scoring unit) in five and minor (change of 1-1.5 scoring unit) in six. Only one patient (2%) showed major early redistribution that could not be appreciated on corresponding SPECT images. In this preliminary investigation, early thallium redistribution sufficient to affect identification of significant exercise-induced ischemia on SPECT imaging was infrequent and of limited clinical importance.
To evaluate the usefulness of 111In-leukocyte scintigraphy for identifying osteomyelitis in the presence of soft-tissue infection, we prospectively studied 45 bone sites adjacent to soft-tissue infection in patients with abnormal findings on radiographs and 99mTc bone scans that were suggestive of osteomyelitis. 111In-leukocyte scans were analyzed in terms of the intensity of abnormal uptake and its location relative to bone. The diagnosis of osteomyelitis was established from results of percutaneous bone biopsy culture (n = 35), histologic examination of surgical specimens (n = 8), and clinical follow-up (n = 2). Osteomyelitis was present at 22 sites, including 16 of 18 sites with increased leukocyte uptake in bone, resulting in a sensitivity of 73%, specificity of 91%, and positive predictive value of 89% for this finding. Osteomyelitis was present at four of 17 sites with predominantly soft-tissue localization of leukocyte activity in the region of bone, none of seven sites with normal leukocyte scans, and two of three sites with diminished leukocyte uptake in bone. Although not helpful in distinguishing infectious from noninfectious bone abnormalities, 3- and especially 24-hr bone scans viewed in conjunction with leukocyte studies provided important correlation to aid in estimating the location of focal abnormal leukocyte uptake. The finding of soft-tissue infection with increased uptake of labeled leukocytes that extends to involve adjacent bone strongly suggests concurrent osteomyelitis. When the presence of abnormal leukocyte uptake in bone is uncertain, additional imaging and possibly biopsy may be required to establish or exclude the diagnosis of osteomyelitis.
The prognostic significance of changes in resting left ventricular ejection fraction was examined in 102 patients who underwent successful coronary artery bypass grafting. Between preoperative and early postoperative radionuclide ventriculography, mean resting left ventricular ejection fraction improved from 47.2% to 53.9% (p less than 0.01). Left ventricular ejection fraction increased by 5% or greater in 64 patients (63%), remained unchanged (within 4%) in 31 (30%), and decreased by at least 5% in 7 (7%). During 14 to 39 months (mean 27 months) of clinical follow-up, patients with normal preoperative left ventricular ejection fraction had a lower prevalence of recurrent angina, congestive heart failure, and mortality resulting from cardiovascular disease. Cardiovascular morbidity and mortality occurred with equal frequency for patients who did and did not show early postoperative improvement in left ventricular ejection fraction (36% versus 39%). Among 69 patients who had a third radionuclide ventriculography at late follow-up, left ventricular ejection fraction was less than the early postoperative value in 69% and less than the preoperative result in 36%. Patients with early postoperative improvement in left ventricular ejection fraction were more likely to retain resting left ventricular contractile function, at least at the preoperative level (71% versus 46%).
Two patients studied with technetium-99m-labeled red blood cells (RBCs) for gastrointestinal bleeding had positive findings only on 24-hr delayed images, at which time the site of bleeding could not be ascertained. In each instance, when additional delayed images suggested that active bleeding was occurring, a second aliquot of RBCs was labeled and injected. Sites of active hemorrhage were identified following further imaging in both patients. When delayed GI bleeding images are positive, further views should be obtained to ascertain if the pattern of intraluminal activity changes. If renewed active hemorrhage is suspected, reinjection with a second dose of labeled RBCs may identify the bleeding site.
A patient with retroperitoneal fibrosis and right peritracheal and hilar lymphadenopathy was studied using gallium-67-citrate. No abnormal uptake was seen in the regions of retroperitoneal fibrosis, while there was avid uptake in chest lesions later shown to represent small cell lung carcinoma. Retroperitoneal fibrosis which does not show gallium uptake is most likely mature, with few inflammatory elements. In patients with multiple retroperitoneal and/or mediastinal masses, gallium imaging may be useful in identifying the most active sites of disease for possible biopsy and for subsequent monitoring of response to therapy.
In summary, PET and SPECT myocardial imaging both have important roles to play in evaluation of patients with suspected coronary artery and myocardial disease. Tl-201 remains the predominant tracer in clinical use, and even when technetium-labeled myocardial perfusion agents are widely available, Tl-201 will undoubtedly continue to be used for the next few years. PET imaging remains the mode of choice for research evaluation of coronary artery and cardiovascular disease, as well as the preferred method for investigating difficult cases which are equivocal on SPECT perfusion imaging. Wider availability of both PET cameras and central radiopharmacies providing cyclotron produced PET radiopharmaceuticals should provide the impetus for expansion of PET myocardial imaging applications. Even at the price of $1,000-1,500 per scan, study results which permit better informed decisions regarding performance of $5,000-50,000 interventional procedures such as PTCA and CABG make the economics of PET justified. Even with the progress of competing modalities such as echocardiography, MR flow imaging, and MR spectroscopy with tissue characterization, nuclear medicine methods for myocardial evaluation should remain of major importance for the foreseeable future.