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Biomedical subjects

A J Fischman

Publications and source records attributed to A J Fischman.

At least 19 recordsLinked to original sources
PubMed2006

Single photon emission computed tomography perfusion differences in mild cognitive impairment.

OBJECTIVE: To relate cerebral perfusion abnormalities to subsequent changes in clinical status among patients with mild cognitive impairment (MCI). METHODS: Perfusion single photon emission computed tomography (SPECT) images were acquired in 105 elderly patients without dementia with MCI, using 99mTc-HMPAO. Clinical outcome after a 5-year follow-up period was heterogeneous. RESULTS: Baseline SPECT data differed in those patients with MCI who were later diagnosed with Alzheimer's disease (the converter group) from those patients with MCI who experienced clinically evident decline but did not progress to a diagnosis of Alzheimer's disease within the follow-up period (the decliner group), from patients with MCI who had no clinical evidence of progression (the stable group), and from a group of 19 normal subjects (the control group). The most consistent decreases in relative perfusion in converters compared with the normal, stable and decliner groups were observed in the caudal anterior cingulate, and in the posterior cingulate. In addition, converters showed increased relative perfusion in the rostral anterior cingulate in comparison to the stable and decliner groups. A group of patients with Alzheimer's disease were also included for purposes of comparison. The group of patients with Alzheimer's disease at baseline differed from each of the other groups, with temporoparietal regions showing the most significant reductions in perfusion. CONCLUSIONS: These results suggest that clinical heterogeneity in MCI is reflected in SPECT perfusion differences, and that the pattern of perfusion abnormalities evolves with increasing clinical severity.

Aged↗
PubMed2006

Detection of inflamed atherosclerotic lesions with diadenosine-5',5'''-P1,P4-tetraphosphate (Ap4A) and positron-emission tomography.

Diadenosine-5',5'''-P(1),P(4)-tetraphosphate (Ap(4)A) and its analog P(2),P(3)-monochloromethylene diadenosine-5',5'''-P(1),P(4)-tetraphosphate (AppCHClppA) are competitive inhibitors of adenosine diphosphate-induced platelet aggregation, which plays a central role in arterial thrombosis and plaque formation. In this study, we evaluate the imaging capabilities of positron-emission tomography (PET) with P(2),P(3)-[(18)F]monofluoromethylene diadenosine-5',5'''-P(1),P(4)-tetraphosphate ([(18)F]AppCHFppA) to detect atherosclerotic lesions in male New Zealand White rabbits. Three to six months after balloon injury to the aorta, the rabbits were injected with [(18)F]AppCHFppA, and microPET imaging showed rapid accumulation of this radiopharmaceutical in the atherosclerotic abdominal aorta, with lesions clearly visible 30 min after injection. Computed tomographic images were coregistered with PET images to improve delineation of aortoiliac tracer activity. Plaque macrophage density, quantified by immunostaining with RAM11 against rabbit macrophages, correlated with PET measurements of [(18)F]AppCHFppA uptake (r = 0.87, P < 0.0001), whereas smooth-muscle cell density, quantified by immunostaining with 1A4 against smooth muscle actin, did not. Biodistribution studies of [(18)F]AppCHFppA in normal rats indicated typical adenosine dinucleotide behavior with insignificant myocardial uptake and fast kidney clearance. The accumulation of [(18)F]AppCHFppA in macrophage-rich atherosclerotic plaques can be quantified noninvasively with PET. Hence, [(18)F]AppCHFppA holds promise for the noninvasive characterization of vascular inflammation.

Animals↗
PubMed2005

Myelofibrosis on F-18 FDG PET Imaging.

A 60-year-old male was referred for a positron emission tomography (PET) scan using F-18 fluoro-2-deoxyglucose (F-18 FDG) for evaluation of a right lung opacity identified on a computed tomography (CT) scan. The patient also had a history of idiopathic myelofibrosis. The PET scan revealed markedly increased uptake throughout the spleen and liver, which were massively enlarged. There was also significantly increased uptake diffusely throughout the bone marrow. These findings are a reflection of the patient's myelofibrosis.

Fluorodeoxyglucose F18↗
PubMed2001

Cerebral metabolic correlates as potential predictors of response to anterior cingulotomy for obsessive compulsive disorder.

BACKGROUND: As interventions for severe, treatment-refractory obsessive compulsive disorder (OCD), neurosurgical procedures are associated with only modest efficacy. The purpose of this study was to identify cerebral metabolic correlates as potential predictors of treatment response to anterior cingulotomy for OCD. METHODS: Clinical data were analyzed in the context of a retrospective design. Subjects were 11 patients who underwent stereotactic anterior cingulotomy for OCD. Symptom severity was measured using the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) before and at approximately 6 months postoperative. Preoperative F-18-fluorodeoxyglucose-positron emission tomography (FDG-PET) data were available. Statistical parametric mapping methods were used to identify loci of significant correlation between preoperative regional cerebral metabolism and postoperative reduction in Y-BOCS scores. RESULTS: One locus within right posterior cingulate cortex was identified, where preoperative metabolism was significantly correlated with improvement in OCD symptom severity following cingulotomy. Specifically, higher preoperative rates of metabolism at that locus were associated with better postoperative outcome. CONCLUSIONS: A possible predictor of treatment response was identified for patients with OCD undergoing anterior cingulotomy. Further research, utilizing a prospective design, is indicated to determine the validity and reliability of this finding. If confirmed, an index for noninvasively predicting response to cingulotomy for OCD would be of great value.

Adult↗
PubMed2001

[(11)C, (127)I] Altropane: a highly selective ligand for PET imaging of dopamine transporter sites.

The E isomer of (123)I-2beta-carbomethoxy-3beta-(4-fluorophenyl)-N-(1-iodoprop-1-en-3-yl)nortropane (Altropane(R)) shows high affinity (IC(50) = 6.62 +/- 0.78 nmol) and selectivity (DA/5-HT = 25) for DAT sites in the striatum. Recently, dynamic SPECT studies in healthy volunteers and patients with Parkinson disease demonstrated that the kinetics of striatal accumulation followed a pattern that is characteristic of a reversible tracer with maximal accumulation within 30 min after injection. These findings suggested that radiolabeling Altropane with [(11)C] might provide an equivalent and complementary tracer for PET studies. [(127)I] Altropane was treated with HCl to hydrolyze the methyl ester bond and yield a precursor for [(11)C] labeling. Introduction of an [(11)C] methyl ester group was achieved by treatment with [(11)C] CH(3)I followed by HPLC purification. Five healthy rhesus monkeys were injected with approximately 10 mCi of [(127)I,(11)C] Altropane and dynamic PET images were acquired over 90 min. Arterial blood samples were collected in parallel with imaging and metabolite analysis was performed by HPLC. The PET and metabolite corrected arterial blood data were to calculate k(3)/k(4) by two methods: 1) nonlinear least-squares fitting, and 2) a linear graphical method for reversible ligands. The synthetic procedure yielded high specific activity tracer, >1,000 mCi/micro mole, with radiochemical purity >95%. Synthesis time was approximately 30 min. The PET images revealed excellent striatal definition, with clear separation of caudate nucleus and putamen and minimal accumulation in brain regions with high 5HT transporter density. Metabolite analysis demonstrated that at 60 min after injection, approximately 80% of circulating tracer was intact [(127)I,(11)C] Altropane and the remainder was converted to polar metabolites. Values for k(3)/k(4) calculated by two analysis methods were remarkably similar: Method 1, 3.48 +/- 0.41; Method 2, 3.77 +/- 0.45 (mean +/- SEM, t = 2.31, df = 8, P = 0.64). These results establish that Altropane has the important characteristics of: 1) rapid and specific striatal binding; 2) high selectivity for DA vs. 5-HT transporter sites; 3) reversible binding kinetics; 4) potential for multiple injection studies; 5) high efficiency labeling with either [(11)C] or [(123)I]; 6) applicability for both PET and SPECT. These properties make Altropane an important DAT ligand for both research and clinical applications.

Animals↗
PubMed2001

Neural substrates of anorexia nervosa: a behavioral challenge study with positron emission tomography.

OBJECTIVE: To delineate functional brain abnormalities associated with anorexia nervosa (AN). STUDY DESIGN: Positron emission tomographic measurements of regional cerebral blood flow (rCBF) were performed on 8 female patients with AN and 8 healthy female control subjects during exposure to 3 types of stimuli: high-calorie foods, low-calorie foods, and non-food items. Heart rate and internal state analog scale scores were also obtained. Stereotactic transformation and statistical parametric mapping techniques were used to analyze imaging data. RESULTS: During the high-calorie condition, control subjects reported a significant desire to eat, whereas subjects with AN reported elevated anxiety and exhibited increases in heart rate. Patients with AN had elevated bilateral medial temporal lobe rCBF compared with control subjects. Planned comparisons for group-by-condition interactions demonstrated greater activation within left occipital cortex and right temporo-occipital cortex for the high-calorie versus low-calorie contrast in patients with AN compared with control subjects. CONCLUSIONS: Our finding of elevated rCBF within bilateral medial temporal lobes is similar to published results in patients with psychotic disorders and may be related to the body image distortion common to AN. The high-calorie food phobia exhibited by patients with AN appears to be associated with exaggerated responses in visual association cortex, as has been previously observed in studies of specific phobias.

Adult↗
PubMed2001

Prefrontal regions supporting spontaneous and directed application of verbal learning strategies: evidence from PET.

The prefrontal cortex has been implicated in strategic memory processes, including the ability to use semantic organizational strategies to facilitate episodic learning. An important feature of these strategies is the way they are applied in novel or ambiguous situations-failure to initiate effective strategies spontaneously in unstructured settings is a central cognitive deficit in patients with frontal lobe disorders. The current study examined strategic memory with PET and a verbal encoding paradigm that manipulated semantic organization in three encoding conditions: spontaneous, directed and unrelated. During the spontaneous condition, subjects heard 24 words that were related in four categories but presented in mixed order, and they were not informed of this structure beforehand. Any semantic reorganization was, therefore, initiated spontaneously by the subject. In the directed condition, subjects were given a different list of 24 related words and explicitly instructed to notice relationships and mentally group related words together to improve memory. The unrelated list consisted of 24 unrelated words. Behavioural measures included semantic clustering, which assessed active regrouping of words into semantic categories during free recall. In graded PET contrasts (directed > spontaneous > unrelated), two distinct activations were found in left inferior prefrontal cortex (inferior frontal gyrus) and left dorsolateral prefrontal cortex (middle frontal gyrus), corresponding to levels of semantic clustering observed in the behavioural data. Additional covariate analyses in the first spontaneous condition indicated that blood flow in orbitofrontal cortex (OFC) was strongly correlated with semantic clustering scores during immediate free recall. Thus, blood flow in OFC during encoding predicted which subjects would spontaneously initiate effective strategies during free recall. Our findings indicate that OFC performs an important, and previously unappreciated, role in strategic memory by supporting the early mobilization of effective behavioural strategies in novel or ambiguous situations. Once initiated, lateral regions of left prefrontal cortex control verbal semantic organization.

Acoustic Stimulation↗
PubMed2001

Phase I and pharmacokinetic study of ecteinascidin 743 administered as a 72-hour continuous intravenous infusion in patients with solid malignancies.

Ecteinascidin 743 (ET-743) is a cytotoxic tetrahydroisoquinoline alkaloid that covalently binds to DNA in the minor groove. The in vitro chemosensitivity of cancer cells to ET-743 is markedly enhanced by prolonging the duration of exposure to the drug. A Phase I study of ET-743 given as a 72-h continuous i.v. infusion every 21 days was performed. Characteristics of the 21 adult patients with refractory solid tumors enrolled in the study were as follows: (a) 12 men; (b) 9 women; (c) median age, 59 years; (d) Eastern Cooperative Oncology Group performance status < or = 1, 20 patients; and (e) two prior regimens of chemotherapy, 7 patients. Dose limiting toxicity (DLT) was defined by typical criteria, except that grade 3 transaminitis did not constitute a DLT. There were no DLTs in the six patients evaluated at the first two dose levels of 600 and 900 microg/m2. Reversible grade 4 transaminitis occurred in two of nine patients after treatment with the first cycle of therapy at the third dose level of 1200 microg/m2. Another patient experienced grade 4 rhabdomyolysis, renal failure requiring hemodialysis, grade 4 neutropenia, and grade 3 thrombocytopenia during the second cycle of therapy with this dose. The maximum tolerated dose was 1200 microg/m2, and an additional six patients were enrolled at an intermediate dose level of 1050 microg/m2. This well-tolerated dose was established as the recommended Phase II dose. The disposition of ET-743 was distinctly biexponential, and a departure from linear pharmacokinetic behavior was evident at the 1200-microg/m2 dose level. Pharmacokinetic parameters determined at 1050 microg/m2 were (mean +/- SD): maximum plasma concentration, 318 +/- 147 pg/ml; initial disposition phase half-life, 9.0 +/- 10.3 min; terminal phase half-life, 69.0 +/- 56.7 h; and total plasma clearance, 28.4 +/- 22.5 liters/h/m2. Prolonged systemic exposure to concentrations of the agent that are cytotoxic in vitro were achieved. Toxicity of the drug is clearly schedule-dependent, because increasing the duration of infusion from 3 or 24 h to 72 h results in decreased myelosuppression and comparable hepatotoxicity. Although there were no objective responses to therapy, clear evidence of antitumor activity was observed in a patient with epithelioid mesothelioma, as confirmed by positron emission tomography studies. A Phase II trial to assess the efficacy of ET-743 against this highly refractory neoplasm has been initiated on the basis of this observation. The therapeutically optimal administration schedule remains to be established, inasmuch as there have been indications of activity against a variety of tumors during Phase I studies when the drug was infused over times ranging from 1 to 72 h. Characterizing the pharmacokinetics of ET-743 during the course of Phase II trials and Phase I combination studies is recommended to assure that this promising new anticancer drug can be used with an acceptable margin of safety.

Adult↗
PubMed2000

Abnormalities in the thalamus and prefrontal cortex during episodic object recognition in schizophrenia.

BACKGROUND: Many patients with schizophrenia demonstrate memory deficits. We studied patterns of brain activity during episodic recognition of new and previously seen three-dimensional objects. METHODS: We used (15)O positron emission tomography to study regional cerebral blood flow in eight normal subjects and nine patients with schizophrenia during a visual object recognition task. RESULTS: In comparison with control subjects, patients with schizophrenia showed less regional cerebral blood flow increases in the pulvinar region of the right thalamus and the right prefrontal cortex during the recognition of new objects and significantly greater left prefrontal cortex regional cerebral blood flow increases during the recognition of previously seen objects. Patients with schizophrenia exhibited alarm rates to new objects similar to those of control subjects, but significantly lower recognition rates for previously seen objects. CONCLUSIONS: Schizophrenia is associated with attenuated right thalamic and right prefrontal activation during the recognition of novel visual stimuli and with increased left prefrontal cortical activation during impaired episodic recognition of previously seen visual stimuli. This study provides further evidence for abnormal thalamic and prefrontal cortex function in schizophrenia.

Adult↗
PubMed2000

Activation of anterior paralimbic structures during guilt-related script-driven imagery.

BACKGROUND: Several recent neuroimaging studies have examined the neuroanatomical correlates of normal emotional states, such as happiness, sadness, fear, anger, anxiety, and disgust; however, no previous study has examined the emotional state of guilt. METHODS: In the current study, we used positron emission tomography and the script-driven imagery paradigm to study regional cerebral blood flow (rCBF) during the transient emotional experience of guilt in eight healthy male participants. In the Guilt condition, participants recalled and imagined participating in a personal event involving the most guilt they had ever experienced. In the Neutral condition, participants recalled and imagined participating in an emotionally neutral personal event. RESULTS: In the Guilt versus Neutral comparison, rCBF increases occurred in anterior paralimbic regions of the brain: bilateral anterior temporal poles, anterior cingulate gyrus, and left anterior insular cortex/inferior frontal gyrus. CONCLUSIONS: These results, along with those of previous studies, are consistent with the notion that anterior paralimbic regions of the brain mediate negative emotional states in healthy individuals.

Adult↗
PubMed2000

Transplantation of embryonic porcine mesencephalic tissue in patients with PD.

OBJECTIVE: To assess the safety and the effect on standardized clinical rating measures of transplanted embryonic porcine ventral mesencephalic (VM) tissue in advanced PD. METHODS: Twelve patients with idiopathic PD underwent unilateral implantation of embryonic porcine VM tissue; six received cyclosporine immunosuppression and six received tissue treated with a monoclonal antibody directed against major histocompatibility complex class I. Patients were followed for 12 months and assessed by clinical examination, MRI, and 18F-levodopa PET. Porcine endogenous retrovirus testing was conducted by PCR-based method on peripheral blood mononuclear cells. RESULTS: Cell implantation occurred without serious adverse events in all patients. Cultures were negative for bacterial and unknown viral contamination. No porcine endogenous retrovirus DNA sequences were found. MRI demonstrated cannula tracts within the putamen and caudate, with minimal or no edema and no mass effect at the transplant sites. In the medication-off state, total Unified Parkinson's Disease Rating Scale scores improved 19% (p = 0.01). Three patients improved over 30%. There were two patients with improved gait. 18F-levodopa PET failed to show changes on the transplanted side. CONCLUSIONS: Unilateral transplantation of porcine embryonic VM cells into PD patients was well tolerated with no evidence of transmission of porcine endogenous retrovirus. Changes in standardized clinical PD rating measures were variable, similar to the results of the first trials of unilateral human embryonic allografts that transplanted small amounts of tissue.

Aged↗
PubMed2000

Novel 3-aminomethyl- and 4-aminopiperidine analogues of 1-[2-(diphenylmethoxy)ethyl]-4-(3-phenylpropyl)piperazines: synthesis and evaluation as dopamine transporter ligands.

We have undertaken a program to develop cocaine antagonists based on the premise that such compounds should block cocaine binding but permit reuptake of dopamine at the dopamine transporter (DAT). To evaluate the structural features of potential cocaine antagonists, 3-aminomethylpiperidine and 4-aminopiperidine moieties were incorporated at the central bridge region (piperazine ring) of GBR 12935. The compounds were assayed as inhibitors of [(125)I]RTI-55 binding at the DAT and monoamine transport. The results indicated that most of the new compounds preferentially inhibited norepinephrine reuptake by its transporter (NET) but in some cases retained binding selectivity for the DAT. In general, the binding selectivity and potency of [(3)H]NE reuptake inhibition were very sensitive to modifications of the central bridge diamine moiety (position of two basic nitrogen atoms). Compound 6 exhibited the highest ratio (14-fold) of DA reuptake inhibition to RTI-55 binding inhibition at the DAT; however, in an in vitro assay of cocaine antagonism, this compound failed to reduce inhibition of [(3)H]DA uptake by cocaine. These results demonstrated that separation of biological activities into the binding and reuptake inhibition can be achieved by alterations in the internal diamine component of GBR 12935, but additional modifications are necessary before these agents constitute lead compounds for development as cocaine antagonists.

Carrier Proteins↗
PubMed2000

Neuroanatomy of human appetitive function: A positron emission tomography investigation.

OBJECTIVE: The mediating neuroanatomy of human appetitive function is poorly understood. A state induction paradigm was employed, in conjunction with positron emission tomography, to test the hypothesis that limbic/paralimbic regions respond to the desirability of food stimuli. METHODS: Eight normal subjects were studied during each of three conditions, involving visual exposure to high-caloric food, low-caloric food, and nonfood stimuli. Subjective indices of hunger were measured via analog scales. RESULTS: Planned contrasts demonstrated significant increases in desire to eat and decreases in left temporoinsular cortical blood flow during the high-caloric versus control conditions. DISCUSSION: Results implicate the temporo-insular cortex in normal appetitive function, suggesting that activity within this region is associated with the desirability or valence of food stimuli, prior to ingestion. These data will provide a broad foundation for future studies of patients with eating disorders.

Adult↗
PubMed2000

Evidence of reduced resting blood flow in viable myocardial regions with chronic asynergy.

OBJECTIVES: We tested the hypothesis in patients (n = 24) with ischemic heart disease that chronic contractile dysfunction occurs in myocardial regions with true reduction in rest blood flow. BACKGROUND: Whether viable myocardial regions with chronic contractile dysfunction have true reduction in rest myocardial blood flow is controversial. METHODS: Positron emission tomography (PET) 13N-ammonia was used to measure myocardial blood flow in combination with 18F-fluorodeoxyglucose (18FDG) to assess myocardial viability. Viability also was assessed by dobutamine echo and recovery of function after coronary artery bypass grafting (CABG). Segments (n = 252) were selected based on PET measured reduced resting blood flow and rest asynergy on echo. RESULTS: Regional myocardial viability was present in 20 of 23 patients by PET, 13 of 23 by dobutamine echo and 10 of 11 by postrevascularization criteria. Rest blood flow in normal regions was 1.14+/-0.52 ml/min/g and by definition exceeded (p < 0.005) that in both viable (0.48+/-0.15; n = 8 patients) and nonviable (0.45+/-0.14; n = 8 patients) regions (post-CABG criteria), which did not differ. Correction of rest myocardial blood flow in viable asynergic segments, only, for fibrosis and incomplete tracer recovery raised the level to 0.67+/-0.21 (p < 0.005 vs. normal). Finally, evidence of both stunning (rest asynergy with normal flow) and hibernation was present in 15 of 23 (65%) patients. CONCLUSIONS: Reduced rest blood flow in viable myocardial regions with chronic asynergy is common and cannot be accounted for by partial volume effect. Thus, hypotheses concerning physiologic mechanisms underlying chronic contractile dysfunction should consider the role played by chronic reduction of basal myocardial blood flow.

Adult↗
PubMed2000

Regional pharmacokinetics of orally administered PET tracers.

Positron emission tomography (PET) is currently the most useful imaging technique for noninvasive measurement of drug pharmacokinetics regionally in a variety of tissues. Over the past decade, PET measurements have provided many critical insights about the tissue distribution of several classes of drugs; neuroleptics, antimicrobials, antineoplastics, etc. PET measurements can be performed after any route of drug administration, intravenous, inhalation or oral, however, intravenously administered drugs have been the most extensively evaluated. Studies of orally administered drugs are clearly of great interest; however, formulation issues have precluded widespread applications in these areas. In this report, we discuss the unique problems associated with studying orally administered drugs and review the results of recent studies performed in our laboratory.

Administration, Oral↗
PubMed2000

Quantitative measurements of medical images for pharmaceutical clinical trials: comparison between on-site and off-site assessments.

OBJECTIVE: In pharmaceutical clinical trials, quantitative measurements on medical images are often conducted to confirm drug efficacy. This study aims to compare the quantitative image analysis performance of an off-site core laboratory with the performance of investigators from multiple clinical sites. MATERIALS AND METHODS: In a phase I clinical trial, 25 healthy subjects underwent dynamic brain single-photon emission computed tomography (SPECT) scintigraphy with 123I-Altropane, a cocaine analogue with high affinity and selectivity for dopamine transporter sites in the striatum. In 20 patients examined on-site and off-site, a total of 80 measurements were made to calculate the drug's binding potential. A trained technologist off-site at a central core laboratory and on-site investigators at different clinical sites performed the image analysis. These results were compared with measurements made by a subspecialty radiologist whose assessments were the reference standard. Statistical analysis was performed using multiple regression analysis. RESULTS: Measurements from the central core laboratory (off-site) highly correlated (r = 0.95) with measurements of the reference standard. Measurements from the clinical sites (on-site) grouped together had lower correlation (r = 0.84) with the reference standard. This difference was statistically significant (p < 0.05). CONCLUSION: Training and experience in the specific type of image analysis are critical in obtaining consistent data. Quantitative analysis by dedicated personnel at a core laboratory provides highly reproducible results. The findings support off-site assessment of medical images in pharmaceutical clinical trials.

Adult↗
PubMed2000

How well can radiologists using neural network software diagnose pulmonary embolism?

OBJECTIVE: This study evaluated and optimized the performance of an automated artificial neural network image interpreter in the diagnosis of pulmonary embolism on ventilation-perfusion lung scans. The computer interpretations were compared with the interpretations of three experienced observers. MATERIALS AND METHODS: Digital data were obtained from 100 patients with normal findings on chest radiographs who were undergoing both radionuclide ventilation-perfusion scanning and pulmonary angiography. Interpretations of differently trained neural networks were compared with those of three experienced nuclear medicine practitioners unaware of the clinical diagnosis. RESULTS: Machines running neural networks performed similarly to experienced scan interpreters in the detection of pulmonary embolism. Both the human observers and the networks performed best in cases with large emboli. Neural network performance was best in the right lung, when the networks were trained using only cases with large emboli and when networks were trained independently in the right and left lungs. The best predictions resulted from a collaborative interpretation incorporating both the human and computer predictions. CONCLUSION: Computers running artificial neural networks using scan data obtained directly from the anterior and posterior ventilation and perfusion images, without human involvement, perform comparably with experienced observers in patients with normal findings on chest radiographs. Human observers can improve their interpretations by incorporating computer output to formulate diagnostic prediction. The method of training the networks is critical to optimizing performance.

Adult↗