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F L Jacobson

Publications and source records attributed to F L Jacobson.

11 recordsLinked to original sources
PubMed2001

Human observer detection experiments with mammograms and power-law noise.

We determined contrast thresholds for lesion detection as a function of lesion size in both mammograms and filtered noise backgrounds with the same average power spectrum, P(f)=B/f3. Experiments were done using hybrid images with digital images of tumors added to digitized normal backgrounds, displayed on a monochrome monitor. Four tumors were extracted from digitized specimen radiographs. The lesion sizes were varied by digital rescaling to cover the range from 0.5 to 16 mm. Amplitudes were varied to determine the value required for 92% correct detection in two-alternative forced-choice (2AFC) and 90% for search experiments. Three observers participated, two physicists and a radiologist. The 2AFC mammographic results demonstrated a novel contrast-detail (CD) diagram with threshold amplitudes that increased steadily (with slope of 0.3) with increasing size for lesions larger than 1 mm. The slopes for prewhitening model observers were about 0.4. Human efficiency relative to these models was as high as 90%. The CD diagram slopes for the 2AFC experiments with filtered noise were 0.44 for humans and 0.5 for models. Human efficiency relative to the ideal observer was about 40%. The difference in efficiencies for the two types of backgrounds indicates that breast structure cannot be considered to be pure random noise for 2AFC experiments. Instead, 2AFC human detection with mammographic backgrounds is limited by a combination of noise and deterministic masking effects. The search experiments also gave thresholds that increased with lesion size. However, there was no difference in human results for mammographic and filtered noise backgrounds, suggesting that breast structure can be considered to be pure random noise for this task. Our conclusion is that, in spite of the fact that mammographic backgrounds have nonstationary statistics, models based on statistical decision theory can still be applied successfully to estimate human performance.

Female↗
PubMed2000

Perceived features reported as nodules: interpretation of spiral chest CT scans.

RATIONALE AND OBJECTIVES: The purpose of this study was to evaluate nontarget locations identified in a study of lung nodule detection with spiral computed tomographic (CT) scans that compared cine and film presentations. MATERIALS AND METHODS: In a previous study of lung nodule detection, eight observers were asked to identify 10 nodule locations in each of five CT scans containing eight simulated nodules. In the current study, each nontarget location that was reported more than once in the previous study was inspected with a stack-mode display in both cine and static modes. The nontarget locations were evaluated for probable identity, shape, and distance from the peripheral lung surface. RESULTS: Fifty-two nontarget locations included clinically undetected pulmonary nodules (n = 12), lymph nodes (n = 2), unclassifiable structures (n = 2), pleural scars (n = 8), and vascular structures (n = 28). Five nontarget locations contained vessels with complex courses apparent only with cine mode. As a group, nontarget locations were significantly closer to the periphery than would be expected by chance (for all locations, P < .0001; for locations not touching the pleural surface, P = .013). CONCLUSION: The lower reporting threshold caused by the observer instructions to find 10 targets resulted in increased reporting of structure with a nodular appearance. The locations of these reports in the lung periphery can be attributed to the relationship between frequent disease and a nearly featureless background in the lung periphery.

Adult↗
PubMed1998

Influence of CT image size and format on accuracy of lung nodule detection.

PURPOSE: To evaluate the effect of reducing image size on observers' ability to detect lung nodules on computed tomographic (CT) scans. MATERIALS AND METHODS: Stimuli were 80 single sections from 13 normal chest CT studies. On half of the images, 3-5-mm-diameter nodules were superimposed electronically at random locations. Four observers viewed images in six formats and sizes that ranged from 6 on 1 (133 x 133 mm) to 80 on 1 (40 x 40 mm). The images were viewed at a fixed distance of 55 cm and at an unrestricted, variable distance. RESULTS: With the fixed viewing distance, nodule detection decreased with smaller image sizes. The area under the receiver operating characteristic curve (Az) decreased from 0.857 for the 6-on-1 format to 0.671 for the 80-on-1 format (P = .0001). With a variable viewing distance, Az decreased from 0.884 to 0.834 across all formats (difference not statistically significant). However, there was a significant drop in performance with the smallest images (P < .05). Overall, Az for the fixed and variable viewing distances was significantly different (P < .001). CONCLUSION: Reducing image size leads to decreased lung nodule detection on CT scans viewed at a fixed distance; however, the observer can compensate for the smaller image by adjusting the viewing distance.

Humans↗
PubMed1995

Spiral CT of the chest: comparison of cine and film-based viewing.

PURPOSE: To determine radiologists' ability to find lung nodules on spiral computed tomographic (CT) scans of the chest with both rapid sequential (cine) and conventional film-based viewing. MATERIALS AND METHODS: Eight radiologists searched for lung nodules on spiral CT images (10-mm collimation, 10 mm/sec table speed) presented in two formats. Cine viewing was performed at a computer work-station; sections were viewed in 2-mm increments at frame rates up to 10 frames per second. Film-based viewing of images from a laser printer was performed with a lightbox; sections were viewed at 4-mm increments. Eight 3-5-mm-diameter simulated nodules were superimposed on each of five normal CT scans. RESULTS: Radiologists found a higher fraction of nodules with the cine presentation than with film (mean, 0.69 +/- 0.02 [standard error] versus 0.58 +/- 0.03, respectively [P = .006]). Diameter thresholds for nodule detection (50% correctly localized) were 3.3 and 3.5 mm, respectively. CONCLUSION: Cine viewing of spiral CT images of the chest improved radiologists' ability to detect nodules.

Humans↗
PubMed1993

Precision electrocautery excision of pulmonary lesions (Perelman technique): radiologic features.

The authors describe the radiologic features of precision electrocautery excision of pulmonary lesions (Perelman technique). Thin-walled cavities were seen on chest radiographs obtained in three patients at the site of the resected lesion subsequent to this surgical procedure. Knowledge of these findings can avoid a false diagnosis of abscess, septic emboli, or additional metastasis.

Adult↗
PubMed1991

Biliary patency imaging after endoscopic retrograde sphincterotomy with gallbladder in situ. Clinical impact of nonvisualization.

We prospectively performed nuclear biliary patency imaging (HIDA scanning) in 62 patients who had undergone endoscopic retrograde sphincterotomy for management of pancreaticobiliary disease with their gallbladders in situ. Elective cholecystectomy was not recommended because of advanced age, comorbidity, or absence of gallstones. All patients had patent cystic ducts at endoscopic retrograde cholangiopancreatography balloon cholangiography. Eighteen (29.1%) of 62 patients had nonvisualizing HIDA scans, and in 44 (70.9%) of 62 visualization was normal or delayed. Six cholecystectomies were required for colic (n = 1), acute cholecystitis (n = 4), and acute cholecystocholedochal fistula with cholangitis (n = 1). Among the patients with cholelithiasis and nonvisualization (n = 13), five (38.5%) required surgery, whereas only one (4.8%) of 21 patients with cholelithiasis and visualization required surgery. Nonvisualizing HIDA scans are frequent (30%) after endoscopic retrograde sphincterotomy and have no clinical relevance in patients without cholelithiasis but predict the need for cholecystectomy within 16 months in 38.5% of patients with cholelithiasis.

Aged↗
PubMed1989

HIV-associated lymphocytic interstitial pneumonia: radiologic manifestations and pathologic correlation.

The authors reviewed chest radiographs of 16 patients with biopsy-proved lymphocytic interstitial pneumonia (LIP) who also had acquired immunodeficiency syndrome (AIDS) or AIDS-related complex (ARC). Radiographs revealed fine reticular or reticulonodular infiltrates in the pulmonary interstitium in five patients, coarse reticulonodular infiltrates in two, and reticular or reticulonodular opacities with superimposed patchy alveolar infiltrates in nine. Pathologic examination of biopsy specimens revealed lymphocytes, plasma cells, and reticulum cells aggregated about the small arteries and compressing the distal airways. Throughout the course of AIDS or ARC, the radiographic findings of LIP remained stable in 12 of 16 patients. AIDS/ARC-related LIP appears to be a benign reaction of bronchial-associated lymphatic tissue to the human immunodeficiency virus (HIV). However, this indolent process cannot be correctly diagnosed based on radiographic findings alone; the use of lung biopsy is required to differentiate LIP from other infections. The authors suggest that patients with these radiographic findings, HIV seropositivity, but no other signs of opportunistic infection or neoplasia should be classified as having AIDS.

AIDS-Related Complex↗
PubMedDate not supplied

Pneumomediastinum after lung packing.

Lung packing (glossopharyngeal insufflation) consists of forcing air into the lungs, using glossopharyngeal muscle contractions similar to swallowing. Breath-hold divers perform this technique after a maximal inhalation prior to diving, thus increasing initial lung volume. However, as suggested by previous authors, this breathing maneuver could theoretically lead to lung rupture. Here we report a pneumomediastinum found on chest CT scan in a diver during a physiological study, when glossopharyngeal insufflation increased the volume of gas in the lungs by 1,040 ml (over his total lung capacity); at the same time, his transpulmonary pressures increased up to 4.1 kPa. We discuss the possibility that the very high transpulmonary pressures during lung packing caused this pneumomediastinum.

Adult↗