Indirect computed tomography lymphography of subdiaphragmatic lymph nodes using iodinated nanoparticles in normal dogs

RATIONALE AND OBJECTIVES: We evaluated the imaging characteristics of an iodinated particulate contrast agent for indirect computed tomography (CT) lymphography of normal subdiaphragmatic lymph nodes in dogs. METHODS: Four milliliters of a 15% (wt/vol) iodinated nanoparticle suspension was injected into the gastric, colonic, rectal, or cervical submucosa, loose paraprostatic fascia, or metatarsal subcutaneous tissues in 10 healthy beagles. Endoscopic, CT, or ultrasound guidance was used when necessary to facilitate contrast agent delivery. CT and radiographic images were obtained prior to contrast administration and at 4 hr, 24 hr, and 7 days postcontrast injection. Postmortem examinations were then conducted. RESULTS: CT images showed enhancement of regional lymph nodes draining the various injection sites. The mean attenuation of opacified nodes was 678 +/- 463 Hounsfield units 24 hr after injection and remained elevated 7 days later. Lymph node opacification on CT images correlated well with the node location observed on postmortem examinations. CONCLUSION: Subdiaphragmatic lymph nodes can be effectively opacified using an iodinated nanoparticle contrast agent for indirect CT lymphography.     

Oxylipin formation in fungi: biotransformation of arachidonic acid to 3-hydroxy-5,8-tetradecadienoic acid by Mucor genevensis

STUDY OBJECTIVE: The objectives of the present study were to evaluate the importance of intrapulmonary lymph nodes (IPLNs) in the differential diagnosis of small pulmonary nodules and to review the CT findings of IPLNs. DESIGN: Retrospective analysis of patient records. SETTING: Chest Disease Research Institute Hospital, Kyoto University. PATIENTS: Between January 1991 and May 1996, we examined 26 patients with pulmonary nodular shadows smaller than 1 cm in diameter that could not be diagnosed before surgery. All patients (19 men, 7 women) underwent chest CT (28 to 72 years old; mean, 52.3 years). RESULTS: The pathologic diagnoses were IPLNs in 46.2% (12/26), pulmonary hamartoma in 23.1% (6/26), lung cancer in 11.5% (3/26), pulmonary tuberculoma in 11.5% (3/26), and metastatic lung tumor in 7.7% (2/26). IPLNs were located in the lower lobe in 72%. The characteristic CT findings of IPLNs were a clear border and location close to the pleura. Two of them resembled lung cancer. The CT features in these two IPLNs and in three small lung cancers overlapped. CONCLUSIONS: In the present study, we investigated small nodular shadows <1 cm in diameter and found that IPLNs located underneath the pleura are important to consider in the differential diagnosis of lung cancer. The CT scan findings of IPLNs were not necessarily specific and sometimes resembled those of lung cancer. Because of their location, video-assisted thoracic surgery is useful in making a definite diagnosis.     

Imaging of mediastinal lymph nodes: CT, MR, and FDG PET

The evaluation of mediastinal lymph nodes is an important aspect of staging in patients with non-small cell lung cancer. Anatomic imaging of lymph nodes with computed tomography (CT) and magnetic resonance (MR) imaging has been limited by the relatively low sensitivity and specificity of these techniques. Advances in physiologic imaging of mediastinal lymph nodes with 2-[fluorine-18] fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) have resulted in improved diagnostic accuracy in the determination of nodal status. Despite the limitations of CT, this technique still plays an important role by aiding in the selection of the most appropriate procedure for staging, by guiding biopsy, and by providing anatomic information for visual correlation with FDG PET images. At present, anatomic MR imaging of lymph nodes is primarily a problem-solving tool for cases with inconclusive CT results. Physiologic MR imaging with iron oxide is an exciting area of investigation, and the accuracy of this technique is being assessed in clinical trials. Anatomic and physiologic imaging techniques should be considered complementary rather than competitive imaging strategies.     

Percutaneous computed tomography lymphography in the rabbit by subcutaneously injected nanoparticulates

RATIONALE AND OBJECTIVES: Surgical lymphangiography is infrequently used in staging cancer because of its inherent limitations. Radiopaque nanoparticulates target lymph nodes draining interstitial tissues and could make percutaneous lymphography feasible. METHODS: Experimental nanoparticulate contrast agent formulations were injected subcutaneously in the forepaw or hindpaw of normal rabbits or rabbits with induced reactive nodal hyperplasia. Axillary and popliteal nodes were imaged with thin-section computed tomography (CT) using quantitative methods to measure node enhancement. Dose-response (0.1-2.0 ml) and time course (4 hr to 10 weeks) of enhancement were assessed. RESULTS: Nodal enhancement above 100 Hounsfield units was consistently obtained. Enhancement was significantly related to dose and peaked at 10 hr with slow washout over the observation period. Nodes with reactive hyperplasia were larger and had heterogeneous enhancement patterns distinctly different from normal nodes. CONCLUSION: Percutaneous CT lymphography effectively depicts the macroscopic intranodal architecture in rabbits.     

Re-mediastinoscopy in the assessment of resectability of lung cancer

OBJECTIVE: Thirty-one patients underwent re-mediastinoscopy in the diagnostic assessment of lung cancer. The reason for a repeat mediastinoscopy was either a negative result at the first operation in spite of CT indication of enlarged nodes or an incomplete first mediastinoscopy. METHODS: All patients underwent a conventional mediastinoscopy. RESULTS: In 22 patients with enlarged mediastinal lymph nodes at computed tomography, 10 had a positive lymph node histology at re-mediastinoscopy, while 12 were negative. In 9 patients with no enlarged mediastinal nodes at CT scan, but incomplete biopsies at the first mediastinoscopy, 1 patient had lymph node metastases. The median duration from the first to the second mediastinoscopy was 43 days. No major complications occurred. The staging of the patients was greatly affected by the re-mediastinoscopy. Of 31 patients judged as operable according to the initial mediastinoscopy only 60% were found to be operable following the second mediastinoscopy. CONCLUSION: This study has demonstrated the value of re-mediastinoscopy in assessment of resectability of lung cancer.     

Mediastinal lymph node metastasis from lung cancer: evaluation with Tl-201 SPECT--comparison with CT

PURPOSE: To assess the usefulness of thallium-201 single photon emission computed tomography (SPECT) in detection of mediastinal lymph node metastasis from lung cancer. MATERIALS AND METHODS: Computed tomography (CT) and Tl-201 SPECT were performed in 113 patients with lung cancer. Surgical staging was performed in all patients, and the results of the two modalities were compared with the pathologic findings in 364 node stations. RESULTS: Cancerous nodes were found in 32.7% of the patients. The sensitivity of CT in detecting mediastinal node metastasis was 62%; specificity was 80%. These rates were higher for Tl-201 SPECT (76% and 92%, respectively). Furthermore, these rates were excellent in patients with enlarged mediastinal nodes at CT (87% and 93%, respectively). However, Tl-201 SPECT had more limited spatial resolution than did CT. CONCLUSION: Tl-201 SPECT is useful in evaluation of mediastinal node metastasis in lung cancer, especially for patients with enlarged nodes at CT.     

IgG response to pneumococcal polysaccharide-protein conjugate appears similar to IgG response to polysaccharide in bone marrow transplant recipients and healthy adults

OBJECTIVE: This study was done to determine if the detection of pericolic lymph nodes on CT scans could be used to differentiate cancer of the colon from diverticulitis. MATERIALS AND METHODS: We retrospectively evaluated 58 CT scans from 57 patients with proven diverticulitis or cancer of the colon. The CT scans were evaluated by five board-certified radiologists who were unaware of the proven diagnosis. Consensus opinions regarding the presence and size of pericolic lymph nodes were recorded. These data were correlated with the proven diagnoses to determine the correlation between the observed findings and the type of colonic abnormality. Fisher's exact test was used to determine statistical significance. RESULTS: Lymph nodes were seen in 22 (71%) of 31 cases of colonic cancer and in four (15%) of 27 cases of diverticulitis. The lymph nodes were 0.5-2.5 cm in short-axis diameter. We saw no difference in node size for patients with colonic cancer versus patients with diverticulitis. The nodes were most commonly located along the blood vessels in the mesenteric fat. Statistical analysis showed a significant difference (p < .001) in the frequency but not in the size of nodes between the two groups of patients. The detection of nodes resulted in a diagnostic sensitivity and specificity for colonic cancer of 71% and 85%, respectively. CONCLUSION: Pericolic lymph nodes are seen much more frequently in patients with colonic cancer than in patients with diverticulitis. The detection of pericolic lymph nodes in patients suspected of having diverticulitis should raise the suspicion of underlying colonic cancer that should, in turn, prompt additional evaluation.     

Magnetic resonance spectroscopy detects cancer in draining lymph nodes

The spread of cancer cells to draining lymph nodes is an important prognostic factor for many cancers and influences postoperative therapy in patients. Histopathology is used routinely to assess if lymph nodes contain metastases. There are, however, time and resource constraints on the volume of lymph node tissue that can be examined by the pathologist in a routine laboratory (less than 2% of each node), thus major sampling errors are possible. Conventional histopathology also relies on identifying aggregates of malignant cells for a positive diagnosis. Proton (1H) magnetic resonance (MR) spectroscopy can detect chemical changes, specifically increased levels of lactate, choline, fucose and amino acids, in lymph nodes infiltrated by cancer. Increase in lactate indicates the presence of anaerobically respiring cells, whereas choline reports that the cells are replicating. Since MR spectroscopy can identify early infiltration by malignant cells, before cell clusters are visible under the light microscope, it detects micrometastases in lymph nodes missed histopathologically. Furthermore, MR spectroscopy eliminates sampling errors since the entire lymph node is examined.     

MR images of mycobacterial infection

With the progress of imaging technologies such as CT and MR imaging, we can obtain various informations from CT and MR images. Especially, thin-section high resolution CT (HRCT) provides very useful information for the diagnosis of mycobacterial infection and other diseases of pulmonary parenchyma. Advantages of MR images over HRCT are higher tissue contrast and multidirection capability. The T2-weighted images and Gd-DTPA enhanced T1-weighted images accurately reflect pathologic structure of the lesion. Therefore, MR images can add many useful findings to CT on the selected cases which are differentiation of tubercloma from lung cancer, chronic empyema from mesothelioma, aspergiloma from lung cancer and lymphadenopathy from lymph node metastasis. We describe the usefulness of MR images for diagnosing mycobacterial infection and its differentiation from other pulmonary diseases.     

A case of advanced gastric carcinoma with disappearance of cancer cells by neoadjuvant chemotherapy

A 74-year-old man was diagnosed by preoperative X-ray and endoscopy with biopsy as having type 2 advanced gastric carcinoma (poorly differentiated adenocarcinoma) in the antrum. CT scan revealed swelling of the paraaortic lymph nodes, which was considered to be metastasis from the gastric carcinoma. As the cancer was judged to be stage IV and too advanced for a curative surgical resection, a neoadjuvant chemotherapy was initiated. One course of the regimen consisted of 10 mg of CDDP (day 1-5, drip) and 300 mg of UFT (day 1-7, oral), and the patient underwent the regimen three times in succession. After the chemotherapy, the swelling of para-aortic lymph nodes disappeared on CT scan. A distal gastrectomy with D2 lymph nodes dissection and sampling of the para-aortic lymph nodes was performed. Histopathological examination revealed that the cancer cells had completely vanished both in the primary tumor and lymph nodes. The effect of this neoadjuvant chemotherapy was judged to be Grade 3 histopathologically.     

Variability in the detection of enlarged mediastinal lymph nodes in staging lung cancer: a comparison of contrast-enhanced and unenhanced CT

OBJECTIVE: Because CT protocols for staging lung cancer vary and little information exists regarding the diagnostic importance of using i.v. contrast material, our intent was to evaluate intra- and interobserver agreement in the detection of enlarged mediastinal lymph nodes, comparing i.v. contrast-enhanced and unenhanced CT. SUBJECTS AND METHODS: Fifty patients with known or suspected bronchogenic carcinoma underwent unenhanced thoracic CT followed by contrast-enhanced CT. Three observers noted enlarged lymph nodes (> 10 mm in the short axis) and assigned the enlarged nodes to American Thoracic Society nodal station designations. Enlarged lymph nodes were grouped two ways: by assigning the exact number of enlarged lymph nodes found (zero, one, two, three, four or more), and by assigning whether at least one, or no, enlarged mediastinal lymph nodes were found at a station ("one or none"). Agreement levels were determined for inter- and intraobserver interpretations using weighted kappa statistics and the McNemar test. RESULTS: The number of enlarged lymph nodes with enhanced CT was 11% higher than on unenhanced studies (418 versus 377; p = .044). Numbers of enlarged lymph nodes were different for five stations; however, the numbers were small except for the right upper paratracheal station (2R) (contrast-enhanced, 68 enlarged lymph nodes; unenhanced, 44 enlarged lymph nodes; p = .014). With regard to all stations together, intraobserver agreement between contrast-enhanced and unenhanced studies was almost perfect (kappa range, .85-.94), and no difference was found for any observer in the proportion of patients with at least one enlarged lymph node. Interobserver agreement was substantial or almost perfect for the total number of enlarged lymph nodes. For specific stations, the lowest kappa value was .48 at 2R. One observer reported more patients with at least one enlarged lymph node with contrast enhancement at station 2R (p = .031). Greater agreement existed between two observers at station 2R with contrast enhancement versus no enhancement (kappa = .85 versus .48; p = .02). Conclusions matched, and calculations of estimated kappa values gave similar results for determination of the specific number of enlarged lymph nodes at a station and the "one or none" category. CONCLUSION: We found high agreement for intra- and interobserver interpretations for contrast-enhanced and unenhanced CT, although contrast-enhanced CT revealed more enlarged lymph nodes, especially at station 2R.     

Modulation of growth factor receptors on acute myeloblastic leukemia cells by retinoic acid

Interleukin-6 (IL-6) production and proliferative responses by draining lymph node cells were studied in mice exposed topically to a series of chemicals. Chemicals with the capacity to induce sensitisation, but not non-sensitisers, promoted both IL-6 production and lymph node cell proliferation ex vivo. The responses exhibited similar kinetics, were dependent upon the dose of topically applied allergen, and correlated significantly. We demonstrate that the main source of IL-6 within draining lymph nodes is not proliferating T lymphocytes. The induction of a strong IL-6 response, and the relationship of this to cellular proliferation indicate that production of this cytokine within the lymph node is closely associated with the induction of contact sensitivity in mice.     

Disadvantages of muscle-sparing thoracotomy in patients with lung cancer

At our institute patients with lung cancer had traditionally undergone lobectomy with mediastinal lymph node dissection using a standard posterolateral approach. The considerable morbidity associated with the standard posterolateral thoracotomy led us to investigate an alternative muscle-sparing approach. A prospective, randomized study of 30 patients with primary lung cancer (stage I or II) was performed to compare the following: operative field size, number of dissected lymph nodes, surgery time, postoperative pain, shoulder range of motion, and pulmonary function test results between patients who underwent either standard thoracotomy (SP group, n = 15) or the muscle-sparing thoracotomy (MS group, n = 15). The procedure should provide enough operative field size to access to mediastinum. Compared with the standard posterior thoracotomy, the muscle-sparing thoracotomy supplied a smaller operative field (218 +/- 31 versus 165 +/- 41 cm2) and required more surgery time (87 +/- 13 minutes) than the standard posterior thoracotomy (66 +/- 12 minutes). There were no significant differences in the number of dissected mediastinal lymph nodes. During the early postoperative days, pain and restriction of shoulder flexion were significantly less in the MS group than in the SP group. There were no significant differences in pulmonary function between the two groups. In terms of the operative field there is a marked disadvantage with the muscle-sparing incision compared with standard thoracotomy. The operative field is significantly smaller than with a standard thoracotomy, requiring more time to dissect the mediastinum; however, the pain is less and shoulder range of motion is superior to what is seen after standard thoracotomy during the early postoperative period. We conclude that there is no overall advantage to using the muscle-sparing incision in patients with lung cancer.     

Comparison of imaging TNM [(i)TNM] and pathological TNM [pTNM] in staging of bronchogenic carcinoma

OBJECTIVE: Precise tumor (T) and nodal (N) staging is imperative in non-small cell lung cancer (NSCLC) as it determines subsequent treatment, certainly when considering neoadjuvant treatment for stage IIIA or IIIB disease. To determine the accuracy of present-day computed tomographic (CT) scanning a prospective study was performed comparing imaging TNM [(i)TNM] and pathological TNM [pTNM]. METHODS: In 74 patients with NSCLC without distant metastases (i)TNM was determined on CT findings. The TNM system advocated by the American Joint Committee on Cancer was used. All patients underwent cervical mediastinoscopy. When superior mediastinal nodes were negative this was followed by thoracotomy and pathological examination of the resected specimen and lymph nodes to determine pTNM. RESULTS: The agreement between (i)TNM and pTNM was only 35.1%. The primary tumor (T) was correctly staged in 54.1%, overstaged in 27.0% and understaged in 18.9% of the patients. Invasion of chest wall, pericardium and of major mediastinal structures (T3, T4) was not reliably detected by CT scan. Sensitivity and specificity of CT regarding hilar and mediastinal lymph node staging were 48.3 and 53.3%, positive and negative predictive value 40 and 61.1% and its overall accuracy 51.4%. The nodal (N) factor was correctly determined by CT scan in 35.1%, overstaged in 44.6%, and understaged in 20.3% of the patients. CONCLUSIONS: Even with present-day CT scanners (i)TNM provides no accurate staging and routine mediastinoscopy is necessary for precise mediastinal lymph node staging. Likewise, (i)T3 and (i)T4 determinations are unreliable and should not contraindicate thoracotomy.     

Mycobacterium bovis (BCG) infection of the lymph nodes of normal, immune, and cortisone-treated guinea pigs

Strain-2 inbred guinea pigs were infected intradermally with 10(5)-10(7) viable BCG (Pasteur) organisms by means of multiple scarifications of shaven midflank skin. The spread of the BCG to the draining lymph nodes and on to the spleen was followed quantitatively for 28 days. The population of bacilli at the inoculation site increased as much as tenfold the first 14 days. The number of viable BCG organisms recovered from the primary draining superficial dorsal axillary and inguinal lymph nodes varied from 0.1 to 1.0% of the inoculum, with a further tenfold to 100-fold drop in counts for the secondary subclavian and lumbar lymph nodes. The bacterial counts for the various nodes increased substantially the first 14 days. By 28 days, as many as 1,000 viable bacilli were recovered from the spleen. Increasing the inoculum size or the number of inoculation sites increased the primary node counts and promoted a more extensive and rapid spread by the BCG population to the secondary lymph nodes and spleen. Prior vaccination of the host with living BCG decreased the spread of the BCG inoculum from the scarification site to the various draining lymph nodes. Multiple injections of cortisone tended to reverse this effect.     

Applications of PET in lung cancer

An estimated 180,000 new cases of lung cancer will be diagnosed in the United States this year, and lung cancer accounts for approximately 25% of all cancer deaths. The overall 5-year survival rate is 14%, and this has not changed over the past several decades. Lung cancer diagnosis and treatment is a major health problem globally. Most lung cancers are detected initially on chest radiographs, but many benign lesions have radiologic characteristics similar to malignant lesions. Thus, additional studies are required for further evaluation. Computed tomography (CT) is most frequently used to provide additional anatomic and morphologic information about the lesion, but it is limited in distinguishing benign from malignant abnormalities in the lung, pleura, and mediastinum. Because of the indeterminate results from anatomic imaging, biopsy procedures including thoracoscopy and thoracotomy may be used even through one-half of the lesions removed are benign and do not need to be removed. FDG-PET imaging provides physiologic and metabolic information that characterizes lesions that are indeterminate by CT and that accurately stages the distribution of lung cancer. Exploiting the fundamental biochemical differences between cancer and normal tissues, FDG imaging takes advantage of the increased accumulation of FDG in transformed cells. FDG-PET is very sensitive (approximately 95%) for the detection of cancer in patients who have indeterminate lesions on CT. The specificity (approximately 85%) of PET imaging is slightly less than the sensitivity because some inflammatory processes such as active granulomatous infections accumulate FDG avidly. The high-negative predictive value of PET suggests that lesions considered negative on the study are benign, biopsy is not needed, and radiographic follow-up is recommended. Several studies have documented the increased accuracy of PET compared with CT in the evaluation of the hilar and mediastinal lymph node status in patients with lung cancer. If the mediastinum is normal on PET imaging and there is no other evidence of metastatic disease, the patient has a thoracotomy. If the mediastinum is abnormal on PET imaging, mediastinoscopy is performed with the PET images providing the lymph node stations to target. Whole-body PET studies detect metastatic disease that is unsuspected by conventional imaging and demonstrate some of the anatomic abnormalities detected by CT to be benign lesions. Management changes have been reported to occur in up to 41% of patients based on the results of the whole-body studies.     

Pleurodesis in malignant pleural effusion

About 50% of the pleural effusions diagnosed are caused by a malignancy, especially by thoracic, pulmonary and ovarian cancer and lymphomas. The accumulation of fluid is caused by metastasization to the pleura and obstruction of lymph vessels and nodes. The effusion generally decreases if the tumour responds to systemic treatment. However, frequently this does not occur and the fluid has to be removed, to alleviate symptoms such as dyspnoea, coughing and a heavy sensation in the chest. Possible surgical therapies are draining through a needle or a drain, (partial) pleural resection and the creation of a pleuro-peritoneal shunt. Disadvantages of these are early recurrences, the severity of the intervention and (or) the high morbidity and mortality. The current standard treatment is pleurodesis brought about by a sclerosing agent, usually via a drain. The substances preferably used for this purpose are, in the order of decreasing importance, tetracycline, bleomycin or talc, doxycycline or minocycline. The most frequent adverse effects are chest pain and fever during and after the pleurodesis.     

Comparison of oncogene mutation detection and telomerase activity for the molecular staging of non-small cell lung cancer

Novel oncogene mutation detection techniques have demonstrated that standard histopathological examination may fail to detect clinically significant metastatic cancer cells. Recently, telomerase activity has been detected in most immortal cell lines and human tumors, potentially providing a novel diagnostic marker. We compared standard histopathological examination with the telomeric repeat amplification protocol assay and either a p53 plaque hybridization or a K-ras mutation ligation assay in the lymph nodes of 12 patents with surgically resectable non-small cell lung cancer. Telomerase activity was detected in 10 of 10 (100%) evaluable tumors. Eight of 9 (89%) histopathologically positive lymph nodes were telomerase positive, and 26 of 48 (54%) histopathologically negative lymph nodes were telomerase positive. In comparison, oligonucleotide plaque hybridization detected metastases in all 3 histopathologically positive nodes and in 3 of 27 histopathologically negative nodes. Similarly, the K-ras mutation ligation assay detected metastases in all 6 histopathologically positive lymph nodes examined and in 1 of 21 histopathologically negative lymph nodes. Thus, most of the "positive" nodes by telomerase assay did not harbor occult neoplastic cells that shared the same genetic alteration as the primary tumor. The high rate of false positives associated with the telomeric repeat amplification protocol assay limits its role in staging lymph nodes in patients with non-small cell lung cancer.     

Imaging and lung disease: uses and interpretation

Diagnostic imaging has undergone a profound revolution since the first computed tomography (CT) unit was conceived in 1971; CT is now an integral part of daily practice in thoracic radiology, and has reached a relative technological maturity. Magnetic Resonance Imaging (MRI) has been introduced more recently. Technical difficulties still exist and are related to cardiac and respiratory motion. The storage-phosphor-based computed radiography system provides several advantages, including compensation for variations in exposure, but is still under evaluation especially in bedside radiography. Nevertheless careful plain film analysis still remains an important examination, and should be done before special procedures are taken to answer specific questions. Routine chest radiography is still the most frequent method of imaging employed today. Radiographic studies can suggest airway pathology such as atelectasis, endobronchial neoplasia or bronchiectasis, but CT provides a unique strategy for the localization and characterization of bronchial and pulmonary parenchymal disease. The most important role of CT is to determine, localize and characterize patterns within the pulmonary parenchyma, and correctly identify bronchiectasis even when bronchography is equivocal. In lung cancer, imaging has an important role in accurate staging with regard to the correct selection of patients and evaluation of prognosis. CT is one of the major tests used for staging. The staging system now adopted worldwide is based upon AJCC and ATS classification, and has two major components: anatomic extent of the disease (TNM) and cell types. The role of MRI with regard to lung cancer is not precisely determined. MRI can play a complementary role in the staging of lung cancer in cases of superior sulcus tumour; pericardial involvement, tumoral extension in subcarinal region and invasion of the superior vena cava. The radiologic detection of the solitary nodule is a difficult charge for the radiologist; CT provides the precise localization of the nodule and is reliable for analysing radiologic features such as calcification, cavitation, and spiculated borders. The problem remains of the discovery of an incidental benign pulmonary nodule in the patient with an extrathoracic malignancy, and often necessitates percutaneous biopsy under CT guidance. The evaluation of diffuse lung disease lies on pattern recognition. Chest radiography is the initial tool for diagnosis, high resolution CT (HRCT) can provide routine visualization of structures of less than 500 mu. HRCT can be useful in formulating a differential diagnosis with recognition of pattern and distribution of the disease.(ABSTRACT TRUNCATED AT 400 WORDS)     

Neural networks for the analysis of small pulmonary nodules

PURPOSE: Small pulmonary nodules can be readily detected by computed tomography (CT). The goal of this detection is to diagnose early lung cancer as the five year survival at this early stage is over 70% in contradistinction to the overall 5-year survival of around 10%. Critical to the efficacy of CT for early lung cancer detection is the ability to distinguish between benign and malignant nodules. We explored the usefulness of neural networks (NNs) to help in this differentiation. METHODS: CT images of 28 pulmonary nodules, 14 benign and 14 malignant, each having a diameter less than 3 cm were selected. All were sufficiently malignant in appearance to require needle biopsy and surgery. The statistical-multiple object detection and location system (S-MODALS) NN technique developed for automatic target recognition (ATR) was used to differentiate between these benign and malignant nodules. RESULTS: S-MODALS was able to correctly identify all but three benign nodules. S-MODALS classified a nodule as malignant because it looked similar to other malignant nodules. It identified the most similar nodules to display them to the radiologist. The specific features of the nodule that determined its classification were also shown, so that S-MODALS is not simply a "black box" technique but gives insight into the NN diagnostics. CONCLUSION: This initial evaluation of S-MODALS NNs using pulmonary nodules whose CT features were very suspicious for lung cancer demonstrated the potential to reduce the number of biopsies without missing malignant nodules. S-MODALS performed well, but additional optimization of the techniques specifically for CT images would further enhance its performance.