Percutaneous CT biopsy of chest lesions: an in vitro analysis of the effect of partial volume averaging on needle positioning

OBJECTIVE

Accurate needle biopsy of chest lesions requires knowledge of both the direction of the needle and the exact location of the tip of the needle. The purpose of this study was to analyze and illustrate the relationships between the location of the nodule, the size of the nodule, the CT slice thickness, and the needle length. An understanding of these relationships should minimize localization errors due to partial volume averaging and thus increase the accuracy of biopsies.

MATERIALS AND METHODS

Geometric principles were used to determine mathematical relationships between the size of the nodule, the CT slice thickness, the length of the needle, and the direction of the needle. A styrofoam model simulating the patient and the lesion to be sampled was developed so that radiographs and CT scans of the model could be obtained with different needle placements to illustrate the phenomenon of partial volume averaging.

RESULTS

The accuracy of the CT-guided biopsy can be increased by reducing the CT slice thickness, using longer needles, minimizing the distance to be traversed within the patient, and maximizing the portion of the lesion contained in the CT section used for needle tip localization. Mathematical equations developed from the in vitro model can be used to select the most appropriate CT section and the best length and angle of the needle. CT scans of the model illustrate the use of these equations.

CONCLUSION

We found these principles helpful in improving the accuracy of CT needle biopsies, particularly when the lesions are very small and when an angled approach is required. Ideally, the smallest possible CT slice thickness and the longest possible needles should be used, but some practical limitations exist.

Angulated needle placement in CT-guided percutaneous needle biopsy of the thorax

Computed tomography (CT)-guided percutaneous needle biopsy is often necessary to evaluate small intrathoracic lesions. Not infrequently, an overlying structure such as a rib or vessel precludes insertion of the biopsy needle within the CT slice containing the lesion. Insertion and angulation of the needle at a site within an adjacent CT slice is then required. In order to determine the optimal skin-entry site and degree of angulation for biopsy needle insertion, we analyzed the geometric relationship between lesion depth, needle length, and needle angulation.

Needle-tip localization for CT-guided biopsies

Exact localization of the needle tip during CT-guided needle biopsy is important for accurate diagnosis. Using a phantom model we evaluated different methods for localization. The most reliable method was direct visualization of a distinct feature of the needle such as a notch near the needle tip. Visualization of a black shadowing artifact and review of adjacent CT images to the one used for needle tip placement were less reliable.

Variables affecting pulmonary nodule detection with computed tomography: evaluation with three-dimensional computer simulation

To meaningfully evaluate factors determining the overall accuracy of computed tomography (CT) for identifying pulmonary nodules, computer-generated nodules were superimposed on normal CT scans and interpreted independently by three experienced chest radiologists. Variables evaluated included nodule size, shape, number, density, location, edge characteristics, and relationship to adjacent vessels, as well as technical factors, including slice thickness and electronic windowing. The overall sensitivity in identifying nodules was 62% and the specificity was 80%. On average, the observers identified 56, 67, and 63% of nodules on 1.5-, 5-, and 10-mm-thick sections, respectively (p = 0.037). Nodules were more difficult to identify on 1.5-mm-thick sections. On average, observers identified 1, 48, 82, and 91% of nodules < 1.5, < 3, < 4.5, and < 7 mm in diameter, respectively (p < 0.001). Other factors that made a significant contribution (p < 0.01) in identifying nodules, as determined by linear discriminant function analysis, included nodule location, angiocentricity, and density. We concluded that computer-generated nodules can be used to assess a large number of imaging variables. We anticipate that this approach will be of considerable utility in assessing the accuracy of interpretation of a wide range of pathologic entities as well as in optimizing three-dimensional scan protocols within the thorax.

Image selection for computed tomography of the chest. A sampling approach

RATIONALE AND OBJECTIVES

High-resolution computed tomography (HRCT) is useful to characterize the presence and extent of lung abnormalities. Contiguous HRCT images of the chest would require 200 images, which is not for practical due to 1) the extensive examination and reading time, and 2) radiation exposure. This article presents a methodologic framework to select the appropriate number of HRCT images to estimate any quantitative parameter with a desired precision. Alternative sampling strategies are introduced, and the sample size requirements are given.

METHODS AND RESULTS

Sample size requirements are developed for the percentage of emphysematous lung using simple random and stratified random sampling. The effect of the number of strata on the sample size requirement also is shown. The marked reduction in the number of HRCT images using different types of sampling plans illustrates the power of sampling techniques.

CONCLUSIONS

Proper stratification is critical to reduce the sample size requirement and to avoid missing key abnormalities, which is particularly critical in the early stages of any disease process when intervention may be most useful. Prior knowledge of the disease is useful in determining the optimum number and location of strata, and can be obtained from available chest radiographs, pulmonary function tests, radionuclide studies, and clinical parameters.

MR appearance of radiation hepatitis

The histopathologic changes of radiation hepatitis have been well described. The magnetic resonance (MR) appearance, however, has been described only in two case reports. We obtained serial MR scans of patients undergoing therapeutic irradiation for Hodgkins lymphoma to determine the time course of changes in signal intensity of the liver. We found an increased signal intensity of the irradiated portion of the liver on T2-weighted images. Changes first detected at 4 weeks following 3600 cGy to the abdomen returned to normal signal intensity within 60 days following completion of radiation therapy. One patient demonstrated a subtle increase in signal intensity of the irradiated region as early as 7 days after receiving 2000 cGy. Our results suggest that MR imaging is a useful noninvasive means of tracing the course of radiation hepatitis.

Pleural diseases: multimodality imaging and clinical management

The parietal and visceral pleura are specialized membranes which are highly efficient in keeping the pleural space essentially dry and free of protein and particulate matter. Radiology has played a pivotal role in the understanding of pleural diseases because radiography and, more recently, computed tomography (CT), sonography, and magnetic resonance imaging (MRI) have allowed in vivo visualization of abnormalities. In addition, these newer modalities have been invaluable in guiding diagnostic and therapeutic measures. Cross-sectional imaging techniques, particularly CT, are frequently of assistance in determining whether tube thoracostomy or other surgical measures are indicated, and when these procedures should be performed. The application of newer imaging modalities in expediting the management of pleural diseases is emphasized. The anatomy, histology, and physiology of the pleura, in both normal and disease states, are also reviewed.

Effect of radiation therapy on thoracic and lumbar bone marrow: evaluation with MR imaging

Bone marrow suppression is often the limiting factor in the use of radiation therapy. In order to determine if MR imaging can be used to quantify bone marrow changes, we performed a serial prospective study of patients with lung cancer (six cases) and lymphoma (six cases). Quantitative and qualitative assessments of T1-weighted sagittal images, 750/33 (TR/TE), obtained at 0.6 T before, during, and after radiotherapy showed increased signal intensity in the radiated portions of the spine. These changes appeared as early as 2 weeks after the beginning of radiation, continued to increase until a maximum value was attained, and then persisted during the follow-up period of 2 years. A significantly higher (p less than .04) ratio of pretreatment to maximum posttreatment signal intensity was seen in patients with lymphoma than in those with lung cancer, and pretreatment values in patients with lymphoma were significantly lower (p less than .01). The lower pretreatment values found in the patients with lymphoma may have been due to the smaller amount of yellow marrow in these patients, who were significantly younger (33 vs 62 years). The higher ratio of pre- and posttreatment signal intensity may have been related to the larger amount of hematopoietic marrow available to undergo fatty replacement. The persistence of elevated signal intensity for as long as 2 years after radiation suggests an endpoint in the process of marrow conversion, but not reversal in the form of regeneration of hematopoietic bone marrow. Quantitative MR evaluation of bone marrow may be of considerable value as a noninvasive means of monitoring the effects of radiotherapy.

MR imaging of pleural effusions

To investigate the in vivo magnetic resonance (MR) characteristics of pleural effusions, MR imaging was performed on 22 patients who also underwent thoracentesis. Correlation of the MR scans with results of thoracentesis revealed significant differences among three types of effusions: transudates (T) (n = 4), simple exudates (SE) (n = 9), which did not have malignant cells or infection, and complex exudates (CE) (n = 9), which did have malignant cells or infection. Using normalized MR intensities, CE were more intense than SE, which were brighter than T. The second and third echoes (TE 66 and 99 ms) provided the best differentiation for these three classes of effusions, with p less than 0.06 and p less than 0.006, respectively. Qualitative visual assessment of the increase in signal intensity was also useful in differentiating among the three types of effusions (p less than 0.02). Effective T2 values (normalized to fat) were significantly shorter for exudates than for T (p less than 0.02). Heterogeneity, loculation, and size of effusions were well evaluated on MR. Magnetic resonance is not specific for the etiology of effusions. Nevertheless, with analysis of both quantitative and qualitative parameters, MR may provide an effective noninvasive means for the initial characterization and serial follow-up of pleural effusions.

Optimizing radiologic costs in the DRG environment

Previously developed consensus algorithms expressing a suggested radiologic workup for the diagnostic related groups (DRGs) specified by the prospective reimbursement policy have proven to be useful tools for investigating radiologic decision making and the resulting economic implications. The mathematical equations for determining diagnostic and therapeutic costs for two alternative algorithms for suspected acute cholecystitis are formulated. Illustrative examples and graphic displays are given regarding how such algorithms and equations are useful in finding answers to questions about the appropriate diagnostic workup, time, and cost. Exploration of the effect of different parameter values on the choice of the appropriate algorithm is illustrated.

The pathogenesis, radiologic evaluation, and therapy of pleural effusions

Radiology has played a pivotal role in the management of patients with pleural effusions. By confirming the presence of an effusion and providing information regarding the size and distribution of fluid, chest radiography greatly facilitates initial diagnostic thoracentesis. Identification of even small effusions is important because these commonly occur and may have clinical significance. The development of improved antibiotics and a wider range of interventional techniques has increased the reliance on the radiologic imaging of pleural disease in order to plan appropriate therapy. The newer imaging modalities of CT and sonography have proved to be particularly valuable in detecting small effusions and demonstrating single or multiple loculations. Additional features, such as the degree to which a pleural process has become organized and whether there is adjacent lung parenchymal disease, are well assessed on CT. Experience with MR has been limited, but preliminary data suggest that it may be a valuable addition and/or alternative to CT.

Pleural effusions: pathogenesis, radiologic evaluation, and therapy

The imaging of pleural effusions by plain radiography, sonography, computed tomography (CT), and magnetic resonance imaging (MRI) has greatly facilitated the planning of both initial diagnostic thoracentesis and subsequent therapeutic management. The normal anatomy and physiology of the pleura, the pathogenesis of effusions, and the clinical criteria for classifying effusions are briefly summarized. The usefulness of each imaging modality is then discussed, particularly with regard to the problems of detecting small effusions, identifying loculation of fluid, distinguishing pleural from intraparenchymal disease, and assessing the extent to which a pleural process has become organized.

Diagnostic protocols for radiologic efficiency

Starting January 1988, New York State started an all-payor prospective reimbursement for inpatient hospitalizations. Medicare had already adopted a prospective reimbursement system for its patients during the previous year. This article reviews our departmental efforts to prepare for the consequences of these new policies.

Detection of bronchial abnormalities: comparison of CT and bronchoscopy

We evaluated the usefulness of CT as compared with both visual and pathologic findings from fiberoptic bronchoscopy (FOB) in detecting bronchial lesions in 100 consecutive patients undergoing both procedures. There was agreement between CT and visual FOB in 83% of cases and CT and pathologic FOB in 68%. In the malignant disease category CT detected bronchial abnormalities in 59% (27 of 46) as compared with 57% (26 of 46) by visual FOB; both agreed in 81% of the cases (37 of 46). On the basis of CT findings alone, we retrospectively divided the cases into those for which we expected FOB to have high diagnostic yield (peribronchial abnormalities, n = 49) and a low diagnostic yield (i.e., no bronchial abnormality, n = 51). For the malignant disease category, selection by CT findings resulted in successful diagnosis by FOB in 69% for the high yield group as compared with 29% for the low yield group. We conclude that CT has excellent correlation with visual and pathologic results of FOB in detecting bronchial abnormalities and that CT, when used as an initial screening test, can enhance the yield by allowing appropriate selection of patients.

Intrathoracic Kaposi sarcoma in AIDS patients: radiographic-pathologic correlation

The chest radiographs and postmortem pathologic findings in 24 patients with acquired immunodeficiency syndrome (AIDS) and autopsy-proved intrathoracic Kaposi sarcoma were reviewed. Premortem radiographic visualization of pulmonary lesions of Kaposi sarcoma depended on the extent of involvement and the presence of concomitant disease. In three patients (13%) the radiographs showed nodular opacities that corresponded in size and configuration to nodules seen at autopsy. In 21 patients (87%) the lesions were not radiographically identifiable, in some cases because they were obscured by infection. The positive and negative predictive values of four radiographic findings for intrathoracic Kaposi sarcoma were evaluated, using a control group of 14 AIDS patients without intrathoracic Kaposi sarcoma at autopsy. Findings with a high positive predictive value were parenchymal nodular and reticular opacities (100%), pleural effusions (89%), and hilar and/or mediastinal lymphadenopathy (92%). None of these findings is specific, but the presence of any one in a patient with AIDS should increase the possibility of intrathoracic involvement by Kaposi sarcoma.

MR imaging of the hilum and mediastinum: effects of cardiac gating

The effect of cardiac gating (CG) on the diagnostic quality of magnetic resonance images of the hilum and mediastinum was evaluated by comparing gated with nongated scans in 20 patients. The advantages of CG varied depending on the regions and structures under study and the presence and extent of disease. In general, CG was more advantageous in normal subjects and patients with small or subtle lesions than in patients with advanced disease. In the posterior and superior portions of the thorax there was no clear-cut advantage of CG. Normal structures were usually seen slightly better on gated images, but lung and mediastinal masses were usually visualized equally well with or without CG. From the level of the pulmonary arteries to the diaphragm, gated images were superior for visualizing normal and abnormal structures in the hilum, mediastinum, and to a lesser extent, the lungs. Both hilar and mediastinal lymphadenopathy and mediastinal invasion at the level of the lung root were consistently better visualized with CG. Large masses were usually well demonstrated without CG, but the relationship of the mass to adjacent structures was better delineated with CG.

Carcinomatous involvement of the hilum and mediastinum: computed tomographic and magnetic resonance evaluation

Magnetic resonance (MR) imaging and computed tomography (CT) were compared in 20 patients who had primary lung tumors, and the results were correlated with findings at surgery and pathologic evaluation. Both studies demonstrated a similar ability to detect hilar and mediastinal tumor. MR imaging detected more enlarged nodes in the mediastinum, but in several patients these enlarged nodes did not contain tumor. Consequently, MR imaging has a slightly higher false-positive rate in the evaluation of the mediastinum. Both modalities were highly sensitive, with specificity limited by the presence of enlarged benign lymph nodes in this series of patients.

Relation between the transmural extent of acute myocardial infarction and associated myocardial contractility two weeks after infarction

To characterize the relation between the transmural extent of acute myocardial infarction (AMI) and associated regional contractility after recovery from ischemia, 11 mongrel dogs underwent occlusion of the proximal left anterior descending coronary artery and were evaluated 2 weeks after infarction. Occlusion was permanent in 5 dogs, and reperfusion was allowed after 2 hours of occlusion in 6 dogs. All dogs had computer-assisted quantitative wall-thickening analysis by 2-dimensional echocardiography and infarct localization by the triphenyl-tetrazolium chloride technique. Percent systolic wall thickening was correlated with the transmural extent of AMI in 40 regions of interest, each measuring approximately 60 arc degrees in circumference. In 11 non-infarct-containing regions, the mean wall thickening was 59 +/- 16% (+/- standard deviation). In 29 infarct-containing segments (with transmural extent of infarction 11 to 100%) systolic wall thickening ranged from -4% to 47%. Wall thickening and transmural extent of AMI were inversely related. Least-squares regression analysis found the relation to be best described by the logarithmic function, percent wall thickening = 61 - 26 log (percent transmural extent of infarction +1), r = -0.87. The nature of this relation between structure and function suggests that salvage of small amounts of myocardium (transmural extent less than 30 to 40%) by coronary reperfusion or other means may have little effect on systolic myocardial function when compared with the function of transmural infarcts. Alternatively, salvage of more than 40% of the jeopardized myocardium should be expected to appreciably augment myocardial function.

The Tanzanian human albino skin. Natural history

Three hundred fifty albinos in the city of Dar-es-Salaam have been registered at the Tanzania Tumor Centre. Their skin changes were followed for at least 2 years. Chronic skin damage was evident in all albinos by the first year of life; by 20 years, the skin of every subject demonstrated subclinical malignant change, and some had clinical epitheliomas. Untreated, the latter tumors become intractable and disseminate, usually causing death in the third or fourth decade of life. Four clinical stages could be identified, each one associated with distinct pathologic changes: Stage 1, erythema; Stage 2, epidermal atrophy with dermal hypertrophy; Stage 3, solar keratosis; and Stage 4, clinical carcinoma (under 3 cm). It was found that clinical Stage 2 only occurs in those skin areas that show evidence of previous Stage 1 change. Similarly, Stage 3 occurs only in areas that have gone through Stages 1 and 2. Stage 4 cancers were only found in those areas that had gone through all of the three prior stages. During the 2-year period of this study, 104 skin cancers, both early and advanced, were recorded at the albino skin clinic. Thirty-three of the 104 cancers were advanced (over 4 cm in diameter). The median age of the latter group was 31.0 years. Whereas there was no sex bias in the distribution of clinical cancer, 28 of the 33 advanced cancers were in men. Histologically, the great majority of the advanced tumors were squamous cell carcinomas: 29 of 33. There was one melanoma and three basal cell tumors. The predominant site of advanced cancers in the study group was the head and neck region (30 patients); the other three occurred on the trunk, which is generally covered by clothes.