Multidisciplinary approach to thoracic tissue sampling.

When choosing the best method to undertake a biopsy of a lesion in the lung or mediastinum, it is important to consider the entire range of possible options, such as surgical, bronchoscopic/endoscopic, and radiologic techniques. Features to be considered include the anatomic location of the lesion, the amount of tissue needed, cost, availability of specific techniques, safety and risks, and expected diagnostic yield/accuracy.

Aortic growth rates in chronic aortic dissection.

AIM: To determine and compare rates of descending aortic enlargement and complications in chronic aortic dissection with and without a proximal aortic graft. METHODS AND MATERIALS: Fifty-two patients with dissection involving the descending aorta and who had undergone at least two computed tomography (CT) examinations at our institution between November, 1993 and February, 2004 were identified, including 24 non-operated patients (four type A, 20 type B) and 28 operated patients (type A). CT examinations per patient ranged from two to 10, and follow-up ranged from 1-123 months (mean 49 months, median 38.5 months). On each CT image, the aortic short axis (SA), false lumen (FL), and true lumen (TL) diameters were measured at the longitudinal midpoint of the dissection and at the point of maximum aortic diameter. Complications were tabulated, including aortic rupture and aortic enlargement requiring surgery. RESULTS: For non-operated patients, the midpoint and maximum point SA, TL, and FL diameters increased significantly over time. For operated patients, the midpoint and maximum point SA and FL diameters increased significantly over time. In both groups, aortic enlargement was predominantly due to FL expansion. Diameter increases in non-operated patients were significantly larger than those in operated patients. The rate of change in aortic diameter was constant, regardless of aortic size. Four non-operated and six operated patients developed aortic complications. CONCLUSIONS: In patients with a dissection involving the descending thoracic aorta, the FL increased in diameter over time, at a constant rate, and to a greater degree in non-operated patients (mostly type B) compared with operated patients (all type A).

Diaphragmatic shape change after lung volume reduction surgery.

Diaphragmatic shape in normal patients was significantly different from shape in emphysema patients. Postoperative diaphragmatic shape in patients with good clinical outcome differed from preoperative shape and was similar to shape in normal patients. In patients with poor clinical outcome, surgery appeared to have little effect on diaphragm shape.

Aortic dissection: CT features that distinguish true lumen from false lumen.

OBJECTIVE: The purpose of this study was to determine which CT findings are reliable indicators of the true or false lumen in an aortic dissection. CONCLUSION: The beak sign and a larger cross-sectional area were the most useful indicators of the false lumen for both acute and chronic dissections. Features generally indicative of the true lumen included outer wall calcification and eccentric flap calcification. In cases showing one lumen wrapping around the other lumen in the aortic arch, the inner lumen was invariably the true lumen.

Evaluation of competence in the interpretation of chest radiographs.

RATIONALE AND OBJECTIVES: The purpose of this study was to determine relative rates of missed diagnoses for radiologists as a measure of competence in interpreting chest radiographs. MATERIALS AND METHODS: Cases involving differing interpretations of chest radiographs were collected from January 1994 through December 1999 by faculty (chest and nonchest radiology specialists) in an academic radiology department. A quarterly peer-review process designated cases months after the fact, and anonymously, as no miss or as class I (nondiagnosable), class II (very difficult diagnosis), class III (should be diagnosed most of time), or class IV (should almost always be diagnosed) missed diagnoses. The rates and classes of missed diagnoses were compared among chest faculty and for the nonchest radiology specialists as a group. RESULTS: Chest radiologists read 184,977 studies, and nonchest radiologists read 300,684 studies. Of these, 243 missed diagnoses were classified (classes I and II, 184 cases; class III, 50; and class IV, nine). No difference was detected in the rate of class III and IV misses among chest faculty, but nonchest faculty had significantly more class III (P = .022) and class IV misses (P = .016). CONCLUSION: Random sampling of differing interpretations can yield a relative rate of missed diagnoses for radiologists. No difference was detected in clinically important misses (ie, classes III and IV) among chest radiologists, but a statistically significantly higher rate of seemingly obvious misdiagnoses was found for nonchest specialty radiologists. Potential biases may have influenced this analysis, including disease prevalence, sampling, clinical factors, observer variability, and truth-in-diagnosis.

Ulcerlike lesions of the aorta: imaging features and natural history.

PURPOSE: To document the natural history of ulcerlike aortic lesions and determine whether any computed tomographic (CT) features predict outcome. MATERIALS AND METHODS: CT scans from 1994 to 1998 that depicted an ulcerlike aortic lesion were retrospectively evaluated. Features evaluated included lesion and aortic size and intramural hematoma. Initial CT findings were correlated with clinical data and subsequent CT findings. RESULTS: There were 56 lesions in 38 patients. Follow-up (mean, 18.4 months) CT scans were available for 33 lesions. Stability of the lesion and adjacent aorta was noted in 21 lesions. Two lesions were unchanged, although associated intramural hematoma regressed over 1-2 months. Ten lesions showed mild to moderate increase in aortic diameter (mean follow-up, 19.8 months) either with (seven lesions) or without (one lesion) increase in size of the lesion or with incorporation of the lesion into the aortic wall contour (two lesions). Of all 56 lesions, 37 were clinically stable, two were associated with recurrent chest and/or back pain, eight underwent surgical resection or stent placement, and two were in patients who died. Seven lesions were in patients lost to follow-up. No initial CT feature was predictive of CT outcome, although lack of pleural effusion correlated with clinical stability. CONCLUSION: Most ulcerlike aortic lesions are asymptomatic and do not enlarge. About one-third of lesions progress, generally resulting in mild interval aortic enlargement.

Solitary pulmonary nodules in patients with extrapulmonary neoplasms.

PURPOSE: To determine the frequency of single lung metastasis, primary lung cancer, and benign lesions in patients with a solitary lung nodule and a primary extrapulmonary neoplasm. MATERIALS AND METHODS: The authors evaluated the electronic charts of 149 patients with an extrapulmonary malignant neoplasm and a solitary pulmonary nodule. The histologic characteristics of the nodule were correlated with those of the extrapulmonary neoplasm and with patient age and smoking history. RESULTS: Patients with carcinomas of the head and neck, bladder, breast, cervix, bile ducts, esophagus, ovary, prostate, or stomach were more likely to have primary bronchogenic carcinoma than lung metastasis (ratio, 25:3 for patients with head and neck cancers; 26:8 for patients with other types of cancer combined). Patients with carcinomas of the salivary glands, adrenal gland, colon, parotid gland, kidney, thyroid gland, thymus, or uterus had fairly even odds (ratio, 13:16). Patients with melanoma, sarcoma, or testicular carcinoma were more likely to have a solitary metastasis than a bronchogenic carcinoma (ratio, 23:9). Thirty patients had a benign nodule. There was substantial overlap in age distribution among the patients with benign disease, lung cancer, and metastasis, although no patient younger than 44 years had a lung cancer. Smokers had a 3.5-fold higher chance of developing lung cancer compared with nonsmokers. CONCLUSION: The likelihood of a primary lung cancer versus a metastasis depends on the histologic characteristics of the extrapulmonary neoplasm and the patient's smoking history.

Radiologic staging of lung cancer.

Preoperative tumor staging in patients with known or suspected non-small cell lung cancer is generally performed using contrast enhanced chest computed tomography (CT) (including the adrenal glands). Abdominal CT is generally unnecessary, given the low frequency of isolated liver metastases. The role of MRI is limited, and it is used mainly as a problem solving tool in certain specific situations. A CT showing no mediastinal lymph node enlargement usually oviates preoperative mediastinal lymph node sampling, with certain exceptions. If enlarged mediastinal lymph nodes are demonstrated at CT, then CT may be used to direct preoperative lymph node sampling via transbronchoscopic Wang needle biopsy, mediastinoscopy, mediastinotomy, or video assisted thoracoscopy.

MR imaging of levator ani muscle recovery following vaginal delivery.

Our aim was to quantify the changes that occur in the levator ani muscles (LA) after vaginal delivery using magnetic resonance imaging. Fourteen women underwent MRI 1 day postpartum. Six of them were also scanned 1, 2, 6 weeks and 6 months after delivery. LA signal intensities and thickness, in areas of the urogenital and the levator hiatus were assessed in the transverse plane. Perineal body position was measured in the sagittal plane. One day postpartum a higher T2-signal intensity of the LA compared to the obturator internus muscle was found in all women and a lower T1-signal intensity in 8 of 12 women. By 6 months these differences were present in only 1 woman in the left LA. An elevation in perineal body position of 13.4 +/- 7.3 mm (P < 0.05), as well as a decrease in the area of the urogenital hiatus by 27% (P<0.05) and of the levator hiatus by 22% (P < 0.05) by 2 weeks postpartum suggest a return of normal LA geometry. LA thickness showed interindividual variations, and a complete loss of LA tissue was found in 1 woman. Changes in LA signal intensity, topography and thickness during the puerperium can be documented using MR imaging.

Risk analysis for aortic surgery using hypothermic circulatory arrest with retrograde cerebral perfusion.

BACKGROUND: Retrospective analysis of 144 patients undergoing aortic arch reconstruction using hypothermic circulatory arrest (HCA) with retrograde cerebral perfusion (RCP) for cerebral protection was performed. METHODS: The diagnosis, procedure, and anatomic site of the arch anastomosis were analyzed to see if they were independent predictors of mortality or morbidity. In addition age, gender, HCA-RCP times, preoperative malperfusion (both treated and untreated), surgical status, and redo surgery status were also examined to determine their influence on the incidence of death and complications. Both multivariate and univariate analysis were performed using linear regression and cross-tabulation with either chi2 or Fisher's exact test where appropriate. RESULTS: Preoperative surgical status (emergent) and the presence of untreated preoperative malperfusion were the only variables that were significant independent predictors for mortality (p <0.05). No variable was significant for the prediction of stroke or other complications. The severity of surgery had no bearing on the patient outcome. CONCLUSIONS: Complex aortic surgery using HCA-RCP can be performed with acceptable risk to the patients.

Synthetic interposition grafts of the thoracic aorta: postoperative appearance on serial CT studies.

PURPOSE: To determine the normal postoperative appearance of thoracic aortic interposition grafts on serial CT studies and to document CT detectable complications. MATERIALS AND METHODS: The 235 CT studies in 114 patients with one or more thoracic aortic interposition grafts were analyzed for the presence or absence of felt rings, felt pledgets, low-attenuation material surrounding the graft, pseudoaneurysm, and dissection flap. A graft was present in the ascending aorta in 93 patients, in the descending aorta in 25, and in the arch in 11. RESULTS: Low-attenuation material was seen adjacent to the ascending graft in 55%-82% of patients and adjacent to the descending graft in 60%-79% of patients, showing diminishing frequency and thickness over time. CT scans in 30 of 53 patients showed residual low-attenuation material adjacent to the graft more than 1 year after surgery. CT scans in four of 93 patients with ascending grafts and one of 25 patients with descending grafts showed a pseudoaneurysm. CONCLUSION: CT studies obtained after aortic interposition grafting show characteristic findings. Knowledge of the type of operative procedure and typical location and CT appearance of surgical materials used is important to correctly diagnose or exclude postoperative complications following thoracic aortic interposition grafting.

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.

CT time-attenuation washout curves of adrenal adenomas and nonadenomas.

OBJECTIVE: The purpose of this study was to analyze the CT contrast enhancement washout curves of adrenal masses and to determine the earliest time after initial enhancement that differentiation of adenomas from nonadenomas is possible. MATERIALS AND METHODS: Contrast enhancement washout curves were generated after delayed contrast-enhanced CT scans of 52 adrenal adenomas and 24 nonadenomas. The optimal threshold value and corresponding sensitivity and specificity for the diagnosis of adenoma were determined according to attenuation values. Also, we calculated the percentage and relative percentage of enhancement washout at time delays from 5 to 45 min after initial enhancement. RESULTS: The mean percentage of enhancement washout for adrenal adenomas was 51% at 5 min and 70% at 15 min, compared with 8% and 20%, respectively, for nonadenomas. The sensitivity and specificity for the diagnosis of adenoma were both 96% at a threshold attenuation value of 37 H on the 15-min delayed enhanced scan. CONCLUSION: On CT, adrenal adenomas show a much earlier and more rapid washout of contrast enhancement than do nonadenomas. Adenomas and nonadenomas can be differentiated by attenuation values or the percentage or relative percentage of washout as early as 5-15 min after enhancement.

Cross-sectional imaging anatomy of the anal sphincters.

BACKGROUND: To describe the cross-sectional anatomy of the anal sphincter mechanism relevant to magnetic resonance imaging (MRI) and ultrasound cross-sectional images. METHOD: Axial, sagittal, and coronal 5-mm sections of female pelves were reviewed from six cadaver specimens (ages 24-72 years). Fetal anatomy was studied in plastinated histologic sections from 19 and 26 weeks' gestation. Images of the anal sphincter were obtained by MRI in six and by ultrasound using an exoanal technique in 12 nulliparous volunteers. EXPERIENCE: The internal anal sphincter is clearly visible in anatomic sections central to the external sphincter and is visible in MRI and ultrasound images. The external anal sphincter can be subdivided into a subcutaneous and a deep portion. On anatomic sections and on MRI, the subcutaneous part shows as two parallel muscle strips in the axial plane; the deep portion presents with a characteristic teardrop form in the section perpendicular to the axis of the anal canal. The puborectalis muscle and the external anal sphincter form a "double bump" in the sagittal section. The longitudinal muscle can be identified by its fiber orientation in anatomic sections but is not clearly visible in imaging studies. CONCLUSION: This information should make it possible to identify accurately anal sphincter anatomy in two-dimensional sectional images of the anal sphincter.

Dose escalation for non-small cell lung cancer using conformal radiation therapy.

PURPOSE: Improved local control of non-small cell lung cancer (NSCLC) may be possible with an increased dose of radiation. Three-dimensional radiation treatment planning (3D RTP) was used to design a radiation therapy (RT) dose escalation trial, where the dose was determined by (a) the effective volume of normal lung irradiated, and (b) the estimated risk of a complication. Preliminary results of this trial were reviewed. METHODS AND MATERIALS: A graph of the iso-normal tissue complication probability (NTCP) levels associated with a dose and effective volume (V(eff)) was derived, using normal tissue parameters derived from the literature. This led to a dose escalation schema, where patients were sorted into 1 of 5 treatment bins, determined by the V(eff) of the best possible treatment plan. The starting doses ranged from 63 to 84 Gy. Each treatment bin was then escalated separately, as in Phase I dose escalation fashion, with Grade > or = 3 radiation pneumonitis defined as dose limiting. To allow for dose escalation, we required patient follow-up to be > or = 6 months for at least three patients. 3D treatment planning was used to irradiate only the radiographically abnormal areas, with 2.1 Gy (corrected for lung inhomogeneity)/day. Clinically uninvolved lymph nodes were not treated prophylactically. RESULTS: A total of 48 NSCLC patients have been treated (Stage I/II: 18 patients; Stage III: 28 patients; mediastinal recurrence postsurgery: 2 patients). No radiation pneumonitis has been observed in the 30 patients currently evaluable beyond the 6-month time point. All treatment bins have been escalated at least once. Current doses in the five treatment bins are 69.3, 69.3, 75.6, 84, and 92.4 Gy. None of the 15 evaluable patients in any bin with > or = 30% NTCP experienced clinical radiation pneumonitis, implying that the actual risk is < 20% (beta error rate 5%). Despite the observation of the clinically negative lymph nodes at high risk, there has been no failure in the untreated mediastinum as the sole site of first failure. Three of 10 patients receiving > or = 84 Gy have had biopsy proven residual or locally recurrent disease. CONCLUSION: Successful dose escalation in a volume-dependent organ can be performed using this technique. By incorporating the effective volume of irradiated tissue, some patients have been treated to a total dose of radiation over 50% higher than traditional doses. The literature-derived parameters appear to overestimate pneumonitis risk with higher volumes. There has been no obvious negative effect due to exclusion of elective lymph node radiation. When completed, this trial will have determined the maximum tolerable dose of RT as a single agent for NSCLC and the appropriate dose for Phase II investigation.

Surgical delay for acute type A dissection with malperfusion.

BACKGROUND: An acute type A aortic dissection is considered a surgical emergency. Review of the risk factors for a type A dissection showed that preoperative malperfusion was associated with a 22% (2/9) intraoperative mortality and an 89% (8/9) hospital mortality. Intraoperative deaths were secondary to pulmonary failure resulting from capillary leak; the remaining patients died of multiorgan failure resulting from reperfusion injury. METHODS: The surgical delay approach was adopted for malperfused patients, and treatment in these patients included percutaneous reperfusion, with aortic fenestration and branch stenting where appropriate. Twenty patients had a type A dissection and malperfusion shown by pulsed-wave Doppler echocardiography, transesophageal echocardiography, or spiral computed tomographic scanning. Malperfusion was documented by angiography. After reperfusion, all patients' conditions were stabilized in the intensive care unit; intravenous beta-blockers were administered to decrease the maximum rate of increase of left ventricular pressure. Once patients completely recovered from the consequences of malperfusion, surgical repair was performed. Statistical comparison of the non-delay and delay groups was performed using Fisher's exact test and Student's t test. Multiple logistic regression analysis was used to establish independent predictors for mortality. RESULTS: The mean delay to repair was 20 days (2 to 67 days). Four (31%) patients were discharged home and readmitted for operation. Three patients (15%) died preoperatively, 1 of retrograde dissection and rupture and 2 of reperfusion injury. Seventeen underwent surgical repair, with two deaths (12%); 15 (75%) were discharged, with an average follow-up of 16.8 months (p < 0.003). Delay was the only independent predictor of outcome. CONCLUSIONS: Patients with an acute type A dissection and malperfusion should undergo percutaneous reperfusion, and surgical repair should be delayed until the reperfusion injury resolves.

Untreated lung cancer: quantification of systematic distortion of tumor size and shape on non-attenuation-corrected 2-[fluorine-18]fluoro-2-deoxy-D-glucose PET scans.

The authors quantitatively evaluated possible distortions of tumor size and shape introduced on non-attenuation-corrected 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) scans obtained in primary lung cancer tumors. Primary lung cancer tumors in 21 patients were measured on x-ray computed tomography (CT), attenuation-corrected FDG PET, and non-attenuation-corrected FDG PET scans. Apparent anteroposterior tumor dimensions on non-attenuation-corrected FDG PET scans were significantly larger (P = .0007; mean difference, 30%) than on attenuation-corrected FDG PET or CT scans (P = .05; mean difference, 28%). Left-to-right tumor dimensions on non-attenuation-corrected FDG PET scans were significantly smaller than on attenuation-corrected FDG PET scans (P = .03; mean difference, 8.5%) but were not significantly different from those on CT scans (P = .3).

Magnetic resonance imaging anatomy of the female urethra: a direct histologic comparison.

OBJECTIVE: To define the urethral structures visible on magnetic resonance imaging (MRI) relevant to stress urinary incontinence. METHODS: The urethra and surrounding tissues were harvested from 13 female cadavers (ages 21-81) and fixed in 10% buffered formalin. High-resolution T1- and T2-weighted images were obtained at 1.5 tesla. Mallory trichrome-stained histologic sections were prepared in corresponding planes from the cadaveric specimens. Immunohistologic stains for smooth muscle (actin) and vascular endothelium (CD-34 and factor VIII) were obtained on two specimens. Histology and MRI were compared using side-by-side correlation of projected images and by superimposing projected images. Comparison was also made to a non-cadaveric urethral MRI of a 29-year-old woman and to the MRI of another specimen imaged pre- and post-fixation. RESULTS: Distinct layers of the cadaveric urethra were seen best on proton density and T2-weighted images. From the center to the periphery, a series of concentric rings were visible: an inner bright ring, the mucosa; a dark ring, the submucosa; an outer bright ring, the smooth muscle of the urethra in a loose connective tissue matrix; and a peripheral dark ring, the striated urogenital sphincter muscle of the urethra in dense connective tissue. No significant alterations were caused by fixation. These cadaveric images matched the non-cadaveric MRI of the 29-year-old woman. CONCLUSION: The internal urethral anatomy visible on high-resolution MRI can be identified and confirmed histologically, and these findings may form the basis for future anatomic investigation of stress urinary incontinence and other urethral abnormalities.

Evaluation of thoracic aortic disease with the use of helical CT and multiplanar reconstructions: comparison with surgical findings.

PURPOSE: To assess the accuracy of helical computed tomography (CT) in differentiating different types of thoracic aortic disease, to determine the incremental value of multiplanar reconstructions, and to determine if helical CT could help to reliably predict the need for intraoperative hypothermic circulatory arrest. MATERIALS AND METHODS: Forty-nine patients underwent pre-operative helical CT with multiplanar reconstructions. Images were reviewed for type and location of pathologic lesions and for features that indicated the need for hypothermic circulatory arrest. The incremental yield of multiplanar reconstructions compared with that of axial images was assessed. Imaging findings were compared with surgical findings. RESULTS: The types of lesions present in the patients included 36 aneurysms (three were ruptured), six penetrating ulcers, five dissections, and two pseudoaneurysms. The accuracy of diagnosis was 92% (45 of 49 patients) with the use of CT (both with and without multiplanar reconstruction). The necessity of hypothermic circulatory arrest was successfully predicted in 94% (45 of 48 patients) of cases. CONCLUSION: Helical CT, both with and without the use of multiplanar reconstruction, enabled highly accurate differentiation among diseases of the thoracic aorta and prediction of the need for hypothermic circulatory arrest.

Delayed enhanced CT for differentiation of benign from malignant adrenal masses.

PURPOSE: To determine whether adenomas can be differentiated from nonadenomas on 1-hour-delayed enhanced computed tomographic (CT) scans. MATERIALS AND METHODS: In a prospective evaluation of 51 adrenal masses in 39 patients, the CT attenuation was measured at the time of contrast enhancement and 1 hour later. The results were compared for adenomas (n = 41) and metastases (n = 10). RESULTS: On 1-hour-delayed enhanced CT scans, the mean attenuation of the adenomas was 11 HU +/- 13 versus 49 HU +/- 8.3 for metastases (P < .001). At a threshold value of 30 HU, specificity and positive predictive value for the diagnosis of adenoma were 100% with a sensitivity of 95%. The mean decrease in attenuation during the 1-hour delay was 74% +/- 37 for the adenomas versus 31% +/- 28 for the metastases (P < .001). CONCLUSION: CT densitometry on delayed scans obtained 1 hour after contrast enhancement may be useful in characterizing an adrenal mass as an adenoma. When CT is performed with a 150-mL bolus injection of contrast material and with the scanning parameters described in this study, other procedures or imaging studies may be unnecessary if the mass measures less than 30 HU on the delayed scans.