Reducing radiation dose in rest-stress cardiac PET/CT by single poststress cine CT for attenuation correction: quantitative validation.

Cardiac PET/CT is optimized by cine CT with dedicated shift software for manual correction of attenuation-emission misregistration. Separate rest and stress CT scans incur greater radiation dose to patients than does standard helical PET/CT or "pure" PET using rotating rod attenuation sources. To reduce radiation dose, we tested quantitative accuracy of using a single poststress cine CT attenuation scan for reconstructing rest perfusion images to eliminate resting CT attenuation scans. METHODS: A total of 250 consecutive patients underwent diagnostic rest-dipyridamole myocardial perfusion PET/CT with (82)Rb and a 16-slice PET/CT scanner using averaged cine CT attenuation data during breathing at rest and stress. After correcting for any attenuation-emission misregistration, we quantitatively compared resting perfusion images reconstructed using rest cine CT attenuation data with the same resting emission data reconstructed with poststress cine CT attenuation data. Automated software quantifying average regional quadrant activity, severity, size, and combined size and severity of perfusion defects was used for this comparison. RESULTS: Resting perfusion images reconstructed using rest cine CT attenuation data were quantitatively comparable to resting images reconstructed with poststress cine CT attenuation data with no clinically significant differences. Twenty-five (10%) of 250 cases required shifting of stress cine CT attenuation data to achieve optimal attenuation-emission coregistration with resting perfusion data. Eliminating rest CT attenuation scans reduced CT radiation dose by 50% below rest-plus-stress cine CT protocols. CONCLUSION: Resting perfusion images reconstructed using poststress cine CT attenuation data are quantitatively comparable to resting images reconstructed with resting cine CT attenuation data. Eliminating the rest CT scan reduces CT radiation dose by 50%.     

Initial experience with FDG-PET/CT in the evaluation of breast cancer

Purpose We retrospectively reviewed FDG-PET/CT images in patients with breast cancer to determine whether PET/CT improved the level of diagnostic confidence as compared with PET and to compare PET/CT and CT findings at the location of suspected malignancies.Methods The study included 75 patients with known breast cancer. The initial PET/CT study for each patient was retrospectively reviewed to determine whether improved diagnostic confidence (IDC) regarding lesion localization and characterization was observed with PET/CT as compared with PET alone. PET/CT and CT findings were compared regarding lesion characterization and staging in 69 of the 75 patients, and in the case of discordant findings, comparison with histological or informative follow-up results was also performed.Results Fifty of the 75 patients exhibited increased FDG uptake in a total of 95 regions. In the comparison of PET/CT and PET, PET/CT resulted in IDC in 30 (60%) of these 50 patients and in 52 (55%) of the 95 regions. In the comparison between PET/CT and CT in 69 patients, PET/CT demonstrated a significantly better accuracy than CT (P<0.05). PET/CT showed definitely positive findings in 60 regions with malignancies, among which CT exhibited positive findings in 43 (72%). PET/CT and CT accurately staged 59 (86%) and 53 (77%) of the 69 patients, respectively.Conclusions PET/CT added incremental diagnostic confidence to PET in more than 50% of patients and regions with increased FDG uptake. PET/CT accurately detected more regions with malignancies than did CT. This initial evaluation suggests that PET/CT is preferable to PET or CT in the diagnosis of breast cancer.     

螺旋CT机的CT值均匀性检测方法的探讨

目的 探讨影响CT值均匀性检测标准的因素，并提出改进意见。方法 通过改变模体条件和CT扫描条件，获得2台不同类型CT机的均匀性，观察影响均匀性检测标准的因素。结果 用头部条件扫描，模体未包铝环时，普通CT机的均匀性优于有软件校正功能的多层螺旋CT机；包铝环后，恰好相反用体部条件扫描时，2种类型的CT机相差不大。结论在CT值均匀性检测时，若采用头部条件进行扫描时应考虑颅骨的影响，在对带有预校正功能的CT机进行检测时，应在模体四周绕1圈约2mm厚的铝环；若不加铝环直接进行CT值均匀性检测时应采用体部条件扫描。     

Evaluation of non-contrast-enhanced CT in blunt abdominal trauma]

We compared the findings of noncontrast-enhanced CT with those of contrast-enhanced CT in 126 patients with blunt abdominal trauma to evaluate the usefulness of noncontrast-enhanced CT. In 112 of the patients, visceral injuries were confirmed by surgery or clinical follow-up including CT. Although noncontrast-enhanced CT diagnosed all patients with 12 intestinal injuries requiring immediate surgery, contrast-enhanced CT missed two of these patients because high density hematomas on noncontrast-enhanced CT became isodense after IV administration of contrast material. However, contrast-enhanced CT was superior to noncontrast-enhanced CT in the diagnosis of hepatic and renal injuries. A case of renal artery occlusion was only visualized on contrast-enhanced CT. We conclude that both noncontrast- and contrast-enhanced CT should be performed for the CT evaluation of blunt abdominal trauma.     

Revealing hepatic metastases from colorectal cancer: value of combined helical CT during arterial portography and CT hepatic arteriography with a unified CT and angiography system

OBJECTIVE: The purpose of our study was to evaluate the use of combined helical CT during arterial portography and CT hepatic arteriography in the preoperative assessment of hepatic metastases from colorectal cancer using a unified CT and angiography system. MATERIALS AND METHODS: Fifty-four patients with hepatic metastases from colorectal cancer preoperatively underwent combined CT during arterial portography and CT hepatic arteriography using the unified CT and angiography system. Three radiologists independently and retrospectively reviewed the images of CT during arterial portography alone, CT hepatic arteriography alone, and combined CT during arterial portography and CT hepatic arteriography. Image review was conducted on a segment-by-segment basis; a total of 432 hepatic segments with (n = 103) 118 metastatic tumors ranging in size from 2 to 160 mm (mean, 25.8 mm) and without (n = 329) tumor were reviewed. RESULTS: Relative sensitivity of combined CT during arterial portography and CT hepatic arteriography (87%) was higher than that of CT during arterial portography alone (80%, p < 0.0005) and CT hepatic arteriography alone (83%, p < 0.005). Relative specificity of CT hepatic arteriography alone (95%, p < 0.0005) and combined CT during arterial portography and CT hepatic arteriography (96%, p < 0.0001) was higher than that of CT during arterial portography alone (91%). Diagnostic accuracy, determined by a receiver operating characteristic curve analysis, was greater with combined CT during arterial portography and CT hepatic arteriography than with CT during arterial portography alone (p < 0.05) or CT hepatic arteriography alone (p < 0.01). CONCLUSION: Using a unified CT and angiography system, we found that combined CT during arterial portography and CT hepatic arteriography significantly raised the detectability of hepatic metastases from colorectal cancer.     

In vitro and in vivo spiral CT to determine bone mineral density: initial experience in patients at risk for osteoporosis

PURPOSE: To evaluate, both experimentally and in vivo, if nondedicated standard spiral computed tomography (CT) may be used to obtain reliable bone mineral density (BMD) data. MATERIALS AND METHODS: Twenty lumbar spine specimens from human cadavers were examined with standard quantitative CT and spiral CT. In addition, 50 patients with a history of lymphoma and chemotherapy were examined. These patients underwent long-term follow-up CT to rule out tumor recurrence. Quantitative CT was performed before contrast medium administration to assess potential posttherapeutic osteoporosis. In addition, fracture status of the spine was determined. Mean BMD values and SDs were calculated, and relationships between measurements obtained with quantitative CT and spiral CT were assessed with linear regression analysis and two-tailed tests of significance (t test). A linear fit was used to calculate quantitative CT data from spiral CT values. RESULTS: For the specimens, a coefficient of determination (r(2) = 0.99, P <.001) was found between BMD measurements obtained with quantitative CT and those obtained with spiral CT. Mean BMD in specimens was 63.6 mg/mL +/- 36.6 with quantitative CT and 74.4 mg/mL +/- 38.2 with spiral CT. Mean BMD in patients was 105.0 mg/mL +/- 34.6 with quantitative CT and 139.5 mg/mL +/- 42.7 with contrast medium-enhanced spiral CT. A coefficient of determination (r(2) = 0.91, P <.001) was obtained between these measurements. Mean BMD from L1 through L3 vertebrae was calculated, and spiral CT data were multiplied by 0.77 to yield quantitative CT data. Differences in BMD were significant (P <.05) for patients with (n = 9) and those without fractures (n = 41), as determined with spiral CT and quantitative CT. CONCLUSION: Correlations between BMD data obtained with spiral CT and standard quantitative CT were highly significant. By using a conversion factor, BMD measurements can be determined with routine abdominal spiral CT scans.     

Survey of conventional and spiral ct doses

PURPOSE: To investigate the radiation dose for conventional computed tomography (CT) and spiral CT during different CT examinations at various hospitals and practices. MATERIALS AND METHODS: CT dose index with an active length of 15 cm was measured in 16 different types of CT scanners by using ionization chamber dosimetry. Twenty-six holders (one who has legal responsibility under national law for a radiologic installation) operating a total of seven conventional and 20 spiral CT scanners were asked for their standard parameters for various CT examinations. Weighted CT dose index and dose-length product were determined for each examination. RESULTS: For most examinations, the tube current time product was significantly higher for conventional CT than for spiral CT (.002 相似文献   

Spiral CT of the thorax with reduced volume of contrast material: a comparative study.

The effectiveness of spiral computed tomography (CT) of the thorax performed with 60 mL of 60% contrast material was compared with that of conventional dynamic incremental CT performed with 120 mL of 60% contrast material. Fifty patients in whom contrast material-enhanced thoracic CT examination was necessary were assigned to undergo either spiral CT or dynamic incremental CT. Vascular opacification and mediastinal-lung image quality were graded independently by two observers. Vascular opacification and lung image quality were better with spiral CT than with conventional CT. Results of this pilot study encourage the use of spiral CT to decrease the volume of contrast medium used in patients undergoing thoracic CT.     

Non-small cell lung cancer: dual-modality PET/CT in preoperative staging

PURPOSE: To determine the accuracy of dual-modality positron emission tomographic (PET)-computed tomographic (CT) imaging, as compared with PET alone and CT alone, in the staging of non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: Twenty-seven patients with NSCLC underwent staging with combined fluorine 18 fluorodeoxyglucose PET and CT. CT, PET, and coregistered PET/CT images were evaluated separately by two different physicians for each imaging modality, and disease stage was determined by using TNM and American Joint Committee on Cancer staging systems. Histopathologic results served as the reference standard. The statistical significance of differences among CT, PET, and PET/CT was determined by using the McNemar test. RESULTS: Overall tumor stage was correctly classified as 0-IV with CT in 19 patients, with PET in 20 patients, and with PET/CT in 26 patients. PET/CT findings when compared with PET findings led to a treatment change for four patients (15%) and when compared with CT findings led to a treatment change for five patients (19%). Differences in the accuracy of overall tumor staging between PET/CT and CT (P =.008) and between PET/CT and PET (P =.031) were significant. Primary tumor stage was correctly determined in more patients with PET/CT than with either PET alone or CT alone. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of regional lymph node staging, respectively, were 89%, 94%, 89%, 94%, and 93%, with PET/CT; 89%, 89%, 80%, 94%, and 89% with PET; and 70%, 59%, 50%, 77%, and 63% with CT. Fourteen distant metastases were detected in four patients with CT, four were detected in two patients with PET, and 17 were detected in four patients with PET/CT. CONCLUSION: Use of dual-modality PET/CT significantly increases the number of patients with correctly staged NSCLC and thus has a positive effect on treatment.     

Single versus multi-detector row CT: comparison of radiation doses and dose profiles

RATIONALE AND OBJECTIVES: The purpose of this study was twofold: (a) to compare the radiation dose profile between computed tomography (CT) with a single detector row (SD) and with a multi-detector row (MD) and (b) to compare specific organ doses between SD CT and MD CT. MATERIALS AND METHODS: Thermoluminescent dosimeters placed within a 32-cm-diameter cylindrical phantom were used to measure and compare dose profiles from one SD CT scanner and from one MD CT scanner. SD CT scanning parameters were 210 mA, 140 kVp, pitch of 1.0, 5-mm section thickness, and 0.8-second gantry rotation speed. MD CT scanning parameters were 130 mA, 140 kVp, pitch of 0.75, 4 x 5-mm section thickness, 15-mm table feed, and 0.8-second gantry rotation speed. To plot radiation dose profile, doses were measured both in the imaging plane and in the area adjacent to the imaging plane. The resultant data were normalized to achieve constant image noise between MD CT and SD CT. Direct doses to individual organs from primary and scattered radiation were measured with an anthropomorphic phantom containing thermoluminescent dosimeters and with a standard pelvic imaging protocol for both MD CT and SD CT. RESULTS: MD CT resulted in a dose profile approximately 27% higher than that from SD CT in the plane of imaging (8.0 vs 6.3 mGy) and 69% higher adjacent to the plane of imaging (6.8 vs 4.0 mGy). The individual doses to the kidneys, uterus, ovaries, and pelvic bone marrow were 92%-180% higher with MD CT than with SD CT. CONCLUSION: With image noise constant between SD CT and MD CT, the radiation dose profile both inside and outside the plane of imaging was higher with MD CT than with SD CT. Organ dose also was higher with MD CT than with SD CT. This difference should be accounted for in the design of MD CT protocols, especially as MD CT technology becomes more widely available for clinical use.     

TNM staging with FDG-PET/CT in patients with primary head and neck cancer

Purpose PET/CT, PET+CT, and CT were compared concerning accuracies in TNM staging and malignancy detection in head and neck cancer. The impact of PET/CT compared to the other imaging modalities on therapy management was assessed. Materials and methods Fifty-five patients with suspected head and neck primary cancer underwent whole-body FDG-PET/CT. PET/CT and PET+CT were evaluated by a nuclear medicine physician and a radiologist; CT was evaluated by two radiologists, PET by two nuclear physicians. Histopathology served as the standard of reference. Differences between the staging modalities were tested for statistical significance by McNemar’s test. Results Overall TNM-staging and T-staging with PET/CT were more accurate than PET+CT and CT alone (p < 0.05). PET/CT was marginally more accurate than CT alone in N-staging (p = 0.04); no statistically significant difference was found when compared to PET+CT for N-staging. PET/CT altered further treatment in 13 patients compared to CT only and in 7 patients compared to PET+CT. Conclusion Combined PET/CT proved to be partly more accurate in assessing the overall TNM-stage than CT and PET+CT. These results were based on a higher accuracy concerning the T-stage, mainly in patients with metallic implants and marginally the N-stage. Therapy decisions have been influenced in a substantial number of patients. PET/CT might be considered as a first line diagnostic tool in patients with suspected primary head and neck cancer.     

Evaluation of integrated whole-body PET/CT in the detection of recurrent ovarian cancer

PURPOSE: To assess the usefulness and reliability of integrated whole-body positron emission tomography/computed tomography (PET/CT) in patients in whom recurrent ovarian cancer is suspected. METHODS: Integrated whole-body PET/CT imaging was performed in 19 patients with suspected ovarian cancer recurrence. CT, PET and fused PET/CT images were evaluated separately and imaging results were compared with pathological findings and clinical follow-up after 6 months. RESULTS: Of the 19 patients studied, 11 were found to have recurrent cancer. In 8 of these 11 patients, recurrence was diagnosed by CT, PET and fused PET/CT. In the remaining three patients, only PET and PET/CT showed a recurrent tumour, while CT was negative. Twelve localisations of ovarian cancer recurrence could be detected by CT, 17 by PET and 18 by PET/CT. In one patient with pulmonary metastases in CT and in the CT component of PET/CT, PET was negative. In the case of three metastases in the diaphragm, the spleen and the thoracic wall, respectively, the determination of the exact localisation was only possible by fused PET/CT. CONCLUSION: In patients with recurrent ovarian cancer, PET/CT detects more lesions than PET or CT alone. PET/CT permits the exact anatomical localisation of pathologic tracer uptake and can thus direct further treatment to the precise site of tumour recurrence. Hence, PET/CT should be considered for follow-up of patients with ovarian cancer.     

Acute stroke assessment with CT: do we need multimodal evaluation?

PURPOSE: To assess detection of stroke and prediction of extent of infarction with multimodal computed tomographic (CT) evaluation (unenhanced CT, perfusion CT, and CT angiography) in patients suspected of having acute stroke. MATERIALS AND METHODS: Forty-four consecutive patients with a mean National Institutes of Health Stroke Scale score of 10.45 and suspected of having ischemic stroke of the anterior circulation were examined with multi-detector row CT within 8 hours (mean, 3.05 hours) of onset of symptoms. All evaluations were performed with the knowledge that acute stroke was suspected but without detailed clinical information. The extent of ischemia or final infarction on the baseline unenhanced CT scan and follow-up images was assessed with the Alberta Stroke Program Early CT score. Different perfusion maps and follow-up images were assessed to determine the percentage of the ischemia-affected hemisphere. Each component, as well as the multimodal CT evaluation, was compared with follow-up unenhanced CT scans or magnetic resonance images after a mean time of 2.32 days. RESULTS: Multimodal CT revealed true-positive findings in 30 of 41 patients and true-negative findings in three, resulting in a sensitivity of 78.9%. Unenhanced CT, CT angiography, and perfusion CT showed sensitivities of 55.3%, 57.9%, and 76.3%, respectively. In eight patients, small infarctions (mean size, 1.47 cm) that were proved at follow-up were missed with all modalities at initial multimodal CT. With perfusion CT, four of these small infarctions were missed within the white matter of the section levels. Maps of cerebral blood flow showed the best correlation with the final size of infarction with an r(2) value of 0.71. CONCLUSION: The presented multimodal CT evaluation improves detection rate and prediction of the final size of infarction in comparison with unenhanced CT, CT angiography, and perfusion CT alone.     

Choroidal melanoma: comparison of CT, fundoscopy, and US

Computed tomography (CT) was compared with fundoscopy and ultrasound (US) in 62 patients with primary choroidal melanoma. All lesions were detected with CT and fundoscopy and all but one with US. Of five cases of extrascleral extension, four were identified with CT and fundoscopy and two with US. CT best depicted the extent of retrobulbar tumor. Tumor thickness was best evaluated with CT, with good correlation between CT and US. Tumor enhancement was noted in all 51 patients who had both noncontrast and contrast CT. Because of its higher density, tumor could be distinguished from retinal detachment on CT scans in most cases.     

F-18-fluoro-2-deoxyglucose positron emission tomography/computed tomography in the follow-up of breast cancer with elevated levels of tumor markers

OBJECTIVE: The value of combined positron emission tomography (PET)/computed tomography (CT) in the follow-up of patients with breast cancer with elevated tumor markers but without proven metastases or local recurrence was assessed. METHODS: Thirty-four women underwent PET/CT. The PET and CT images were first analyzed separately; fused findings were then interpreted, blinded to the results of the other modalities. The results of CT, PET, and PET/CT were compared with each other and correlated to the final diagnosis. RESULTS: The PET/CT identified 149 malignant foci in 24 patients (71%). The CT detected 96 of these foci in 18 patients, whereas PET identified 124 foci in 17 patients. Differences between CT and PET were not significant. Differences between PET/CT and CT (P < 0.01) and PET/CT and PET (P < 0.01) were significant. The person-based sensitivity of PET/CT, PET, and CT was 96%, 88% and 96%, respectively. Specificity of PET/CT, PET, and CT was 89%, 78%, and 78%, respectively. CONCLUSIONS: The PET/CT is a valuable modality for the follow-up of patients with breast cancer and elevated levels of tumor markers.     

Tumor staging of pancreatic adenocarcinoma using early- and late-phase helical CT.

OBJECTIVE: We compared early-phase CT with late-phase CT in the evaluation of pancreatic adenocarcinoma. MATERIALS AND METHODS: Both early- and late-phase CT images of 25 pancreatic adenocarcinomas were compared with surgical-pathologic findings. We evaluated tumor detectability, tumor size, and local tumor invasion. RESULTS: Tumor detectability was 96% on early-phase CT imaging and 64% on late-phase CT imaging (p < .01). Sensitivity for anterior serosal invasion, retroperitoneal invasion, and arterial invasion on early-phase CT exceeded sensitivity on late-phase CT (p < .05). However, specificity for all factors on early-phase CT was less than or equal to specificity on late-phase CT. The grade of local tumor invasion on early-phase CT achieved better agreement with the surgical-pathologic results than did late-phase CT, especially for tumor size and retroperitoneal invasion. CONCLUSION: Early-phase CT was better than late-phase CT in revealing tumors, tumor size, and retroperitoneal invasion.     

Increased hepatic arterial blood flow after decreased portal supply to the liver parenchyma owing to intrahepatic portosystemic venous shunt: angiographic demonstration using helical CT

This study was conducted to investigate the haemodynamics of the liver parenchyma in the presence of intrahepatic portosystemic venous shunt. 3 patients with intrahepatic portosystemic venous shunts and 24 patients with normal intrahepatic haemodynamics underwent both CT arterial portography and CT during hepatic arteriography. Angiographic findings with helical CT were compared, and CT attenuated values were measured in both groups. The liver parenchyma on CT arterial portography had lower attenuation than on CT during hepatic arteriography in all patients with intrahepatic portosystemic venous shunts. Overall average CT attenuation was 92.2 +/- 7.7 Hounsfield units (HU) on CT arterial portography and 149.9 +/- 8.5 HU after CT during hepatic arteriography, with the opposite findings in all patients without intrahepatic portosystemic venous shunt: CT attenuation 142.0 +/- 25.7 HU on CT arterial portography and 100.7 +/- 16.4 HU after CT during hepatic arteriography. In conclusion, the portal venous supply to the liver parenchyma decreased due to intrahepatic portosystemic venous shunts, with a compensatory increase in hepatic arterial blood supply.     

Contrast-enhanced FDG-PET/CT vs. SPIO-enhanced MRI vs. FDG-PET vs. CT in patients with liver metastases from colorectal cancer: a prospective study with intraoperative confirmation

BACKGROUND: The choice of imaging before liver surgery is debated regarding the use of magnetic resonance (MR) imaging, computed tomography (CT), and positron emission tomography (PET). No studies have compared contrast-enhanced PET/CT with superparamagnetic iron oxide (SPIO)-enhanced MR imaging. PURPOSE: To compare PET/CT with superparamagnetic iron oxide (SPIO)-enhanced MR imaging, PET, and CT in the detection of liver metastases (LM) and extrahepatic tumor from colorectal cancer (CRC). MATERIAL AND METHODS: Thirty-five patients with suspected LM underwent PET/CT with a contrast-enhanced CT protocol and SPIO-enhanced MR imaging. Readers independently analyzed images from MR imaging, PET/CT, and the CT part and PET part of the PET/CT study. Imaging findings were compared with surgical and histological findings. RESULTS: Lesion-by-lesion sensitivity and accuracy for liver lesions was 54% and 77% for PET alone, 66% and 83% for PET/CT, 82% and 82% for SPIO-enhanced MR imaging, and 89% and 77% for CT alone, respectively. CT and SPIO-enhanced MR imaging were less specific but significantly more sensitive than PET (P<0.0001). For extrahepatic tumor, sensitivity and specificity was 83% and 96% for PET/CT and 58% and 87% for CT, respectively. CONCLUSION: CT and SPIO-enhanced MR imaging are more sensitive but less specific than PET in the detection of LM. PET/CT can detect more patients with extrahepatic tumor than CT alone.     

FDG-PET/CT in restaging of patients with recurrent breast cancer: possible impact on staging and therapy

We aimed to compare the value of combined positron emission tomography (PET)/CT, PET+CT (viewed side by side), CT alone and PET alone concerning the rTNM stage and influence on therapy in patients with recurrent breast cancer. 44 patients with suspicion of recurrent breast cancer underwent whole-body [18F]-2-fluoro-2-deoxy-d-glucose (FDG)-PET/CT. Images of combined PET/CT, PET+CT, PET alone and CT alone were evaluated by four blinded reader teams. Diagnostic accuracies and influence on therapy were compared. Histology and a mean clinical follow up of 456 days served as the standard of reference. Differences between the staging procedures were tested for statistical significance by McNemar's test. Overall TNM tumour stage was correctly determined in 40/44 patients with PET/CT, in 38/44 with PET+CT, in 36/44 with PET alone and in 36/44 patients with CT alone. No statistically significant difference was detected between all tested imaging modalities. PET/CT changed the therapy in two patients compared with PET+CT, in four patients compared with PET alone and in five patients compared with CT alone. Combined PET/CT appeared to be more accurate in assessing the rTNM and showed a moderate impact on therapy over PET and CT. Minor improvements were noted when compared with PET+CT. Experienced readers might therefore be able to provide accurate staging results for further therapy from separately acquired studies.     

Needle-tip localization during CT-guided abdominal biopsy: comparison of conventional and spiral CT.

OBJECTIVE. This study was performed to determine whether the time required for needle-tip localization during biopsy of the abdomen would be reduced if continuous-volume data acquisition, also known as spiral CT, were used for guidance instead of conventional CT. SUBJECTS AND METHODS. Forty patients had biopsies of an abdominal mass; half underwent needle-tip localizations with conventional CT and half with spiral CT. The times required to localize the needle for 104 needle passes were calculated; scanning and reconstruction times were included, and the radiologist's technique and procedural difficulties were deliberately excluded. The mean needle localization times with conventional and spiral CT were compared for the upper abdominal and pelvic regions by using the two-tailed unpaired Student's t-test. RESULTS. The mean time (+/- SE) for spiral CT was 35 +/- 2 sec compared with 105 +/- 18 sec for conventional CT (p < .001). When analyzed by region, times with spiral CT were shorter in both the upper abdomen (means, 37 sec for spiral CT vs 150 sec for conventional CT, p < .001) and pelvis (means, 25 sec for spiral CT vs 74 sec for conventional CT, p = .038); the magnitude of the improvement was greater in the upper abdomen. CONCLUSION. The time required to find the needle tip during guided biopsy of an abdominal mass is reduced with spiral CT compared with conventional CT. This improvement is partly a result of the ability to eliminate respiratory misregistration with spiral CT, which is not possible with conventional multisectional CT; hence the greater advantage in upper abdominal biopsy.