201
|
Dalal T, Maher MM, Kalra MK, Mueller PR. Extraadrenal pheochromocytoma: a rare cause of tachycardia and hypertension during percutaneous biopsy. AJR Am J Roentgenol 2005; 185:554-5. [PMID: 16037537 DOI: 10.2214/ajr.185.2.01850554] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
202
|
Kalra MK, Blake MA, Boland GW, Hahn PF. CT features of adrenal pheochromocytomas: attenuation value and loss of contrast enhancement. Radiology 2005; 236:1112-3. [PMID: 16118181 DOI: 10.1148/radiol.2363050302] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
203
|
Kalra MK, Rizzo S, Maher MM, Halpern EF, Toth TL, Shepard JAO, Aquino SL. Chest CT Performed with Z-Axis Modulation: Scanning Protocol and Radiation Dose. Radiology 2005; 237:303-8. [PMID: 16183938 DOI: 10.1148/radiol.2371041227] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Institutional review board approval of the study protocol and waiver of informed consent were obtained. This study was compliant with the Health Insurance Portability and Accountability Act. The purpose of this study was to retrospectively assess the scanning protocol and radiation dose associated with z-axis automatic tube current modulation in multi-detector row CT scanning of the chest. Fifty-three patients (mean age, 54 years; age range, 26-77 years; 25 men, 28 women) underwent 16-detector row chest CT with z-axis modulation and noise indexes of 10.0, 12.5, and 15.0 HU. Two radiologists independently compared images acquired with z-axis modulation and fixed tube current (180-300 mA) techniques for image noise, diagnostic acceptability, and depiction of peripheral bronchovascular markings. Tube current-time product was calculated for each study. There was good interobserver agreement between the two readers (kappa = 0.72). Compared with the fixed tube current technique, z-axis modulation provides acceptable image noise for chest CT, with an 18% and 26% reduction in tube current-time product at 10.0- and 12.5-HU noise indexes, respectively.
Collapse
|
204
|
Maher MM, Kalra MK, Titton RL, Boland GW, Wittram C, Aquino S, Mueller PR, Shepard JAO. Percutaneous Lung Biopsy in a Patient with a Cavitating Lung Mass: Indications, Technique, and Complications. AJR Am J Roentgenol 2005; 185:989-94. [PMID: 16177421 DOI: 10.2214/ajr.05.0489] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
|
205
|
Dalal T, Kalra MK, Rizzo SMR, Schmidt B, Suess C, Flohr T, Blake MA, Saini S. Metallic prosthesis: technique to avoid increase in CT radiation dose with automatic tube current modulation in a phantom and patients. Radiology 2005; 236:671-5. [PMID: 16040924 DOI: 10.1148/radiol.2362041565] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The institutional review board approved this Health Insurance Portability and Accountability Act-compliant study protocol, with waiver of informed consent. The purpose of the study was to retrospectively evaluate the combined automatic tube current modulation technique in patients with orthopedic metallic prostheses. Five hundred abdominal-pelvic computed tomographic (CT) studies performed with combined modulation technique were reviewed to identify nine patients with metallic prostheses (mean age, 66 years; range, 35-86 years; male-female ratio, 5:4). On the basis of age and transverse abdominal images, these patients were matched with nine others with no metallic prostheses (mean age, 56 years; range, 36-72 years; male-female ratio, 4:5) who were control patients. Images were graded for extent and severity of streak artifacts (grade 1, streak artifact present but not substantially compromising evaluation of adjacent structures; grade 2, streak artifact present and slightly compromising evaluation of adjacent structures; and grade 3, streak artifact present and severely compromising evaluation of adjacent structures). Student t test was performed for statistical analysis. There was no difference in mean effective tube current-time product between study and control patients (P > .49). With automatic tube current modulation, an increase in CT dose caused by metallic prostheses can be successfully avoided.
Collapse
|
206
|
Wittram C, Maher MM, Yoo AJ, Kalra MK, Shepard JAO, McLoud TC. CT angiography of pulmonary embolism: diagnostic criteria and causes of misdiagnosis. Radiographics 2005; 24:1219-38. [PMID: 15371604 DOI: 10.1148/rg.245045008] [Citation(s) in RCA: 209] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Computed tomographic (CT) pulmonary angiography is becoming the standard of care at many institutions for the evaluation of patients with suspected pulmonary embolism. This pathologic condition, whether acute or chronic, causes both partial and complete intraluminal filling defects, which should have a sharp interface with intravascular contrast material. In acute pulmonary embolism that manifests as complete arterial occlusion, the affected artery may be enlarged. Partial filling defects due to acute pulmonary embolism are often centrally located, but when eccentrically located they form acute angles with the vessel wall. Chronic pulmonary embolism can manifest as complete occlusive disease in vessels that are smaller than adjacent patent vessels. Other CT pulmonary angiographic findings in chronic pulmonary embolism include evidence of recanalization, webs or flaps, and partial filling defects that form obtuse angles with the vessel wall. Factors that cause misdiagnosis of pulmonary embolism may be patient related, technical, anatomic, or pathologic. The radiologist needs to determine the quality of a CT pulmonary angiographic study and whether pulmonary embolism is present. If the quality of the study is poor, the radiologist should identify which pulmonary arteries have been rendered indeterminate and whether additional imaging is necessary.
Collapse
|
207
|
Kalra MK, Rizzo SMR, Novelline RA. Reducing radiation dose in emergency computed tomography with automatic exposure control techniques. Emerg Radiol 2005; 11:267-74. [PMID: 16133620 DOI: 10.1007/s10140-004-0395-7] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2004] [Accepted: 11/12/2004] [Indexed: 12/24/2022]
Abstract
Computed tomography (CT) scanning is being increasingly used for evaluation of trauma, which most commonly involves younger individuals. As younger patients are at higher risk for radiation-induced cancer compared to older patients, radiation dose reduction is an important issue in emergency CT scanning. With automatic exposure control techniques, users select a desired image quality and the system adapts tube current to obtain the desired image quality with greater radiation dose efficiency. These techniques can help in reducing radiation dose by 10-60% in most instances. This review article presents a comprehensive description of fundamentals, clinical applications and radiation dose benefits of automatic exposure control in emergency CT scanning.
Collapse
|
208
|
Kalra MK, Maher MM, D'Souza RV, Rizzo S, Halpern EF, Blake MA, Saini S. Detection of Urinary Tract Stones at Low-Radiation-Dose CT with Z-Axis Automatic Tube Current Modulation: Phantom and Clinical Studies. Radiology 2005; 235:523-9. [PMID: 15770037 DOI: 10.1148/radiol.2352040331] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To evaluate depiction of urinary tract calculi at computed tomography (CT) with a z-axis modulation technique at various noise indexes to reduce radiation dose and preserve image quality. MATERIALS AND METHODS Sixteen radiopaque kidney stones (2.5-19.2 mm in diameter) were embedded in the collecting systems of two bovine kidneys immersed in a water bath. A kidney phantom was made by placing the kidneys in an elliptical Plexiglas phantom (32 x 20 x 20 cm) filled with physiologic saline. The phantom was scanned at 16-detector row CT with a fixed tube current (300 mA) and z-axis modulation at noise indexes of 14, 20, 25, 35, and 50; remaining imaging parameters were held constant. Two abdominal radiologists reviewed images from most to least noisy. Images were evaluated for presence of stones and size, site, and attenuation value of each stone. Readers also graded conspicuity and margins of each stone on a five-point scale. In addition, follow-up studies of 22 patients (mean age, 46 years; range, 26-57 years; male-female ratio, 14:8) with kidney and ureteral stones who underwent CT with z-axis modulation (noise index, 14 and 20) were evaluated in the same manner. Statistical analysis was performed with the Student t test, Wilcoxon signed rank test, and kappa test of interobserver agreement. Institutional review board approval was obtained, and informed consent was not needed. RESULTS In the phantom study, all 16 stones were identified on images obtained with a fixed tube current and z-axis modulation at noise indexes of 14, 20, and 25 (with a reduction in radiation dose of up to 77% compared with that of fixed tube current scanning). Three stones (<5 mm) were not visualized with z-axis modulation at noise indexes of 35 and 50. No significant difference was shown for conspicuity of kidney stones in 22 patients who underwent CT with z-axis modulation (with a 43%-66% reduction in radiation dose) when compared with results of previous fixed tube current studies (P > .05). CONCLUSION Kidney stones (< or =2.5 mm) can be adequately depicted with the z-axis modulation technique, with a 56%-77% reduction in radiation dose. In patients with urinary tract stones, the technique results in a 43%-66% reduction in radiation dose at noise indexes of 14 and 20 without compromising stone depiction.
Collapse
|
209
|
Rizzo SMR, Kalra MK, Maher MM, Blake MA, Toth TL, Saini S. Do metallic endoprostheses increase radiation dose associated with automatic tube-current modulation in abdominal-pelvic MDCT? A phantom and patient study. AJR Am J Roentgenol 2005; 184:491-6. [PMID: 15671369 DOI: 10.2214/ajr.184.2.01840491] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
OBJECTIVE Our objective was to assess the effect of orthopedic metallic prostheses on radiation dose associated with MDCT using z-axis automatic tube-current modulation and a fixed tube current in a phantom and patient study. CONCLUSION Z-modulation is associated with a 34.1% increase in the mean tube current-time product and no change in the extent of streak artifacts in patients with a metallic prosthesis, compared with patients without a prosthesis. However, compared with the fixed-tube-current technique, z-modulation is associated with a 28.9% decrease in the mean tube current-time product.
Collapse
|
210
|
Rizzo SMR, Kalra MK, Schmidt B. Automatic Exposure Control Techniques for Individual Dose Adaptation. Radiology 2005; 235:335-6; author reply 336. [PMID: 15798174 DOI: 10.1148/radiol.2351041751] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
211
|
Kalra MK, Rizzo SMR, Novelline RA. Technologic innovations in computer tomography dose reduction: implications in emergency settings. Emerg Radiol 2005; 11:127-8. [PMID: 16028314 DOI: 10.1007/s10140-004-0396-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
212
|
Dreyer KJ, Kalra MK, Maher MM, Hurier AM, Asfaw BA, Schultz T, Halpern EF, Thrall JH. Application of recently developed computer algorithm for automatic classification of unstructured radiology reports: validation study. Radiology 2004; 234:323-9. [PMID: 15591435 DOI: 10.1148/radiol.2341040049] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To validate the accuracy of Lexicon Mediated Entropy Reduction (LEXIMER), a new information theory-based computer algorithm developed by the authors for independent analysis and classification of unstructured radiology reports based on the presence of clinically important findings (F(T), where (T) represents "true") and recommendations for subsequent action (R(T)). MATERIALS AND METHODS The study was approved by the Human Research Committee of the institutional review board. Consecutive de-identified radiology reports (n = 1059) comprising results of barium studies (n = 99), computed tomography (n = 107), mammography (n = 90), magnetic resonance imaging (n = 108), nuclear medicine (n = 99), positron emission tomography (n = 106), radiography (n = 212), ultrasonography (n = 131), and vascular procedures (n = 107) were independently analyzed by two radiologists and then with LEXIMER to categorize the reports into F(T) and F(T)0 (containing or not containing clinically important findings) categories and R(T) and R(T)0 (containing or not containing recommendations for subsequent action) categories. Accuracy, sensitivity, specificity, and positive and negative predictive values of LEXIMER for placing reports into F(T) and F(T)0 and R(T) and R(T)0 categories were assessed by using appropriate statistical tests. RESULTS There was strong interobserver concordance between the two radiologists for placing radiology reports into F(T) and R(T) categories (kappa = 0.9, P < .01). For the LEXIMER program, accuracy, sensitivity, specificity, and positive and negative predictive values, respectively, were 97.5% (95% confidence interval [CI]: 96.6%, 98.5%), 98.9% (95% CI: 97.9%, 99.6%), 94.9% (95% CI: 93.1%, 96.0%), 97.5% (95% CI: 96.6%, 98.0%), and 97.7% (95% CI: 95.8%, 98.8%) for placing radiology reports into F(T) and F(T)0 categories and 99.6% (95% CI: 99.2%, 99.9%), 98.2% (95% CI: 95.0%, 99.6%), 99.9% (95% CI: 99.4%, 99.99%), 99.4% (95% CI: 96.3%, 99.9%), and 99.7% (95% CI: 98.9%, 99.9%) for placing reports into R(T) and R(T)0 categories. CONCLUSION LEXIMER is an accurate automated engine for evaluating the percentage positivity of clinically important findings and rates of recommendation for subsequent action in unstructured radiology reports.
Collapse
|
213
|
Kalra MK, Maher MM, Toth TL, Schmidt B, Westerman BL, Morgan HT, Saini S. Techniques and applications of automatic tube current modulation for CT. Radiology 2004; 233:649-57. [PMID: 15498896 DOI: 10.1148/radiol.2333031150] [Citation(s) in RCA: 507] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Introduction of slip-ring technology with subsequent development of single- and multi-detector row helical computed tomographic (CT) scanners have expanded the applications of CT, leading to a substantial increase in the number of CT examinations being performed. Owing to concerns about the resultant increase in associated radiation dose, many technical innovations have been introduced. One such innovation is automatic tube current modulation. The purpose of automatic tube current modulation is to maintain constant image quality regardless of patient attenuation characteristics, thus allowing radiation dose to patients to be reduced. This review discusses the principles, clinical use, and limitations of different automatic tube current modulation techniques.
Collapse
|
214
|
Rizzo S, Kalra MK, Maher MM. Importance of an Expedited Review of Images After an Adverse Reaction to CT Contrast Material. AJR Am J Roentgenol 2004; 183:1174-5. [PMID: 15385329 DOI: 10.2214/ajr.183.4.1831174a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
215
|
Kalra MK, Maher MM, Kamath RS, Horiuchi T, Toth TL, Halpern EF, Saini S. Sixteen–Detector Row CT of Abdomen and Pelvis: Study for Optimization of Z-Axis Modulation Technique Performed in 153 Patients. Radiology 2004; 233:241-9. [PMID: 15454622 DOI: 10.1148/radiol.2331031505] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To retrospectively determine the optimal noise indexes required to obtain diagnostically acceptable computed tomographic (CT) images of the abdomen and pelvis with z-axis modulation. MATERIALS AND METHODS Ninety-five patients underwent 16-section multi-detector row CT of the abdomen and pelvis with z-axis modulation at noise indexes of 10.5, 11.0, 11.5, and 12.0 HU with 10-380 mA. Subsequently, 58 patients were scanned at noise indexes of 12.5 and 15.0 HU with 75-380 mA. The weights of all subjects were recorded, and transverse and anteroposterior diameters were measured. The CT images were evaluated for abnormalities and graded for image quality in terms of noise and diagnostic acceptability by using a five-point scale. Objective noise in the liver parenchyma was measured, and the tube current was recorded at each section in all 153 patients. Statistical analyses were performed to determine the appropriate noise index and to assess the effect of patient weight and abdominal diameters on image noise and diagnostic acceptability at different noise indexes. Tube current-time products (in milliampere seconds) at various noise indexes were compared with those at CT previously performed without z-axis modulation. RESULTS No significant difference in subjective image noise or diagnostic acceptability was found at noise indexes of 10.5-15.0 HU (P =.14), and objective noise was significantly inferior only at a noise index of 15.0 HU (P =.009). Compared with CT scanning at a 10.5-HU noise index, CT scanning at 12.5- and 15.0-HU noise indexes yielded, respectively, 10.0% and 41.3% reductions in radiation exposure. Patient weight and abdominal diameters affected subjective image quality. CONCLUSION Use of a 15.0-HU noise index at 75-380 mA results in acceptable subjective image noise and diagnostic acceptability but significantly greater objective image noise at routine abdominal-pelvic CT. For greater image quality demands, a noise index of 12.5 HU results in acceptable image quality and a 19.6% reduction in radiation exposure.
Collapse
MESH Headings
- Abdomen/anatomy & histology
- Adult
- Aged
- Aged, 80 and over
- Artifacts
- Body Weight
- Cohort Studies
- Female
- Humans
- Image Processing, Computer-Assisted/methods
- Liver/diagnostic imaging
- Male
- Middle Aged
- Pelvis/diagnostic imaging
- Phantoms, Imaging
- Radiation Dosage
- Radiographic Image Enhancement/methods
- Radiography, Abdominal/instrumentation
- Radiography, Abdominal/methods
- Radiography, Abdominal/statistics & numerical data
- Retrospective Studies
- Statistics, Nonparametric
- Tomography Scanners, X-Ray Computed
- Tomography, Spiral Computed/instrumentation
- Tomography, Spiral Computed/methods
- Tomography, Spiral Computed/statistics & numerical data
Collapse
|
216
|
|
217
|
Kalra MK, Maher MM, Toth TL, Kamath RS, Halpern EF, Saini S. Radiation from "extra" images acquired with abdominal and/or pelvic CT: effect of automatic tube current modulation. Radiology 2004; 232:409-14. [PMID: 15286312 DOI: 10.1148/radiol.2322031151] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
PURPOSE To retrospectively determine the number and usefulness of images acquired beyond the intended anatomic area of interest with abdominal and/or pelvic computed tomography (CT) and to assess the effect of automatic tube current modulation (ATCM) on associated radiation. MATERIALS AND METHODS Superior and inferior levels at routine abdominal and/or pelvic CT were defined as the dome of the diaphragm and the inferior margin of the pubic symphysis, respectively. Records of 106 consecutive examinations (male-to-female ratio, 45:61; age range, 21-86 years) performed from June 1 to June 30, 2003, were reviewed to determine the number of "extra" images. Sixty-two abdominal and/or pelvic CT examinations performed concurrently with chest or thigh CT or for trauma were not included in the 106. Abdominal and/or pelvic CT was performed with either ATCM (n = 44) or manual selection of tube current (n = 62). CT parameters recorded for each extra image included tube current, peak kilovoltage, and gantry rotation time. Mean and median tube current-time products were calculated for extra images. Extra images were analyzed for pathologic findings. Statistical analysis was performed with the Student t test. RESULTS Extra images were acquired above the dome of the diaphragm in 103 (97%) of 106 examinations and below the pubic symphysis in 100 (94%) of 106. A total of 1,280 extra images were acquired in 106 examinations (mean, 12 images per examination). Nineteen additional findings were observed on extra images. With ATCM, mean tube current-time product was 74.5 and 120.6 mAs for extra images acquired above the diaphragm and below the pubic symphysis, respectively; with manual selection, mean tube current-time products were 167.5 and 168.3 mAs (P <.05). CONCLUSION Most extra images acquired at abdominal and/or pelvic CT contributed no additional information. With ATCM, the radiation dose was reduced by a mean of 56% (median, 72%) for extra images above the diaphragm and 29% (median, 36%) for images below the pubic symphysis, compared with dose levels with manual selection.
Collapse
|
218
|
Kalra MK, Maher MM, Blake MA, Lucey BC, Karau K, Toth TL, Avinash G, Halpern EF, Saini S. Detection and Characterization of Lesions on Low-Radiation-Dose Abdominal CT Images Postprocessed with Noise Reduction Filters. Radiology 2004; 232:791-7. [PMID: 15333797 DOI: 10.1148/radiol.2323031563] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To assess the effect of noise reduction filters on detection and characterization of lesions on low-radiation-dose abdominal computed tomographic (CT) images. MATERIALS AND METHODS Low-dose CT images of abdominal lesions in 19 consecutive patients (11 women, eight men; age range, 32-78 years) were obtained at reduced tube currents (120-144 mAs). These baseline low-dose CT images were postprocessed with six noise reduction filters; the resulting postprocessed images were then randomly assorted with baseline images. Three radiologists performed independent evaluation of randomized images for presence, number, margins, attenuation, conspicuity, calcification, and enhancement of lesions, as well as image noise. Side-by-side comparison of baseline images with postprocessed images was performed by using a five-point scale for assessing lesion conspicuity and margins, image noise, beam hardening, and diagnostic acceptability. Quantitative noise and contrast-to-noise ratio were obtained for all liver lesions. Statistical analysis was performed by using the Wilcoxon signed rank test, Student t test, and kappa test of agreement. RESULTS Significant reduction of noise was observed in images postprocessed with filter F compared with the noise in baseline nonfiltered images (P =.004). Although the number of lesions seen on baseline images and that seen on postprocessed images were identical, lesions were less conspicuous on postprocessed images than on baseline images. A decrease in quantitative image noise and contrast-to-noise ratio for liver lesions was noted with all noise reduction filters. There was good interobserver agreement (kappa = 0.7). CONCLUSION Although the use of currently available noise reduction filters improves image noise and ameliorates beam-hardening artifacts at low-dose CT, such filters are limited by a compromise in lesion conspicuity and appearance in comparison with lesion conspicuity and appearance on baseline low-dose CT images.
Collapse
|
219
|
Maher MM, Gervais DA, Kalra MK, Lucey B, Sahani DV, Arellano R, Hahn PF, Mueller PR. The inaccessible or undrainable abscess: how to drain it. Radiographics 2004; 24:717-35. [PMID: 15143224 DOI: 10.1148/rg.243035100] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Percutaneous abscess drainage is a safe, effective, and widely used technique for the treatment of patients with abdominal or pelvic sepsis. The majority of abdominal and pelvic abscesses afford reasonably straightforward access and are amenable to percutaneous drainage. However, requests are occasionally received for drainage of abscesses or fluid collections that initially appear unsuitable for percutaneous drainage. Factors that render collections seemingly unsuitable for imaging-guided drainage include inaccessibility due to surrounding organs, difficult location, and thickened contents (eg, clotted blood, thick pus). Well-established alternative approaches (eg, transgluteal, transvaginal, transrectal) can be used to facilitate drainage of deep-seated collections that are inaccessible via more traditional routes. Other factors that may improve the accessibility of collections include modifications in patient positioning or in the use of imaging hardware (eg, angling of the computed tomography scanner gantry). Use of these techniques and modifications can allow percutaneous drainage of less accessible intraabdominal abscesses, thus eliminating the need for laparotomy.
Collapse
|
220
|
Kalra MK, Maher MM, Toth TL, Kamath RS, Halpern EF, Saini S. Comparison of Z-Axis Automatic Tube Current Modulation Technique with Fixed Tube Current CT Scanning of Abdomen and Pelvis. Radiology 2004; 232:347-53. [PMID: 15286306 DOI: 10.1148/radiol.2322031304] [Citation(s) in RCA: 150] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To compare image quality, diagnostic acceptability, and radiation exposure associated with 16-section multi-detector row computed tomographic (CT) examinations of abdomen and pelvis performed with z-axis modulation technique of automatic tube current modulation and with manual selection of fixed tube current. MATERIALS AND METHODS Sixty-two consecutive subjects (mean age, 60 years; age range, 19-84 years; male-to-female ratio, 35:27) underwent follow-up CT of abdomen and pelvis with use of a 16-section multi-detector row scanner and z-axis modulation technique (10.5-12.0-HU noise index, 10-380 mA). Scanning parameters included 140 kVp, 0.5-1.0-second gantry rotation time, 0.938:1 beam pitch, and 5-mm reconstructed section thickness. For each subject, images obtained with z-axis modulation were compared with previous images obtained with fixed tube current (200-300 mA) and with other parameters identical. Images were compared for noise and diagnostic acceptability by two subspecialty radiologists using a five-point scale (1, unacceptable; 3, acceptable; 5, excellent) at five levels: upper liver at diaphragm, porta hepatis, right kidney hilum, iliac crest, and upper margin of acetabulum. Tube current and gantry rotation time used for acquisitions at these levels were recorded. Data were analyzed with parametric and nonparametric statistical tests. RESULTS Although no significant differences were found (P =.34), images acquired with z-axis modulation at the levels of the upper liver (diaphragm) and acetabulum had a higher noise and lower diagnostic quality, compared with images acquired with fixed tube current. Compared with fixed tube current, z-axis modulation resulted in tube current-time product reduction in 54 (87%) of 62 examinations (mean reduction, 71.2 mAs) and increase in eight (13%) (mean increase, 17.0 mAs). CONCLUSION Compared with manually selected fixed tube current, z-axis automatic tube current modulation resulted in reduced tube current-time product and similar image noise and diagnostic acceptability at CT of abdomen and pelvis.
Collapse
|
221
|
|
222
|
Abstract
By virtue of its speed and isotropic resolution of thin slices, multidetector-row computed tomography (MDCT) offers unique advantages over previous single-detector-row CT, with improved temporal and spatial resolution. This review describes the historical perspective and growth trends of MDCT scanners and highlights the current status and emerging developments in multidetector technology based on presentations at the symposium "Advances in Multidetector CT," under the auspices of the Institute for Advanced Medical Education in Washington, DC.
Collapse
|
223
|
Kalra MK, Maher MM, Rizzo S, Saini S. Radiation Exposure and Projected Risks With Multidetector-Row Computed Tomography Scanning. J Comput Assist Tomogr 2004; 28 Suppl 1:S46-9. [PMID: 15258493 DOI: 10.1097/01.rct.0000120856.80935.f4] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A substantial increase in computed tomography (CT) scanning with availability of state-of-the-art multidetector-row CT scanners has generated debate about its safety and considerable interest in formulating clinical and technologic strategies to reduce radiation exposure. This review describes the magnitude of radiation exposure associated with CT scanning and projected radiation risks as well as clinical strategies and major technologic innovations for reducing radiation dose to patients undergoing CT scanning.
Collapse
|
224
|
Abstract
With ever-expanding applications, increasing availability, and accessibility of CT scanners, concerns have been raised about radiation exposure associated with CT scanning. Global statistics and projections suggest increasing use of CT scanning and its contribution to radiation exposure is a cause for concern. Several strategies based on modulation of scanning parameters and technologic improvisations have been developed in an effort to reduce associated radiation dose. This article discusses the basis for rising concern regarding radiation dose associated with CT scanning. The fundamentals of CT dose estimation are described along with strategies that aim to reduce radiation dose associated with CT scanning based on patient characteristics, study indications, and technological innovations.
Collapse
|
225
|
Maher MM, Kalra MK, Rizzo S, Mueller PR, Saini S. Multidetector CT urography in imaging of the urinary tract in patients with hematuria. Korean J Radiol 2004; 5:1-10. [PMID: 15064553 PMCID: PMC2698107 DOI: 10.3348/kjr.2004.5.1.1] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
This review article comprehensively discusses multidetector CT urography protocols and their role in imaging of the urinary tract in patients with hematuria.
Collapse
|