Magnetic resonance angiography of the human middle meningeal artery: implications for migraine

PURPOSE: To describe a novel noninvasive method for studying middle meningeal artery (MMA) diameter changes in vivo in humans. Dilatation of the MMA has been implicated in the pathophysiology of migraine headache, but no direct evidence has been obtained in humans. MATERIALS AND METHODS: The diameter of the MMA (the extracranial part) was measured in 19 healthy volunteers before and after administration of a vasodilator (nitroglycerin (NTG), 1.2 mg sublingually) known to provoke headache. We used magnetic resonance angiography (MRA) in combination with a 47-mm microscopy coil and a semiautomatic contour detection program. RESULTS: The diameter of the MMA was 1.5+/-0.26 mm (mean+/-SD) before and 1.79+/-0.30 mm after NTG administration. This increase was 20.1% (95% CI=12.9-27.3; P<0.001). The mean increase in subjects who developed headache (N=11) was 0.34+/-0.19 mm as compared to 0.22 mm+/-0.20 mm in the eight subjects who did not (95% CI for difference=-0.07 to 0.31; P=0.188). CONCLUSION: MRA in combination with a 47-mm microscopy coil is a novel, noninvasive method to measure changes in the diameter of human meningeal vessels, with potential applications for migraine and other fields of neurovascular research.     

Can virtual simulation of breast tangential portals accurately predict lung and heart volumes?

A treatment portal or simulator image has traditionally been used to demonstrate the lung and heart coverage of the breast tangential portal. In many cases, these images were acquired as a planning session on the linear accelerator. The patients were also CT scanned to assess the lung/heart volume and to determine the surgical site depth for the electron-boost energy. A study using 50 consecutive patients was performed comparing the digitally reconstructed radiograph (DRR) from the virtual simulation with treatment portal images. Modification to the patient's arm position is required when performing the planning CT scans due to the aperture size of the CT scanner. Virtual simulation was used to assess the potential variation of lung and heart measurements. The average difference in lung volume between the DRR and portal image was less than 2 mm, with a range of 0-5 mm. Arm position did not have a significant impact on field deviation; however, great care was taken to minimize any changes in arm position. The modification of the arm position for CT scanning did not lead to significant variations between the DRRs and portal images. The Advantage Sim software has proven capable of producing good quality DRR images, providing a realistic representation of the lung and heart volume included in the treatment portal.     

Evaluation of a Laser System for CT Software Simulation (EXOMIO) in Patients with Breast Cancer

PURPOSE: To develop a manually movable laser system connected to the CT table for alignment of the isocenter cross of irradiation fields on the patient's skin directly after CT software simulation. MATERIAL AND METHODS: The specially designed laser system was constructed in the authors' department, and the mean focusing accuracy of isocenter translations was analyzed using Alderson phantom measurements. The mean overall accuracy from setup to treatment of the whole procedure of CT software simulation was measured by the comparison of bone structures and mamma contour of the digitally reconstructed radiograph (DRR) with the verification film. The time taken for the different setup procedure steps was evaluated for 70 breast cancer patients who were treated using tangential fields. RESULTS: The mean focusing accuracy of the manually movable laser system after defined isocenter translation was measured as 0.8 +/- 0.5 mm, the mean patient movement on the CT table as 2.0 +/- 1 mm, and the mean positioning accuracy of the first treatment after patient positioning corresponding to the skin alignments as 3.9 +/- 1.5 mm. The time periods for the different steps of the CT software simulation were measured, and the total duration was found to be 35.8 +/- 3.3 min. CONCLUSION: In general, the main advantage of well-known CT software simulation when compared to conventional simulation is the relief of the real X-ray simulator which is feasible with fast planning software (EXOMIO) and the presented movable laser system.     

New method of verification of the position of target points in stereotactic radiosurgery by linear accelerator

A method for quantitatively checking the position to be used for stereotactic radiosurgery was devised using a digital reconstruction radiogram (DRR) and electric portal images (EPI). On each image, the radiation field and head contour were extracted by binary-coded processing. The center of gravity position vector of the extracted image was calculated, and the vector from the head contour to the radiation field was obtained. By comparing the difference in DRR and EPI, an index was made of positional error. The error in the center of gravity position coordinate in changing 40~80 of 256 image tones in the binary operation was 0.5mm or less. The effect on the center of gravity position vector caused by the image distortion of EPI was within 0.5mm in the 200x200mm(2) region. Statistical processing was carried out on this index value, and a 95% confidence interval was estimated. The index value of the Z component of the lateral image became -1.43+/-0.66, and it shifted to the negative side. Error was evaluated by the verification method devised for the target point position. Results indicate the usefulness of the verification method using center of gravity for the target point position.     

Study of optimal imaging parameters for digitally reconstructed radiographs (DRR) in radiotherapy treatment planning using single-slice helical CT

In recent years, by making digitally reconstructed radiographs (DRR) from helical CT images in the position check of an irradiation field, the verification performed by DRR, lineacgraphy (LG), or an electronic portal imaging device (EPID) has become possible. We examined the optimal parameters of single-slice helical scanning in DRR image construction and the usefulness of DRR replaced with the simulation film. We performed a section sensitivity profile at the Z-axis (SSPz) as evaluation of a physical characteristic of helical CT equipment and the form of image of DRR, fixed quantity evaluation of imaging distortion, and visual verification of images. It was determined that DRR was influenced by the partial volume effect depending on slice thickness and pitch, such that this influence occurred when slice thickness and pitch were large. Between a simulation film and DRR reconstructed using imaging parameters with a slice thickness of 3 mm, pitch of 1.0, and reconstruction slice thickness of 3 mm, coincidence was not complete. However, the distortion of DRR was small and the difference was not statistically; thus it was considered to be useful. In conclusion, we consider that DRR reconstructed using the parameters of single-slice helical scanning is useful for clinical evaluation in radiotherapy planning.     

A Technique for Verification of Isocenter Position in Tangential Field Breast Irradiation

Treatment verification and reproducibility of the breast treatment portals play a very important role in breast radiotherapy. We propose a simple technique to verify the planned isocenter position during treatment using an electronic portal imaging device. Ten patients were recruited in this study and (CT) computed tomography-based planning was performed with a conventional tangential field technique. For verification purposes, in addition to the standard medial (F1) and lateral (F2) tangential fields, a field (F3) perpendicular to the medial field was used for verification of the treatment portals. Lead markers were placed along the central axis of the 2 defined fields (F1 and F3) and the separation between the markers was measured on the portal images and verified with the marker separation on the digitally reconstructed radiographs (DRRs). Any deviation will identify the shift in the planned isocenter position during treatment. The average deviation observed between the markers measured from the DRR and portal image was 1.6 and 2.1 mm, with a standard deviation of 0.4 and 0.9 mm for fields F1 and F3, respectively. The maximum deviation observed was 3.0 mm for field F3. This technique will be very useful in patient setup for tangential breast radiotherapy.     

Repositioning accuracy with the Laitinen frame for fractionated stereotactic radiation therapy in adult and pediatric brain tumors: preliminary report

PURPOSE: To determine the repositioning accuracy, patient tolerance, and clinical efficacy of stereotactic radiation therapy for brain tumors in children and adults performed with the Laitinen stereotactic localizer and head holder. MATERIALS AND METHODS: In this retrospective analysis, stereotactic frame tolerance was assessed by recording patient discomfort or pain in the ear and nose during each treatment in 34 patients, including 21 children and 13 adults with 37 lesions treated with fractionated stereotactic radiation therapy. Radiation doses ranged from 10-60 Gy at 1.0-4.0 Gy per fraction. Repositioning accuracy was assessed by comparing portal radiographs with setup fields on computed tomographic (CT) scout images. Clinical efficacy was assessed by analyzing posttreatment CT and magnetic resonance images. RESULTS: The stereotactic localizer was well tolerated. The mean isocenter shifts observed after studying 305 portal radiographs were x-coordinate shift of 1.0 mm +/- 0.7 (SD), y-coordinate shift of 0.8 mm +/- 0.8, and z-coordinate shift of 1.7 mm +/- 1.0. At a median follow-up of 16 months, local control was achieved in 18 of 22 primary and in one of eight of recurrent tumors. CONCLUSION: The Laitinen stereotactic localizer is well tolerated with accurate reproducibility during stereotactic radiation therapy. Preliminary local control rates are consistent with those in other reports.     

Evaluation of daily online set-up errors and organ displacement uncertainty during conformal radiation treatment of the prostate

We have studied and analysed the magnitude of interfraction set-up errors and gold seed marker and prostate displacement in 118 patients using three gold seeds implanted within the prostate. Set-up errors and gold seed marker displacements were determined from bony anatomy and gold seed marker mismatch between the electronic portal image and the simulation digitally reconstructed radiograph (DRR), respectively. Prostate displacement relative to bony anatomy was determined from the difference between gold seed marker and bony anatomy displacement. Daily online repositioning of patients was accomplished through image matching using Varian Portal-Vision software. A total of 4878 electronic portal images and 236 DRRs from 118 patients were acquired over the course of the study. The means and standard deviations of the systematic error of gold seed marker displacement of 118 patients were 2.1+/-2.7 mm for anteroposterior (AP), -0.5+/-1.7 mm for left-right (L-R), and 1.0+/-1.9 mm for superoinferior (SI) directions; the random errors were 3.2 mm (0.9-4.9 mm) for AP, 1.9 mm (0.7-5.3 mm) for L-R, and 2.1 mm (0.7-4.5 mm) for SI directions. The mean and standard deviation of the isocentre set-up systematic error of 20 patients was 1.2+/-2.2 mm for AP, -0.1+/-1.4 mm for L-R, and -0.8+/-2.6 mm for SI directions. The isocentre set-up random errors were 1.6 mm (1.2-4.8 mm) for AP, 1.3 mm (0.6-2.5 mm) for L-R and 1.3 mm (1.0-2.6 mm) for SI directions. The mean and standard deviation of the prostate displacement systematic error relative to bony anatomy was 0.0+/-1.4 mm for AP, 0.0+/-1.1 mm for L-R and -0.2+/-2.4 mm for SI directions. Prostate displacement random errors were 1.5 mm (1.2-3.3 mm) for AP, 0.9 mm (0.4-1.5 mm) for L-R and 1.4 mm (1.2-2.4 mm) for SI directions.     

Accuracy of zoomed digital image in the detection of periodontal bone defect: in vitro study

OBJECTIVES: (1) To evaluate the intraobserver agreement related to image interpretation and (2) to compare the accuracy of 100%, 200% and 400% zoomed digital images in the detection of simulated periodontal bone defects. METHODS: Periodontal bone defects were created in 60 pig hemi-mandibles with slow-speed burs 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm and 3.0 mm in diameter. 180 standardized digital radiographs were made using Schick sensor and evaluated at 100%, 200% and 400% zooming. The intraobserver agreement was estimated by Kappa statistic (kappa). For the evaluation of diagnostic accuracy receiver operating characteristic (ROC) analysis was performed followed by chi-square test to compare the areas under ROC curves according to each level of zooming. RESULTS: For 100%, 200% and 400% zooming the intraobserver agreement was moderate (kappa=0.48, kappa=0.54 and kappa=0.43, respectively) and there were similar performances in the discrimination capacity, with ROC areas of 0.8611 (95% CI: 0.7660-0.9562), 0.8600 (95% CI: 0.7659-0.9540), and 0.8368 (95% CI: 0.7346-0.9390), respectively, with no statistical significant differences (chi2-test; P=0.8440). CONCLUSIONS: A moderate intraobserver agreement was observed in the classification of periodontal bone defects and the 100%, 200% and 400% zoomed digital images presented similar performances in the detection of periodontal bone defects.     

Target Motion Variability and On-Line Positioning Accuracy during External-Beam Radiation Therapy of Prostate Cancer with an Endorectal Balloon Device

PURPOSE: To prospectively define the setup error and the interfraction prostate localization accuracy of the planning target volume (PTV) in the presence of an endorectal balloon (ERB) device. PATIENTS AND METHODS: Weekly portal images (PIs) of 15 patients undergoing external-beam radiotherapy were analyzed. Displacements of the isocenter and the center of the ERB were measured. The setup and target motion variability were assessed with regard to the position variability of the ERB. RESULTS: The setup error was random and target motion variability was largest in the craniocaudal direction. The mean displacement of the isocenter was 2.1 mm (+/-1.2 mm SD [standard deviation]), 2.4 mm (+/-2.2 mm SD), and 3.8 mm (+/-4.0 mm SD) in the left-right, craniocaudal, and anteroposterior directions, respectively (p=0.1). The mean displacement of the ERB was 2.0 mm (+/-1.4 mm SD), 4.1 mm (+/-2.0 mm SD), and 3.8 mm (+/-3.3 mm SD; p=0.03). Setup margin and internal margin contributed equally to the PTV margin. Cumulative placement insecurity of the field and the ERB together was 4.0 mm (+/-2.1 mm SD) laterally, 6.4 mm (+/-2.5 mm SD) craniocaudally, and 7.7 mm (+/-7.0 mm SD) anteroposteriorly. The 95% CIs (confidence intervals) were 2.9-5.2 mm, 5.1-7.8 mm, and 3.8-11.5 mm. In 35% of cases, the estimation of the dorsal margin exceeded 1 cm. CONCLUSION: Margin estimate dorsally may exceed 1 cm and on-line position verification with an ERB cannot be recommended for dose escalation>70 Gy.     

Coincidence imaging using 2 dual-head gamma-camera systems, with and without attenuation correction

OBJECTIVE: Coincidence imaging enhances the potential for imaging a greater number of patients with 18F-FDG in centers that do not have dedicated PET systems. The purpose of this study was to compare, in a clinical setting, coincidence imaging for tumor detection using 2 dual-head gamma-camera systems, one equipped with a 5/8-in. (16 mm) detector (CoDe5) and the other equipped with a newly designed 1-in. (25.4 mm) detector (CoDe8) with an x-ray tube installed in its gantry. METHODS: Thirty consecutive patients were studied by both systems during the same visit and had 4 image sets for comparison: CoDe5 without attenuation correction (CoDe5NC), CoDe8 with (CoDe8AC) and without (CoDe8NC) attenuation correction, and fused coincidence-CT images. The target-to-background ratio (T/Bg ratio) and target-to-nontarget ratio (T/NT ratio) were calculated for each tumor site. RESULTS: On visual assessment, 61 tumor sites were detected on CoDe8AC images. Of these, 59 (97%) were detected on CoDe8NC and 54 (88%) were detected on CoDe5NC images. Fused images improved image interpretation in 10 patients (33%) compared with coincidence images alone. Data added by fusion were of clinical relevance in 6 patients (20%). On quantitative assessment, the number of accepted events by the CoDe8 was significantly higher than that by CoDe5 (5.21 +/- 1.46 million vs. 1.27 +/- 0.36 million, P <0.001). When comparing CoDe5 with CoDe8 images without attenuation correction, the T/Bg and T/NT ratios were significantly higher on the CoDe8 images (P <0.0005 and P <0.0005, respectively). When comparing CoDe8 images with and without attenuation correction, the T/Bg ratio was better on the attenuation-corrected images (P <0.0005). CONCLUSION: Coincidence imaging with 1-in. detectors and attenuation correction improve image quality and, to a lesser extent, the tumor detection rate compared with the 5/8-in. detectors and noncorrected images. The data added by fusion of coincidence images to CT findings were clinically relevant in 20% of the patients.     

Correlation of diffusion-weighted MRI with whole mount radical prostatectomy specimens

The purpose of this study was to compare the apparent diffusion coefficient (ADC) of benign central gland (bCG), benign peripheral zone (bPZ) and cancer using diffusion-weighted MRI and whole mount specimens. 11 patients with biopsy-proven prostate cancer underwent diffusion-weighted MRI prior to radical prostatectomy. A single-shot echo planar image technique was used with b-values of 0 s mm(-2), 300 s mm(-2), 500 s mm(-2) and 800 s mm(-2). Whole mount specimens were compared with ADC maps. Areas of cancer, bCG and bPZ were identified, and regions of interest were drawn on ADC maps. Mean ADC values were recorded for all regions of interest, and paired t-tests were performed to compare mean values. Cancer was outlined in nine patients. In two patients, the tumours were too small to correlate with images; bCG was identified in 11 patients and bPZ was identified in 10 patients. Mean ADC values for bCG, bPZ and cancer were, 1.5 x 10(-3) mm(2) s(-1) (standard error (SE) = 0.04), 1.7 x 10(-3) mm(2) s(-1) (SE = 0.1), and 1.3 x 10(-3) mm(2) s(-1) (SE = 0.09), respectively. The most significant difference between benign tissue and cancer existed at b-values of 0-300 s mm(-2) (bCG vs cancer: mean difference = 0. 29, p = 0.001, 95% confidence interval (CI) = 0.17-0.41; bPZ vs cancer: mean difference = 0.34, p = 0.003, 95% CI = 0.18-0.61). In conclusion, we have confirmed, using whole mount verification, a significant difference in the ADC between benign tissue and cancer.     

Performance characteristics and quality assurance aspects of kilovoltage cone-beam CT on medical linear accelerator.

A medical linear accelerator equipped with optical position tracking, ultrasound imaging, portal imaging, and radiographic imaging systems was installed at University of Pittsburgh Cancer Institute for the purpose of performing image-guided radiation therapy (IGRT) and image-guided radiosurgery (IGRS) in October 2005. We report the performance characteristics and quality assurance aspects of the kilovoltage cone-beam computed tomography (kV-CBCT) technique. This radiographic imaging system consists of a kilovoltage source and a large-area flat panel amorphous silicon detector mounted on the gantry of the medical linear accelerator via controlled arms. The performance characteristics and quality assurance aspects of this kV-CBCT technique involves alignment of the kilovoltage imaging system to the isocenter of the medical linear accelerator and assessment of (a) image contrast, (b) spatial accuracy of the images, (c) image uniformity, and (d) computed tomography (CT)-to-electron density conversion relationship were investigated. Using the image-guided tools, the alignment of the radiographic imaging system was assessed to be within a millimeter. The low-contrast resolution was found to be a 6-mm diameter hole at 1% contrast level and high-contrast resolution at 9 line pairs per centimeter. The spatial accuracy (50 mm +/- 1%), slice thickness (2.5 mm and 5.0 mm +/- 5%), and image uniformity (+/- 20 HU) were found to be within the manufacturer's specifications. The CT-to-electron density relationship was also determined. By using well-designed procedures and phantom, the number of parameter checks for quality assurance of the IGRT system can be carried out in a relatively short time.     

Time-resolved MR angiography with generalized autocalibrating partially parallel acquisition and time-resolved echo-sharing angiographic technique for hemodialysis arteriovenous fistulas and grafts

PURPOSE: To evaluate the imaging of hemodialysis arteriovenous (AV) fistulas and grafts with use of magnetic resonance (MR) angiography with generalized autocalibrating partially parallel acquisition (GRAPPA) and time-resolved echo-sharing angiographic technique (TREAT) and compare the findings with those of digital subtraction angiography (DSA). MATERIALS AND METHODS: The vascular tree directly related to AV fistulas and grafts was divided into nine segments. Images of each segment obtained on GRAPPA MR angiography were evaluated for the presence of stenosis, occlusion, and any other disease (eg, pseudoaneurysm) by two independent observers and compared with a consensus reading of the same segments on DSA imaging. Sensitivity and specificity were calculated with use of DSA as the gold standard modality, and each image on MR angiography and DSA was rated for quality. Linear-weighted kappa scores were calculated as a measure of interobserver variability in the detection of pathologic processes. RESULTS: A total of 80 segments were evaluated by each observer. For both observers, sensitivity rates for the detection of stenosis, occlusion, and any disease were 100% (95% CI, 52%-100%), 100% (95% CI, 20%-100%), and 100% (95% CI, 60%-100%), respectively. For observer 1, specificity rates for the detection of stenosis, occlusion, and any disease were 96% (95% CI, 88%-99%), 100% (95% CI, 94%-100%), and 96% (95% CI, 88%-99%), respectively. For observer 2, the specificity rates for the detection of stenosis, occlusion, and any disease were 93% (95% CI, 84%-98%), 100% (95% CI, 94%-100%), and 93% (95% CI, 84%-97%), respectively. Linear-weighted kappa values for MR angiography and DSA were 0.78+/-0.084 and 0.62+/-0.152, respectively. CONCLUSION: Time-resolved MR angiography with GRAPPA and TREAT offers excellent image quality and provides an accurate and reliable modality for the detection of pathologic processes in hemodialysis AV fistulas and grafts.     

Detection of colorectal polyps: comparison of multi-detector row CT and MR colonography in a colon phantom

PURPOSE: To compare multi-detector row (four- and 16-section) computed tomography (CT), including a low-dose protocol, with high-field-strength (1.5- and 3.0-T) magnetic resonance (MR) imaging for reader detection of colorectal polyps in a colon phantom. MATERIALS AND METHODS: A colon phantom with simulated haustral folds and 10 polyps of varying size (2.0-8.0 mm) was imaged at four- and 16-section CT (section thicknesses of 1.25 and 0.75 mm, reconstruction increments of 0.8 and 0.7 mm, and 100 and 10 mAs, respectively, and 120 kV for both) and at 1.5- and 3.0-T MR imaging (three-dimensional gradient-recalled echo sequence, section thickness of 1.4 mm). Three-dimensional endoluminal images were assessed by 10 reviewers for each modality regarding polyp detection. Comparisons of sensitivities were performed by using logistic regression. RESULTS: Overall, polyps were detected with a sensitivity of 87% (95% confidence interval [CI]: 80%, 94%) at four-section CT, 92% (95% CI: 87%, 97%) at 16-section CT, 56% (95% CI: 46%, 66%) at 1.5-T MR imaging, and 55% (95% CI: 45%, 65%) at 3.0-T MR imaging. The detection of polyps at least 4 mm in diameter was not influenced by the modality or radiation dose (sensitivity of 100%). CT performed in low-dose mode depicted all polyps with a diameter of at least 3 mm. Polyps smaller than 3 mm in diameter were detected with a sensitivity of 7.5% (1.5-T MR imaging), 22.5% (3.0-T MR imaging), and 20% (low-dose CT); detection rates were significantly greater (P < .001) with normal-dose CT (four section, 67.5%; 16 section, 82.5%). Increased spatial resolution (with CT) and higher field strength (with MR imaging) had no significant effect on polyp detection. CONCLUSION: With both multi-detector row CT and MR imaging, readers detected polyps above the clinically relevant threshold diameter of 6 mm, with similar sensitivities.     

Correction of systematic setup errors in prostate radiation therapy: how many images to perform?

The purpose of this study was to develop an evidence-based off-line setup correction protocol for systematic errors in prostate radiation therapy. Daily orthogonal electronic portal images were acquired from 30 patients. Field displacements were measured in the medial-lateral (ML), superior-inferior (SI), and anterior-posterior (AP) directions for each treatment fraction. The off-line protocol corrects the mean field displacement found from n consecutive images, starting at a particular fraction of treatment, with a fixed tolerance level. Simulations were performed with the measured data to determine (1) how many images (n) should be averaged to determine the systematic error; (2) on which treatment fraction should the protocol be initiated; and (3) what tolerance level should be applied to determine whether the patient position should be corrected. Uncorrected systematic errors in the ML, SI, and AP directions were (mean position +/- 1 standard deviation [SD]): -0.7 +/- 2.2 mm, -1.5 +/- 1.3 mm, and 1.4 +/- 2.6 mm, respectively. Random errors (1 SD and range) were 1.9 mm (1.3 - 3.3), 1.5 mm (0. - 4.1), and 1.8 mm (1.0-2.6), respectively. A correction based on a single image taken on the first fraction actually increased the systematic errors in the ML and SI directions compared with no correction. More accurate correction of systematic errors was achieved with increasing number of images averaged, with only small benefit after 5 images. With fewer images averaged, delaying the start of the protocol resulted in more accurate correction because of the influence of unrepresentative positions at early fractions. The number of corrections made on patients with small (< 2 mm) systematic errors was minimized for tolerance values of 2 mm and n > or = 5 images averaged. The optimal off-line setup correction protocol would be to shift the patient by the mean displacement of the first 5 portal images of a radical course of radiation therapy. A small tolerance level should be utilized with 2 mm giving good accuracy with minimal unnecessary shifts.     

Development of computerized patient setup verification and correction system in radiotherapy

Visual comparison of a reference image with a verification image is commonly used for setup verification in external beam radiation therapy. However, it sometimes lacks reproducibility and provides insufficient quantitative evidence. The present study was performed to develop computerized methods for determining landmarks to verify a portal image with digital reconstruction radiograph (DRR), and to investigate the clinical effectiveness of our method. Our computer algorithm consisted of three main procedures--preprocessing, determination of landmarks, and verification--none of which required manual operation. Finally, our system indicated the distance for setup correction. We evaluated the accuracy of our system using pelvic phantom images, and the maximum magnitude of error was shown to be 1.12 (n=9). The results indicated that the error range of our system was sufficiently small to examine patient positioning error, which should be less than 5 mm, as described in AAPM report TG40. Our system will aid operators in positioning patients accurately for external radiation therapy.     

Use of a saline chaser in abdominal computed tomography: a systematic review

PurposeTo perform a systematic review of the literature regarding the use of a saline chaser in abdominal computed tomography (CT).Materials and methodsThe MEDLINE database was searched from 1966 to March 2007. Studies were included if they compared the magnitude of contrast enhancement with and without a saline chaser in CT and reported CT contrast enhancement values of the liver, portal vein, or abdominal aorta. For randomized controlled trials (RCTs) comparing the same dose of contrast material with and without a saline chaser, mean differences in the magnitude of contrast enhancement were pooled by using a fixed-effects model.ResultsSeventeen studies met the inclusion criteria. Three RCTs using clinical images were included in the meta-analysis. The mean differences in contrast enhancement of the liver, portal vein, and aorta were ?0.4 (95% CI, ?2.4 to 1.7), 7.4 (95% CI, 1.3 to 14), and 11 (95% CI, -5.3 to 27), respectively. Three RCTs using a time–density analysis were included in the meta-analysis. The mean differences in peak contrast enhancement of the liver, portal vein, and aorta were 8.2 (95% CI, 4.2 to 12), 28 (95% CI, 16 to 40), and 15 (95% CI, 0.3 to 30), respectively.ConclusionIn clinical images, a saline chaser did not improve contrast enhancement of the liver. In time-density analysis, however, a saline chaser improved peak contrast enhancement of the liver.     

Primary interpretation of thoracic MDCT images using coronal reformations

OBJECTIVE: The objective of this study was to evaluate the accuracy and efficiency of primary interpretation of thoracic MDCT using coronal reformations as compared with transverse images. SUBJECTS AND METHODS: Fifty patients (18 females, 32 males; age range, 15-93 years; mean age, 63.6 years) underwent 4-MDCT of the chest (detector width, 1 mm; beam pitch, 1.5). Contrast material was administered in 20 of the 50 patients. Coronal and transverse sections were reformatted into 5-mm-thick sections at 3.5-mm intervals. All available image and clinical data consensually reviewed by two thoracic radiologists served as the reference standard. Subsequently, three other thoracic radiologists independently evaluated reformatted coronal and transverse images at two separate review sessions. Each image set was assessed in 58 categories for abnormalities of the lungs, mediastinum, pleura, chest wall, diaphragm, abdomen, and skeleton. Interpretation times and number of images assessed were recorded. Sensitivity, specificity, and interobserver concordance were calculated. Differences in mean sensitivities and specificities were evaluated with Wilcoxon's signed rank test. RESULTS: The most common findings identified were pulmonary nodules (n = 73, transverse images; n = 72, coronal images) and emphysema (n = 45, transverse; n = 40, coronal). The mean detection sensitivity of all lesions was significantly (p = 0.001) lower on coronal (44% +/- 26% [SD]) than on transverse (51% +/- 22%) images, whereas the mean detection specificity was significantly (p = 0.005) higher (96% +/- 5% vs 95% +/- 6%, respectively). Reporting findings for significantly (p < 0.001) fewer coronal images (mean, 63.0 +/- 4.6 images) than transverse images (mean, 91.9 +/- 8.8 images) took significantly (p = 0.025) longer (mean, 263 +/- 56 sec vs 238 +/- 45 sec, respectively). CONCLUSION: Primary interpretation of thoracic MDCT is less sensitive and more time-consuming using 5-mm-thick coronal reformations as compared with transverse images.     

Scrotal scintigraphy in varicocele compared with physical examination and venography

Scrotal scintigraphy using a gamma-camera and 740 MBq of 99mTc-labeled human serum albumin was performed on 43 patients with suspected varicocele. In 39 patients (37 left-sided, 2 bilateral) with proven varicoceles, sensitivities by the static and dynamic images were 92.3% and 51.3%, respectively. There were no false positive cases in either image (4 cases with no varicocele). It has been suggested that static images are useful for the detection of varicocele in infertile men. A comparison between the static and clinical grades showed that the static grades appeared to become higher in proportion to the clinical grades. A comparison between the static grades and the diameter of the internal spermatic vein (ISV) showed that the mean value of the diameter of the ISV in SG 1, SG 2 and SG 3 was 4.1 +/- 0.66 mm, 5.1 +/- 0.68 mm, and 6.2 +/- 0.79 mm, respectively. Patients with higher static grades had ISVs of significantly larger diameter (SG 1 vs SG 2; p less than 0.05, SG2 vs SG3; p less than 0.01, SG 1 vs SG 3; p less than 0.01, t-test). A comparison between the dynamic images and the degree of reflux in the ISV showed that patients with positive dynamic images had a significantly greater degree of reflux (p less than 0.01, Chi-square test). From these observations, scintigraphic findings would reflect the degree of reflux in the ISV, the diameter of ISV, and the size of the varicocele. Furthermore, from the remarkable changes between pre- and post-therapeutic findings on the scintigrams, therapeutic effects could be easily and objectively assessed by scintigraphy.