Optimization of radiation doses for open lumbar spinal fusion using C-arm fluoroscopy and impact on radiation-induced cancer: a pilot study.

PURPOSE: Intraoperative fluoroscopy use is essential during spinal fusion procedures. The amount of radiation dose should always be minimized. This study aimed to determine the feasibility of halving the frame rate from 12.5 to 6.25 frames per second (fps) and to quantify the reduction in the risk of developing radiation-induced cancer. METHODS: This pilot study included 34 consecutive patients operated for open lumbar posterolateral fusion (PLF) with or without transforaminal lumbar interbody fusion (TLIF). C-arm modes were changed from half-dose (12.5 frames per second (fps), group I) to quarter-dose (6.25 fps, group II). Age, body mass index, surgical procedure, number of treated levels, and complications were collected. Kerma area product (KAP), cumulative air kerma (CAK), and fluoroscopy time were compared. Effective dose and radiation-induced cancer risk were estimated. RESULTS: Eighteen and 16 patients were, respectively, included in group I and II. Demographic, surgical data, and fluoroscopy time were similar in both groups. However, CAK, KAP, and effective dose were significantly lower in group II, respectively, 0.56 versus 0.41 mGy (p = 0.03), 0.09 versus 0.06 Gy cm2 (p = 0.04), and 0.03 versus 0.02 mSv (p = 0.04). Radiation-induced cancer risk decreased by 47.7% from 1.49 × 10-6 to 7.77 × 10-7 after optimization. No complications were recorded in either group. CONCLUSION: This study demonstrates the feasibility of setting 6.25 fps for TLIF with and without PLF. By halving the fps, radiation-induced cancer risk could be almost divided by two, without compromising surgical outcome. Finally, after optimization, the risk of developing radiation-induced cancer was less than one in a million.

Efficacy of Chest CT for COVID-19 Pneumonia Diagnosis in France.

Background The role and performance of chest CT in the diagnosis of the coronavirus disease 2019 (COVID-19) pandemic remains under active investigation. Purpose To evaluate the French national experience using chest CT for COVID-19, results of chest CT and reverse transcription polymerase chain reaction (RT-PCR) assays were compared together and with the final discharge diagnosis used as the reference standard. Materials and Methods A structured CT scan survey (NCT04339686) was sent to 26 hospital radiology departments in France between March 2, 2020, and April 24, 2020. These dates correspond to the peak of the national COVID-19 epidemic. Radiology departments were selected to reflect the estimated geographic prevalence heterogeneities of the epidemic. All symptomatic patients suspected of having COVID-19 pneumonia who underwent both initial chest CT and at least one RT-PCR test within 48 hours were included. The final discharge diagnosis, based on multiparametric items, was recorded. Data for each center were prospectively collected and gathered each week. Test efficacy was determined by using the Mann-Whitney test, Student t test, χ2 test, and Pearson correlation coefficient. P < .05 indicated a significant difference. Results Twenty-six of 26 hospital radiology departments responded to the survey, with 7500 patients entered; 2652 did not have RT-PCR test results or had unknown or excess delay between the RT-PCR test and CT. After exclusions, 4824 patients (mean age, 64 years ± 19 [standard deviation], 2669 male) were included. With final diagnosis as the reference, 2564 of the 4824 patients had COVID-19 (53%). Sensitivity, specificity, negative predictive value, and positive predictive value of chest CT in the diagnosis of COVID-19 were 2319 of 2564 (90%; 95% CI: 89, 91), 2056 of 2260 (91%; 95% CI: 91, 92), 2056 of 2300 (89%; 95% CI: 87, 90), and 2319 of 2524 (92%; 95% CI: 91, 93), respectively. There was no significant difference for chest CT efficacy among the 26 geographically separate sites, each with varying amounts of disease prevalence. Conclusion Use of chest CT for the initial diagnosis and triage of patients suspected of having coronavirus disease 2019 was successful. © RSNA, 2021 Online supplemental material is available for this article.

COVID-19 impact assessment on the French radiological centers: a nationwide survey.

PURPOSE: To determine the impact of the COVID-19 on the CT activities in French radiological centers during the epidemic peak. MATERIALS AND METHODS: A cross-sectional prospective CT scan survey was conducted between March 16 and April 12, 2020, in accordance with the local IRB. Seven hundred nine radiology centers were invited to participate in a weekly online survey. Numbers of CT examinations related to COVID-19 including at least chest (CTcovid) and whole chest CT scan activities (CTchest) were recorded each week. A sub-analysis on French departments was performed during the 4 weeks of the study. The impact of the number of RT-PCRs (reverse transcriptase polymerase chain reactions) on the CT workflow was tested using two-sample t test and Pearson's test. RESULTS: Five hundred seventy-seven structures finally registered (78%) with mean response numbers of 336 ± 18.9 (323; 351). Mean CTchest activity per radiologic structure ranged from 75.8 ± 133 (0-1444) on week 12 to 99.3 ± 138.6 (0-1147) on week 13. Mean ratio of CTcovid on CTchest varied from 0.36 to 0.59 on week 12 and week 14 respectively. There was a significant relationship between the number of RT-PCR performed and the number of CTcovid (r = 0.73, p = 3.10-16) but no link with the number of positive RT-PCR results. CONCLUSION: In case of local high density COVID-19, CT workflow is strongly modified and redirected to the management of these specific patients. KEY POINTS: • Over the 4-week survey period, 117,686 chest CT (CTtotal) were performed among the responding centers, including 61,784 (52%) CT performed for COVID-19 (CTcovid). • Across the country, the ratio CTcovid/CTtotal varied from 0.36 to 0.59 and depended significantly on the local epidemic density (p = 0.003). • In clinical practice, in a context of growing epidemic, in France, chest CT was used as a surrogate to RT-PCR for patient triage.

Breast dose reduction options during thoracic CT: influence of breast thickness.

OBJECTIVE: Little is known about the effectiveness of dose reduction options according to breast thickness. The purpose of this phantom study was to compare the effects on dose and noise of bismuth shielding versus a low kilovoltage for different breast thicknesses. MATERIALS AND METHODS: CT acquisitions were performed first at 120 kVp (reference acquisition), then at 120 kVp with shielding and at 100 kVp without shielding on a phantom with three different prosthetic breast thicknesses, corresponding to the minimum, median, and maximum values first measured in a sample of 30 female thoracic CT examinations, which were randomly selected. Breast doses were measured with optically stimulated luminescence dosimeters placed on and beneath the prosthetic breast. For noise evaluation, the CT number SDs were measured within six ROIs at increasing depths. RESULTS: Taking into account all breast thicknesses, the average breast dose was reduced by 42.1% with shielding and by 33.0% at 100 kVp (p=0.009). In-depth noise increased less with shielding (19.0% vs 32.1%, p<0.0001). For 1-cm breast thickness, the breast dose fell by 46.5% and 29.7% with shielding and 100 kVp, respectively (p=0.01), and in-depth noise increased by 19.5% and 33.9% (p=0.01). The corresponding values for 2-cm breast thickness were -38.5% and -30.1%, (p=0.02) and 16.5% and 33.5% (p=0.001), whereas those for 4-cm thickness were -40.6% and -40.5% (p=0.95) and 20.7 and 29.2% (p=0.02). CONCLUSION: Greater breast dose reduction is achieved by shielding for breast thicknesses less than 4 cm. Regardless of breast thickness, shielding leads to a smaller increase in in-depth noise.

Detection of residual packets in cocaine body packers: low accuracy of abdominal radiography-a prospective study.

OBJECTIVE: To evaluate the accuracy of abdominal radiography (AXR) for the detection of residual cocaine packets by comparison with computed tomography (CT). METHODS: Over a 1-year period unenhanced CT was systematically performed in addition to AXR for pre-discharge evaluation of cocaine body packers. AXR and CT were interpreted independently by two radiologists blinded to clinical outcome. Patient and packet characteristics were compared between the groups with residual portage and complete decontamination. RESULTS: Among 138 body packers studied, 14 (10 %) had one residual packet identified on pre-discharge CT. On AXR, at least one reader failed to detect the residual packet in 10 (70 %) of these 14 body packers. The sensitivity and specificity of AXR were 28.6 % (95 % CI: 8.4-58.1) and 100.0 % (95 % CI: 97.0-100.0) for reader 1 and 35.7 % (95 % CI: 12.8-64.9) and 97.6 % (95 % CI: 93.1-99.5) for reader 2. There were no significant patient or packet characteristics predictive of residual portage or AXR false negativity. All positive CT results were confirmed by delayed expulsion or surgical findings, while negative results were confirmed by further surveillance. CONCLUSION: Given the poor performance of AXR, CT should be systematically performed to ensure safe hospital discharge of cocaine body packers. KEY POINTS: • Both abdominal radiography and computed tomography can identify gastrointestinal cocaine packets. • Ten per cent of body packers had residual packets despite two packet-free stools. • Seventy per cent of these residual packets were missed on AXR. • No patient or packet characteristics predicted residual packets or AXR false negativity. • CT is necessary to ensure safe medical discharge of body packers.

Spectral performance of two split-filter dual-energy CT systems: A phantom study.

BACKGROUND: Recently, a second generation of split filter dual-energy CT (SFCT) platform has been developed. The thicknesses of the gold and tin filters used to obtain both low- and high-energy spectra have been changed. These differences in filter thickness may affect the spectral separation between the two spectra and thus the quality of spectral images. PURPOSE: To compare the spectral performance of two Split-Filter Dual-Energy CT systems (SFCT-1st and SFCT-2nd ) on virtual monoenergetic images (VMIs) and iodine map. METHODS: A Multi-Energy CT phantom was scanned on two SFCT with a tube voltage of 120 kVp for both systems (SFCT-1st -120 and SFCT-2nd -120) and 140 kVp only for the second generation (SFCT-2nd -140). Acquisitions were performed on the phantom with a CTDIvol close to 11 mGy. Noise power spectrum (NPS) and task-based transfer function (TTF) were evaluated on VMIs from 40 to 70 keV. A detectability index (d') was computed to assess the detection of two contrast-enhanced lesions on VMIs. Hounsfield Unit (HU) accuracy was assessed on VMIs and the accuracy of iodine concentration was assessed on iodine maps. RESULTS: For all keV, noise magnitude values were lower with the SFCT-2nd -120 than with the SFCT-1st -120 (on average: -22.5 ± 2.9%) and higher with the SFCT-2nd -140 than with the SFCT-2nd -120 (on average: 25.0 ± 6.2%). Average NPS spatial frequencies (fav ) were lower with the SFCT-1st -120 than with the SFCT-2nd -120 (-6.0 ± 0.5%) and the SFCT-2nd -140 (-3.6 ± 1.6%). Similar TTF50% values were found for both systems and both kVp for blood and iodine inserts at 2 mg/mL (0.29 ± 0.01 mm-1 ) and at 4 mg/mL (0.31 ± 0.01 mm-1 ). d' values peaked at 40 keV for the SFCT-2nd and at 70 keV for the SFCT-1st . Highest d' values were found for the SFCT-2nd -120 for both simulated lesions. Accuracy of HU values and iodine concentration was higher with the SFCT-2nd than with the SFCT 1st . CONCLUSION: Compared to the SFCT-1st , with similar spatial resolution and noise texture values, the SFCT-2nd -120 exhibited the lowest values for noise magnitude, the highest detectability index values, and more accurate HU values and iodine concentrations.

Impact of tin filter on the image quality of ultra-low dose chest CT: A phantom study on three CT systems.

PURPOSE: The purpose of this study was to assess the impact of a tin filter on the image quality of ultra-low dose (ULD) chest computed tomography (CT) on three different CT systems. MATERIALS AND METHODS: An image quality phantom was scanned on three CT systems including two split-filter dual-energy CT (SFCT-1 and SFCT-2) scanners and one dual-source CT scanner (DSCT). Acquisitions were performed with a volume CT dose index (CTDIvol) of 0.4 mGy, first at 100 kVp without tin filter (Sn), and second, at Sn100/Sn140 kVp, Sn100/Sn110/Sn120/Sn130/Sn140/Sn150 kVp and Sn100/Sn150 kVp for SFCT-1, SFCT-2 and DSCT respectively. Noise-power-spectrum and task-based transfer function were computed. The detectability index (d') was computed to model the detection of two chest lesions. RESULTS: For DSCT and SFCT-1, noise magnitude values were higher with 100kVp than with Sn100 kVp and with Sn140 kVp or Sn150 kVp than with Sn100 kVp. For SFCT-2, noise magnitude increased from Sn110 kVp to Sn150 kVp and was higher at Sn100 kVp than at Sn110 kVp. For most kVp with the tin filter, the noise amplitude values were lower than those obtained at 100 kVp. For each CT system, noise texture and spatial resolution values were similar with 100 kVp and with all kVp used with a tin filter. For all simulated chest lesions, the highest d' values were obtained at Sn100 kVp for SFCT-1 and DSCT and at Sn110 kVp for SFCT-2. CONCLUSION: For ULD chest CT protocols, the lowest noise magnitude and highest detectability values for simulated chest lesions are obtained with Sn100 kVp for the SFCT-1 and DSCT CT systems and at Sn110 kVp for SFCT-2.

Impact of Phantom Size on Low-Energy Virtual Monoenergetic Images of Three Dual-Energy CT Platforms.

The purpose of this study was to compare the quality of low-energy virtual monoenergetic images (VMIs) obtained with three Dual-Energy CT (DECT) platforms according to the phantom diameter. Three sections of the Mercury Phantom 4.0 were scanned on two generations of split-filter CTs (SFCT-1st and SFCT-2nd) and on one Dual-source CT (DSCT). The noise power spectrum (NPS), task-based transfer function (TTF), and detectability index (d') were assessed on VMIs from 40 to 70 keV. The highest noise magnitude values were found with SFCT-1st and noise magnitude was higher with DSCT than with SFCT-2nd for 26 cm (10.2% ± 1.3%) and 31 cm (7.0% ± 2.5%), and the opposite for 36 cm (-4.2% ± 2.5%). The highest average NPS spatial frequencies and TTF values at 50% (f50) values were found with DSCT. For all energy levels, the f50 values were higher with SFCT-2nd than SFCT-1st for 26 cm (3.2% ± 0.4%) and the opposite for 31 cm (-6.9% ± 0.5%) and 36 cm (-5.6% ± 0.7%). The lowest d' values were found with SFCT-1st. For all energy levels, the d' values were lower with DSCT than with SFCT-2nd for 26 cm (-6.2% ± 0.7%), similar for 31 cm (-0.3% ± 1.9%) and higher for 36 cm (5.4% ± 2.7%). In conclusion, compared to SFCT-1st, SFCT-2nd exhibited a lower noise magnitude and higher detectability values. Compared with DSCT, SFCT-2nd had a lower noise magnitude and higher detectability for the 26 cm, but the opposite was true for the 36 cm.

Technical note: Design and initial evaluation of a novel physical breast phantom to monitor image quality in digital breast tomosynthesis.

PURPOSE: To describe the creation process of a new breast phantom specifically designed to monitor quality control (QC) metrics consistency over several months in digital breast tomosynthesis (DBT). METHODS: The semi-anthropomorphic Tomomam® phantom was designed and evaluated twice monthly on a single Hologic Selenia Dimensions® unit over 5 months. The phantom is manufactured in a one-piece epoxy resin homogeneous material as the basis for manufacturing, simulating breast tissue as 50% equivalent glandular (GL)/50% equivalent adipose (AD) and compressed thickness of 60 mm. The distribution of test objects on different planes inside the phantom should allow the quantification of 10 image quality metrics: reproducibility, signal difference-to-noise ratio (SDNR), geometric distortions in the plane, missing or added tissue at chest wall, at the top and bottom of images stack and lateral sides, in-plane homogeneity, image scoring, artifact spread function (ASF), geometric distortions in the volume. SDNR was quantified according to GL and AD tissues. Tolerance criteria per parameter were described to analyze results over the study time. RESULTS: Mean scores were equal to 15.4, 15.0, and 11.6 for masses, microcalcifications, and fibers, respectively. A large difference between GL and AD tissues for SDNR metrics was noted over the study time: the best results were obtained from GL tissues. Both geometric distortions and local homogeneity in the plane conformed to expected values. The mean volume value of the triangular prism was 11.3% greater than the expected value due to a reconstruction height equal to 66 mm instead of 60 mm. CONCLUSIONS: In this study, we monitored several QC metrics discriminating GL and AD tissues by using a new breast phantom developed by us. The preliminary clinical tests demonstrated that the Tomomam® phantom could be used to reliably and efficiently track 10 QC metrics with a single acquisition. More data need to be acquired to refine tolerance criteria for some metrics.

Synthesis and activation of an iron oxide immobilized drug-mimicking reporter under conventional and pulsed X-ray irradiation conditions.

An efficient nano-sized delivery system is presented here allowing the immobilized, picolinium-tethered organic ligand to be released by X-ray irradiation. A marked difference was observed in the fragmentation efficiency by using conventional Cs-137 vs. pulsed sources.

Experimental evaluation of seven quality control phantoms for digital breast tomosynthesis.

PURPOSES: The introduction of digital breast tomosynthesis (DBT) into the French breast cancer screening program is forecast by the authorities. The aim of the present study was to evaluate image quality phantoms to be used as internal quality controls. METHODS: Seven breast phantoms dedicated to quality control in mammography were evaluated on reconstructed DBT images: ACR Model 015, BR3D, DBT QC model 021, Mam/Digi-EPQC, MTM100, TOMOMAM® and TOMOPHAN®. Two representative image parameters of DBT images were studied: image score and z-resolution, when inserts were included in the phantom, on five DBT systems of three different brands. Three observers were involved. RESULTS: The MTM100, Mam/Digi-EPQC, BR3D, DBT QC model 021 phantoms' images presented artefacts affecting the image score. The ACR Model 015, TOMOMAM® and TOMOPHAN® phantoms appeared to be pertinent for DBT image score analysis. Due to saturation artefacts, Z-resolution results were not coherent with the theory for all phantoms except by using aluminium beads in the TOMOMAM® phantom. CONCLUSIONS: Phantom manufacturers should be encouraged to collaborate with DBT system manufacturers in order to design universal phantoms suitable for all systems for more complete quality control. From our study we can propose several specifications for an ideal and universal phantom designed for internal quality control in DBT. Phantoms should allow sensitive image score measurements. The background structure should be realistic to avoid artefacts. Phantoms should have a standard breast-like shape and size.

Impact of anatomical location on value of CT-PET co-registration for delineation of lung tumors.

PURPOSE: To derive guidelines for the need to use positron emission tomography (PET) for delineation of the primary tumor (PT) according to its anatomical location in the lung. METHODS AND MATERIALS: In 22 patients with non-small-cell lung cancer, thoracic X-ray computed tomography (CT) and PET were performed. Eleven radiation oncologists delineated the PT on the CT and on the CT-PET registered scans. The PTs were classified into two groups. In Group I patients, the PT was surrounded by lung or visceral pleura, without venous invasion, without extension to chest wall or the mediastinum over more than one quarter of its surface. In Group II patients, the PT invaded the hilar region, heart, great vessels, pericardium, mediastinum over more than one quarter of its surface and/or associated with atelectasis. A comparison of interobserver variability for each group was performed and expressed as a local standard deviation. RESULTS: The comparison of delineations showed a good reproducibility for Group I, with an average SD of 0.4 cm on CT and an average SD of 0.3 cm on CT-PET (p = 0.1628). There was also a significant improvement with CT-PET for Group II, with an average SD of 1.3 cm on CT and SD of 0.4 cm on CT-PET (p = 0.0003). The improvement was mainly located at the atelectasis/tumor interface. At the tumor/lung and tumor/hilum interfaces, the observer variation was similar with both modalities. CONCLUSIONS: Using PET for PT delineation is mandatory to decrease interobserver variability in the hilar region, heart, great vessels, pericardium, mediastinum, and/or the region associated with atelectasis; however it is not essential for delineation of PT surrounded by lung or visceral pleura, without venous invasion or extension to the chest wall.

Retrospective attenuation correction of PET data for radiotherapy planning using a free breathing CT.

PURPOSE: To evaluate the image quality of retrospectively attenuation corrected Positron Emission Tomography (PET) scans used for gross tumor volume (GTV) delineation in lung cancer patients. MATERIALS AND METHODS: Data of 13 lymph node positive lung cancer patients were acquired on separate CT and PET scanners under free breathing conditions (for radiotherapy planning). First we determined a protocol for CT/PET registration. Second, we compared the image quality of attenuation-corrected PET images using positron transmission images and CT images, in terms of signal-to-noise ratio (SNR) and lesion-to-background ratio (contrast). RESULTS: The largest differences between manual and automatic CT/PET registration were found in the anterior-posterior direction with a mean of 1.8 mm (SD 1.0 mm). Differences in rotations were always smaller than 1.0 degrees . The attenuation-corrected images using CT showed a larger SNR (mean 30%, SD 17%) and larger contrast (mean 14.0%, SD 8.5%) compared to attenuation-corrected images using positron transmission. For lymph nodes, the mean contrast was 16% (SD 6.4%) larger. CONCLUSIONS: This study demonstrated that attenuation correction based on CT provides a better image quality for GTV delineation than when using positron transmission for attenuation correction. Retrospective attenuation correction of PET scans based on registered CT is a good alternative for a dedicated PET/CT scanner if a free-breathing CT is available, e.g., for radiotherapy planning, and allows the use of CT with diagnostic quality for attenuation correction.

Reduction of observer variation using matched CT-PET for lung cancer delineation: a three-dimensional analysis.

PURPOSE: Target delineation using only CT information introduces large geometric uncertainties in radiotherapy for lung cancer. Therefore, a reduction of the delineation variability is needed. The impact of including a matched CT scan with 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) and adaptation of the delineation protocol and software on target delineation in lung cancer was evaluated in an extensive multi-institutional setting and compared with the delineations using CT only. METHODS AND MATERIALS: The study was separated into two phases. For the first phase, 11 radiation oncologists (observers) delineated the gross tumor volume (GTV), including the pathologic lymph nodes of 22 lung cancer patients (Stages I-IIIB) on CT only. For the second phase (1 year later), the same radiation oncologists delineated the GTV of the same 22 patients on a matched CT-FDG-PET scan using an adapted delineation protocol and software (according to the results of the first phase). All delineated volumes were analyzed in detail. The observer variation was computed in three dimensions by measuring the distance between the median GTV surface and each individual GTV. The variation in distance of all radiation oncologists was expressed as a standard deviation. The observer variation was evaluated for anatomic regions (lung, mediastinum, chest wall, atelectasis, and lymph nodes) and interpretation regions (agreement and disagreement; i.e., >80% vs. <80% of the radiation oncologists delineated the same structure, respectively). All radiation oncologist-computer interactions were recorded and analyzed with a tool called "Big Brother." RESULTS: The overall three-dimensional observer variation was reduced from 1.0 cm (SD) for the first phase (CT only) to 0.4 cm (SD) for the second phase (matched CT-FDG-PET). The largest reduction in the observer variation was seen in the atelectasis region (SD 1.9 cm reduced to 0.5 cm). The mean ratio between the common and encompassing volume was 0.17 and 0.29 for the first and second phases, respectively. For the first phase, the common volume was 0 in 4 patients (i.e., no common point for all GTVs). In the second phase, the common volume was always >0. For all anatomic regions, the interpretation differences among the radiation oncologists were reduced. The amount of disagreement was 45% and 18% for the first and second phase, respectively. Furthermore, the mean delineation time (12 vs. 16 min, p<0.001) and mean number of corrections (25 vs. 39, p<0.001) were reduced in the second phase compared with the first phase. CONCLUSION: For high-precision radiotherapy, the delineation of lung target volumes using only CT introduces too great a variability among radiation oncologists. Implementing matched CT-FDG-PET and adapted delineation protocol and software reduced observer variation in lung cancer delineation significantly with respect to CT only. However, the remaining observer variation was still large compared with other geometric uncertainties (setup variation and organ motion).

Impact of coronal and sagittal views on lung gross tumor volume delineation.

BACKGROUND AND PURPOSE: To study the impact of coronal and sagittal views (CSV) on the gross tumor volume (GTV) delineation on CT and matched PET/CT scans in non-small cell lung cancer. MATERIAL AND METHODS: GTV delineations were performed by 11 experienced radiation oncologists on CT and PET/CT in 22 patients. Two tumor groups were defined: Group I: Primary tumors surrounded by lung or visceral pleura, without venous invasion, and without large extensions to the chest wall or the mediastinum. Group II: Tumors invading the hilar region, heart, large vessels, pericardium, and the mediastinum and/or associated with atelectasis. Tumor volumes and inter-observers variations (SD) were calculated and compared according to the use of axial view only (AW), axial/coronal/sagittal views (ACSW) and ACSW/PET (ACSWP). RESULTS: CSV were not frequently used (57.4% out of 242 delineations on CT). For group I, ACSW didn't improve significantly mean GTVs. SDs were small on CT and on PET (SD=0.3cm). For group II, ACSW had 27-46% smaller observer variation (mean SD=0.7cm) than AW (mean SD=1.1cm). The smaller observer variation of ACSW users was associated with, on average, a 40% smaller delineated volume (p=0.038). Mean GTV of ACSWP was 21% larger than mean GTV of ACSW on CT. CONCLUSIONS: For smaller lung tumors surrounded by healthy lung tissue the effect of multiple axis delineation is limited. However, application of coronal and sagittal windows is highly beneficial for delineation of more complex tumors, with atelectasis and/or pathological lymph nodes even if PET is used.

Observer variation in target volume delineation of lung cancer related to radiation oncologist-computer interaction: a 'Big Brother' evaluation.

BACKGROUND AND PURPOSE: To evaluate the process of target volume delineation in lung cancer for optimization of imaging, delineation protocol and delineation software. PATIENTS AND METHODS: Eleven radiation oncologists (observers) from five different institutions delineated the Gross Tumor Volume (GTV) including positive lymph nodes of 22 lung cancer patients (stages I-IIIB) on CT only. All radiation oncologist-computer interactions were recorded with a tool called 'Big Brother'. For each radiation oncologist and patient the following issues were analyzed: delineation time, number of delineated points and corrections, zoom levels, level and window (L/W) settings, CT slice changes, use of side windows (coronal and sagittal) and software button use. RESULTS: The mean delineation time per GTV was 16 min (SD 10 min). The mean delineation time for lymph node positive patients was on average 3 min larger (P = 0.02) than for lymph node negative patients. Many corrections (55%) were due to L/W change (e.g. delineating in mediastinum L/W and then correcting in lung L/W). For the lymph node region, a relatively large number of corrections was found (3.7 corr/cm2), indicating that it was difficult to delineate lymph nodes. For the tumor-atelectasis region, a relative small number of corrections was found (1.0 corr/cm2), indicating that including or excluding atelectasis into the GTV was a clinical decision. Inappropriate use of L/W settings was frequently found (e.g. 46% of all delineated points in the tumor-lung region were delineated in mediastinum L/W settings). Despite a large observer variation in cranial and caudal direction of 0.72 cm (1 SD), the coronal and sagittal side windows were not used in 45 and 60% of the cases, respectively. For the more difficult cases, observer variation was smaller when the coronal and sagittal side windows were used. CONCLUSIONS: With the 'Big Brother' tool a method was developed to trace the delineation process. The differences between observers concerning the delineation style were large. This study led to recommendations on how to improve delineation accuracy by adapting the delineation protocol (guidelines for L/W use) and delineation software (double window with lung and mediastinum L/W settings at the same time, enforced use of coronal and sagittal views) and including FDG-PET information (lymph nodes and atelectasis).

Impact of knee support and shape of tabletop on rectum and prostate position.

PURPOSE: To evaluate the impact of different tabletops with or without a knee support on the position of the rectum, prostate, and bulb of the penis; and to evaluate the effect of these patient-positioning devices on treatment planning. METHODS AND MATERIALS: For 10 male volunteers, five MRI scans were made in four different positions: on a flat tabletop with knee support, on a flat tabletop without knee support, on a rounded tabletop with knee support, and on a rounded tabletop without knee support. The fifth scan was in the same position as the first. With image registration, the position differences of the rectum, prostate, and bulb of the penis were measured at several points in a sagittal plane through the central axis of the prostate. A planning target volume was generated from the delineated prostates with a margin of 10 mm in three dimensions. A three-field treatment plan with a prescribed dose of 78 Gy to the International Commission on Radiation Units and Measurements point was automatically generated from each planning target volume. Dose-volume histograms were calculated for all rectal walls. RESULTS: The shape of the tabletop did not affect the rectum and prostate position. Addition of a knee support shifted the anterior and posterior rectal walls dorsally. For the anterior rectal wall, the maximum dorsal shift was 9.9 mm (standard error of the mean [SEM] 1.7 mm) at the top of the prostate. For the posterior rectal wall, the maximum dorsal shift was 10.2 mm (SEM 1.5 mm) at the middle of the prostate. Therefore, the rectal filling was pushed caudally when a knee support was added. The knee support caused a rotation of the prostate around the left-right axis at the apex (i.e., a dorsal rotation) by 5.6 degrees (SEM 0.8 degrees ) and shifts in the caudal and dorsal directions of 2.6 mm (SEM 0.4 cm) and 1.4 mm (SEM 0.6 mm), respectively. The position of the bulb of the penis was not influenced by the use of a knee support or rounded tabletop. The volume of the rectal wall receiving the same dose range (e.g., 40-75 Gy) was reduced by 3.5% (SEM 0.9%) when a knee support was added. No significant differences were observed between the first and fifth scan (flat tabletop with knee support) for all measured points, thereby excluding time trends. CONCLUSIONS: The rectum and prostate were significantly shifted dorsally by the use of a knee support. The rectum shifted more than the prostate, resulting in a dose benefit compared with irradiation without knee support. The shape of the tabletop did not influence the rectum or prostate position.

Uterine artery embolization for leiomyomata: optimization of the radiation dose to the patient using a flat-panel detector angiographic suite.

The purpose of this study was to assess the ability of low-dose/low-frame fluoroscopy/angiography with a flat-panel detector angiographic suite to reduce the dose delivered to patients during uterine fibroid embolization (UFE). A two-step prospective dosimetric study was conducted, with a flat-panel detector angiography suite (Siemens Axiom Artis) integrating automatic exposure control (AEC), during 20 consecutive UFEs. Patient dosimetry was performed using calibrated thermoluminescent dosimeters placed on the lower posterior pelvis skin. The first step (10 patients; group A) consisted in UFE (bilateral embolization, calibrated microspheres) performed using the following parameters: standard fluoroscopy (15 pulses/s) and angiography (3 frames/s). The second step (next consecutive 10 patients; group B) used low-dose/low-frame fluoroscopy (7.5 pulses/s for catheterization and 3 pulses/s for embolization) and angiography (1 frame/s). We also recorded the total dose-area product (DAP) delivered to the patient and the fluoroscopy time as reported by the manufacturer's dosimetry report. The mean peak skin dose decreased from 2.4 +/- 1.3 to 0.4 +/- 0.3 Gy (P = 0.001) for groups A and B, respectively. The DAP values decreased from 43,113 +/- 27,207 microGy m(2) for group A to 9,515 +/- 4,520 microGy m(2) for group B (P = 0.003). The dose to ovaries and uterus decreased from 378 +/- 238 mGy (group A) to 83 +/- 41 mGy (group B) and from 388 +/- 246 mGy (group A) to 85 +/- 39 mGy (group B), respectively. Effective doses decreased from 112 +/- 71 mSv (group A) to 24 +/- 12 mSv (group B) (P = 0.003). In conclusion, the use of low-dose/low-frame fluoroscopy/angiography, based on a good understanding of the AEC system and also on the technique during uterine fibroid embolization, allows a significant decrease in the dose exposure to the patient.