Slow CT Scan Research Articles

P3.16-16 Long Term Outcomes of Body Gamma-Ray Stereotactic Ablative Radiotherapy for Patients with Stage I/II Non-Small Cell Lung Cancer

The authors evaluated the efficacy, patterns of failure, toxicity and cost of body gamma-ray stereotactic ablative radiotherapy (Body Gamma-ray SABR) for patients with medically inoperable, clinical stage I/II non-small cell lung cancer (NSCLC) with 8 years of follow-up. Clinical staging was performed according to the sixth edition of the American Joint Committee on Cancer TNM staging system. Eligible patients who had no previous treatments, with histologically confirmed NSCLC, determined as clinical stage I /II, underwent OUR-QGD type of the body gamma-ray SABR (70 grays in 10 fractions for gross target volume) at the Radiation Oncology Department, People's Liberation Army Airforce General Hospital, Beijing, China from January 2007 to July 2010. All patients were immobilized by vacuum bag, and then a slow CT scan was performed without any respiration gating. The total radiation dose of 50%, 60%, and 70% isodose line were prescribed in 50, 60, and 70 Grey (Gy) correspondingly, covering 100% of the planning target volume (PTV), 90% of the clinical target volume (CTV), and 80% of the gross target volume (GTV) in 10 fractions. The CT scan and/or positron emission tomography/computed tomography were every 3 months for the first 2 years, every 6 months for the next 3 years, and then annually thereafter to evaluate the efficacy of the treatment. The primary endpoint was overall survival. A total of 29 patients were eligible for analysis. The median age of the patients was 71 years (55-87), and the median follow-up was 8.1 years (6.8-10.3). The 1-year, 3-year, 5-year and 8-year overall survival rates were 93.1%, 72.1%, 59.4% and 44.8%, and the local, regional and distant disease recurrence were 10.3%, 13.8% and 13.8% at 5 years and 10.3%, 17.2% and 20.7% at 8 years. Two patients (6.9%) experienced grade 3 treatment-related adverse events. No patients developed grade 4 or 5 adverse events. The median cost of body gamma-ray SABR is 4838 dollars (4615-4923 dollars). With long-term follow-up, the results of the current study demonstrated outstanding local control and low toxicity after body gamma-ray SABR in patients with clinical stage I/II NSCLC. The dominant failure included regional and distant disease recurrence. And the body Gamma-ray SABR is pretty cost-effective.

OA015] Evaluation of optimized slow-CT parameters with freebreathing marges based on spirometric system analysis

Introduction The free-breathing gated technique (FB) requires a synchronization between the CT-scan and breathing cycles but is not included in every system. The Slow-CT scan is an alternative to the monitoring of target motion. Reconstruction artefacts are identified in the literature. This study’s purpose is to evaluate an optimization of Slow-CT parameters and the impact of spirometric management concerning image qualities, breath amplitude marges and treatment safety. Materials and methods Breathing interfraction impacts are based on retrospective study including 80 archived patient curves from Dyn’R® SDX system. Standard, Slow and 4D-CT acquisitions are made on SIEMENS Somatom® Scope. Image quality indexes are analyzed on Catphan®. A lung equivalent cylindrical insert including a 30.0 mm diameter sphere is set in motion by Quasar®. Reconstruction performances are evaluated for breaths from 10 to 30 breaths per minute (BPM). The CT-scan radiation exposures are recorded. On prospective study from 5 patients, target reconstructions are compared for 4D-CT Average (4D-Ave) and Slow-CT. Results Mean interfraction amplitude is 163 ± 33 mL including a 60 mL calibration uncertainty. Catphan® study showed mean noise reduction up to 30% in Slow-CT (3.0 UH) in comparison with 4D-Ave (4.9 UH). The low contrasts score increases in 4D-Ave. Slow-CT reconstructions are optimized for 15 BPM by using collimation of 16 × 0.6 mm, 2 mm slice, pitch of 0.4 and rotation time of 1.5 s. A new inclusion criteria are defined as the ratio Acquisition time(s)/BPM ≤ 4. In Slow-CT and 4D-CT, image qualities and doses are in agreement with French recommendations. On patients, Slow-CT shows a motion blur and noise reductions compared to 4D-Ave. A protocol is proposed with two Slow-CT slice thickness: 2 mm to increase target limit accuracy and 5 mm to smooth target UH. Spirometric system allows the patient to check its breath by staying in recorded area. Conclusions Slow-CT parameters present an alternative to manage target motion and must be optimized with respect of inclusion criteria. Interfraction respiratory impacts can be controlled with breath margins optimization. Combined technics increase the FB reproducibility and the treatment accuracy especially with the machine feedback control.

2. Optimization of CT-scan acquisition parameters and choice of the breathing amplitude margins for non-synchronized freebreathing technique

Introduction Spirometry allows an indirect control of moving targets in breathing hold (BH) or their monitoring in freebreathing (FB). FB technique requires a synchronization between the CT-scan acquisition (4D-CT) and the breathing cycles. This technique is not included in every system. The Slow-CT scan is a possible alternative to optimize the monitoring of moving targets. The purpose of this study is to evaluate the feasibility of non-synchronized FB using Slow-CT scan in terms of image quality, breathing amplitude and respiratory rate. Methods Standard-CT, Slow-CT and 4D-CT acquisitions are made with a Siemens Somatom Scope Power scan, with a voltage of 130 kV and modulated intensity (CARE Dose 4D®). UH, low contrasts, slice thickness and spatial resolution are analyzed on Catphan® 504. The moving target, a lung equivalent cylindrical insert including a 3 cm diameter sphere, is set in motion by Quasar™ Respiratory Motion. The breathing cycles are created by Trace Generator. Reconstruction performances are evaluated for breaths from 10 to 30 breaths per minute (BPM) and an amplitude of 2 cm. The radiation dose is estimated by the volumetric computed tomography dose index (CTDI). The choice of the FB amplitude margins is made from a retrospective analysis of 15 patients treated in BH conditions. The image quality of the 4D-CT Average and Slow-CT sequences is examined on patients. Results Noise is reduced up to 30% in Slow-CT (σ = 3.0 UH) in comparison with 4D-CT Average (σ = 4.9 UH). A systematic error of +0.35 mm of slice thickness reconstruction occurs for 4D-CT Average. The low contrasts score (visual) increases in 4D-CT Average. In 4D-CT Average (>50 s), the amplitude reconstruction is faithful (49.8 mm instead of 50.0 mm in theory) with the 10 BPM/2 cm amplitude couple. In Slow-CT (>60 s), for BPM between 12 and 18, the mean reconstructed amplitude is 47 mm. It is 41 mm for BPM ⩽10 or ⩾30. The amplitude reconstruction is optimized for 15 BPM (49.5 mm). In Standard-CT (6–20 s), it appears distortions in the 3 reconstruction planes and relatives errors up to 60 %. In Slow-CT and 4D-CT, the mean CTDI are respectively 16.4 mGy and 15.2 mGy. The optimized Slow-CT acquisition parameters are 130 kV, collimation of 16x0.6 mm, 2 mm reconstructed slice, pitch of 0.4, rotation time of 1.5 s and a ratio (Acquisition time (s))/BPM⩾4. The retrospective analysis of patients shows a maximum interfraction amplitude difference of 100 mL. The spirometer calibration includes a 60 mL uncertainty (2% of 3 L). A margin of 100 mL is chosen as upper limit (inhalation); the baseline, allowing an automatic stabilization of the system display, is the lower limit (exhalation). On clinical images, Slow-CT shows a motion blur reduction (heart, mediastinum) and a noise reduction in a range of 10–15%. Conclusions The Slow-CT sequence offers an alternative to 4D-CT for incompatible systems. Parameters such as collimation, pitch, rotation time and the ratio (Acquisition time (s))/BPM⩾4 must be adapted. CTDI are similar for Slow-CT and 4D-CT. Margins optimization and further clinical cases are ongoing. A study about dose optimization while obtaining the same amount of signal will be carried out using different level of noise reduction algorithm.

A comparative study of target volume definition in radiotherapy with “Slow CT Scan” vs. 4D PET/CT Scan in early stages of non-small cell lung cancer

ObjectivesTo evaluate the use of 4D PET/CT to quantify tumor respiratory motion compared to the «Slow»-CT (CTs) in the radiotherapy planning process. Material and methodsA total of 25 patients with inoperable early stage non small cell lung cancer (NSCLC) were included in the study. Each patient was imaged with a CTs (4s/slice) and 4D PET/CT.The adequacy of each technique for respiratory motion capture was evaluated using the volume definition for each of the following: Internal target volume (ITV) 4D and ITVslow in relation with the volume defined by the encompassing volume of 4D PET/CT and CTs (ITVtotal).The maximum distance between the edges of the volume defined by each technique to that of the total volume was measured in orthogonal beam's eye view. ResultsThe ITV4D showed less differences in relation with the ITVtotal in both the cranio-caudal and the antero-posterior axis compared to the ITVslow. The maximum differences were 0.36mm in 4D PET/CTand 0.57mm in CTs in the antero-posterior axis.4D PET/CT resulted in the definition of more accurate (ITV4D/ITVtotal 0.78 vs. ITVs/ITVtotal 0.63), and larger ITVs (19.9cc vs. 16.3cc) than those obtained with CTs. ConclusionPlanning with 4D PET/CT in comparison with CTs, allows incorporating tumor respiratory motion and improving planning radiotherapy of patients in early stages of lung cancer.

Clinical profile of seizure disorder in hospitalized patients

Background: Hughling Jackson in 1870 described first “seizures as intermittent derangement of central nervous system and abnormal and excessive discharge of central nervous tissue on muscles” and the same was refined further. Average incidence rate for epilepsy is 0.3 - 0.5% in patients. Methods: A total of 100 patients admitted with sign and symptoms suggestive of seizure disorder in tertiary care hospital during the period of 1 st December 2012 to 31 st July 2014. A detailed clinical history, examination and investigation with following patients were included in study; (1) age of the patients above 13 years; (2) patient present with history of seizure the cross sectional observational study was carried out at Dr. V. M. Government Medical College, Solapur, Maharashtra, India. Results: Generalized tonic clonic were the commonest type seen in 69 patients (69%) and cerebrovascular disease because seen in 25 patients (25%) is the second most common cause. Conclusions: ( 1) Ring enhancing lesion were seen in 15% patients, among most common was tuberculoma that is seen in 10 patients and neurocysticercosis was seen in 5 patients; (2) cerebral tumour was seen in 4 patients; (3) EEG was abnormal in 31% cases of seizure and most common EEG abnormality was focal slow waves and (4) CT scan abnormality was seen in 47 cases (47%).

Outcome Study of Cobalt Based Stereotactic Body Radiation Therapy for Patients with Inoperable Stage III Non-small Cell Lung Cancer.

Aim of this paper is to retrospectively evaluate the efficacy and toxicity of specialized Body Cobalt based system (BCBS) treatment in the senior patients group (.65 years) with Stage III non-small cell lung carcinoma (NSCLC). A total of 49 patients (41 males and 8 females) with Stage III NSCLC according to UICC TNM classification (6(th) edition) were treated using OUR-QGD™ BCBS which was designed and manufactured in China. Post treatment evaluation with follow-up information was collected from April 2001 to December 2006 in our department. Median age of enrolled patients was 71 years old (65-85). Among those patients, 36 patients were pathologically identified with squamous cell carcinoma, and the other 13 patients were confirmed as adenocarcinoma. All patients were immobilized by vacuum based immobilization mold and then performed slow CT scan without any respiration gating devices. The daily radiation prescription dose was defined at 50% isodose line covering primary lesions and metastatic lymph nodes with doses from 2.5 to 6 Gy in 5 fractions per week according to the tumor stage and internally approved treatment protocols by the Institutional Review Board (IRB). Median daily dose and total delivery dose of 50% isodose line were 4 Gy and 41 Gy, respectively. In this study group, total of 3 patients received neoadjuvant cisplatin-based chemotherapy. Tumor response evaluated 12 weeks after radiation has demonstrated 13 complete responses (26.5%), 21 partial responses (42.9%). The overall survival (OS) rate of 1-year, 2-year and 3-year was 63.3%, 40.8% and 20.4%, respectively. The median and mean survival time was 22 and 24 months. All 49 patients tolerated the treatment well and have completed the planned therapy regiment. Body Cobalt based system treatment of those over 65 years old patients with Stage III NSCLC had reasonable and superior curative effect as well as local control, and at the same time without severe radiation side effects.

SU‐E‐T‐289: Optimal Slow Scan Technique on a Single Slice CT Scanner

Purpose: Adoption of slow scan CT (SSCT) for contouring targets affected by respiratory motion artifacts is an accepted practice. The goal of this study was to propose a CT technique which would yield a target shape that would most closely reproduce that of the ideal excursion volume traced by a moving target sphere. Methods: A single‐slice, large‐bore Marconi scanner was used to acquire axial and spiral scans of a moving plastic sphere. 1 cm movement in the superior‐inferior and anterior‐posterior directions was considered separately to isolate directional issues. Scan techniques such as 1 sec fast scan, 4 sec slow scan, over‐scanning and pitch variations were used to produce target volumes of different shapes due to the interplay between the movement of the target and the x‐ray tube. Shapes were compared to the true excursion volume by scoring them with the Paddick conformity index (CI) as well as by visual inspection. Results: For anterioposterior movement, the average CI was 0.777 (STDEV=0.05) and the largest CI occurred for the axial slow scan, yet visual interpretation showed best agreement with Axial SSCT with overscan. For inferior‐superior movement, the average CI was 0.83 (STDEV=0.05) and the largest CI of 0.872, occurred for the spiral scan with pitch 0.5, which did agree with visual inspection. Conclusions: Optimal scanning technique, depended on the direction of movement and the interpretation method. Furthermore, it required either a pitch of 0.5 or an axial overscan technique in order to reduce respiratory motion induced target artifacts.

Treatment Planning in Stereotactic Body Radiation Therapy of Lung Cancer: Which Image Set is Appropriate for Dose Calculation?

Stereotactic body radiation therapy (SBRT) is frequently used to treat stage I/II non-small-cell lung cancer. The hypofractionated nature of the delivery necessitates highly accurate tumor delineation. Four-dimensional (4D) CT imaging is normally used for the definition of tumor motion envelope in the presence of organ motion. Therefore, in addition to the conventional free-breathing (FB) CT scan, a couple of other CT images are reconstructed, including the average intensity projection (AIP) CT and the untagged slow-scan CT (SCT).

SU‐GG‐T‐570: Selection of CT Image Sets for Treatment Planning in Stereotactic Body Radiation Therapy of Lung Cancer

Purpose: This study investigated the impact on tumor dose coverage of treatment plans performed on various CT image sets in stereotactic body radiation therapy (SBRT) of lung cancer. Methods and Materials: Five patients underwent SBRT for lung cancers were retrospectively investigated. For each patient, a free breathing (FB) CT and a four‐dimensional (4D) CT were acquired. Based on the 4DCT scans, two post‐processing CT images were reconstructed: average intensity projection CT (AIP) and a low pitch, slow‐scan CT (SCT). The gross target volumes (GTVs) were delineated on the 4DCT images and combined to create the internal target volume (ITV). The planning target volume (PTV) was created by adding a 5 mm margin to the ITV. Treatment plans were performed on the FB CT, ATP CT, and SCT. Plan quality was evaluated by calculating and comparing the 4D dose for each plan using deformable‐image registration. Results: No matter which CT image sets were used in treatment planning, lung tumors always receive at least the prescribed dose. The average difference in tumor D100 (minimum dose received by 100% of the tumor) is 0.28±0.61Gy (p=0.363) between the plans performed on AIP CT and those on FB CT, 0.62±1.35Gy (p=0.379) between the plans performed on AIP CT and those on SCT, and 0.34±0.77Gy (p=0.379) between the plans performed on FB CT and those on SCT. As for the mean lung dose, the average difference is −0.07±0.15Gy (p=0.390), 0.07±0.11Gy (p=0.221), and 0.14±0.15Gy (p=0.107) respectively. For the total lung V20, the average difference is −0.19±0.26% (p=0.186), 0.13±0.25% (p=0.321), and 0.31±0.27% (p=0.06) respectively. Conclusions: The differences in tumor and lung dose coverage for treatment plans performed on ATP CT, FB CT and SCT are indistinguishable. Those three CT data sets are equally well in term of dose coverage for treatment planning in lung SBRT.

Poster — Wed Eve—32: Internal Target Volume Dose Coverage Measurement for Respiratory Tumor Motion

The purpose of this study was to evaluate the difference between planned and delivered doses within the ITV generated by the co‐alignment of the standard and slow CT scan. A QUASAR™ phantom with a cedar insert (to simulate the lung) and an ionization chamber with buildup cap was scanned twice using modified slow CT scan technique. The respiratory cycle used for CT scan was 4 seconds/cycle and 10.0 mm amplitude along the longitudinal axis of the phantom. The two image sets were co‐aligned using the same reference points. The volume of the ionization chamber was used as a gross tumor volume (GTV) and was contoured on each scan. The ITV was generated by enveloping two GTVs from the two CT scans. The PTV was created by adding a 5mm margin around the ITV. If the chamber movement is within 1 cm, the minimum ITV dose coverage is 98.5%. The ITV dose coverage drops dramatically when the movement is larger than 1cm. The ITV dose coverage drops from 96.3% in 1.1cm motion to 90.7% in 1.5 cm motion. This study evaluated the difference between planned and delivered dose to the GTV using an ITV generated by the co‐alignment of the standard and slow CT scan. Co‐alignment of a slow CT and a standard CT underestimates the amplitude of GTV motion by 6mm. This results in under‐dosing of the ITV by 1.5%. The discrepancy between the TPS and measurement was 0.8%, for a total discrepancy of 2.3 %.

Poster — Wed Eve—33: Respiratory Internal Target Volume Assessment Using a Modified Slow CT Scan and CBCT

The purpose of this study was to investigate the volume of the ITV generated by a modified slow CT scan and CBCT using a QUASAR™ phantom. The standard CT scan (CTstandard) was acquired with pitch 1.7 and scan time 1 second followed by the slow CT scan (CTslow) limited to the tumor region with pitch 1 and scan time 3 seconds. The two image sets were co‐aligned using the same reference point, which was independent of bony anatomy changes with respiration. A gross tumor volume was contoured on each scan; Volume A is for CTstandard and Volume B is for CTslow; The ITV was generated from A∪B in Pinnacle TPS. Nine data sets of CTstandard and CTslow plus CBCT were acquired under free‐breathing. The ITV generated from the CTstandard is smaller than that from the CTslow (80% vs. 93% for 3 cm cube); however, the ITV generated from the co‐alignment of two image sets are improved compared to the sing CT alone. The ITV generated from the co‐alignment of CTstandard and CTslow is 98% for the 3cm cube and acceptable as depicted extent of motion. Modified slow CT scan provides complimentary information for the respiratory tumor motion. It compares favorably with the ITV generated with a cone beam CT. Modified slow CT scan and CBCT with tighter margin were used for lung radiosurgery with daily twice CBCT. It is a useful technique for optimizing the ITV resulting in tighter margins which may reduce toxicity and facilitate dose escalation.

Attenuation correction of PET cardiac data with low‐dose average CT in PET/CT

We proposed a low-dose average computer tomography (ACT) for attenuation correction (AC) of the PET cardiac data in PET/CT. The ACT was obtained from a cine CT scan of over one breath cycle per couch position while the patient was free breathing. We applied this technique on four patients who underwent tumor imaging with 18F-FDG in PET/CT, whose PET data showed high uptake of 18F-FDG in the heart and whose CT and PET data had misregistration. All four patients did not have known myocardiac infarction or ischemia. The patients were injected with 555-740 MBq of 18F-FDG and scanned 1 h after injection. The helical CT (HCT) data were acquired in 16 s for the coverage of 100 cm. The PET acquisition was 3 min per bed of 15 cm. The duration of cine CT acquisition per 2 cm was 5.9 s. We used a fast gantry rotation cycle time of 0.5 s to minimize motion induced reconstruction artifacts in the cine CT images, which were averaged to become the ACT images for AC of the PET data. The radiation dose was about 5 mGy for 5.9 s cine duration. The selection of 5.9 s was based on our analysis of the respiratory signals of 600 patients; 87% of the patients had average breath cycles of less than 6 s and 90% had standard deviations of less than 1 s in the period of breath cycle. In all four patient studies, registrations between the CT and the PET data were improved. An increase of average uptake in the anterior and the lateral walls up to 48% and a decrease of average uptake in the septal and the inferior walls up to 16% with ACT were observed. We also compared ACT and conventional slow scan CT (SSCT) of 4 s duration in one patient study and found ACT was better than SSCT in depicting average respiratory motion and the SSCT images showed motion-induced reconstruction artifacts. In conclusion, low-dose ACT improved registration of the CT and the PET data in the heart region in our study of four patients. ACT was superior than SSCT for depicting average respiration motion in a patient study.

Physical evaluation of CT scan methods for radiation therapy planning: comparison of fast, slow and gating scan using the 256-detector row CT scanner

Although slow-rotation CT scanning (slow-scan CT: SSCT) has been used for radiation therapy planning, based on the rationale that the average duration of the human respiratory cycle is 4 s, a number of physical and quantitative questions require answering before it can be adopted for clinical use. This study was performed to evaluate SSCT physically in comparison with other scan methods, including respiratory-gated CT (RGCT), and to develop procedures to improve treatment accuracy. Evaluation items were geometrical accuracy, volume accuracy, water equivalent length and dose distribution using the 256-detector row CT with three scan methods. Fast-scan CT (FSCT) was defined as obtaining all respiratory phases in cine scan mode at 1.0 s per rotation. FSCT-ave was the averaged FSCT images in all respiratory phases, obtained by reconstructing short time intervals. SSCT has been defined as scanning with slow gantry rotation to capture the whole respiratory cycle in one rotation. RGCT was scanned at the most stable point in the respiratory cycle, which provides the same image as that by FSCT at the most stable point. Results showed that all evaluation items were dependent on motion characteristics. The findings of this study indicate that 3D planning based solely on SSCT under free breathing may result in underdosing of the target volume and increase toxicity to surrounding normal tissues. Of the three methods, RGCT showed the best ability to significantly increase the accuracy of dose distribution, and provided more information to minimize the margins. FSCT-ave is a satisfactory radiotherapy planning alternative if RGCT is not available.