Separate evaluation of unilateral lung function using upright/supine CT in a patient with diaphragmatic paralysis

BackgroundUnilateral diaphragmatic paralysis is a condition in which the unilateral diaphragm is paralyzed and elevated. Orthopnea due to lung compression by an elevated diaphragm in the supine position is common in patients with unilateral diaphragmatic paralysis. Although its symptom is posture-dependent, the effect of posture on lung function in unilateral diaphragmatic paralysis has not been studied. Computed tomography (CT) can be used to assess lung volume. However, conventional CT cannot be performed in the upright position. A pulmonary function test can be performed in both upright and supine positions. However, it cannot evaluate the function of each lung separately.Case presentationWe report a case of a 79-year-old man with unilateral diaphragmatic paralysis. He presented with difficulty in inspiration, specifically in the supine position, and underwent both conventional supine CT and newly developed upright CT to assess the effect of posture on the function of each lung. The difference between expiratory and inspiratory lung volumes on CT in the supine position was less than that in the upright position by 46% and 4% on affected and healthy sides, respectively. We previously reported that the difference between expiratory and inspiratory lung volumes on CT correlated with inspiratory capacity on the pulmonary function test. A 46% decline in inspiratory capacity on the affected side in the supine position likely caused orthopnea in this patient.ConclusionsSupine/upright CT is helpful to assess the influence of posture on unilateral lung function in patients with unilateral diaphragmatic paralysis.     

Advantages of upright position imaging with medium-energy collimator for sentinel node lymphoscintigraphy in breast cancer patients

OBJECTIVE: To evaluate the advantage of upright position imaging with a medium-energy collimator for the detection of sentinel lymph node (SLN). METHODS: Thirty-four patients with operable breast cancer underwent sentinel node lymphoscintigraphy with 99mTc-tin colloid. Images were obtained in 5 different positions and paired images from the same patient were compared using side-by-side interpretation. Images were compared in 3 groups: group 1 (anterior view); supine (SAV) vs. upright (UAV), group 2 (oblique view); supine (SOV) vs. upright (UOV), and group 3 (oblique view); modified supine (MOV) vs. UOV. Image quality was evaluated using a 3-grade scale of clear, faint, and equivocal depiction, and correlated to 3 parameters: distance from injection site to lymph node (hot node), counts in hot node, and image contrast. Parameters in group 1 were compared by classifying the primary tumor site into 4 subregions. RESULTS: Image quality in all 3 groups was more enhanced on the image obtained in the upright position than that in the supine position. Obtaining images in an upright position increased the mean distances by 1.5-3.2 cm, and mean contrasts were significantly increased by 0.13-0.31 (p < 0.05). It was shown that image quality was more greatly affected by image contrast than by counts in the hot node. Image contrast of 0.5 seemed an appropriate threshold level for detection of the hot node. On comparison of tumor sites, the upper outer quadrant (C) region of the 4 subregions demonstrated greater contrast enhancement on upright position images. CONCLUSION: Clinical images obtained in an upright position with a medium-energy collimator were superior to those obtained in a supine position. Use of this procedure is recommended to enhance lymph node detection on sentinel node lymphoscintigraphy.     

A technique to re-establish dose distributions for previously treated brain cancer patients in external beam radiotherapy.

Tumor recurrences or new tumors may develop after irradiation of local lesion(s) in the brain, and additional radiotherapy treatments are often needed for previously treated patients. It is critical to re-establish the dose distributions delivered during the previous treatment in the current patient geometry, so that the previous dose distributions can be accurately taken into consideration in the design of the current treatment plan. The difficulty in re-establishing the previous treatment dose distributions in the current patient geometry arises from the fact that the patient position at the time of reirradiation is different from that at the previous treatment session. Simple re-entry of the previous isocenter coordinates, gantry, and couch and collimator angles into the new treatment plan would result in incorrect beam orientations relative to the new patient anatomy, and therefore incorrect display of the previous dose distributions on the current patient anatomy. To address this issue, a method has been developed so that the previous dose distributions can be accurately re-established in the framework of the current brain treatment. The method involves 3 matrix transformations: (1) transformation of beams from machine coordinate system to patient coordinate system in the previous treatment; (2) transformation of beams from patient coordinate system in the previous treatment to patient coordinate system in the current treatment; and (3) transformation of beams from patient coordinate system in the current treatment to machine coordinate system. The transformation matrices used in the second transformation are determined by registration using a mutual information-based algorithm with which the old and new computed tomography (CT) scan sets are registered automatically without human interpretation. A series of transformation matrices are derived to calculate the isocenter coordinates, the gantry, couch, and collimator angles of the beams for the previous treatment in the current patient geometry, and the previous dose distributions are re-established on the current CT images. The method has been proven to be successful and robust.     

直立位椎管造影对腰椎间盘突出的诊断价值

目的　评价直立位椎管造影对腰椎间盘突出的诊断价值。方法　经CT或MRI诊断的腰椎间盘突出 196例术前进行直立位椎管造影检查。结果　直立位椎管造影的诊断结果与CT或MRI基本符合 ,但有 7例直立位椎管造影发现L4～ 5椎间盘突出并伴有神经根受压 ,而CT或MRI未能显示。结论　直立位椎管造影对腰椎间盘突出的诊断可能优于CT或MRI ,尤其对L4 5椎间盘突出伴有神经根受压的病例。     

Comparison of CT and positron emission tomography/CT coregistered images in planning radical radiotherapy in patients with non-small-cell lung cancer

Imaging with F-18 fluorodeoxyglucose positron emission tomography (PET) significantly improves lung cancer staging, especially when PET and CT information are combined. We describe a method for obtaining CT and PET images at separate acquisitions, which allows coregistration and incorporation of PET information into the radiotherapy (RT) planning process for non-small-cell lung cancer. The influence of PET information on RT planning was analysed for 10 consecutive patients. Computed tomography and PET images were acquired with the patient in an immobilization device, in the treatment position. Using specially written software, PET and CT data were coregistered using fiducial markers and imported into our RT planning system (Cadplan version 6). Treatment plans were prepared with and without access to PET/CT coregistered images and then compared. PET influenced the treatment plan in all cases. In three cases, geographic misses (gross tumour outside planning target volume) would have occurred had PET not been used. In a further three cases, better planning target volume marginal coverage was achieved with PET. In four patients, three with atelectasis, there were significant reductions in V20 (percentage of the total lung volume receiving 20 Gy or more). Use of coregistered PET/CT images significantly altered treatment plans in a majority of cases. This method could be used in routine practice at centres without access to a combined PET/CT scanner .     

Procedure for creating a three-dimensional (3D) model for superficial hyperthermia treatment planning

Purpose

To make a patient- and treatment-specific computed tomography (CT) scan and to create a three-dimensional (3D) patient model for superficial hyperthermia treatment planning (SHTP).

Patients, Materials, and Methods

Patients with recurrent breast adenocarcinoma in previously irradiated areas referred for radiotherapy (RT) and hyperthermia (HT) treatment and giving informed consent were included. After insertion of the thermometry catheters in the treatment area, a CT scan in the treatment position was made.

Results

A total of 26 patients have been, thus far, included in the study. During the study period, five types of adjustments were made to the procedure: (1) marking the RT field with radioopaque markers, (2) making the CT scan after the first HT treatment instead of before, (3) using an air- and foam-filled (dummy) water bolus, (4) a change to radiolucent catheters for which radioopaque markers were needed, and (5) marking the visible/palpable extent of the tumor with radioopaque markers, if necessary. With these adjustments, all necessary information is visible on the CT scan. Each CT slice was automatically segmented into muscle, fat, bone, and air. RT field, catheters, applicators, and tumor lesions, if indicated, were outlined manually using the segmentation program iSeg. Next the model was imported into SEMCAD X, a 3D electromagnetic field simulator.

Conclusion

Using the final procedure to obtain a patient- and treatment-specific CT scan, it is possible to create a 3D model for SHTP.     

The role of eye movement in upright postural control

Vision contributes to upright postural control by providing afferent feedback to the cerebellum. Vision is generally classified into central and peripheral vision. In measurements of postural sway, in which participants are required to maintain a stable upright posture while fixating on a visual target, non-retinal eye positional information due to the fixation is used as well as the retinal information from both visual fields. However, little is known about the role of non-visual eye positional information in postural control. This study examined the role of non-visual eye position information in upright postural control by comparing participants’ centre of pressure (COP) sway between two experimental conditions: (1) a space-fixed visual target condition (control), in which eye movement was not controlled, and (2) a head-fixed visual target condition (treatment), in which eye movement was inhibited. Using 12 university students, COP sway and electrooculograms (EOG) were measured under both conditions. In the space-fixed condition, participants maintain an upright posture while fixating on a visual target fixed on a screen 1 m in front of them. In the head-fixed condition, participants maintained an upright posture while gazing at a target moving in sync with their head sway on the screen. The COP was evaluated by path length, area, root mean square, velocity and position. Eye movements were evaluated by the mean eye movement angle. The mean eye movement angle was significantly larger in the vertical direction then in the horizontal direction in both experimental conditions and was also found to be larger in the space-fixed condition than in the head-fixed condition. No significant different was found in any COP parameter between both conditions. It was suggested that non-visual eye position information from the external eye muscles to the sensory perception system contributes little to postural stabilisation under the measurement conditions used in this study.     

A method for integrating computed tomography into radiotherapy planning and treatment

A technique is described for accurate localisation and radiotherapy treatment planning for a wide range of intrathoracic, abdominal and pelvic tumours. It allows the patient to proceed in one step from a single examination by computed tomography (CT) to treatment and avoids the need for separate treatment simulation. Compatible laser-beam positioning systems between the CT scanner and treatment-machine rooms ensure accurate reproduction of patient position, so that CT data are directly applicable to treatment. The use of appropriate skin markers, which appear on the CT scan, allows accurate measurements of the distance of the centre of the planned volume from a tattoo placed on the patient at the time of the scan, and ensures that the planned treatment fields are accurately directed.     

Radionuclide absolute left ventricular volumes during upright exercise: validation in normal subjects by simultaneous hemodynamic measurements

A nongeometric radionuclide technique for the determination of absolute left ventricular volumes was validated during exercise in nine normal subjects. Simultaneous reference stroke volume and cardiac output measurements were obtained by the Fick method. The reference left ventricular volumes were calculated by combining the Fick stroke volume and the isotopic ejection fraction. Data were collected at rest in the supine and upright positions and during 60 degrees upright exercise, at three levels of increasing severity. At rest, from supine to upright position, the reference end-diastolic volume decreased significantly from 182 +/- 24 ml to 154 +/- 21 ml (mean +/- SD, P less than 0.005); during upright exercise of low intensity, end-diastolic volume increased to 176 +/- 24 ml (P less than 0.05); at maximal exercise, end-diastolic volume was not different from the resting value in upright position. The end-systolic volume gradually decreased at rest from 67 +/- 11 ml in the supine position to 54 +/- 8 ml in the upright position (P less than 0.05). Compared with these reference data, the scintigraphic measurements were significantly lower on average by 23% for stroke volume, 21% for cardiac output, 22% for end-diastolic volume, and 23% for end-systolic volume. The overall changes in stroke volume (P less than 0.05) and end-systolic volume (P less than 0.001) occurring at rest and during exercise were correctly detected by the scintigraphic method but the smaller changes in end-diastolic volume (less than 15%) were not (P less than 0.15) because they were within the range of the precision of the technique.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intensity modulation with respiratory gating for radiotherapy of the pleural space.

We wanted to describe a technique for the implementation of intensity-modulated radiotherapy (IMRT) with a real-time position monitor (RPM) respiratory gating system for the treatment of pleural space with intact lung. The technique is illustrated by a case of pediatric osteosarcoma, metastatic to the pleura of the right lung. The patient was simulated in the supine position where a breathing tracer and computed tomography (CT) scans synchronized at end expiration were acquired using the RPM system. The gated CT images were used to define target volumes and critical structures. Right pleural gated IMRT delivered at end expiration was prescribed to a dose of 44 Gy, with 55 Gy delivered to areas of higher risk via simultaneous integrated boost (SIB) technique. IMRT was necessary to avoid exceeding the tolerance of intact lung. Although very good coverage of the target volume was achieved with a shell-shaped dose distribution, dose over the targets was relatively inhomogeneous. Portions of target volumes necessarily intruded into the right lung, the liver, and right kidney, limiting the degree of normal tissue sparing that could be achieved. The radiation doses to critical structures were acceptable and well tolerated. With intact lung, delivering a relatively high dose to the pleura with acceptable doses to surrounding normal tissues using respiratory gated pleural IMRT is feasible. Treatment delivery during a limited part of the respiratory cycle allows for reduced CT target volume motion errors, with reduction in the portion of the planning margin that accounts for respiratory motion, and subsequent increase in the therapeutic ratio.     

A head immobilization system for radiation simulation, CT, MRI, and PET imaging

An aquaplast mask/marker immobilization system for the routine radiation therapy treatment of head and neck disease is described. The system utilizes a commercially available thermoplastic mesh indexed and mounted to a rigid frame attached to the therapy couch. The apparatus is designed to permit CT, MRI, and PET diagnostic scans of the patient to be performed in the simulation and treatment position utilizing the same mask, thereby facilitating image correlation. Studies employing weekly simulation indicate that patient treatment position movement can be restricted to 3 mm over the course of treatment. This easily constructed system permits rapid mask formation to be performed on the treatment simulator, resulting in an immobilization device comparable to masks produced with vacuum-forming techniques. Details of construction, verification, and central axis CT, MRI, PET markers are offered.     

Dynamic targeting image-guided radiotherapy.

Volumetric imaging and planning for 3-dimensional (3D) conformal radiotherapy and intensity-modulated radiotherapy (IMRT) have highlighted the need to the oncology community to better understand the geometric uncertainties inherent in the radiotherapy delivery process, including setup error (interfraction) as well as organ motion during treatment (intrafraction). This has ushered in the development of emerging technologies and clinical processes, collectively referred to as image-guided radiotherapy (IGRT). The goal of IGRT is to provide the tools needed to manage both inter- and intrafraction motion to improve the accuracy of treatment delivery. Like IMRT, IGRT is a process involving all steps in the radiotherapy treatment process, including patient immobilization, computed tomography (CT) simulation, treatment planning, plan verification, patient setup verification and correction, delivery, and quality assurance. The technology and capability of the Dynamic Targeting IGRT system developed by Varian Medical Systems is presented. The core of this system is a Clinac or Trilogy accelerator equipped with a gantry-mounted imaging system known as the On-Board Imager (OBI). This includes a kilovoltage (kV) x-ray source, an amorphous silicon kV digital image detector, and 2 robotic arms that independently position the kV source and imager orthogonal to the treatment beam. A similar robotic arm positions the PortalVision megavoltage (MV) portal digital image detector, allowing both to be used in concert. The system is designed to support a variety of imaging modalities. The following applications and how they fit in the overall clinical process are described: kV and MV planar radiographic imaging for patient repositioning, kV volumetric cone beam CT imaging for patient repositioning, and kV planar fluoroscopic imaging for gating verification. Achieving image-guided motion management throughout the radiation oncology process requires not just a single product, but a suite of integrated products to manipulate all patient data, including images, efficiently and effectively.     

Using kV-kV and CBCT imaging to evaluate rectal cancer patient position when treated prone on a newly available belly board

The goal of this work was to use daily kV-kV imaging and weekly cone-beam CT (CBCT) to evaluate rectal cancer patient position when treated on a new couch top belly board (BB). Quality assurance (QA) of the imaging system was conducted weekly to ensure proper performance. The positional uncertainty of the combined kV-kV image match and subsequent couch move was found to be no more than ± 1.0 mm. The average (1 SD) CBCT QA phantom match was anterior-posterior (AP) = ?0.8 ± 0.2 mm, superior-inferior (SI) = 0.9 ± 0.2 mm, and left-right (LR) = ?0.1 ± 0.1 mm. For treatment, a set of orthogonal kV-kV images were taken and a bony anatomy match performed online. Moves were made along each axis (AP, SI, and LR) and recorded for analysis. CBCT data were acquired once every 5 fractions for a total of 5 images per patient. The images were all taken after the couch move but before treatment. A 3-dimensional (3D-3D) bony anatomy auto-match was performed offline and the residual difference in position recorded for analysis. The average (± 1 SD) move required from skin marks, calculated over all 375 fractions (15 patients × 25 fractions/patient), were AP = ?2.6 ± 3.7 mm, SI = ?0.3 ± 4.9 mm, and LR = 1.8 ± 4.5 mm. The average residual difference in patient position calculated from the weekly CBCT data (75 total) were AP = ?1.7 ± 0.4 mm, SI = 1.1 ± 0.6 mm, and LR = ?0.5 ± 0.2 mm. These results show that the BB does provide simple patient positioning that is accurate to within ± 2.0 mm when using online orthogonal kV-kV image matching of the pelvic bony anatomy.     

Use of the BrainLAB ExacTrac X-Ray 6D System in Image-Guided Radiotherapy

The ExacTrac X-Ray 6D image-guided radiotherapy (IGRT) system will be described and its performance evaluated. The system is mainly an integration of 2 subsystems: (1) an infrared (IR)-based optical positioning system (ExacTrac) and (2) a radiographic kV x-ray imaging system (X-Ray 6D). The infrared system consists of 2 IR cameras, which are used to monitor reflective body markers placed on the patient's skin to assist in patient initial setup, and an IR reflective reference star, which is attached to the treatment couch and can assist in couch movement with spatial resolution to better than 0.3 mm. The radiographic kV devices consist of 2 oblique x-ray imagers to obtain high-quality radiographs for patient position verification and adjustment. The position verification is made by fusing the radiographs with the simulation CT images using either 3 degree-of-freedom (3D) or 6 degree-of-freedom (6D) fusion algorithms. The position adjustment is performed using the infrared system according to the verification results. The reliability of the fusion algorithm will be described based on phantom and patient studies. The results indicated that the 6D fusion method is better compared to the 3D method if there are rotational deviations between the simulation and setup positions. Recently, the system has been augmented with the capabilities for image-guided positioning of targets in motion due to respiration and for gated treatment of those targets. The infrared markers provide a respiratory signal for tracking and gating of the treatment beam, with the x-ray system providing periodic confirmation of patient position relative to the gating window throughout the duration of the gated delivery.     

Treatment Planning of Tangential Breast Irradiation Using a Simulator with CT-Option Compared to a Conventional CT

PURPOSE: Treatment planning for breast cancer is often performed using a conventional computed tomography (CT), which does not allow patient positioning in the treatment set-up. Using a simulator with CT option the scanning procedure can be performed in an identical position as the treatment. Aim of the present study was to investigate feasibility and accuracy of a simulator with CT option compared to treatment planning with a conventional CT for breast irradiation. PATIENTS AND METHODS: Twenty patients submitted for radiotherapy after breast conserving surgery underwent simulation with the SLS-CT (Elekta Oncology Systems, EOS). Additionally, a planning CT with a diagnostic CT scanner (Somatom Plus, Siemens,) was performed. All the patients were scanned with both modalities and had 3 to 5 slices. For Somatom-CT patients lay flat, for SLS-CT they rested on a breast angle board. The target volume was delineated in the CT scans obtained with both modalities, the planning procedure was carried out using the 3-D planning system Helax-TMS. RESULTS: The median values for SLS-CT (1) and Somatom (2) were: Target volume: 679 cm3 (1) and 670 cm3 (2) for all patients and 1,025 cm3 (1) and 1,100 cm3 (2) for large breasts. Maximal dose in the dose-volume histogram (DVH): 109.3% (1) and 109.7% (2). Lung volume in the 20% isodose: 119 cm3 (1) and 123 cm3 (2). The distance between entrance and exit point in the central axis: 13.8 (1) and 14.6 cm (2). CONCLUSION: Treatment planning with a CT option is feasible, the simulation procedure can be performed with 1 single device and under identical set-up conditions as the treatment itself. Our data show a tendency towards sparing of irradiated volume with SLS-CT, the clinical relevance cannot yet be determined.     

三维CT模拟定位计划系统在放射治疗中的应用研究

目的：通过三维CT模拟定位计划系统的临床应用研究,评价其在放疗中的作用。方法：将螺旋CT,三维激光定位系统和Focus 9200三维计划系统通过网络连接,形成放疗科专用的集影像诊断,图像传送,肿瘤定位和三维计划为一体的三维CT模拟定位计划系统。分别对143例肿瘤病人进行CT模拟定位和治疗计划。结果：CT模拟定位和X线模拟定位一样可人定位到体表标记的全过程。利用CT进行定位,可为靶区的确定,复杂多野照射,适形调强放疗以及立体定向放疗提供更多的图象信息和更高的定位精度,使治疗中心和实际靶中心的重复误差＜2mm。结论：CT模拟定位可用于大多数肿瘤病人的定位,是实现高精度放疗的必备设备之一。     

Preoperative localization of small pulmonary lesions with a short hook wire and suture system: experience with 168 procedures

PURPOSE: To evaluate use of a short hook wire and suture system for preoperative localization of pulmonary nodular lesions. MATERIALS AND METHODS: Percutaneous localization of 168 lesions was performed with computed tomographic (CT) guidance in 150 patients. Patients were classified into three groups: a 3-year early-learning experience of treatment of 40 lesions mainly in one institution (group A1), a more recent 4-year experience of treatment of 88 lesions in the same institution (group A2), and the roughly synchronous recent 3-year experience of treatment of 40 lesions in a different hospital (group B). RESULTS: The hook wire was successfully placed without dislodgment in 146 patients, accounting for 164 (97.6%) of 168 lesions. Group A2 showed a success rate of 100%. There was no difference in patients among the three groups in regard to size of lesions or their distance from the pleural surface. In patients in groups A2 and B, the proportion of nodules with ground-glass opacity and primary lung carcinoma at CT was significantly greater than that in patients in group A1. In 168 placements, nonsymptomatic pneumothorax cases were observed in 54 (32.1%), hemorrhages into the lung were observed in 25 (14.9%), and hemorrhage into the pleural space was observed in one (0.6%). No patient complained of notable pain during or after the procedure, and no serious complication was experienced. Unsuccessful placement was caused by too shallow a puncture with the introducer needle. CONCLUSION: This system with a flexible suture for preoperative localization has a high success rate.     

Daily CT planning during boost irradiation of prostate cancer. Feasibility and time requirements.

BACKGROUND: In the irradiation of prostate cancer internal organ movement leads to uncertainties in the daily localization of the clinical target volume. Therefore more or less large safety margins are added when designing the treatment portals. With daily CT planning internal organ movement can be compensated to some extent, safety margins can be reduced and irradiated normal tissue can be spared. The feasibility of daily CT-based 3D treatment planning is studied in a patient with localized prostate carcinoma using a new patient positioning system. METHODS: Daily CT planning was applied during boost irradiation of a patient with prostate cancer: After patient immobilization the pelvis was scanned in 3 mm CT slices. Planning was done with the BrainSCAN planning system for stereotactic body irradiation. The prostate was contoured in all slices and the safety margins of the micromultileafs were automatically set to the distance chosen by the physician (0.8 cm). Patient positioning was done with the BrainLAB ExacTrac positioning system on the basis of skin attached stereotactic body markers. Before each treatment verification images of the isocenter were taken. RESULTS: The total time requirement for planning and irradiation was about 1 hour 15 minutes. Patient positioning on the treatment couch took about 10 minutes. The accuracy of the positioning system was good (75% of the deviations were smaller than 3 mm). The shift of the single markers from CT scan to CT scan was more extensive than those of the center of all 7 markers combined (47% of the deviations were smaller than 3 mm). The location of the markers seems to influence the magnitude of their dislocation. CONCLUSION: Daily CT planning is feasible but time consuming. The new patient positioning system ExacTrac is an interesting tool especially for daily CT planning since conventional simulation can be omitted.     

Imaging doses from the Elekta Synergy X-ray cone beam CT system

The Elekta Synergy is a radiotherapy treatment machine with integrated kilovoltage (kV) X-ray imaging system capable of producing cone beam CT (CBCT) images of the patient in the treatment position. The aim of this study is to assess the additional imaging dose. Cone beam CT dose index (CBDI) is introduced and measured inside standard CTDI phantoms for several sites (head: 100 kV, 38 mAs, lung: 120 kV, 152 mAs and pelvis: 130 kV, 456 mAs). The measured weighted doses were compared with thermoluminescent dosimeter (TLD) measurements at various locations in a Rando phantom and at patients' surfaces. The measured CBDIs in-air at the isocentre were 9.2 mGy 100 mAs(-1), 7.3 mGy 100 mAs(-1) and 5.3 mGy 100 mAs(-1) for 130 kV, 120 kV and 100 kV, respectively. The body phantom weighted CBDI were 5.5 mGy 100 mAs(-1) and 3.8 mGy 100 mAs(-1 )for 130 kV and 120 kV. The head phantom weighted CBDI was 4.3 mGy 100 mAs(-1) for 100 kV. The weighted doses for the Christie Hospital CBCT imaging techniques were 1.6 mGy, 6 mGy and 22 mGy for the head, lung and pelvis. The measured CBDIs were used to estimate the total effective dose for the Synergy system using the ImPACT CT Patient Dosimetry Calculator. Measured CBCT doses using the Christie Hospital protocols are low for head and lung scans whether compared with electronic portal imaging (EPI), commonly used for treatment verification, or single and multiple slice CT. For the pelvis, doses are similar to EPI but higher than CT. Repeated use of CBCT for treatment verification is likely and hence the total patient dose needs to be carefully considered. It is important to consider further development of low dose CBCT techniques to keep additional doses as low as reasonably practicable.     

Stereotactic breast biopsy: recumbent biopsy using add-on upright equipment

OBJECTIVE: The purpose of the study was to show that stereotactic breast biopsy can be performed effectively and accurately using add-on stereotactic equipment when it is performed with the patient in a decubitus or recumbent position. MATERIALS AND METHODS: We retrospectively reviewed the results of 225 stereotactic core breast biopsies performed during a 42-month period. The biopsies were performed using a reclining mammography chair and add-on stereotactic equipment. Procedures were performed with the patient in the right or left lateral decubitus position or upright. Patients with benign biopsy results were followed up mammographically at 6 months initially, then yearly. RESULTS: Of the 225 lesions biopsied stereotactically, 205 lesions (91%) were biopsied with the patient in the decubitus (right or left) position and 20 (9%) biopsied with the patient upright. Pathology results were classified as abnormal in 45 lesions (20%) and normal in 180 lesions (80%). All but one of the abnormal lesions were followed up with surgical excision. One hundred thirty-four of the 180 benign lesions have been followed up with at least one 6-month mammogram (follow-up range, 6-40 months), and none of the lesions has been subsequently proven malignant. CONCLUSION: Stereotactic core biopsy can be performed effectively and accurately using standard add-on equipment when it is performed with the patient in the decubitus position. This approach obviates the use of dedicated prone stereotactic equipment.