DISCLAIMER: TO THEA EduXltT RoEuNtinTe CAheLstL –OAbWdoEmDen -BPeYlvi sL COT PCroAtoLco Lls AVeWrsio, n 1.0 02/20/14 THIS INFORMATION IS PROVIDED TO YOU BY THE AMERICAN ASSOCIATION OF PHYSICISTS IN MEDICINE, A NON-PROFIT ORGANIZATION ORGANIZED TO PROMOTE THE APPLICATION OF PHYSICS TO MEDICINE AND BIOLOGY, ENCOURAGE INTEREST AND TRAINING IN MEDICAL PHYSICS AND RELATED FIELDS ("AAPM"), 'AS IS' WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, WHETHER ORAL OR WRITTEN, EXPRESS OR IMPLIED. AAPM SPECIFICALLY DISCLAIMS ANY IMPLIED WARRANTIES OR CONDITIONS OF MERCHANTABILITY, SATISFACTORY QUALITY, NONINFRINGEMENT AND FITNESS FOR A PARTICULAR PURPOSE. SOME JURISDICTIONS DO NOT ALLOW EXCLUSIONS OF IMPLIED WARRANTIES OR CONDITIONS, SO THE ABOVE EXCLUSION MAY NOT APPLY TO YOU. YOU MAY HAVE OTHER RIGHTS THAT VARY ACCORDING TO LOCAL LAW. TO THE EXTENT ALLOWED BY LOCAL LAW, IN NO EVENT WILL AAPM OR ITS SUBSIDIARIES, AFFILIATES OR VENDORS BE LIABLE FOR DIRECT, SPECIAL, INCIDENTAL, CONSEQUENTIAL OR OTHER DAMAGES (INCLUDING LOST PROFIT, LOST DATA, OR DOWNTIME COSTS), ARISING OUT OF THE USE, INABILITY TO USE, OR THE RESULTS OF USE OF THE PROVIDED INFORMATION, WHETHER BASED IN WARRANTY, CONTRACT, TORT OR OTHER LEGAL THEORY, AND WHETHER OR NOT ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. YOUR USE OF THE INFORMATION IS ENTIRELY AT YOUR OWN RISK. THIS INFORMATION IS NOT MEANT TO BE USED AS A SUBSTITUTE FOR THE REVIEW OF SCAN PROTOCOL PARAMETERS BY A QUALIFIED AND CERTIFIED PROFESSIONAL. USERS ARE CAUTIONED TO SEEK THE ADVICE OF A QUALIFIED AND CERTIFIED PROFESSIONAL BEFORE USING ANY PROTOCOL BASED ON THE PROVIDED INFORMATION. AAPM IS NOT RESPONSIBLE FOR A USER'S FAILURE TO VERIFY OR CONFIRM APPROPRIATE PERFORMANCE OF THE PROVIDED SCAN PARAMETERS. SOME JURISDICTIONS DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR DAMAGES, SO THE ABOVE LIMITATION MAY NOT APPLY TO YOU. 1 Copyright © February 20, 2014 by AAPM. All rights reserved. The disclaimer on page 1 is an integral part of this document. Routine Adult ChAedsultt- RAobudtinoem Cheens-t P–Aeblvdoism eCnT-P ePlvrios tCoTc Porlo tocols Version 1.0 02/20/14 Indications (include but are not limited to) • Evaluation of known or suspected masses or fluid collections in chest, abdomen and pelvis • Diagnosis of malignancies, primary, or metastatic, including melanoma • Trauma • Evaluation of inflammatory processes in chest, abdomen, and pelvis • Evaluation of lymphadenopathy above and below the diaphragm • Work up of fever or suspected abscess • Evaluation of ascites or effusions • Evaluation of vascular abnormalities such as aortic aneurysm • Identification of locations of shunts/tubes/catheters that may cross the diaphragm For reference, see ACR–SPR Practice Guideline for the Performance of Computed Tomography (CT) of the Abdomen and Computed Tomography (CT) of the Pelvis Diagnostic Tasks (include but are not limited to) • Detect nodules or soft tissue masses and determine sizes and shape and relationships to organs • Identify air outside the normal lung anatomy or intestinal tract • Detect nodules or soft tissue masses adjacent to vascular structures • Detect calcifications in abnormal locations or in organs • Characterize soft tissue edema, fluid collections, or ascites • Detect abnormalities that extend above and below the diaphragm Key Elements Contrast • Oral: Per radiologist. • Injected: Certain indications require administration of intravenous contrast media. • Intravenous contrast enhancement should be performed as directed by the supervising radiologist using appropriate injection protocols and in accordance with the ACR-SPR Practice Guideline for the Use of Intravascular Contrast Media and the ACR Manual on Contrast Media. • In some circumstances, an additional scan may be needed after a delay period in order to visualize contrast enhancement that, due to physiological reasons, appears somewhat later. Sites should consider performing this delayed phase scan with reduced scan parameters (lower dose). Scan mode & Patient Positioning • Scanning should be performed in helical mode. • Patient supine, arms above head. CT Localizer Radiograph • Center the patient within the gantry; this is critical for proper functioning of AEC systems. • If the patient is not sufficiently centered in the vertical direction, substantial magnification or minification can affect the appearance of the anterior-posterior or posterior-anterior CT localizer radiograph, which in turn can affect the accuracy of the AEC system performance (the scanner may be fooled into thinking the patient is either larger or smaller than he/she actually is). • Confirming that the table height is correct for each patient should be part of the routine workflow, whenever feasible (e.g. checking vertical height using a lateral CT localizer radiograph). • When vertically centering a patient with an unusual body habitus in the gantry, it is recommended that the liver region be positioned at the gantry center, as this is typically the most challenging region for diagnostic interpretation. 2 Copyright © February 20, 2014 by AAPM. All rights reserved. The disclaimer on page 1 is an integral part of this document. • If the patient table height is adjusted, thAedu Clt TRo luotcinael iCzheers tr a–Adbiodgomraepnh-P eslhvios uClTd P broet orceoplse Vaetresdio ns o1. 0th a02t /t2h0e/ 14 AEC system will use an accurate representation of the patient position and size. • Users need to know whether or not the order in which the CT localizer radiographs are acquired will affect the technique factors, and hence radiation dose, in subsequent scans. In most scanners, only the CT localizer radiograph acquired immediately preceding the scan is used for AEC technique calculations (whether anterior-posterior/posterior-anterior or lateral). In other scanners, both the anterior-posterior/posterior-anterior and lateral CT localizer radiographs are considered, if both are present. Of particular importance, the orientation in which the CT localizer radiograph was acquired (anterior-posterior vs. posterior-anterior vs. lateral) will affect the AEC technique on some scanners. Thus, AEC settings may need to be adjusted based on the orientation of the CT localizer radiograph in order to achieve consistent levels of image quality or noise. • Each manufacturer has unique nomenclature and operating characteristics for their AEC system(s). Users must be very familiar with how the AEC systems on their particular scanners operate. See the Educational Slides tab at http://www.aapm.org/pubs/CTProtocols/ for additional information regarding the specific details of each manufacturer’s AEC system. Scan Range – CT localizer radiograph and longitudinal scan range • The CT localizer radiograph should extend beyond the anticipated scan range in the superior- inferior direction. If a helical (or axial) scan acquisition extends beyond the superior or inferior edge of the CT localizer radiograph, the AEC system may use unexpected technique values in that region due to missing patient information. This may compromise image quality or use unnecessarily high doses. • A typical scan range extends from the top of the lungs to either the iliac crest or pubic symphysis, depending on the clinical indications. • Scan only the indicated regions. Images of the neck region or below the pubic symphysis are typically NOT required and can add substantially to the patient’s exposure. Suspension of Respiration • Patient should be instructed to hold his/her breath at end of inspiration during both the CT localizer radiograph and during the entire scan, recognizing that for some patients this may not be feasible. When the patient is unable to hold his/her breath over the entire scan duration, the scan should be performed in the cranial to caudal direction such that the chest region is scanned first. Breathing motion is less problematic below the diaphram. Additional Image Reconstructions • Certain indications may require that images be reconstructed in coronal and/or sagittal planes. • High-resolution (i.e. thin) images may be reconstructed from the helical data set to provide an additional set of thin images. A sharp reconstruction filter is often used for these images, especially for the chest region. • Very thin axial images (approximately ≤ 1 mm) may need to be reconstructed to serve as source images for the sagittal and/or coronal reformatted images. • Creation, use, and archival of these (very thin) additional images are at the discretion of the supervising radiologist and/or departmental policy. Very large datasets may result from these additional reconstructions. Radiation Dose Management • Automatic Exposure Control (AEC) should be used whenever possible. • Users need to pay careful attention to the values selected to define the desired level of image quality (e.g., Noise Index, Quality Reference mAs, Standard Deviation). 3 Copyright © February 20, 2014 by AAPM. All rights reserved. The disclaimer on page 1 is an integral part of this document. • Each manufacturer will have recommeAnddualtt iRoonusti nuen Ciqhueset –tAob tdhoemire ns-yPsetlveims CsT aPnrodt oscyolsst Veemrs ifoena 1tu.0r e 0s2./ 20/14 Be sure to work with your CT equipment manufacturer and a qualified medical physicist to ensure safe and appropriate operation of AEC systems. CTDI measurements and calculations • Some manufacturers utilize a z-axis “flying focal spot”, in which two unique projections are acquired at the same z-axis table position. The CTDIvol displayed on the scanner console accurately accounts for use of this feature. Single or Split Acquisition Examination of the chest, abdomen and pelvis can be performed as one long scan acquisition (a single “beam-on” event) from the top of the chest to the bottom of the pelvis, or in shorter scan segments by scanning one or more regions separately, such as scanning the chest separate from a combined abdomen-pelvis scan. There are distinct advantages to each approach. The best approach for a specific exam should be decided by the supervising radiologist, taking into account the specific patient and exam indication, as well as the technical capabilities of the CT scanner to be used. Characteristic to be considered Single Acquisition Split Acquisition X-ray tube load May be too high for some Can more readily accommodate patient/scanner combinations larger patients AEC Usually a single image quality Image quality and radiation parameter is required for the dose can be customized for entire scan range (future each region of the exam (chest, scanner models may allow for abdomen or pelvis) different image quality settings in each region) Anatomic discontinuities Not an issue – a single May be some anatomic acquisition guarantees smooth discontinuities at the boundaries transitions between each region of the different regions (chest, of the exam (chest, abdomen or abdomen or pelvis) in axial and pelvis) in axial, coronal, and reformatted images; reformatted sagittal views image sets might be split between regions IV contrast timing May require a compromise of IV IV contrast injection protocols contrast injections protocols to can be tailored for optimal accommodate all regions (chest, enhancement in each region abdomen or pelvis) (chest, abdomen or pelvis) Scan (exposure) overlap Not an issue Overlap of scan regions results in an increase in overall radiation exposure Exam splitting for interpretation May require CT technologist to Exam splitting is likely to be a by different radiologists manually split the exam more efficient process if according to the interpreting acquisitions are tailored to radiologist address this need Breath hold May be too difficult for patients It is likely easier for most to hold their breath during the patients to perform a separate entire acquisition interval, breath hold for each separate resulting in some motion acquisition event artifacts 4 Copyright © February 20, 2014 by AAPM. All rights reserved. The disclaimer on page 1 is an integral part of this document. Adult Routine Chest –Abdomen-Pelvis CT Protocols Version 1.0 02/20/14 Approximate Volume CT Dose Index (CTDIvol) Values • Split Acquisition - Approximate values for CTDIvol are listed for three different patient sizes using a split acquisition scan approach: Approx. Weight CHEST ABD/PELVIS Approx. Weight (lbs) Approx. Approx. (kg) CTDIvol (mGy) CTDIvol (mGy) Small Patient 50-70 110-155 6-11 10-17 Average Patient 70-90 155-200 10-18 15-25 Large Patient 90-120 200-265 13-23 22-35 • Single Acquisition - If scanned together, the resulting CTDIvol values reported by the scanner should be roughly in this range: Approx. Weight Approx. Weight Approx. (kg) (lbs) CTDIvol (mGy) Small Patient 50-70 110-155 7-16 Average Patient 70-90 155-200 11-24 Large Patient 90-120 200-265 14-34 The dose values for the single acquisition approach are estimated; these values represent an average of the scan technique over the entire scan range. It is rarely appropriate to add the chest and abd/pelvis CTDIvol values together directly; summing CTDIvol values is appropriate only for multiple passes over identical anatomical regions (such a dual-phase liver). The approximate CTDIvol values are for reference only and represent a dose to the CT Dose Index phantom under very specific conditions. The CTDIvol displayed on the scanner for a patient of a given size should be similar, but not necessarily an exact match, to those listed in the above table. The provided values are all based on the 32-cm diameter “body” CTDI phantom. It is essential that users recognize that the CTDIvol values reported on the user console prior to acquiring CT localizer radiographs on a particular patient do not represent the CTDIvol that will be delivered during that patient’s scan. CT systems rely on the CT localizer radiograph to 1) estimate the patient’s size, 2) determine the tube current settings for each tube angle and table position that will yield the requested level of image quality, and 3) calculate the average CTDIvol for the patient over the prescribed scan range. Until the CT localizer radiograph is acquired, the reported CTDIvol is not patient-specific, but is based on an assumed generic patient size, which may differ between manufacturers. The CTDIvol values provided here are approximate, and are intended only to provide reference ranges for the user to consider. They are for a routine CT of an adult’s chest/abdomen/pelvis for the general indications given at the beginning of this document. Other indications or diagnostic tasks may have different image quality and dose requirements, and hence reasonable ranges of CTDIvol may differ according to those requirements. In this document, a small patient is considered to be approximately 50-70 kg (110-155 lbs), an average patient approximately 70-90 kg (155-200 lbs), and a large patient 90-120 kg (200-265 lbs). However, weight is not a perfect indication of patient size. A person’s height, gender and distribution 5 Copyright © February 20, 2014 by AAPM. All rights reserved. The disclaimer on page 1 is an integral part of this document. Adult Routine Chest –Abdomen-Pelvis CT Protocols Version 1.0 02/20/14 of weight across the body also must be taken into account. The thickness of the body over the area to be scanned is the best indication of patient size. Body mass index (BMI) may also be considered: • Underweight = BMI <18.5 • Normal weight = BMI of 18.5–24.9 • Overweight = BMI of 25–29.9 • Obesity = BMI of 30 or greater It is recognized that the median (50th percentile) patient size for adults in the USA is larger than 70 kg. However, the 70 kg patient represents the “Reference Man”, as defined by the International Commission on Radiation Protection (ICRP), upon which AEC systems and tissue weighting factors (used for effective dose estimation) are based. 6 Copyright © February 20, 2014 by AAPM. All rights reserved. The disclaimer on page 1 is an integral part of this document. Adult Routine Chest –Abdomen-Pelvis CT Protocols Version 1.0 02/20/14 INDEX OF ADULT ROUTINE ABDOMEN-PELVIS PROTOCOLS (by manufacturer) GE Hitachi Neusoft Philips Siemens Toshiba 7 Copyright © February 20, 2014 by AAPM. All rights reserved. The disclaimer on page 1 is an integral part of this document. Adult Routine Chest –Abdomen-Pelvis CT Protocols Version 1.0 02/20/14 CHEST, ABDOMEN & PELVIS ROUTINE (Selected GE scanners) (Back to INDEX) SINGLE ACQUISITION SCOUT: AP, S60-I600 if automatic exposure control is used. PA scout if manual mA is used. Lateral scout optional. LightSpeed VCT Discovery CT750 HD GE LightSpeed Pro 16*** (w/ASIR) ** (w/ASIR) ** Scan Type Helical Helical Helical Rotation Time (s) 0.5 0.5 0.5 16 x 1.25 mm 64 x 0.625 mm 64 x 0.625 mm Detector Configuration (20 mm, 4i) (40 mm, 8i) (40 mm, 8i) Pitch 1.375 1.375 1.375 Table Feed/Interval (mm) 27.5 55.0 55.0 kV 120 120 120 Average mA 350 260 300 Auto-mA range 100-650 50-670 100-750 Noise Index (NI)* 11.57 22 (DR 50%) 35.42 SFOV Large Large Large ASiR none SS50 SS50 RECON 1 Axial; DMPR create Axial; DMPR create Plane Axial thick Sag/Cor thick Sag/Cor reformat reformat Algorithm Stnd Stnd Stnd Recon Mode Plus Plus Plus Thickness (mm) 5 0.625 0.625 Interval (mm) 5 0.625 0.625 ASiR none SS50 SS50 RECON 2 Axial; DMPR create Axial; DMPR create Plane Axial thick Sag/Cor thick Sag/Cor reformat reformat Algorithm Stnd Lung Lung Recon Mode Plus Plus Plus Thickness (mm) 1.25 0.625 0.625 Interval (mm) 0.625 0.625 0.625 ASiR none SS50 SS50 Approx. Weight (lbs) Approx. CTDIvol Approx. Weight (kg) (mGy) Small Patient 50-70 110-155 7-16 Average Patient 70-90 155-200 11-24 Large Patient 90-120 200-265 14-34 8 Copyright © February 20, 2014 by AAPM. All rights reserved. The disclaimer on page 1 is an integral part of this document. Adult Routine Chest –Abdomen-Pelvis CT Protocols Version 1.0 02/20/14 RECON 3 Plane Axial Axial Axial Algorithm Lung Stnd Stnd Recon Mode Plus Plus Plus Thickness (mm) 1.25 5 5 Interval (mm) 0.625 5 5 ASiR none SS50 SS50 RECON 4 Plane Axial Axial Axial Algorithm Lung Lung Lung Recon Mode Plus Plus Plus Thickness (mm) <5 <5 <5 Interval (mm) <5 <5 <5 ASiR none SS50 SS50 *Operator-selected noise index and primary image reconstruction thickness will both strongly impact both CTDIvol and patient dose. [See: Kanal KM et al. Impact of Operator-Selected Image Noise Index and Reconstruction Slice Thickness on Patient Radiation Dose in 64-MDCT. AJR 2007; 189: 219-225.] ** These protocols are running direct multi-planar reconstruction (DMPR) on Recon 1 and Recon 2 to automatically create thicker Sagittal and Coronal reformatted images. Thicker axial images are created in Recon 3 and Recon 4. User could define Reformats for Axial, Sagittal and Coronal in DMPR at image thicknesses specified in the Reformat protocol selected, usually 3-5mm. ***LightSpeed Pro16, Recon 4 would need to be done in Retro Recon. Recon 2 and 3 used in Reformat to create Sag/Cor images at 3-5mm thick. Approx. Weight (lbs) Approx. CTDIvol Approx. Weight (kg) (mGy) Small Patient 50-70 110-155 7-16 Average Patient 70-90 155-200 11-24 Large Patient 90-120 200-265 14-34 9 Copyright © February 20, 2014 by AAPM. All rights reserved. The disclaimer on page 1 is an integral part of this document. Adult Routine Chest –Abdomen-Pelvis CT Protocols Version 1.0 02/20/14 CHEST, ABDOMEN & PELVIS ROUTINE (selected GE scanners) (Back to INDEX) SPLIT ACQUISITION SCOUT: AP, S60-I600 if automatic exposure control is used. PA scout if manual mA is used. Lateral scout optional. LightSpeed BrightSpeed 16 LightSpeed 16 GE Ultra (8) Select BrightSpeed 16 Scan Type Helical Helical Helical Rotation Time (s) 0.6/0.6 0.8/0.8 0.5/0.5 (Chest/Abd-Pelvis) 8 x 1.25 mm 16 x 1.25 mm 16 x 1.25 mm Detector Configuration (10 mm, 2i) (20 mm, 4i) (20 mm, 4i)` Pitch (Chest/Abd-Pelvis) 1.35/1.35 1.375/0.938 1.375/1.375 Table Feed/Interval (mm) 13.5/13.5 27.5/18.75 27.5/27.5 (Chest/Abd-Pelvis) kV 120 120 120 Average mA (Chest/Abd- 200/250 125/170 200/300 Pelvis) Auto-mA range 50-440 50-350 100-440 Noise Index (NI)* 13/11.57 13/12 13/11.57 (Chest/Abd-Pelvis) SFOV Large Large Large RECON 1 Plane Axial Axial Axial Algorithm Stnd Stnd Stnd Recon Mode Plus Plus Plus Thickness (mm) 5 5 5 Interval (mm) 5 5 5 RECON 2 Plane Axial Axial Axial Algorithm Lung Lung Lung Recon Mode Plus Plus Plus Thickness (mm) <5 <5 <5 Interval (mm) <5 <5 <5 RECON 3 Plane **Axial **Axial **Axial Algorithm Stnd Stnd Stnd Recon Mode Plus Plus Plus Thickness (mm) 1.25 1.25 1.25 Interval (mm) 1.25 1.25 0.625 *Operator-selected noise index and primary image reconstruction thickness will both strongly impact both CTDIvol and patient dose. [See: Kanal KM et al. Impact of Operator-Selected Image Noise Index and Reconstruction Slice Thickness on Patient Radiation Dose in 64-MDCT. AJR 2007; 189: 219-225.] **Use Reformat to create Sag/Cor reformatted images 3-5mm thick using images from Recon 3. Additional Retro Reconstructions may be needed to create thin images to create Sag/Cor reformats in Lung algorithm. Approx. Weight (lbs) CHEST Approx. ABD/PELVIS Approx. Approx. Weight (kg) CTDIvol (mGy) CTDIvol (mGy) Small Patient 50-70 110-155 6-11 10-17 Average Patient 70-90 155-200 10-18 15-25 Large Patient 90-120 200-265 13-23 22-35 10 Copyright © February 20, 2014 by AAPM. All rights reserved. The disclaimer on page 1 is an integral part of this document.