DirectDensity Cookbook: A guide to personalized CT imaging in RT

DirectDensity cookbook A guide to personalized CT imaging in RT siemens-healthineers.com/radiotherapy/ct-for-rt For users of SOMATOM CT systems The scientific overlay is not that of the individual pictured and is not from a device of Siemens Healthineers. It was modified for better visualization. SIEMENS Healthineers DirectDensity cookbook · Foreword and Contributors Content · DirectDensity cookbook Foreword Content Radiation oncology is experiencing growth in This cookbook is intended to propagate Benefits of image optimization and its challenges in RT 4 the use of personalized imaging for treatment this information to users of DirectDensity on planning and this trend has been embraced by SOMATOM® CT systems. It presents a series Three key points about DirectDensity 5 physicists and physicians alike. of study protocols and practical tips and tricks from implementation to clinical routine, so that Technical implementation 6 Clinical expert users have investigated and everyone can benefit from the clinical experts’ Aim 6 implemented novel image optimization experience. The information provided here can Step 1: Protocol setup 6 technologies and we are pleased to be able help your entire clinic to optimize workflows Step 2: Phantom setup 7 to share these with you. and provide the best imaging possible to cancer Step 3: Acquisition for calibration phantom 7 patients undergoing radiation therapy. Step 4: Image analysis 8 Step 5: Calibration curve evaluation 8 We look forward to hearing your feedback and Step 6: Calibration curve generation 10 suggestions, so that we at Siemens Healthineers Step 7: Commissioning (TPS registration) 11 can continue improving and helping you care for your patients. Dosimetric evaluation 12 Aim 12 Contributors Step 1: Series generation 12 Step 2: Dose calculation 12 Step 3: Dose volume histogram analysis (Dmax, Dmin, mean) 14 Step 4: Point-to-point analysis (optional) 14 Step 5: Check other clinical areas 15 DirectDensity workflow in clinical routine 17 Aim 17 Manuel Algara Enric Fernández-Velilla Nuria Rodríguez Oscar Pera Jaume Quera Head of Radiation Oncology Medical Physicist Radiation Oncologist, Medical Physicist, Medical Physicist, Step 1: Acquisition 17 Department, Hospital del Mar, Hospital del Mar, Hospital del Mar, Hospital del Mar, Hospital del Mar, Step 2: Reconstruction 18 Universitat Autònoma, Barcelona, Spain Universitat Pompeu Fabra, Barcelona, Spain Barcelona, Spain Barcelona, Spain Barcelona, Spain Step 3: Patient marking and contouring 19 Step 4: Treatment planning 19 Clinical cases 20 Conclusion 23 Rafael Jimenez Soufian Audia Takeshi Kamomae Masaru Nakamura Naoki Kaneda RT Supervisor, Head Medical Physicist, Clinical Assistant Professor Chief Radiological Radiological Technologist, Hospital del Mar, Chirec hospital group, and Medical Physicist, Technologist and Aichi Medical University Barcelona, Spain Brussels, Belgium Nagoya University Hospital, Medical Physicist, Hospital, Aichi, Japan Aichi, Japan Aichi Medical University Hospital, Aichi, Japan Kazuhiko Nakamura Yoshitaka Minami Firas Mourtada Radiological Technologist Radiological Technologist Chief of Clinical Physics and Medical Physicist, and Medical Physicist, Radiation Oncology, Aichi Medical University Aichi Medical University ChristianaCare's Helen F. Graham Hospital, Aichi, Japan Hospital, Aichi, Japan Cancer Center & Research Institute, Newark, USA 2 3 DirectDensity cookbook · Benefits of image optimization Three key points · DirectDensity cookbook Benefits of image optimization and its Three key points about DirectDensity challenges in RT When performing a CT examination, the tube voltage is typically adjusted to the patient (e.g. body size, body part...) in order to maximize the image quality. In Radiation Therapy, CT images 1. What is DirectDensity? are transferred to the treatment planning system with two purposes, 1) contouring of target and 2) dose calculation where the CT parameters – in particular tube voltage – have been calibrated CT images are transferred to the treatment planning system with two to convert the image intensity to an electron density. For the first purpose,an essential factor purposes, 1) contouring of target and 2) dose calculation. For the second for CT image quality is the tube voltage expressed as the kV value. Siemens Healthineers has purpose DirectDensity is an innovative technology that potentially enables developed CARE kV, which allows you to automatically select optimal tube voltage and effective the use of a single calibration curve for all tube voltage and beam filtration tube current to provide a predefined image quality level at the technically lowest possible settings. It is available for selected CT and PET CT systems1. radiation dose. Optimization is based on the patient-specific attenuation estimation from topogram data. Image quality is predefined by the quality ref. mAs value for a reference kV value for a standard patient. CARE kV can then adjust the actual effective mAs value depending on actual patient size and tube voltage. The objective is to obtain the same image quality as for the standard patient. Image quality is measured based on a CNR (contrast-to-noise ratio) relevant for 2. What does DirectDensity do? a certain clinical use case. For radiation treatment planning, and especially for advanced therapies such as SRT, the technology can help increase confidence in contouring. DirectDensity removes the constraint of a fixed tube voltage setting and thereby enables the unconstrained use of tube voltage optimization such as for obese patients (with high tube voltage for low noise imaging), Attenuation breast cancer patients (with low tube voltage for good CNR), pediatric patients data from (with low tube voltage for good CNR). It results in high-quality optimized topogram 70 kV images and a standardized workflow. Clinical 80 kV use case 100 kV 120 kV V 3. What are the potential benefits in RT? 140 kV . ........ Contouring quality and consistency depends on image quality. DirectDensity removes the constraints on optimal tube voltage adapation by allowing CARE kV or the user to choose the optimal tube voltage for each patient. Ideally, the optimized kV setting suggested by CARE kV should be used in fully automated mode. However, due to the second purpose, but this would imply that the treatment planning is able to accept any tube voltage. Even when this is possible, it is is usually very cumbersome and prone to Clinical kV usage before Clinical kV usage after error due to the necessity of having multiple calibration curves. This is why Siemens Healthineers has introduced DirectDensity. 100% 100% 80% 80% 60% 60% 40% 40% usage [%] usage [%] 20% 20% 0% 0% 70 80 100 120 140 70 80 100 120 140 Tube voltage [kV] Tube voltage [kV] Clinical kV usage before (left) and after (right) CARE kV implementation (Source: Based on customer usage measured with Siemens Utilization Management) Image impression at 120 kV (left) and 100 kV (right) in a brain case with the same reconstruction parameters. 1 Please contact your representative of Siemens Healthineers for further information about availability. 4 5 DirectDensity cookbook · Technical implementation Technical implementation · DirectDensity cookbook Technical implementation Aim Step 2: Phantom scan setup The goal of this step is to define the scan protocols for algorithm validation. The aim of this step is to find out whether the DirectDensity algorithm provides a calibration With the setup (example from Hospital Del Mar, Barcelona, Spain), the following five protocols curve proportional to electron density regardless of the acquisition conditions. To do this, were adapted to the DirectDensity (DD) workflow: the Advanced Electron Density Phantom from Sun Nuclear was used. Acquisitions are performed 1) Brain 2) Head and Neck 3) Breast 4) Abdomen 5) Prostate using both the small and the large phantom (this allows you to check how the patient thickness affects the Hounsfield units). The complete set of images acquired for calibration Step 1: Protocol setup is composed of four series for each tube voltage setting with two different reconstructions (standard reconstruction and DirectDensity reconstruction) for two different phantoms (small and large phantom). Clinical area Default protocol Parameters to be changed Important remarks Calibration phantom Brain RT_Brain 1st recon: I30 / Br381 CARE Dose4D:2 Yes 2nd recon: F30 / Sd40 (DD) CARE kV (semi mode/manual kV) Various calibration phantoms are available on the market. We used the Advanced Electron Density Phantom Head and Neck RT_HeadNeck 1st recon: I30 / Br38 CARE Dose4D: Yes from Sun Nuclear, featuring Gammex® technology1 to 2nd recon: F30 / Sd40 (DD) evaluate DirectDensity for this cookbook. O CARE kV (semi mode/manual kV) The features of this phantom are as follows: 0 0 • Adherence to ICRU-44 and ICRP material performance Breast RT_Breast 1st recon: I30 / Br38 CARE Dose4D: Yes • Expanded phantom size for wide-beam systems that 2nd recon: F30 / Sd40 (DD) CARE kV can be used for CBCT as this phantom is thicker than (semi mode/manual kV) the previous version • Inserts include Air, LN-300 Lung, LN-450 Lung, HE Abdomen RT_Abdomen 1st recon: I30 / Br38 CARE Dose4D: Yes General Adipose, HE Breast 50:50, HE Solid Water, 2nd recon: F30 / Sd40 (DD) CARE kV Water, HE Brain, HE Liver, HE Inner Bone, 30% CaCO3, (semi mode/manual kV) 50% CaCO3, HE Cortical Bone Prostate RT_Pelvis 1st recon: I30 / Br38 CARE Dose4D: Yes Step 3: Acquisition for calibration phantom 2nd recon: F30 / Sd40 (DD) CARE kV (semi mode/manual kV) 1) Place a Gammex® phantom the large Tips: CARE kV (Advanced Electron Density Phantom) on the table. SIEMENS Healthingers 2) Adjust the position of the phantom to the • CARE kV is a dose-saving mechanism that guarantees a predefined image quality. center of the bore and align it with the scan axis Semi mode or manual kV is required in order to evaluate CT values for different tube voltages. (use gantry lasers and markings or distinct features of the phantom). 3) Select the RT Abdomen protocol. SOMATOM go. platform SOMATOM Definition AS Open/Confidence/Drive 4) Set up scan and make sure that the scan range is centered on the phantom. 5) Perform repeated scans for all the tube voltages --- (e.g., 80 kV, 100 kV, 120 kV, and 140 kV). 6) Repeat all the scans with the large phantom for: “off” CARE Dose4D™ off and manual kV and mAs selection Breast protocol, - “manual kV” CARE Dose4D on and CARE kV similar to “semi” mode of SOMARIS/7 Prostate protocol. - 7) Repeat all the scans with the small phantom for: 69 “full” CARE Dose4D on and CARE kV similar to “auto” mode of SOMARIS/7 Head and Neck protocol, - - "full" doesn't allow you to select tube voltage to change. After the evaluation is complete, Brain protocol. Positioning of the Advanced Electron CARE kV may be set to full auto mode. Density Phantom from Sun Nuclear 1 Reconstruction kernels may vary based on software versions. 1 Gammex is a wholly owned subsidiary of Sun Nuclear Corporation. The Advanced Electron Density Phantom, Model 1467, 6 2 CARE Dose4D is an automatic exposure control based on attenuation of the projection in real time. is Siemens PN GA805810. 7 DirectDensity cookbook · Technical implementation Technical implementation · DirectDensity cookbook Step 4: Image analysis 1) Open the series in the TPS to measure CT values. Figure 1A: Calibration curves for RT Abdomen protocol with large phantom 2) Use the middle slice position of the Advanced Electron Density Phantom. with standard reconstruction 3) A 2 cm ROI is used on the center of each rod (make sure that the ROI does not cover the edge of the rod). 1.8 80 kV 1.6 --- y 100 kV 1.4 120 kV 1.2 140 kV V 1.0 0.8 0.6 0.4 Image analysis using the large phantom (Breast, Abdomen, and Pelvis) and the small phantom (Brain and Head and 0.2 Neck). The edge of the inserted material must be avoided, otherwise it introduces uncertainty to the CT values due to 0.0 Electron density relative to water overshoot (orange arrows). -1,000 0 1,000 2,000 CT Value [HU] Step 5: Calibration curve evaluation Figure 1B: Calibration curves with DirectDensity 1) Open Microsoft Excel, or an equivalent program. Enter your measured values into a table1. 2) The CT values for different materials using RT Abdomen and the large phantom are shown 1.8 80 kV in the table below. 1.6 100 kV 3) Calibration curves at different kV settings with and without DirectDensity are created as below. 1.4 120 kV 4) Repeat this step for the different protocols (e.g. use the small phantom for the Brain protocol). 1.2 140 kV 1.0 Phantom certificate CT value with standard reconstruction CT value with DirectDensity 0.8 Material Relative 0.6 Electron 80 kV 100 kV 120 kV 140 kV 80 kV 100 kV 120 kV 140 kV physical density (HU) (HU) (HU) (HU) 0.4 density 0.2 Air 0.000 0.000 -996.0 -997.1 -997.1 -997.5 -993.8 -995.4 -995.8 -996.8 0.0 Electron density relative to water -1,000 -500 0 500 1,000 LN-300 Lung 0.289 0.279 -698.6 -704.6 -705.8 -705.6 -697.2 -702.9 -703.9 -703.6 CT value LN-450 Lung 0.462 0.447 -532.2 -538.3 -539.9 -539.6 -531.5 -537.5 -538.9 -538.7 HE General Adipose 0.962 0.951 -83.1 -73.5 -67.7 -64.2 -83.7 -74.4 -68.0 -64.5 HE Breast 50:50 0.983 0.969 -46.7 -38.4 -35.6 -33.5 -46.3 -40.1 -36.1 -33.2 HE Solid Water 1.022 0.998 6.6 6.2 4.2 5.5 3.9 2.7 3.1 4.7 Water 1.000 1.000 4.0 5.0 4.1 4.3 1.1 1.2 2.4 3.5 HE Brain 1.051 1.025 39.1 35.0 33.4 31.9 29.6 26.7 29.4 29.0 HE Liver 1.081 1.054 66.0 63.1 61.1 59.8 50.2 49.7 53.5 53.2 HE Inner Bone 1.214 1.164 413.2 347.1 305.7 278.9 166.8 171.8 170.9 168.9 30% CaCO3 1.332 1.268 621.3 528.7 474.5 438.5 245.0 255.6 260.0 259.7 50% CaCO3 1.559 1.462 1145.1 957.1 845.2 777.8 462.6 468.7 466.9 463.8 HE Cortical Bone 1.924 1.774 1876.7 1575.7 1390.3 1276.7 812.8 816.9 806.9 797.8 1 These steps may also be achieved with RapidCHECK™ software from Sun Nuclear. Use RapidCHECK with the Advanced Electron Density Phantom to automatically locate and identify the material of each rod, and to streamline the CT-to-Electron Density 8 table report. 9 DirectDensity cookbook · Technical implementation Technical implementation · DirectDensity cookbook Step 6: Calibration curve generation by averaging CT values obtained for different tube voltages Step 7: Commissioning (TPS1 registration) Calculate the average DirectDensity value by averaging the CT values obtained for different tube voltages for each material. In the example below, we took the average of all four protocols (Breast, Prostate with large phantom, and Head and Neck and Brain with small phantom). Phantom certificate Material Physical Electron 80 kV DD 100 kV DD 120 kV DD 140 kV DD Average density density image image image image DirectDensity value value value value image value Air 0.000 -993.8 -995.4 -995.8 -996.8 -995.5 LN-300 Lung 0.289 0.279 -697.2 -702.9 -703.9 -703.6 -701.9 LN-450 Lung 0.462 0.447 -531.5 -537.5 -538.9 -538.7 -536.7 HE General 0.962 0.951 -83.7 -74.4 -68.0 -64.5 -72.7 Calibration curve examples from Hospital Del Mar (left) and Nagoya University Hospital (right): Adipose The curve should be almost a straight line. HE Breast 50:50 0.983 0.969 -46.3 -40.1 -36.1 -33.2 -38.9 1) Log in to the TPS with an administrator (physicist) account 2) Go to calibration curve registration HE Solid Water 1.022 0.998 3.9 2.7 3.1 4.7 3.6 (e.g., Eclipse, beam configuration → Beam data → CT calibration) Water 1.000 1.000 1.1 1.2 2.4 3.5 2.0 3) Enter corresponding pairs of average DirectDensity image value and relative electron/physical density values (use air, LN-300 and 450, General Adipose, Breast 50:50, Liquid Water, Brain, HE Brain 1.051 1.025 29.6 26.7 29.4 29.0 28.7 Liver, Inner Bone, 30% CaCO3, 50% CaCO3, and Cortical Bone; enter CT value and relative HE Liver 1.081 1.054 50.2 49.7 53.5 53.2 51.7 density accordingly (see example above)) 4) Extrapolation of the relative density to 6.0 might be optional (otherwise high-density single HE Inner Bone 1.214 1.164 166.8 171.8 170.9 168.9 169.6 pixel can trigger a warning message that must be accepted every time)2 30% CaCO3 1.332 1.268 245.0 255.6 260.0 259.7 255.1 5) Check calibration curve – the line should be almost straight (see examples, left) 6) Save the calibration curve 50% CaCO3 1.559 1.462 462.6 468.7 466.9 463.8 465.5 HE Cortical Bone 1.924 1.774 812.8 816.9 806.9 797.8 808.6 Tips for handling metal implants: 1) iMAR (iterative metal artifact reduction) is recommended to minimize metal artifacts in order to improve the certainty of dose calculation and contouring 2) Beam placement should not overlap with metal implants 3) To avoid warning messages due to high density, please insert 29768 for physical density (19.32 g/cm3)2 1 Using Eclipse from Varian Medical Systems. Procedures may vary depending on the software versions or different TPS systems. 2 Non-natural materials, for example metals and contrast agents like iodine, will decrease accuracy and – as with conventional CT images – can potentially lead to image artifacts. 10 11 DirectDensity cookbook · Dosimetric evaluation Dosimetric evaluation · DirectDensity cookbook Dosimetric evaluation Aim On Figures (1A, 1B), we showed that varying the acquisition kV has almost no influence on the Insert New Plan Sum calibration curve when the DirectDensity reconstruction kernel is used. Before implementing in General clinical routine, we recommend preliminary evaluation with a few clinical cases (e.g., four most Course D Estudi DD Plan Sum D Man Suma Cancel important cancer sites, two cases each) in order to double check the dosimetric impact. Add New Pia Srled plans to include In the sum Step 1: Series generation % Plan Normalantion Mod Jume Typel Edudi DD MA weam TUMOR TUMOR [TUMOR] 15 Son Value: 100.00 Estudi DD MAMA DO TUMOR [TUMOR 150 8 15 1) Head and Neck scan with CARE kV Titudi DD 1.00 TUMOR |TUMOR] with full mode (in this case, 100 kV)1 2) Reconstruct two series, one with the standard reconstruction kernel, one with the DirectDensity kernel. If there are predefined scan protocols (see technical implementation step), two adequate reconstructions should already be defined. Reference 100 kV with DirectDensity (left), 6) Calculate the new plan on the DirectDensity images and compare the dose with the data: 100 kV standard reconstruction. and without (right) reference plan (see example above) Comparison data: 100 kV with DirectDensity. 3) Export the two series to the TPS. In the TPS, make Tip: sure that the correct imaging device is selected (so • Please make sure that the corresponding calibration that the TPS uses the appropriate calibration curve). curve is selected when performing dose calculation. • For simple analysis, the monitor units (MU) should be Step 2: Dose calculation equal for both plans. 1) Open the images in the TPS with standard reconstruction. 2) Contour organs at risk (OAR) and target. 3) Copy the contours to the DirectDensity reconstruction. 4) Calculate dose on standard reconstruction using Anisotropic Analytical Algorithm (AAA)2 after optimizing a plan or setting some beams3. 100 kV with DirectDensity (left), and without (right) 5) Copy the plan and assign to the corresponding DirectDensity datasets. 1 If 120 kV is required as reference, repeat the scan with 120 kV, and add reconstruction accordingly. 2 Using Eclipse (Varian Medical Systems). 12 13 DirectDensity cookbook · Dosimetric evaluation Dosimetric evaluation · DirectDensity cookbook Step 5: Check other clinical areas. Step 3: Dose-volume histograms (DVH) for maximum dose (Dmax), After looking into head and neck, we recommend applying the same procedure minimum dose (Dmin), and mean dose to other clinical areas. The purpose of this step is to compare the DVH dose plan for standard reconstruction and Breast 2,000 Color scale from 0.2% to – 0.1% for dosimetric DirectDensity reconstruction. We recommend comparing the Dmax, Dmin, and mean dose case 1,500 differences between 100 kV DirectDensity vs for each volume. 100 kV standard reconstruction. 1,000 500 Frequency 0 -2 -1.6 -1.2 -0.8 0 0.4 0.8 1.2 1.6 2.0 Dose difference (%) DVH comparison between DirectDensity reconstruction and standard reconstruction for following structures. Red → PTV Pink → Cervel The total dose to the planning target volume of the breast was 49.5 Gy and there was only 0.08 Gy difference. Dose comparison in terms of Dmax, Dmin, and mean dose for each volume. Step 4: Voxel-by-voxel evaluation of dose distributions (optional) For further evaluation, dose distributions of the plans based on the standard reconstruction and the DirectDensity reconstruction can be compared voxel by voxel. For example, you can use a dose difference frequency histogram. It provides a visualization of the distribution of dose differences between the two plans, as well as the mean and standard deviation of those differences. Within our evaluation, the DirectDensity-based plan shows a good alignment with the standard/conventional plan. 2,000 Tips: For voxel-by-voxel evaluation, dose 1,500 distributions usually have to be exported from the TPS (usually in DICOM format) 1,000 and then processed via suitable third-party DVH evaluation (bottom right) for min, max, and average dose for OARs and PTV respectively. applications capable of reading DICOM Red → PTV (Breast) Pink → Tumor Light blue → Lung Beige → Heart Frequency 500 image data (e.g., ImageJ, MATLAB, Python/ scipy-stack/pydicom, R). Be aware of any 0 parameters such as dose-scaling factors; -2 -1.6 -1.2 -0.8 -0.4 0 0.4 0.8 1.2 1.6 2 they can be found in the DICOM header. Dose difference (%) 14 15 DirectDensity cookbook · Dosimetric evaluation DirectDensity workflow in clinical routine · DirectDensity cookbook DirectDensity workflow in clinical routine Aim Pelvis 10,000 Color scale from 0.2% to – 0.1% for dosimetric This section describes how DirectDensity can be used in clinical routine. After implementing the case differences between 140 kV DirectDensity vs necessary changes in the treatment planning system and verifying on a few clinical cases that the 8,000 6,000 140 kV standard reconstruction. algorithm performs as designed, it is important to also spend time understanding the implications of the implementation of DirectDensity on your clinical workflow. 4,000 2,000 0 Step 1: Acquisition Frequency -2 -1.6 -1.2 -0.8 0 0.4 0.8 1.2 1.6 2.0 Dose difference (%) Ci 70 kV 80 kV 100 kV Make sure that CARE kV is activated in native/soft tissue contrast mode. It automatically chooses the optimum kV 120 kV based on attenuation data from the topogram 140 kV The total dose to the planning target volume of the pelvic bone was 49.5 Gy and there was only 0.006 Gy difference. 25 20 ELLLI 15 10 5 Number of cases 0 HeadNeck Thorax Abdomen Pelvis Clinical kV usage shows that different kVs 100 kV 120 kV 140 kV are used depending on clinical area, patient, and cancer type. Also note that Thorax CTs Distribution of the optimum kV as suggested by are mostly performed with 140 kV when high CARE kV1 (Aichi Medical University Hospital city, Japan). attenuation area (shoulders) is included in Please note that Aichi Medical University Hospital chose planning CT to ensure sufficient contrast-to- to limit the CARE kV options to 100, 120, and 140kVp. If no constrains is set with CARE kV, the software would noise level in upper lung area. potentially pick 80kV or 70kV. DVH evaluation (bottom right) for min, max, and average dose for OARs and PTV respectively. Red → PTV (Pelvis) Yellow → Femoral head Brown → Rectum 16 17 DirectDensity cookbook · DirectDensity workflow in clinical routine DirectDensity workflow in clinical routine · DirectDensity cookbook Step 2: Reconstruction Step 3: Patient marking and contouring Two reconstructions are automatically performed as follows: 1) Open the case with CT simulation software 1) Standard reconstruction (for contouring) (e.g., Sim&GO or syngo.via RT Image Suite) 2) DirectDensity reconstruction (for primary series) 2) Perform patient marking on DirectDensity series 3) Make sure that DirectDensity series is selected as primary series (left) 4) Contour on standard reconstruction (right), which presents the optimal image quality/ contrast. 5) Export following data to your Oncology Information System such as ARIA or your TPS: DirectDensity reconstruction - Isocenter/reference point - OAR (organs-at-risk) contouring – - CTV, PTV, ITV, etc. DD Optimal image Tips: • To perform contouring on soft tissue, we recommend using a smooth kernel (such as I30 or Br38) designed for soft-tissue visualization. • Tips: Low kV enables more contrast. The fast window feature can be used to automatically • SAFIRE (iterative reconstruction) can be applied routinely; iMAR (metal artefact reduction) adapt the window to the acquisition kV in order to set the appropriate image impression or HD FOV (extended field of view) can be used if applicable. for contouring (otherwise manual windowing needs to be applied). • We recommend discussing optimal reconstruction parameters in your department. The example on the right shows different image impressions with different reconstruction kernels and windows. Step 4: Treatment planning 1) Select study to open the case in the TPS 2) Calibration curve for DirectDensity is automatically selected 3) Perform dose calculation in the TPS 18 19 DirectDensity cookbook · Clinical cases Clinical cases · DirectDensity cookbook Clinical cases 120 kV CARE kV 120 kV CARE kV 100 kV Radiotherapy after lumpectomy: 100 kV Comparison of images at 120 kV (left) and 100 kV (right) after brain surgery: The edema needs to be contoured as CTV for tumor bed radiotherapy. 100 kV with SAFIRE provides a sufficient level of soft-tissue contrast in fat and mammary glands for breast contouring. As breast cancer patients have good survival rates, optimal dose (ideally After window level is optimized by radiation oncologist, 100 kV shows improved visualization dose reduction) is very important. of the edema for confident CTV contouring. CARE kV provides a predefined CNR level for certain clinical tasks at the lowest possible dose, specific to the patient. DirectDensity enables the user to select any reconstruction kernel with advanced technique (e.g., SAFIRE) CARE kV 100 kV with iodine contrast in head and neck cancer patient. Some institutions have implemented DirectDensity with iodine contrast for dose calculation in head and neck cases. It potentially eliminates native scan 80 kV and registration error between native and Lung cancer (paratracheal lymph node) case showing Thorax acquisition with 120 kV (left) and contrast scans. 80 kV (right): Compared to 120 kV, 80 kV provides better soft-tissue contrast. 100 kV Tips: Influence of iodine contrast on dose calculation by using DirectDenstiy • In general, even without using DirectDensity, Choi et al [1] evaluated the influence of intravenous contrast agent on dose calculations of intensity-modulated radiation therapy plans for head and neck cancer and concluded that the difference between the doses calculated from the CTs with and without contrast agent enhancement was tolerably small. Using intravenous contrast agent could therefore be recommended for the planning of CT of head and neck IMRT without having to acquire a native non-enhanced scan for dose calculation. • Minami et al [2] investigated the influence of iodine contrast with DirectDensity for six patients. The result shows that DVH for the OARs (spinal cord and parotids) are almost the same. 140 kV Radiotherapy case after prostatectomy: 140 kV (right) shows suitable level of image noise for PTV (tumor bed) compared to 120 kV (left) for obese patient. 20 21 DirectDensity cookbook · Clinical cases Conclusion · DirectDensity cookbook Conclusion Using one tube voltage setting is not ideal for all patients or all treatment sites. In general, 100 100 100 Spinal cord Rt parotid Lt parotid lower tube voltage (e.g. kV setting) scans provide improved soft-tissue contrast. Patient size will 80 80 80 also affect which kV setting is the most suitable. Larger patients, for instance, require a higher 60 60 60 kV value to ensure sufficient signal.[3] To summarize, the DirectDensity workflow offers the 40 40 40 following benefits: Ratio of total 20 20 20 0 0 0 • Improved soft-tissue contrast in low-kV imaging for brain, head and neck, lung, and breast cases 0 20 40 60 0 20 40 60 80 0 20 40 60 80 • DirectDensity provide images without compromising on individualization. structure volume (%) Dose (Gy) Dose (Gy) Dose (Gy) • DirectDensity images eliminate the need for tube voltage-dependent calibration. The ratio of the total structure volume (%) shows that DVH for the OARs (spinal cord, left parotid, and right parotid) DirectDensity is compatible with all other RT-relevant features – such as SAFIRE, iMAR, are almost the same using DirectDensity with iodine, standard reconstruction, or standard reconstruction with iodine. HD FOV, and 4D CT – making its clinical implementation easy and seamless. With minimal changes in the workflow, DirectDensity gives users another level of flexibility in image acquisition, and enables them to produce optimal and personalized images for each patient – without 100 compromising the accuracy of the dose calculation. 0,6 80 This document provides helpful insights and step-by-step guidance for this procedure. 60 0,4 We hope that these will help you successfully implement DirectDensity in your practice and that 40 0,2 0.203 0.195 your patients will soon benefit from this innovative technology. Ratio of total 0.133 0.111 20 Absolute dose difference (Gy)0,8 0 0 Dmean Dmax 60 65 70 75 80 structure volume (%) Dose (Gy) DirectDenstiy + iodine Standard reconstruction Standard reconstruction + iodine • DVH of the PTV (right) shows that: standard reconstruction with iodine contrast results in a smaller dose than when - using standard reconstruction without iodine contrast; using iodine contrast on DirectDensity results in slightly lower influence than standard - reconstruction with iodine contrast (absolute dose differences are shown on left). 22 23 DirectDensity cookbook · Conclusion Read more · DirectDensity cookbook The creation of this cookbook was supported by the key experts from the healthcare industry: Read more from our series Don´t miss out on other guides for imaging in RT with practical tips and tricks for the implementation and use of our solutions – intended for experts and novice users alike. 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Evaluation of the Direct Technical principles and Density Algorithm for Energy- Jainil Shah Lynn Mueller-Hegemann Hikaru Tanikawa Kenneth Ruchala implications for radiotherapy DirectDensity' Independent Radiotherapy Senior Research Scientist Product Marketing Manager Product Manager Product Manager, -- Treatment Planning Collaborations Manager, Radiation Oncology, Radiation Oncology, Sun Nuclear Corporation CT for Radiation Oncology, Siemens Medical Solutions Siemens Japan siemens-healthineers.com/ Siemens Medical Solutions USA, Inc. radiotherapy/ct-for-rt siemens-healthineers.com/ USA, Inc. radiotherapy/ct-for-rt ...... MR imaging for RT planning MR-integrated workflows MReadings: MR in RT in radiation therapy for 6th Edition ESTRO 2020 MRcodings: MR In RT MAGNETOM systems magnetomworld. siemens-healthineers.com/ siemens-healthineers.com/ radiotherapy/mri-for-rt/ hot-topics/mri-in- mri-training radiation-therapy [1] Choi Y, et al. et al, Influence of intravenous contrast agent on dose calculations of intensity modulated radiation therapy plans for head and neck cancer. Radiother Oncol. 2006;81(2):158-162. [2] Yoshitaka M, et al. 32nd Annual Meeting of the Japanese society for Radiation Oncology. O21-4. 2019 [3] Nelson G, et al. Technical Note: The use of DirectDensityTM and dual-energy CT in the radiation oncology clinic. J Appl Clin Med Phys. 2019 Mar;20(3):125-131. doi: 10.1002/acm2.12546. Epub 2019 Mar 9. PMID: 30851087; PMCID: PMC6414137. 24 25 DirectDensity cookbook · Notes Clinical cases · Notes Notes Notes 26 27 On account of certain regional limitations of sales rights Note: Any technical data contained in this document may and service availability, we cannot guarantee that all vary within defined tolerances. Original images always products included in this brochure are available through lose a certain amount of detail when reproduced. the Siemens Healthineers sales organization worldwide. Availability and packaging may vary by country and The information presented in this cookbook is for are subject to change without prior notice. Some/all illustration only and is not intended to be relied upon ofthe features and products described herein may not by the reader for instruction as to the practice of be available in the United States. medicine. Any healthcare practitioner reading this information is reminded that they must use their own The information in this document contains general learning, training and expertise in dealing with their technical descriptions of specifications and options as individual patients. well as standard and optional features which do not always have to be present in individual cases, and which This material does not substitute for that duty and is may not be commercially available in all countries. not intended by Siemens Healthineers to be used for any purpose in that regard. The Operating Instructions must Due to regulatory reasons their future availability always be strictly followed when operating the CT system. cannot be guaranteed. Please contact your local Siemens Healthineers organization for further details. Siemens Healthineers reserves the right to modify the design, packaging, specifications, and options described herein without prior notice. Please contact your local Siemens Healthineers sales representative for the most current information. Siemens Healthineers Headquarters Siemens Healthcare GmbH Henkestr. 127 91052 Erlangen, Germany Phone: +49 9131 84-0 siemens-healthineers.com Published by Siemens Healthcare GmbH · Printed in Germany · 8836 0920 · ©Siemens Healthcare GmbH, 2020