University of Wisconsin–Madison
Poonam Yadav, MD headshot

Poonam Yadav, PhD

Assistant Professor

Department of Human Oncology

I am an assistant professor in the Department of Human Oncology. Much of my current work involves the ViewRay MRIdian System, an MRI-guided radiation therapy machine that enables clinicians to monitor tumors and surrounding tissues during treatment. This technology allows us to adapt to changes in the patient’s anatomy to ensure accurate delivery of radiation. I conduct patient-specific quality assurance and pre-treatment and real-time treatment setup verification. I am also involved in commissioning and acceptance testing of new radiotherapy machines and establishing clinical protocols and planning techniques for various disease sites. My role also includes mentoring radiation oncology physics and radiation oncology residents, physicians, staff and graduate students in clinical practices.

Education

PhD, VIT University (in collaboration with the University of Wisconsin–Madison), Radiation Oncology Physics (2011)

MS, Kurukshetra University, Physics (2004)

BS, Andhra University, Math, Physics and Computer Science (2002)

Academic Appointments

Assistant Professor, Human Oncology (2016)

Research Associate VIT University, VIT University (2006)

Visiting Scholar, Indira Gandhi Atomic Research Center (2006)

Physics Lecturer, Department of Technical Education, Haryana, India (2005)

Research Associate, Department of Physics, Kurukshetra University (2002)

Boards, Advisory Committees and Professional Organizations

International Editor, Journal of Radiotherapy in Practice

Abstract reviewer, Conference of American Association of Physicists in Medicine (2017)

Treasurer and secretary, North Central Chapter of the American Association of Physicists in Medicine

Member, American Association of Physicists in Medicine

Member, American Brachytherapy Society

Member, American College of Radiology

Member, North Central Chapter of the American Association of Physicists in Medicine

Member, Radiological Society of North America

Member, Wisconsin Radiological Society

  • Hybrid volumetric modulated arc therapy for chest wall irradiation: For a good plan, get the right mixture. Phys Med
    Balaji K, Yadav P, BalajiSubramanian S, Anu Radha C, Ramasubramanian V
    2018 Aug; 52: 86-92
    • More

      PURPOSE: To find the optimal dose weighting for hybrid volumetric modulated arc therapy (H-VMAT), a combination of conventional 3DCRT and VMAT plans for left sided chest wall and supraclavicular radiation therapy.

      METHODS & MATERIALS: 20 left-sided breast cancer patients who received adjuvant radiotherapy were considered for this study. To find the optimal weighting, 5 H-VMAT plans were generated for each study case by combining different dose proportions of 3DCRT and VMAT plans including: 90% 3DCRT/10% VMAT, 80% 3DCRT/20% VMAT, 70% 3DCRT/30% VMAT, 60% 3DCRT/40% VMAT, 50% 3DCRT/50% VMAT. Further field-in-field, optimal H-VMAT and VMAT alone plans were compared.

      RESULTS: All H-VMAT plans achieved the expected target coverage. A higher conformity index was achieved for 50% 3DCRT/50% VMAT plan, while better homogeneity index was achieved for 80% 3DCRT/20% VMAT plan. Mean and low doses were less in 90% 3DCRT/10% VMAT plan. Compared with other proportions, 80% 3DCRT/20% VMAT and 70% 3DCRT/30% VMAT weighted H-VMAT plans achieved balanced results for PTVs and OARs.

      CONCLUSION: The optimal dose mixture for H-VMAT technique is 70% to 80% for 3DCRT and 20% to 30% for VMAT. The optimal H-VMAT achieved balanced results for the PTVs and OARs compared with field-in-field and VMAT alone plans.

      View details for PubMedID 30139614
  • Long-term dosimetric stability of multiple TomoTherapy delivery systems. J Appl Clin Med Phys
    Smilowitz JB, Dunkerley D, Hill PM, Yadav P, Geurts MW
    2017 May; 18 (3): 137-143
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      The dosimetric stability of six TomoTherapy units was analyzed to investigate changes in performance over time and with system upgrades. Energy and output were tracked using monitor chamber signal, onboard megavoltage computed tomography (MVCT) detector profile, and external ion chamber measurements. The systems (and monitoring periods) include three Hi-Art (67, 61, and 65 mos.), two TomoHDA (31 and 26 mos.), and one Radixact unit (11 mos.), representing approximately 10 years of clinical use. The four newest systems use the Dose Control Stability (DCS) system and Fixed Target Linear Accelerator (linac) (FTL). The output stability is reported as deviation from reference monitor chamber signal for all systems and/or from an external chamber signal. The energy stability was monitored using relative (center versus off-axis) MVCT detector signal (beam profile) and/or the ratio of chamber measurements at 2 depths. The clinical TomoHDA data were used to benchmark the Radixact stability, which has the same FTL but runs at a higher dose rate. The output based on monitor chamber data of all systems is very stable. The standard deviation of daily output on the non-DCS systems was 0.94-1.52%. As expected, the DCS systems had improved standard deviation: 0.004-0.06%. The beam energy was also very stable for all units. The standard deviation in profile flatness was 0.23-0.62% for rotating target systems and 0.04-0.09% for FTL. Ion chamber output and PDD ratios supported these results. The output stability on the Radixact system during extended treatment delivery (20, 30, and 40 min) was comparable to a clinical TomoHDA system. For each system, results are consistent between different measurement tools and techniques, proving not only the dosimetric stability, but also these quality parameters can be confirmed with various metrics. The replacement history over extended time periods of the major dosimetric components of the different delivery systems (target, linac, and magnetron) is also reported.

      View details for PubMedID 28464517
  • Dosimetric aspects of breast radiotherapy with three-dimensional and intensity-modulated radiotherapy helical tomotherapy planning modules. Med Dosim
    Yadav P, Yan Y, Ignatowski T, Olson A
    2017 Spring; 42 (1): 42-46
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      In this work, we investigated the dosimetric differences between the intensity-modulated radiotherapy (IMRT) plans and the three-dimensional (3D) helical plans based on the TomoTherapy system. A total of 15 patients with supine setup were randomly selected from the data base. For patients with lumpectomy planning target volume (PTV), regional lymph nodes were also included as part of the target. For dose sparing, the significant differences between the helical IMRT and helical 3D were only found in the heart and contralateral breast. For the dose to the heart, helical IMRT reduced the maximum point dose by 6.98Gy compared to the helical 3D plan (p = 0.01). For contralateral breast, the helical IMRT plans significantly reduced the maximum point dose by 5.6Gy compared to the helical 3D plan. However, compared to the helical 3D plan, the helical IMRT plan increased the volume for lower dose (13.08% increase in V5Gy, p = 0.01). In general, there are no significant differences in dose sparing between helical IMRT and helical 3D plans.

      View details for PubMedID 28129971
  • Radiation therapy for breast cancer: Literature review. Med Dosim
    Balaji K, Subramanian B, Yadav P, Anu Radha C, Ramasubramanian V
    2016; 41 (3): 253-7
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      Concave shape with variable size target volume makes treatment planning for the breast/chest wall a challenge. Conventional techniques used for the breast/chest wall cancer treatment provided better sparing of organs at risk (OARs), with poor conformity and uniformity to the target volume. Advanced technologies such as intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) improve the target coverage at the cost of higher low dose volumes to OARs. Novel hybrid techniques present promising results in breast/chest wall irradiation in terms of target coverage as well as OARs sparing. Several published data compared these technologies for the benefit of the breast/chest wall with or without nodal volumes. The aim of this article is to review relevant data and identify the scope for further research in developing optimal treatment plan for breast/chest wall cancer treatment.

      View details for PubMedID 27545009
  • Dosimetric differences in flattened and flattening filter-free beam treatment plans. J Med Phys
    Yan Y, Yadav P, Bassetti M, Du K, Saenz D, Harari P, Paliwal BR
    2016 Apr-Jun; 41 (2): 92-9
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      This study investigated the dosimetric differences in treatment plans from flattened and flattening filter-free (FFF) beams from the TrueBeam System. A total of 104 treatment plans with static (sliding window) intensity-modulated radiotherapy beams and volumetric-modulated arc therapy (VMAT) beams were generated for 15 patients involving three cancer sites. In general, the FFF beam provides similar target coverage as the flattened beam with improved dose sparing to organ-at-risk (OAR). Among all three cancer sites, the head and neck showed more important differences between the flattened beam and FFF beam. The maximum reduction of the FFF beam in the mean dose reached up to 2.82 Gy for larynx in head and neck case. Compared to the 6 MV flattened beam, the 10 MV FFF beam provided improved dose sparing to certain OARs, especially for VMAT cases. Thus, 10 MV FFF beam could be used to improve the treatment plan.

      View details for PubMedID 27217620
  • Acute Toxicity From Breast Cancer Radiation Using Helical Tomotherapy With a Simultaneous Integrated Boost. Technol Cancer Res Treat
    Wojcieszynski AP, Olson AK, Rong Y, Kimple RJ, Yadav P
    2016 Apr; 15 (2): 257-65
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      PURPOSE: To evaluate 2 simultaneous integrated boost treatment planning techniques using helical tomotherapy for breast conserving therapy with regard to acute skin toxicity and dosimetry.

      METHODS: Thirty-two patients were studied. The original approach was for 16 patients and incorporated a directional block of the ipsilateral lung and breast. An additional 16 patients were planned for using a modified approach that incorporates a full block of the ipsilateral lung exclusive of 4 cm around the breast. Dose-volume histograms of targets and critical structures were evaluated. Skin toxicity monitoring was performed throughout treatment and follow-up using the Common Terminology Criteria for Adverse Events.

      RESULTS: Treatment was well tolerated with patients receiving a median dose of 59.36 Gy. Of the 16 patients in both groups, 8 had grade 2 erythema immediately after radiation. On 3-week follow-up, 10 and 7 patients in the original and modified groups showed grade 1 erythema. On 3- and 6-month follow-up, both groups had minimal erythema, with all patients having either grade 0 or 1 symptoms. No grade 2 or 3 toxicities were reported. Mean treatment time was 7.5 and 10.4 minutes using the original and modified methods. Adequate dose coverage was achieved using both methods (V95 = 99.5% and 98%). Mean dose to the heart was 10.5 and 1.8 Gy, respectively (P < .01). For right-sided tumors, the original and modified plans yielded a mean of 8.8 and 1.1 Gy (P < .01) versus 11.7 and 2.4 Gy for left-sided tumors (P < .01). The mean dose to the ipsilateral lung was also significantly lower in the modified plans (11.8 vs. 5.0 Gy, P < .01).

      CONCLUSIONS: Tomotherapy is capable of delivering homogeneous treatment plans to the whole breast and lumpectomy cavity using simultaneous integrated boost treatment. Using the treatment methods described herein, extremely low doses to critical structures can be achieved without compromising acute skin toxicity.

      View details for PubMedID 25780060
  • Dosimetric comparison of photon and proton treatment techniques for chondrosarcoma of thoracic spine. Med Dosim
    Yadav P, Paliwal BR, Kozak K
    2013; 38 (3): 233-7
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      Chondrosarcomas are relatively radiotherapy resistant, and also delivering high radiation doses is not feasible owing to anatomic constraints. In this study, the feasibility of helical tomotherapy for treatment of chondrosarcoma of thoracic spine is explored and compared with other available photon and proton radiotherapy techniques in the clinical setting. A patient was treated for high-grade chondrosarcoma of the thoracic spine using tomotherapy. Retrospectively, the tomotherapy plan was compared with intensity-modulated radiation therapy, dynamic arc photon therapy, and proton therapy. Two primary comparisons were made: (1) comparison of normal tissue sparing with comparable target volume coverage (plan-1), and (2) comparison of target volume coverage with a constrained maximum dose to the cord center (plan-2). With constrained target volume coverage, proton plans were found to yield lower mean doses for all organs at risk (spinal cord, esophagus, heart, and both lungs). Tomotherapy planning resulted in the lowest mean dose to all organs at risk amongst photon-based methods. For cord dose constrained plans, the static-field intensity-modulated radiation therapy and dynamic arc plans resulted target underdosing in 20% and 12% of planning target volume2 volumes, respectively, whereas both proton and tomotherapy plans provided clinically acceptable target volume coverage with no portion of planning target volume2 receiving less than 90% of the prescribed dose. Tomotherapy plans are comparable to proton plans and produce superior results compared with other photon modalities. This feasibility study suggests that tomotherapy is an attractive alternative to proton radiotherapy for delivering high doses to lesions in the thoracic spine.

      View details for PubMedID 23541524
  • Feasibility study on effect and stability of adaptive radiotherapy on kilovoltage cone beam CT. Radiol Oncol
    Yadav P, Ramasubramanian V, Paliwal BR
    2011 Sep; 45 (3): 220-6
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      BACKGROUND: We have analyzed the stability of CT to density curve of kilovoltage cone-beam computerized tomography (kV CBCT) imaging modality over the period of six months. We also, investigated the viability of using image value to density table (IVDT) generated at different time, for adaptive radiotherapy treatment planning. The consequences of target volume change and the efficacy of kV CBCT for adaptive planning issues is investigated. MATERIALS AND METHODS.: Standard electron density phantom was used to establish CT to electron density calibrations curve. The CT to density curve for the CBCT images were observed for the period of six months. The kV CBCT scans used for adaptive planning was acquired with an on-board imager system mounted on a "Trilogy" linear accelerator. kV CBCT images were acquired for daily setup registration. The effect of variations in CT to density curve was studied on two clinical cases: prostate and lung.

      RESULTS: The soft tissue contouring is superior in kV CBCT scans in comparison to mega voltage CT (MVCT) scans. The CT to density curve for the CBCT images was found steady over six months. Due to difficulty in attaining the reproducibility in daily setup for the prostate treatment, there is a day-to-day difference in dose to the rectum and bladder.

      CONCLUSIONS: There is no need for generating a new CT to density curve for the adaptive planning on the kV CBCT images. Also, it is viable to perform the adaptive planning to check the dose to target and organ at risk (OAR) without performing a new kV CT scan, which will reduce the dose to the patient.

      View details for PubMedID 22933960
  • Postmastectomy radiotherapy with integrated scar boost using helical tomotherapy. Med Dosim
    Rong Y, Yadav P, Welsh JS, Fahner T, Paliwal B
    2012; 37 (3): 233-9
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      The purpose of this study was to evaluate helical tomotherapy dosimetry in postmastectomy patients undergoing treatment for chest wall and positive nodal regions with simultaneous integrated boost (SIB) in the scar region using strip bolus. Six postmastectomy patients were scanned with a 5-mm-thick strip bolus covering the scar planning target volume (PTV) plus 2-cm margin. For all 6 cases, the chest wall received a total cumulative dose of 49.3-50.4 Gy with daily fraction size of 1.7-2.0 Gy. Total dose to the scar PTV was prescribed to 58.0-60.2 Gy at 2.0-2.5 Gy per fraction. The supraclavicular PTV and mammary nodal PTV received 1.7-1.9 dose per fraction. Two plans (with and without bolus) were generated for all 6 cases. To generate no-bolus plans, strip bolus was contoured and overrode to air density before planning. The setup reproducibility and delivered dose accuracy were evaluated for all 6 cases. Dose-volume histograms were used to evaluate dose-volume coverage of targets and critical structures. We observed reduced air cavities with the strip bolus setup compared with what we normally see with the full bolus. The thermoluminescence dosimeters (TLD) in vivo dosimetry confirmed accurate dose delivery beneath the bolus. The verification plans performed on the first day megavoltage computed tomography (MVCT) image verified that the daily setup and overall dose delivery was within 2% accuracy compared with the planned dose. The hotspot of the scar PTV in no-bolus plans was 111.4% of the prescribed dose averaged over 6 cases compared with 106.6% with strip bolus. With a strip bolus only covering the postmastectomy scar region, we observed increased dose uniformity to the scar PTV, higher setup reproducibility, and accurate dose delivered beneath the bolus. This study demonstrates the feasibility of using a strip bolus over the scar using tomotherapy for SIB dosimetry in postmastectomy treatments.

      View details for PubMedID 22365416
  • Adaptive planning using megavoltage fan-beam CT for radiation therapy with testicular shielding. Med Dosim
    Yadav P, Kozak K, Tolakanahalli R, Ramasubramanian V, Paliwal BR, Welsh JS, Rong Y
    2012; 37 (2): 157-62
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      This study highlights the use of adaptive planning to accommodate testicular shielding in helical tomotherapy for malignancies of the proximal thigh. Two cases of young men with large soft tissue sarcomas of the proximal thigh are presented. After multidisciplinary evaluation, preoperative radiation therapy was recommended. Both patients were referred for sperm banking and lead shields were used to minimize testicular dose during radiation therapy. To minimize imaging artifacts, kilovoltage CT (kVCT) treatment planning was conducted without shielding. Generous hypothetical contours were generated on each "planning scan" to estimate the location of the lead shield and generate a directionally blocked helical tomotherapy plan. To ensure the accuracy of each plan, megavoltage fan-beam CT (MVCT) scans were obtained at the first treatment and adaptive planning was performed to account for lead shield placement. Two important regions of interest in these cases were femurs and femoral heads. During adaptive planning for the first patient, it was observed that the virtual lead shield contour on kVCT planning images was significantly larger than the actual lead shield used for treatment. However, for the second patient, it was noted that the size of the virtual lead shield contoured on the kVCT image was significantly smaller than the actual shield size. Thus, new adaptive plans based on MVCT images were generated and used for treatment. The planning target volume was underdosed up to 2% and had higher maximum doses without adaptive planning. In conclusion, the treatment of the upper thigh, particularly in young men, presents several clinical challenges, including preservation of gonadal function. In such circumstances, adaptive planning using MVCT can ensure accurate dose delivery even in the presence of high-density testicular shields.

      View details for PubMedID 21925866
  • A planning study for palliative spine treatment using StatRT and megavoltage CT simulation. J Appl Clin Med Phys
    Rong Y, Yadav P, Paliwal B, Shang L, Welsh JS
    2010 Oct 30; 12 (1): 3348
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      Megavoltage CT (MVCT) simulation on the TomoTherapy Hi·Art system is an alternative to conventional CT for treatment planning in the presence of severe metal artifact. StatRT is a new feature that was implemented on the TomoTherapy operator station for performing online MVCT scanning, treatment planning and treatment delivery in one session. The clinical feasibility of using the StatRT technique and MVCT simulation to palliative treatment for a patient with substantial spinal metallic hardware is described. A patient with metastatic non-small-cell lung cancer involving the thoracic spine underwent conventional kilovoltage CT simulation. The metal artifact due to stainless steel spine-stabilizing rods was too severe for treatment planning, despite attempts to correct using density override. The patient was then re-scanned using MVCT on a tomotherapy unit. Plans were generated using both StatRT and conventional tomotherapy planning (Tomo plan) with different settings for comparison. StatRT planning ran a total of five iterations in a short planning window (10-15 min). Two Tomo plans were generated using: (1) five iterations in the "full scatter" mode, and (2) 300 iterations in the "beamlet" mode. It was noted that the DVH of the StatRT plan was almost identical to the Tomo plan optimized by the "full scatter" mode and the same number of iterations. Dose distribution analysis reveals that these three planning methods yielded comparable doses to heart, lungs and targets. This work also demonstrated that undermodulation can result in a high degree of thread effects. The overall time for the treatment process (including 7 minutes for simulation, 15 minutes for contouring, 10 minutes for planning and 5 minutes for delivery) decreases from hours to around 40 minutes using the StatRT procedure. StatRT is a feasible treatment-planning tool for physicians to scan, contour and treat patients within one hour. This can be particularly beneficial in urgent palliative treatments.

      View details for PubMedID 21330983
  • The effect and stability of MVCT images on adaptive TomoTherapy. J Appl Clin Med Phys
    Yadav P, Tolakanahalli R, Rong Y, Paliwal BR
    2010 Jul 02; 11 (4): 3229
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      Use of helical TomoTherapy-based MVCT imaging for adaptive planning is becoming increasingly popular. Treatment planning and dose calculations based on MVCT require an image value to electron density calibration to remain stable over the course of treatment time. In this work, we have studied the dosimetric impact on TomoTherapy treatment plans due to variation in image value to density table (IVDT) curve as a function of target degradation. We also have investigated the reproducibility and stability of the TomoTherapy MVCT image quality over time. Multiple scans of the TomoTherapy "Cheese" phantom were performed over a period of five months. Over this period, a difference of 4.7% in the HU values was observed in high-density regions while there was no significant variation in the image values for the low densities of the IVDT curve. Changes in the IVDT curves before and after target replacement were measured. Two clinical treatment sites, pelvis and prostate, were selected to study the dosimetric impact of this variation. Dose was recalculated on the MVCTs with the planned fluence using IVDT curves acquired before and after target change. For the cases studied, target replacement resulted in an overall difference of less than 5%, which can be significant for hypo-fractionated cases. Hence, it is recommended to measure the IVDT curves on a monthly basis and after any major repairs/replacements.

      View details for PubMedID 21081878

Contact Information

Poonam Yadav, PhD

600 Highland Avenue,
K4/b100
Madison, WI 53792