Researcher:
Alpan, Vildan

Profile Picture
ORCID

Job Title

Other

First Name

Vildan

Last Name

Alpan

Name

Name Variants

Alpan, Vildan

Email Address

Birth Date

Filters

2019 - 201912020 - 20212

Advanced Search

Filter by

Settings

Researcher Of Publications: search.filters.isAuthorOfPublication.ad543a20-dd7c-4529-86ec-e060250a970f

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    PublicationOpen Access
    VMAT vs eight field IMRT: dosimetric comparison of pelvic radiotherapy for patients with high-risk prostate cancer in terms of bone marrow sparing
    (Kare Yayıncılık, 2019) Sezen, Duygu; Alpan, Vildan; Bölükbaşı, Yasemin; Sağlam, Yücel; Selek, Uğur; Faculty Member; Faculty Member; Faculty Member; School of Medicine; Koç University Hospital; N/A; N/A; 216814; N/A; 27211
    Objective: although there is no complete consensus on elective pelvic nodal irradiation for patients with - risk prostate cancer, pelvic radiotherapy with androgen ablation has been more commonly used in many centers. An important part of bone marrow (BM) reserve remains in the pelvic radiation treatment field. This study aimed to evaluate and compare the intensity modulated (step-and-shoot IMRT: ssIMRT) and volumetric modulated arc radiotherapy (VMAT) techniques for pelvic radiotherapy in terms of pelvic BM doses. Methods: this study was based on the simulation scan data of 10 patients with prostate cancer as 3-mm slice thickness using a full bladder and rectal balloon. The first phase of the treatment planning prescribed to pelvic lymphatic (46 Gy/2 Gy/fraction). The second phase consisted of the seminal vesicles and prostate (32 Gy/2 Gy/fraction). The PTV margin was 0.4 cm posteriorly due to rectum and 0.6 cm in all other (including PTVlymphatic) directions. Using same target volumes, ssIMR'l with eight angles (225 degrees, 260 degrees, 295 degrees, 330 degrees, 30 degrees, 65 degrees, 100 degrees, 135 degrees) and double arc (182 degrees, -178 degrees arc angle) VMAT were planned for each patient data set. The planning objective was to cover the PTV by at least 95% of the prescribed isodose and CTV by 98% of the prescribed isodose line. No special dose constraint was given for BM sparing. Each technique was compared by using dose volume histograms (DVH) of V5, V10, V20, V30, V40 of the sacral BM (SBM), iliac BM (IBM), and ischium, pubis, and proximal femora (lower pelvis) and femoral BM (IBM). In addition, V20 V30, V40, and V70 for bladder, and V30, V40, V76, and V80 for the rectum, homogeneity index and the monitor units (MU) were evaluated. The two-sided Wilcoxon's test was used for statistical analysis (p<0.05). Results: for the same PTV coverage, VMAT and ssIMRT plans had similar dose distributions for FBM, IBM, SBM, and total BM as well as the other critical structures. However, VMAT plans in comparison to IMRT ensured significantly lower high dose volumes on rectum such as bringing V80 from 1.6% to 0.9% (p=0.01), and provided similar homogeneity index with lowered monitor units (1048 vs. 1591, p=0.018). Conclusion: in this cohort, VMAT plans without a specific constraint for BM are not found to be superior to ssIMRT in terms of BM reserve irradiation; while VMAT could be encouraged for patients with higher rectum doses such as V80.
  • Thumbnail Image
    PublicationOpen Access
    Double isocenter optimization with HD-MLC linear accelerator to treat extended fields in patients with head and neck cancers
    (Bakis Productions LTD, 2021) Küçük, Ahmet; Topkan, Erkan; Selek, Uğur; Bölükbaşı, Yasemin; Durankuş, Nilüfer Kılıç; Sezen, Duygu; Sağlam, Yücel; Atasoy, Ali İhsan; Karaköse, Fatih; Alpan, Vildan; Akdemir, Eyüb Yaşar; Şenyürek, Şükran; Faculty Member; Faculty Member; Faculty Member; Doctor; Doctor; School of Medicine; Koç University Hospital; 27211; 216814; N/A; 170535; N/A; N/A; N/A; N/A; N/A; N/A
    Purpose: for departments with a congested patient burden or with a limited number of eligible LINACs, we investigated whether LINACS dedicated for SRS-SBRT with limited field high-definition (HD) multi-leaf collimator (MLC) could help to carry this load, and utilized a double-isocenter (DI) optimization with a limited field size of HD-MLC to defeat the craniocaudal field size restriction to match treated plans in a wide-field MLC LINAC for head and neck cancer patients. Methods: fourteen patients with locally advanced head and neck cancers were included, previously treated with simultaneous integrated boost volumetric modulated arc treatment (VMAT) in 33 fractions of clinical target volumes (CTV) of 70Gy, 63Gy, and 57Gy, via single isocenter (SI) plans in Millennium MLC-120 of Varian Trilogy. The DI plans were generated on Pinnacle TPS to be delivered in HD 120 leaves MLC on Varian TrueBeam. The organs at risk (OAR) doses and the prescription volume parameters were compared. Results: DI plans in HD-MLC LINACs were successfully matching the previously treated plans for OAR and CTV constraints. The CI (1.18 versus 1.26; p=0.004) and HI (0.23 versus 0.29; p<0.001) were significantly improved with DI, while the MUs (1321.5 versus 800.3; p<0.001) and the treatment delivery times (6.1 versus 3.7 min; p<0.001) per fraction increased modestly with DI compared to SI, respectively. Conclusions: we revealed that DI optimization plans prepared for HD-MLC could effectively accomplish our goal dosimetrically in locoregionally advanced head and neck cases, despite a modest increase in the MU and treatment delivery times per fraction. This technique may provide an alternative in case of downtimes of standard MLC systems or a standalone treatment machine in case of high volumes requiring extended-field IMRT procedures, or possibly shorten the lengthy waiting times in facilities with limited SRS or SBRT patients.
  • Thumbnail Image
    PublicationOpen Access
    Novel clinically weight-optimized dynamic conformal arcs (WO-DC A) for liver SBRT: a comparison with volumetric modulated arc therapy (VMAT)
    (Dove Medical Press, 2021) Topkan, Erkan; Selek, Uğur; Bölükbaşı, Yasemin; Sağlam, Yücel; Atasoy, Ali İhsan; Karaköse, Fatih; Budak, Mustafa; Alpan, Vildan; Faculty Member; Faculty Member; Doctor; Medical Physicist; School of Medicine; Koç University Hospital; 27211; 216814; N/A; N/A; N/A; N/A; N/A
    Purpose: to evaluate the feasibility of shortening the duration of liver stereotactic radiotherapy (SBRT) without jeopardizing dosimetry or conformity by utilizing weight-optimized dynamic conformal arcs (WO-DCA) as opposed to volumetric modulated arc therapy (VMAT) for tumors away from critical structures. Methods: nineteen patients with liver metastasis were included, previously treated with 50 Gy in 4 fractions with VMAT technique using two partial coplanar arcs of 6 MV beams delivered in high-definition multi-leaf collimator (HD-MLC). Two coplanar partial WODCA were generated on Pinnacle treatment planning system (TPS) for each patient; and MLC aperture around the planning target volume (PTV) was automatically generated at different margins for both arcs and maintained dynamically around the target during arc rotation. Weight of the two arcs using optimization method was adjusted between the arcs to maximize tumor coverage and protect organs at risk (OAR) based on the RTOG-0438 protocol. Results: the WO-DCA plans successfully ""agreed"" with the standard VMAT for OAR (liver, spinal cord, stomach, duodenum, small bowel, and heart) and PTV (D-mean, D-98%, D-2%, CI, and GI), with superior mean quality assurance (QA) pass rate (97.06 vs 93.00 for VMAT; P < 0.001 and t = 8.87). Similarly, the WO-DCA technique additionally reduced the beam-on time (3.26 vs 4.43; P < 0.001) and monitor unit (1860 vs 2705 for VMAT; P < 0.001) values significantly. Conclusion: the WO-DCA plans might minimize small-field dosimetry errors and defeat patient-specific VMAT QA requirements due to the omission of MLC beam modulation through the target volume. The WO-DCA plans may additionally enable faster treatment delivery times and lower OAR without sacrificing target doses in SBRT of liver tumors away from critical structures.