ORCID Profile
0000-0002-4861-2108
Current Organisation
Liverpool Hospital
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Publisher: Wiley
Date: 03-08-2018
DOI: 10.1002/JMRS.298
Publisher: Elsevier BV
Date: 11-2015
Publisher: Elsevier BV
Date: 11-2016
DOI: 10.1016/J.IJROBP.2016.08.002
Abstract: To determine whether T2-weighted MRI improves seroma cavity (SC) and whole breast (WB) interobserver conformity for radiation therapy purposes, compared with the gold standard of CT, both in the prone and supine positions. Eleven observers (2 radiologists and 9 radiation oncologists) delineated SC and WB clinical target volumes (CTVs) on T2-weighted MRI and CT supine and prone scans (4 scans per patient) for 33 patient datasets. In idual observer's volumes were compared using the Dice similarity coefficient, volume overlap index, center of mass shift, and Hausdorff distances. An average cavity visualization score was also determined. Imaging modality did not affect interobserver variation for WB CTVs. Prone WB CTVs were larger in volume and more conformal than supine CTVs (on both MRI and CT). Seroma cavity volumes were larger on CT than on MRI. Seroma cavity volumes proved to be comparable in interobserver conformity in both modalities (volume overlap index of 0.57 (95% Confidence Interval (CI) 0.54-0.60) for CT supine and 0.52 (95% CI 0.48-0.56) for MRI supine, 0.56 (95% CI 0.53-0.59) for CT prone and 0.55 (95% CI 0.51-0.59) for MRI prone) however, after registering modalities together the intermodality variation (Dice similarity coefficient of 0.41 (95% CI 0.36-0.46) for supine and 0.38 (0.34-0.42) for prone) was larger than the interobserver variability for SC, despite the location typically remaining constant. Magnetic resonance imaging interobserver variation was comparable to CT for the WB CTV and SC delineation, in both prone and supine positions. Although the cavity visualization score and interobserver concordance was not significantly higher for MRI than for CT, the SCs were smaller on MRI, potentially owing to clearer SC definition, especially on T2-weighted MR images.
Publisher: Wiley
Date: 03-12-2018
Abstract: Magnetic Resonance Imaging (MRI) provides excellent soft tissue definition of pelvic tumours and organs. The aim of this study was to quantify differences in delineated clinical target volumes (CTVs) between computed tomography (CT) and MRI. Twenty patients with locally advanced gynaecological malignancies were recruited. Patients underwent dedicated MRI simulation following CT simulation. Four clinicians independently contoured each CT and MRI. CTV structures were contoured using the Radiation Therapy Oncology Group (RTOG) guidelines and lymph node CTV (LN-CTV) according to published guidelines. Interobserver variability was analysed using the dice similarity coefficient (DSC) and mean absolute surface distance (MASD). Gross tumour volume delineation was more consistent on MRI compared to CT, the DSC improved from 0.77 on CT to 0.81 on MRI, P < 0.01. GTV volumes were significantly smaller on MRI compared to CT (MRI 92 cc vs. CT 117 cc, P < 0.01). The LN-CTV and combined CTV volumes were both significantly smaller on MRI compared to CT (LN-CTV: MRI 324 cc vs CT 354 cc, P < 0.01 and combined CTV: MRI 560 cc vs CT 600 cc, P < 0.01). The LN-CTV DSC was 0.75 for both MRI and CT, and the combined CTV DSC was 0.81 for MRI and 0.80 for CT, P = 0.27. Vagina and parametria volumes exhibited more variability compared to other structures. Magnetic Resonance Imaging contouring resulted in smaller and more consistently delineated volumes when compared to CT for most CTV structures. An MRI contouring atlas is provided to complement the existing RTOG contouring guidelines.
Publisher: Wiley
Date: 04-01-2019
Abstract: This study quantified inter-observer contouring variations for multiple male pelvic structures, many of which are of emerging relevance for prostate cancer radiotherapy progression and toxicity response studies. Five prostate cancer patient datasets (CT and T2-weighted MR) were distributed to 13 observers for contouring. CT structures contoured included the clinical target volume (CTV), seminal vesicles, rectum, colon, bowel bag, bladder and peri-rectal space (PRS). MR contours included CTV, trigone, membranous urethra, penile bulb, neurovascular bundle and multiple pelvic floor muscles. Contouring variations were assessed using the intraclass correlation coefficient (ICC), Dice similarity coefficient (DSC), and multiple additional metrics. Clinical target volume (CT and MR), bladder, rectum and PRS contours showed excellent inter-observer agreement (median ICC = 0.97 0.99 1.00 0.95 0.90, DSC = 0.83 ± 0.05 0.88 ± 0.05 0.93 ± 0.03 0.81 ± 0.07 0.80 ± 0.06, respectively). Seminal vesicle contours were more variable (ICC = 0.75, DSC = 0.73 ± 0.14), while colon and bowel bag contoured volumes were consistent (ICC = 0.97 0.97), but displayed poor overlap (DSC = 0.58 ± 0.22 0.67 ± 0.21). Smaller MR structures showed significant inter-observer variations, with poor overlap for trigone, membranous urethra, penile bulb, and left and right neurovascular bundles (DSC = 0.44 ± 0.22 0.41 ± 0.21 0.66 ± 0.21 0.16 ± 0.17 0.15 ± 0.15). Pelvic floor muscles recorded moderate to strong inter-observer agreement (ICC = 0.50-0.97), although large outlier variations were observed. Inter-observer contouring variation was significant for multiple pelvic structures contoured on MR.
Publisher: Wiley
Date: 04-05-2017
Abstract: The purpose of this survey was to explore the current patterns of practice for brachytherapy in cervix cancer in Australia and New Zealand. The survey was also intended to explore clinician attitudes towards image-guided adaptive brachytherapy (IGABT) and identify barriers to the implementation of IGABT. Electronic surveys were sent to all radiotherapy centres in Australia and New Zealand under collaboration with Australia New Zealand Gynaecology and Oncology Group (ANZGOG), in order to identify patterns of radiotherapy practice. The survey was sent out in December 2013, with a reminder in February 2014. Of the 75 radiotherapy centres in Australia and New Zealand, 23 centres replied (31% response rate). Twenty-two responding departments treat cervix cancer with external beam radiation (EBRT) (22/23 96%). Fourteen responses were from departments that also use intracavitary brachytherapy (14/22 64%). The remaining eight departments who do not offer intracavitary brachytherapy referred their patients on to other centres for brachytherapy. Ultrasound was used by 86% for applicator guidance. CT and MRI were used by 79%, and 50% respectively for planning. Optimisation was based on organs at risk (93%) and target volumes (64%). Brachytherapy remains an integral component of definitive treatment for cervix cancer in Australia and New Zealand. There was increased use of soft tissue imaging modalities with emphasis on verification high rates of volumetric planning, and adherence to a defined overall treatment period. Brachytherapy was not substituted with other EBRT modalities. Despite this, there remain barriers to implementation of image-guided brachytherapy.
Publisher: Informa UK Limited
Date: 19-10-2016
Publisher: Elsevier BV
Date: 09-2014
DOI: 10.1016/J.IJROBP.2014.05.039
Abstract: The widespread use of intensity modulated radiation therapy (IMRT) for cervical cancer has been limited by internal target and normal tissue motion. Such motion increases the risk of underdosing the target, especially as planning margins are reduced in an effort to reduce toxicity. This study explored 2 adaptive strategies to mitigate this risk and proposes a new, automated method that minimizes replanning workload. Thirty patients with cervical cancer participated in a prospective clinical study and underwent pretreatment and weekly magnetic resonance (MR) scans over a 5-week course of daily external beam radiation therapy. Target volumes and organs at risk (OARs) were contoured on each of the scans. Deformable image registration was used to model the accumulated dose (the real dose delivered to the target and OARs) for 2 adaptive replanning scenarios that assumed a very small PTV margin of only 3 mm to account for setup and internal interfractional motion: (1) a preprogrammed, anatomy-driven midtreatment replan (A-IMRT) and (2) a dosimetry-triggered replan driven by target dose accumulation over time (D-IMRT). Across all 30 patients, clinically relevant target dose thresholds failed for 8 patients (27%) if 3-mm margins were used without replanning. A-IMRT failed in only 3 patients and also yielded an additional small reduction in OAR doses at the cost of 30 replans. D-IMRT assured adequate target coverage in all patients, with only 23 replans in 16 patients. A novel, dosimetry-triggered adaptive IMRT strategy for patients with cervical cancer can minimize the risk of target underdosing in the setting of very small margins and substantial interfractional motion while minimizing programmatic workload and cost.
No related grants have been discovered for Karen Lim.