T2*-weighted Image/T2-weighted Image Fusion in Postimplant Dosimetry of Prostate Brachytherapy

Abstract

Computed tomography (CT)/magnetic resonance imaging (MRI) fusion is considered to be the best method for postimplant dosimetry of permanent prostate brachytherapy; however, it is inconvenient and costly. In T2*-weighted image (T2*-WI), seeds can be easily detected without the use of an intravenous contrast material. We present a novel method for postimplant dosimetry using T2*-WI/T2-weighted image (T2-WI) fusion. We compared the outcomes of T2*-WI/T2-WI fusion-based and CT/T2-WI fusion-based postimplant dosimetry. Between April 2008 and July 2009, 50 consecutive prostate cancer patients underwent brachytherapy. All the patients were treated with 144 Gy of brachytherapy alone. Dose-volume histogram (DVH) parameters (prostate D90, prostate V100, prostate V150, urethral D10, and rectal D2cc) were prospectively compared between T2*-WI/T2-WI fusion-based and CT/T2-WI fusion-based dosimetry. All the DVH parameters estimated by T2*-WI/T2-WI fusion-based dosimetry strongly correlated to those estimated by CT/T2-WI fusion-based dosimetry (0.77 ≤ R ≤ 0.91). No significant difference was observed in these parameters between the two methods, except for prostate V150 (p = 0.04). These results show that T2*-WI/T2-WI fusion-based dosimetry is comparable or superior to MRI-based dosimetry as previously reported, because no intravenous contrast material is required. For some patients, rather large differences were observed in the value between the 2 methods. We thought these large differences were a result of seed miscounts in T2*-WI and shifts in fusion. Improving the image quality of T2*-WI and the image acquisition speed of T2*-WI and T2-WI may decrease seed miscounts and fusion shifts. Therefore, in the future, T2*-WI/T2-WI fusion may be more useful for postimplant dosimetry of prostate brachytherapy.

Development and clinical implementation of SeedNet: A sliding‐window convolutional neural network for radioactive seed identification in MRI‐assisted radiosurgery (MARS)

“…The first approach relies on co‐registration of separate CT and MR images for seed identification and anatomy delineation, respectively . The second approach is based on MRI only, using either a single pulse sequence or multiple pulse sequences for different image contrasts . However, because the radioactive seeds do not produce MR signals, conclusively identifying their locations in MR images can be challenging, especially in the presence of other similar image features, such as needle tracks.…”

WITHDRAWN: Image-guided navigation systems for interstitial brachytherapy

“…However, information provided by each of these modalities alone, due to their own limitations, does not meet all the requirements for brachytherapy, thus it necessitates image fusion so as to take full advantage of acquired information. Image fusion and image co-registration is the technique to merge multiple images from different imaging modalities or from the same imaging modality but acquired at different time points, to one display and align them image-guided surgery spatially to each other [75,76]. Therefore, by the overlay of one dataset with additional second dataset or functional dataset (functional MR, SPECT, PET), multimodality image fusion can provide additional information without the physical presence of MRI, CT, PET or SPECT during brachytherapy procedure with navigation.…”

“…Therefore, by the overlay of one dataset with additional second dataset or functional dataset (functional MR, SPECT, PET), multimodality image fusion can provide additional information without the physical presence of MRI, CT, PET or SPECT during brachytherapy procedure with navigation. Recently, novel imaging techniques are being developed (3D US, power Doppler US imaging, PET, MRI-MRS and CBCT are among them) and being increasingly applied in medical practice [17,[76][77][78]. A review of recent representative applications of navigated brachytherapy in different imaging modalities is shown in Table 2.…”

Registration free automatic identification of gold fiducial markers in MRI target delineation images for prostate radiotherapy

“…[20][21][22][23][24][25][26] Combinations of different MRI sequences has also been suggested. 27,28 The use of more exotic sequences to even enable a positive contrast of the metal has been developed. [29][30][31][32] The use of multiple dedicated MRI sequences for prostate RTP is common.…”