Techniques to Visualize the Stages of Prostate Cancer - Essay Example

?Programme Radiotherapy and Oncology – RT02 Assignment The Use of CT, MRI and PET Scan Imaging in Visualizing the Early and Late Stage of Prostate Cancer. Discuss how the image findings may influence the radiotherapy planning process. Candidate Number: Word Count: 2,010 Early diagnosis is important to ensure that the patient will receive proper medication and treatment to improve their overall quality of life (i.e. radiation therapy, chemotherapy, surgery, and androgen-deprivation hormone therapy among others) (Braun & Anderson, 2007, p. 180). Because of the small size of the prostate gland, it is difficult to detect early signs of prostate cancer. Therefore, the use of radiographic imaging is necessary. Radiology plays a significant role in the early and late detection of prostate cancer. However, each type of radiographic imaging technology has its own strengths and limitations. Therefore, this essay will focus on comparing and contrasting between the three imaging modalities known as the computerized tomography (CT) scan, magnetic resonance imaging (MRI), and the Positron Emission Tomography (PET) scan. Eventually, the second part of this essay will discuss the impact of imaging on planning radiotherapy. Early detection of prostate cancer is important. In general, the transrectal ultrasound (TRUS) can be used to provide accurate sampling of the prostate tissue which would eventually be used for histological examination on patients who are at high risk of developing prostate cancer (i.e. high levels of prostate-specific antigen or the presence of abnormal digital rectal examination) (Tsai et al., 2007). Aside from being used in guiding needle biopsies, the use of TRUS is also useful in “identifying the outlines of the prostate in sagittal and transverse planes” (Hou, Swanson and Barqawi, 2009). For these reasons, TRUS is a significant part of a systematic biopsy procedure which is commonly performed when tracing possible signs of prostate cancer (Halpern et al., 2012; Hou, Swanson and Barqawi, 2009l Tsai et al., 2007). Using the prolate ellipsoid formula, both the CT scan and TRUS can be used in measuring the prostate volume of patients with prostate cancer (Kalkner et al., 2006; Hoffelt et al., 2003). After comparing the use of CT scan and TRUS in measuring the prostate volume of patients with prostate cancer, Hoffelt et al. (2003) found out that even though there is a strong correlation between the measurement of prostate volume with the use of CT scan and TRUS (Pearson’s correlation coefficient = 0.925), the use of CT scan tend to overestimate the prostate volume by almost 50% as compared to the use of TRUS. In a more recent study, Kalkner et al. (2006) found out that the use of CT scan provides a higher average prostate volume of 34 cc as compared to TRUS-step and TRUS-ellipsoid with 28 cc and 24 cc respectively. As explained by Kalkner et al. (2006), one of the possible reason why the use of CT scan provides a higher prostate volume estimate is because of the vagueness in definining the apex of the prostate. Therefore, when it comes to determining the PSA density, the use of TRUS is more preferred than the use of CT scan because the useof TRUS can provide a more accurate estimate of the prostate volume (Hou, Swanson and Barqawi, 2009). To increase the accuracy of detecting a high grade or high volume prostate cancer, the use of contrast enhanced TRUS is necessary (Halpern et al., 2012). A grey-scale TRUS can be used in providing images related to prostate cancer (Hou, Swanson and Barqawi, 2009). In early 1960s, a 3.5 MHz transducer was used in the design of TRUS technology. Therefore, the images that were created in the past were of poor quality (Applewhite et al., 2001). It was in 1980s when the transducer used in TRUS was increased to 7 MHz. Therefore, the modern TRUS design is capable of providing us with a better image of the prostate (Applewhite et al., 2001). Based on the TRUS-guided biopsy specimen of 200 patients with less than 20 ng/mL prostate specific antigen values or a positive result on digital rectal examination (DRE) who agreed to participate in the study of Spakic et al. (2007), 31.8% of them were diagnosed with prostate cancer whereas the rest 60.6% and 7.6% had hypoechoic and hyperechoic lesions. Furthermore, Spakic et al. (2007) found out that hyperechoic lesions are positively related to prostate cancer. Even though TRUS can be used in creating prostate cancer images, the use of this type of imaging modality is not the best choice because of the higher chance of generating hypoechoic as compared to 1% hyperechoic lesions on TRUS (Hou, Swanson and Barqawi, 2009). Furthermore, the accuracy of the imaging results when using grey-scale TRUS is only 52.7% (Kuligowska et al., 2001). Since there is a higher chance of getting a false-positive signs of prostate carcinoma when using the grey-scale TRUS (67%), the use of this particular imaging modality is not advisable when used in localization and detection of prostate cancer (Hou, Swanson and Barqawi, 2009; Kuligowska et al., 2001). Based on the size of lymph nodes, what the CT scan does it to detect the presence of nodal metastases (Hou, Swanson and Barqawi, 2009). However, not all patients with prostate cancer at an early stage would show huge signs of nodal metastases (Hricak et al., 2007). Therefore, when it comes to diagnosing patients for prostate cancer or the staging of cancer, one can say that the role of CT scan is very limited. Instead, CT scan is commonly used or is highly recommended for patients who are at stage 3 prostate cancer (i.e. PSA of more than 20 ng/mL and Gleason score of more than 7) (Hou, Swanson and Barqawi, 2009). In case the prostate carcinoma has spread and metastasized in the pelvic bones, the use of CT scan is often times less superior as compared to other imaging modalities like the MRI (Hricak et al., 2007; Groves et al., 2006). For this reason, it is necessary to limit the use of CT scan when it comes to detecting the early and late stage of prostate cancer. Better yet, CT scan imaging should be reserved as a second-line imaging test when detecting nodal or bone metastases on prostate cancer patients (Tombal and Lecouvet, 2012). Functional MRI is more useful than the CT scan in the sense that the MRI can be used in detecting not only the localization of the tumour but also determine its characteristics, morphological changes, and its extent (Isebaert et al., 2013; Iwazawa et al., 2011; Kelloff et al., 2009; Haider et al., 2007). It is also possible to use MRI to get a detailed visualisation of the “prostatic, periprostatic, and pelvic anatomy” of patients with prostate cancer (Carroll, Coakley and Kurhanewicz, 2006, p. S4). When used with an endorectal coil and four other external pelvic phased array coils, MRI can give better spatial and contrast resolution of the prostate zone (Yu et al., 2004; Kurhanewicz et al., 2002). To get a clear “visualization of the zonal anatomy of the prostate and better delineation of tumour location, volume, and extent (stage)”, the use of endorectal MRI (endoMRI) and magnetic resonance spectroscopic imaging (MRSI) is the best choice (Carroll, Coakley and Kurhanewicz, 2006, p. S4). In fact, endoMRI/MRSI is highly recommended each time there is a need to test the degree of prostate cancer based on a set of metabolic criteria (Kelloff, Choyke and Coffey, 2009). Since MRI imaging is clear in terms of spatial and contrast resolution, the use of this particular imaging modality is best when studying the differences in the normal peripheral zone of patients with prostate cancer and benign prostatic hyperplasia (Hao et al., 2005). As defined by Parikh et al. (2008, p. 46), the term sensitivity is all about “the ability of a test to correctly classify an individual as diseased” whereas the term specificity is pertaining to the “ability of a test to correctly classify an individual as disease-free”. It means that both sensitivity and specificity often times are inversely proportional with one another. To get a higher sensitivity test when it comes to detecting cancer cells within the prostate area, the use of a “combined T2 and DWI MRI is better than the use of T2 imaging test alone” (Haider et al., 2007). To get a higher sensitivity test when detecting an accurate localization of intraprostatic tumour nodules, the use of diffusion-weighted (DW) MRI at 1.5T is considered as highly sensitive for tumour localization (44.5%) as compared to the use of T2-weighted MRI (31.1%) and dynamic contrast-enhanced (DCE) MRI (27.4%) and that the combination of these three types of MRI increases the sensitivity test up to 58.8% (Isebaert et al. 2013). This explains why the use of DW MRI, T2-weighted MRI, and dynamic contrast-enhanced MRI is highly recommended when it comes to examining prostate cancer localization and detecting a more aggressive prostate cancer in an advanced stage (Isebaert et al., 2013). Similar to MRI, the use of PET scan is also significant when it comes to detecting the early and late stage of prostate cancer. However, the use of PET can lead to a suboptimal sensitivity test results as compared to MRI (Hou, Swanson and Barqawi, 2009; Liu et al., 2001). In general, it is normal for prostate cancer patients to have a high metabolic rate and this group of individuals consume more glucose in their glycotic pathway and based on the increased metabolism, what the PET does is to measure that metabolic rate in trying to detect cancerous lesions (Hou, Swanson and Barqawi, 2009). However, continuous bladder irrigation or the use of diuretic drugs like furosemide hours before the PET scan decreases PET sensitivity to detect either lymph node metastases or prostate cancer (Hou, Swanson and Barqawi, 2009; Sung et al., 2003). When combined with the use of specific molecular probes, the use of PET and SPECT detects the pathological processes that undergo prostate cancer metastases (Kelloff et al., 2009). In most cases, PET Tracers like C-acetate, C-choline, and F-choline can be used to increase the sensitivity or specificity of PET when utilized for prostate cancer detection (Kelloff et al., 2009; Akin and Hricak, 2007; Albracht et al., 2007). Therefore, by increasing either the sensitivity or specificity of PET, one can easily determine whether the imaging test that was conducted to determine whether a person has a prostate cancer or is free of prostate cancer is accurate and correct. For instance, after examining the diagnostic capabilities of (11)C-acetate PET in early detection of prostate cancer recurrence, Albracht et al. (2007) found out that the use of this particular imaging tool is highly recommended in the early evaluation of prostate cancer. C-choline PET/CT is the best choice when it comes to getting an accurate test with regards to the stage of high-risk prostate cancer patients (Skanjeti and Pelosi, 2011). Even though the use of a single imaging modality is more sensitive than the other, it is always best to determine the reasons for requiring an imaging test. For instance, although the use of CT scan has a high sensitivity for detecting the presence of nodal metastases, the use of this modality may not be effective in terms of detecting signs of prostate cancer during the early stage. Therefore, the use of either MRI or PET scan can be the best choice when diagnosing patients for early signs of prostate cancer. Learning more about the effectiveness of imaging modalities has a significant impact on planning radiotherapy. In the absence of useful information about the sensitivity of MRI, CT, and PET scan, it is difficult to plan a treatment based on the specific health condition of each patient who are at risk of developing prostate cancer or is currently at different stages of the said disease. For example, as compared to CT, the use of TRUS has a higher sensitivity when it comes to measuring the prostate volume. Therefore, the use of TRUS should be the preferred choice each time there is a need to measure the patients’ prostate volume. In case there is a need to trace nodal metastases, the use of CT scan is better than the use of other imaging modalities. If there is a need to get a clear visualization of the prostate zone or the localization of the prostate carcinoma, the use of MRI is the best choice. References Akin, O., & Hricak, H. (2007). Imaging of prostate cancer. Radiologic Clinics of North America, 45(1), 207-222. 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