Evaluation of the heart and lung dosimetric parameters in deep inspiration breath hold using 3D Slicer

Purpose@#The present study was conducted to compare dosimetric parameters for the heart and left lung between free breathing (FB) and deep inspiration breath hold (DIBH) and determine the most important potential factors associated with increasing the lung dose for left-sided breast radiotherapy using image analysis with 3D Slicer software. @*Materials and Methods@#Computed tomography-simulation scans in FB and DIBH were obtained from 17 patients with left-sided breast cancer. After contouring, three-dimensional conformal plans were generated for them. The prescribed dose was 50 Gy to the clinical target volume. In addition to the dosimetric parameters, the irradiated volumes and both displacement magnitudes and vectors for the heart and left lung were assessed using 3D Slicer software. @*Results@#The average of the heart mean dose (Dmean) decreased from 5.97 to 3.83 Gy and V25 from 7.60% to 3.29% using DIBH (p < 0.001). Furthermore, the average of Dmean for the left lung was changed from 8.67 to 8.95 Gy (p = 0.389) and V20 from 14.84% to 15.44% (p = 0.387). Both of the absolute and relative irradiated heart volumes decreased from 42.12 to 15.82 mL and 8.16% to 3.17%, respectively (p < 0.001); however, these parameters for the left lung increased from 124.32 to 223.27 mL (p < 0.001) and 13.33% to 13.99% (p = 0.350). In addition, the average of heart and left lung displacement magnitudes were calculated at 7.32 and 20.91 mm, respectively. @*Conclusion@#The DIBH is an effective technique in the reduction of the heart dose for tangentially treated left sided-breast cancer patients, without a detrimental effect on the left lung.

Body outlining using Tc-99m filled flood source for lymphoscintigraphy imaging

In the current study, we evaluated the feasibility of body outlining using Tc-99m filled flood source for lymphoscintigraphy imaging. 80 patients were included in the study. Sentinel node mapping was done using Tc-99m Antimony sulfide colloid. For outlining the body a Tc-99m filled flood source was used which was placed behind or lateral to the patients for Anterior and lateral images respectively. The flood source was filled with 0.5 mCi, 1 mCi, 2 mCi, and 5 mCi for 10, 47, 10, and 3 patients respectively. The quality of outline images was assessed by two nuclear medicine specialists independently. Radiation exposure to the patients was also evaluated using thermoluminescent dosimeter [TLD-100]. The quality of body contour images were good in images taken by 1, 2, and 5 mCi filled flood source. However the quality of images was poor in 8 out of 10 lymphoscintigraphies taken by 0.5 mCi filled flood source. The measured dose rate from the Tc-99m flood source was 1.07 +/- 0.04 micro Sv/MBq/hr [39 +/- 1.5 micro Sv/mCi/hr] or 3.25 micro Sv for 5 min acquisition times. Body outlining is feasible with Tc-99m filled flood source. To assure high quality, at least 1 mCi of Tc-99m pertechnetate should be used for filling the source. This technique can be very useful especially when Co-57 is not available or has decayed. The need to prepare the flood source for each patient and difficulty in handling the source especially for the lateral views are the major limitations

Comparison between early and delayed images of [67]Ga scintigraphy for evaluation of recurrent lymphoma

Despite widespread use of [67]Gallium for lymphoma evaluation, timing of imaging after injection is a matter of controversy and to the extent of our knowledge no direct comparison has been made between early and delayed gallium images. We aimed to compare 24 and 48 hours post injection planar gallium imaging for evaluation of lymphoma recurrence. 255 patients suspicious of recurrent lymphoma were included in the study. Twenty four and 48 hours post injection [10 mCi] whole body Gallium imaging was performed. Semi-quantitative evaluation [background corrected] was carried out in positive whole body [67]Gallium scans. Diagnosis of recurrence was made by combination of clinical or pathologic examination if possible. In 59 patients the final diagnosis was made by tissue biopsy. In case of uncertain diagnosis, follow up of the patients [mean duration of 13 months] was used. The diagnosis was finally made by the referring hematologist. Whole body gallium scintigraphy was positive in 115 out of 150 patients with recurrence [sensitivity of 76%]. Comparison of the 24 and 48 hour images did not show any new lesion in the 48 hour images. However, delayed 48 hours images were required for definite detection of the gallium avid lesions in the abdominal and pelvic areas in 40 patients. Semi-quantitative evaluation of the lesion showed higher lesion to background ratio for 48 compared to the 24 hour images [p<0.001]. Considering higher lesion to background activity in the 48 hour images, delayed whole body [67]Gallium imaging may be more desirable for diagnosis of recurrent lymphoma, however 24 hour images may be sufficient. Delayed imaging can be reserved for suspicious activities [such as in abdominal images]. The strategy can save time and is more convenient for the imaging centers

Persistent sub diaphragmatic activity on the myocardial perfusion scan with [99m] Tc Sestamibi

We present a female patient with atypical chest pain who was referred to our department for ischemia evaluation. 99mTc-MIBI myocardial perfusion scan with dipyridamole stress was performed. Sub-diaphragmatic activity in the hepatic tissue and then in the bowel loops caused severe overlap on the inferior wall even on consecutive delayed images. Dipyridamole stress was repeated for the patient with 201Tl. The study was interpretable this time without any interfering sub-diaphragmatic activity

Evaluation of attenuation correction process in cardiac SPECT images

Attenuation correction is a useful process for improving myocardial perfusion SPECT and is dependent on activity and distribution of attenuation coefficients in the body [attenuation map]. Attenuation artifacts are a common problem in myocardial perfusion SPECT. The aim of this study was to compare the effect of attenuation correction using different attenuation maps and different activities in a specially designed heart phantom. The SPECT imaging for different activities and different body contours were performed by a phantom using tissue-equivalent boluses for making different thicknesses. The activity was ranged from 0.3-2mCi and the images were acquired in 180 degree, 32 steps. The images were reconstructed by OSEM method in a PC computer using Matlab software. Attenuation map were derived from CT images of the phantom. Two quality and quantity indices, derived from universal image quality index have been used to investigate the effect of attenuation correction in each SPECT image. The result of our measurements showed that the quantity index of corrected image was in the range of 3.5 to 5.2 for minimum and maximum tissue thickness and was independent of activity. Comparing attenuation corrected and uncorrected images, the quality index of corrected image improved by increasing body thickness and decreasing activity of the voxels. Attenuation correction was more effective for images with low activity or phantoms with more thickness. In our study, the location of the pixel relative to the associated attenuator tissues was another important factor in attenuation correction. The more accurate the registration process [attenuation map and SPECT] the better the result of attenuation correction

Diffuse bilateral breast uptake on the myocardial perfusion SPECT of a nursing female

Bilateral diffuse intense breast uptake was noted in a 40 year old female who was evaluated with Tc-99m sestamibi [MIBI] myocardial perfusion scan for possible ischemia. She was breast feeding her 1.5 year old child. The intense uptake in the breasts was superimposed on the apical and anteroapical regions of the myocardium and caused interpretation problem. We recommend considering Tc-99m MIBI breast uptake during breast feeding as a possible cause of non-interpretable, superimposition of radiotracer on the myocardium in myocardial perfusion scan