A comparison of dosimetric variance for external-beam partial breast irradiation using three-dimensional and four-dimensional computed tomography.

PURPOSE: To investigate the potential dosimetric benefits from four-dimensional computed tomography (4DCT) compared with three-dimensional computed tomography (3DCT) in radiotherapy treatment planning for external-beam partial breast irradiation (EB-PBI). PATIENTS AND METHODS: 3DCT and 4DCT scan sets were acquired for 20 patients who underwent EB-PBI. The volume of the tumor bed (TB) was determined based on seroma or surgical clips on 3DCT images (defined as TB3D) and the end inhalation (EI) and end exhalation (EE) phases of 4DCT images (defined as TBEI and TBEE, respectively). The clinical target volume (CTV) consisted of the TB plus a 1.0 cm margin. The planning target volume (PTV) was the CTV plus 0.5 cm (defined as PTV3D, PTVEI, and PTVEE). For each patient, a conventional 3D conformal plan (3D-CRT) was generated (defined as EB-PBI3D, EB-PBIEI, and EB-PBIEE). RESULTS: The PTV3D, PTVEI, and PTVEE were similar (P=0.549), but the PTV coverage of EB-PBI3D was significantly less than that of EB-PBIEI or EB-PBIEE (P=0.001 and P=0.025, respectively). There were no significant differences in the homogeneity or conformity indexes between the three treatment plans (P=0.125 and P=0.536, respectively). The EB-PBI3D plan resulted in the largest organs at risk dose. CONCLUSION: There was a significant benefit for patients when using 3D-CRT based on 4DCT for EB-PBI with regard to reducing nontarget organ exposure. Respiratory motion did not affect the dosimetric distribution during free breathing, but might result in poor dose coverage when the PTV is determined using 3DCT.

Phase I/II study of induction chemotherapy plus concurrent chemotherapy and SMART-IMRT-based radiotherapy in locoregionally-advanced nasopharyngeal cancer.

This study aimed to evaluate the efficacy, toxicity and tolerability of simultaneous modulated accelerated radiation therapy (SMART)-intensity modulated radiotherapy (IMRT) plus cisplatin and 5-fluorouracil (5-FU) chemotherapy for patients with advanced nasopharyngeal cancer (NPC). Forty-five patients with stage II-IV NPC, determined by the American Joint Committee on Cancer system, were treated with prescribed doses of 72 Gy total to the gross tumor volume, 60 Gy to the clinical target volume and metastatic nodal station, and 54 Gy to the clinically-negative neck region. Before radiotherapy, two cycles of cisplatin (30 mg/m(2)/day on days 1-3) plus 5-FU (400 mg/m(2)/day on days 1-5) were delivered every three weeks for two cycles. Patients received two cycles of cisplatin (30 mg/m(2) day on days 1-3) every three weeks during radiotherapy. In addition, two cycles of cisplatin and 5-FU were given after radiation. All patients completed the prescribed radiotherapy and all scheduled cycles of chemotherapy. Thirty of the 45 patients (66.6%) had a complete response at the end of treatment. Grade 3 mucositis occurred in 4/45 patients (8.8%) and grade 3 dermatitis occurred in 5/45 (11.1%) during radiotherapy. Grade 3 neutropenia occurred in 6/45 (13.3%) during concurrent chemotherapy. There was no treatment-related mortality. After a median follow-up time of 51 months, only three patients' treatments had failed. Local and distant failure rates were 1.5 and 3.0%, respectively. SMART-IMRT plus cisplatin and 5-FU chemotherapy showed promising activity with manageable toxicity. It is a feasible regimen and improves locoregional disease control.

RapidArc radiotherapy for whole pelvic lymph node in cervical cancer with 6 and 15 MV: a treatment planning comparison with fixed field IMRT.

Dosimetric differences were investigated among single and dual arc RapidArc and fixed-field intensity-modulated radiotherapy (f-IMRT) treatment plans for whole pelvic irradiation of lymph nodes. A total of 12 patients who had undergone radical surgery for cervical cancer and who had demonstrated multiple pelvic lymph node metastases were treated with radiotherapy. For all 12 cases, 7-field IMRT, single-arc RapidArc and dual-arc RapidArc were applied with 6 MV and 15 MV X-ray energies. The radiation dosimetric parameters for the different plans were compared with one another. All the plans met the clinical requirements. The homogeneity, conformity and external volume indices of f-IMRT and dual-arc RapidArc were better than for single-arc RapidArc (P < 0.05), while the differences between f-IMRT and dual-arc RapidArc were not significant. There were no significant differences in the radiation dose to organs at risk, except for the small bowel receiving >40 Gy (f-IMRT and dual-arc < single-arc, P < 0.05). The differences in dose distributions between the two applied X-ray energies for each of the modality plans were not significant. RapidArc plans resulted in fewer monitor units than the corresponding f-IMRT plans. Also, there were no differences between the two photon energies, except for a reduction in the number of MUs for 15 MV (P > 0.05). Compared to f-IMRT, no significant dosimetric benefits were found using RapidArc for whole pelvic lymph node irradiation. However, RapidArc has been associated with shorter treatment time and fewer monitor units, supporting the case for its safety and efficacy for pelvic irradiation.

[Measurement of intrafraction displacement of the mediastinal metastatic lymph nodes of non-small cell lung cancer based on four-dimensional computed tomography (4D-CT)].

OBJECTIVE: To measure the intrafraction displacement of the mediastinal metastatic lymph nodes of non-small cell lung cancer (NSCLC) based on four-dimensional computed tomography (4D-CT), and to provide the basis for the internal margin of metastatic mediastinal lymph nodes. METHODS: Twenty-four NSCLC patients with mediastinal metastatic lymph nodes confirmed by contrast enhanced CT (short axis diameter ≥ 1 cm) were included in this study. 4D-CT simulation was carried out during free breathing and 10 image sets were acquired. The mediastinal metastatic lymph nodes and the dome of ipsilateral diaphragma were separately delineated on the CT images of 10 phases of breath cycle, and the lymph nodes were grouped as the upper, middle and lower mediastinal groups depending on the mediastinal station. Then the displacements of the lymph nodes in the left-right, anterior-posterior, superior-inferior directions and the 3-dimensional vector were measured. The differences of displacement in three directions for the same group of metastatic lymph nodes and in the same direction for different groups of metastatic lymph nodes were compared. The correlation between the displacement of ipsilateral diaphragma and mediastinal lymph nodes was analyzed in superior-inferior direction. RESULTS: The displacements in left-right, anterior-posterior and superior-inferior directions were (2.24 ± 1.55) mm, (1.87 ± 0.92) mm and (3.28 ± 2.59) mm for the total (53) mediastinal lymph nodes, respectively. The vectors were (4.70 ± 2.66) mm, (3.87 ± 2.45) mm, (4.97 ± 2.75) mm and (5.23 ± 2.67) mm for the total, upper, middle and lower mediastinal lymph nodes, respectively. For the upper mediastinal lymph nodes, the displacements in left-right, anterior-posterior and superior-inferior directions showed no significant difference between each other (P > 0.05). For the middle mediastinal lymph nodes, the displacements merely in anterior-posterior and superior-inferior directions showed significant difference (P = 0.005), while the displacements were not significantly different in the left-right and anterior-posterior, left-right and superior-inferior directions (P > 0.05). The displacements of the total and the lower mediastinal lymph nodes in left-right and superior-inferior, or anterior-posterior and superior-inferior directions were significantly different (P < 0.05), but was not significantly different in left-right and anterior-posterior directions (P > 0.05). The displacements of different group of mediastinal lymph nodes in a single direction or vector showed no significant difference (P > 0.05). In the superior-inferior direction, the correlation between the displacements of ipsilateral diaphragma and mediastinal lymph nodes were not statistically significant (P > 0.05). CONCLUSIONS: During free breathing, the differences between the intrafractional displacement of mediastinal metastatic lymph nodes in the same direction and its station were not statistically significant. The displacements of the total mediastinal metastatic lymph nodes in the superior-inferior direction were greater than that in the left-right and anterior-posterior directions, especially for the middle and lower mediastinal metastatic lymph nodes. There was no significant correlation between the displacements of ipsilateral diaphragma and the mediastinal metastatic lymph nodes in the superior-inferior direction, so it was unreasonable to estimate and predict the displacement of mediastinal metastatic lymph nodes by the displacement of ipsilateral diaphragma.

Evaluation of the geometric accuracy of anatomic landmarks as surrogates for intrapulmonary tumors in image-guided radiotherapy.

OBJECTIVES: The purpose of this study was to evaluate the geometric accuracy of thoracic anatomic landmarks as target surrogates of intrapulmonary tumors for manual rigid registration during image-guided radiotherapy (IGRT). METHODS: Kilovolt cone-beam computed tomography (CBCT) images acquired during IGRT for 29 lung cancer patients with 33 tumors, including 16 central and 17 peripheral lesions, were analyzed. We selected the "vertebrae", "carina", and "large bronchi" as the candidate surrogates for central targets, and the "vertebrae", "carina", and "ribs" as the candidate surrogates for peripheral lesions. Three to six pairs of small identifiable markers were noted in the tumors for the planning CT and Day 1 CBCT. The accuracy of the candidate surrogates was evaluated by comparing the distances of the corresponding markers after manual rigid matching based on the "tumor" and a particular surrogate. Differences between the surrogates were assessed using 1-way analysis of variance and post hoc least-significant-difference tests. RESULTS: For central targets, the residual errors increased in the following ascending order: "tumor", "bronchi", "carina", and "vertebrae"; there was a significant difference between "tumor" and "vertebrae" (p=0.010). For peripheral diseases, the residual errors increased in the following ascending order: "tumor", "ribs", "vertebrae", and "carina". There was a significant difference between "tumor" and "carina" (p=0.005). CONCLUSIONS: The "bronchi" and "carina" are the optimal surrogates for central lung targets, while "ribs" and "vertebrae" are the optimal surrogates for peripheral lung targets for manual matching of online and planned tumors.

[Evaluation of dosimetric variance in forward intensity modulated radiotherapy of the breast based on 4D CT and 3D CT during free breathing].

OBJECTIVE: To explore the dosimetric variance in forward intensity modulated radiotherapy (IMRT) based on 4D CT and 3D CT after breast conserving surgery. METHODS: Seventeen patients after breast conserving surgery underwent 3D CT simulation scans followed by respiration-synchronized 4D CT simulation scans at free breathing state. The treatment plan constructed using the end inspiration (EI) scan was then copied and applied to the end expiration (EE), and 3D scans and dose distribution were calculated separately. Dose-volume histograms (DVHs) parameters for the CTV, PTV, ipsilateral lung and heart were evaluated and compared. RESULTS: The CTV volume difference was biggest between T0 and 3D CT, and the volume difference was 4.10 cm(3). Mean dose of PTV at EE was lower than that at EI (P = 0.019), but there were no statistically significant difference between 3D and EI, EE (all P > 0.05). The homogeneity index (HI) at EI, EE, 3D plans were 0.149, 0.159 and 0.164, respectively, and a significant difference was only between EI and EE (P = 0.039). The highest conformal index (CI) was at EI phase (P < 0.05), and there was no significant difference between EE and 3D (P = 0.758). The V(40) and V(50) of ipsilateral lung at EE phase were lower than that at EI (P < 0.05). There were no significant differences in all the indexes for heart (P > 0.05). CONCLUSIONS: The breast deformation during respiration may be disregarded in whole breast IMRT. PTV dose distribution is significantly changed between EI and EE phases, and the differentiation of the lung high dose area between EI and EE phases may be induced by thorax expansion. 3D treatment planning is sufficient for whole breast forward IMRT, but 4D CT scans assisted by respiratory gating ensures more precise delivery of radiation dose.

Comparison of the planning target volume based on three-dimensional CT and four-dimensional CT images of non-small-cell lung cancer.

BACKGROUND AND PURPOSE: To compare positional and volumetric differences of planning target volumes (PTVs) based on axial three-dimensional CT (3DCT) and four-dimensional CT (4DCT) for the primary tumor of non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: Twenty-eight patients with NSCLC underwent 3DCT and 4DCT scans of the thorax during normal free breathing. PTV(vector) was defined on 3DCT using the individual tumor motion vector measured by 4DCT accounting for tumor motion; PTV(4D) was defined on all phases of 4DCT images. In addition, a 7mm margin for microscopic disease and a 3mm setup margin were used for above PTVs, respectively. The differences in target position, volume and coverage between PTV(vector) and PTV(4D) were evaluated for tumors in different lobes, respectively. RESULTS: The median motion vector for tumors located in the upper lobe (group A) and in the middle lower lobe (group B) was 2.8 and 7mm, respectively. The mean centroid shifts between PTV(vector) and PTV(4D) in the LR, AP and CC directions for group A and B were close to zero. The median size ratio of PTV(4D) to PTV(vector) was 0.75 and 0.52 for group A and B. The motion vector showed a significant correlation to the ratio of PTV(4D) to PTV(vector) for group A and B (p=0.008 and 0.003). The median DI of PTV(vector) in PTV(4D) was 69.19% for group A and 51.60% for group B. The median DI of PTV(4D) in PTV(vector) was 98.99% for group A and 99.94% for group B. CONCLUSION: It is necessary to expand the internal margin isotropically in a single direction for 3DCT treatment planning due to the uncertainty of the 3DCT-based target position. The 3DCT-based PTV using individual margins provides a good coverage of the 4DCT-based PTV, meanwhile encompasses relatively large normal tissues, especially for middle and lower lobe tumors. We should be cautious about the use of the individual PTV derived from 3DCT in treatment planning.

Protection of lung function by introducing single photon emission computed tomography lung perfusion image into radiotherapy plan of lung cancer.

BACKGROUND: The lung functional status could be displayed on lung perfusion images. With the images, the radiotherapy plans of lung cancer could be guided to more optimized. This study aimed to assess quantitatively the impact of incorporating functional lung imaging into 3-dimensional conformal radiotherapy (3DCRT) and intensity-modulated radiation therapy (IMRT) planning for non-small cell lung cancer (NSCLC). METHODS: Ten patients with NSCLC who had undergone radiotherapy were included in this study. Before radiotherapy, each patient underwent CT simulation and lung perfusion imaging with single photon emission computed tomography (SPECT). The SPECT images were registered with simulation planning CT and used to contour functional lung (lung-F) and non-functional lung (lung-NF). Two 3DCRT plans and two IMRT plans were designed and compared in each patient: two anatomic plans using simulation CT alone and two functional plans using SPECT-CT in addition to the simulation CT. Dosimetric parameters of the four types of plans were compared in terms of tumor coverage and avoidance of normal tissues. Total radiation dose was set at 66 Gy (2 Gy x 33 fractions). RESULTS: In incorporating perfusion information in 3DCRT and IMRT planning, the reductions on average in the mean doses to the functional lung in the functional plan were 168 cGy and 89 cGy, respectively, compared with those in the anatomic plans. The median reductions in the percentage of volume irradiated with > 5 Gy, > 10 Gy, > 20 Gy, > 30 Gy and > 40 Gy for functional lung in the functional plans were 6.50%, 10.21%, 14.02%, 22.30% and 23.46% in 3DCRT planning, respectively, and 3.05%, 15.52%, 14.16%, 4.87%, and 3.33% in IMRT planning, respectively. No greater degree of sparing of the functional lung was achieved in functional IMRT than in 3DCRT. CONCLUSION: Function-guided 3DCRT and IMRT plannings both appear to be effective in preserving functional lung in NSCLC patients.

[FDG PET/CT versus PET alone for pre-surgical detection of lymph node metastasis in esophageal carcinoma].

OBJECTIVE: To compare the combined FDG PET/CT with PET alone in the detection of lymph node metastasis (LNM) for esophageal carcinoma patient. METHODS: From November 2003 to August 2005, 35 patients with esophageal carcinoma underwent FDG PET/CT before esophagectomy and lymph node (LN) dissection. The patients who had history of previous anticancer treatment or diabetes mellitus and inflammatory lung diseases as well as being inoperable for medical reasons were excluded. The results of LNM detection by PET/CT and PET alone were compared with pathological results. RESULTS: Twenty-nine men and 6 women were eligible for this study, with a mean age of 57 years (range: 40 to 72 years). Of these 35 patients, 3 had lesion at the upper third thoracic esophagus, 22 at the middle third and 10 at the lower third. All patients underwent surgical resection successfully. Twenty-five patients and 65 out of 313 excised nodal groups were found to have metastases by pathological examination. The true positive and true negative LNM interpretation reached 61 and 229 LN groups on PET/CT versus 53 and 217 LN groups on PET alone. False negative LNM interpretation was found in 12 LN groups on PET alone, and 8 of them were corrected by PET/CT including one cervical LN, 4 paraesophageal LNs, one left gastric arterial LN, one left gastric cardia LN, one lesser gastric curve LN. False positive interpretations on PET alone were found in 31 LN groups, 12 of them were corrected by PET/CT which included 9 false-positive interpretations due to physical tracer uptake (2 in the cervical region and 7 in gastrointestinal tract ) and 3 lesions with heterogeneous tracer uptake in the primary tumor. The sensitivity, specificity and accuracy of LNM detection by PET alone was 81.54% (53/65), 87.50% (217/248), and 86.26% (270/313), whereas by PET/CT, which was 93.85% (61/65), 91.24% (229/248) and 92.65% (290/313), respectively. There were statistically significant differences in sensitivity and accuracy of LNM detection between PET/CT and PET alone (0.033 and 0.009). CONCLUSION: Compared with FDG PET alone, FDG PET combined with CT can improve the sensitivity and accuracy in detection of lymph node metastasis in esophageal carcinoma.

[Impact of PET/CT on precise radiotherapy planning for non-small cell lung cancer].

OBJECTIVE: To investigate the impact of PET/CT on the clinical staging, target volume delineation and precise radiotherapy (PAR) planning for patients with non-small cell lung cancer (NSCLC). METHODS: PET/CT scanning was performed in 58 histologically proven NSCLC patients for radical radiotherapy or surgery. The clinical staging of all patients was determined by PET/CT according to 1997 World Health Organization (WHO) staging system. The gross tumor volume (GTV) was delineated and three-dimensional conformal radiotherapy (3D-CRT) planning was established with identical parameters based on CT image and PET/CT fused image, respectively. The indexes including volume of GTV (V(GTV)), percentage of the total lung volume which received more than 20 Gy (V(20)), mean lung dose (MLD), tumor control probability (TCP), normal tissue complication probability (NTCP), and dose to spinal cord (Ds) were selected and evaluated. The quality of the two plans and the impact of PET/CT on PAR planning was compare and analyzed. RESULTS: 1. PET/CT image results changed the clinical stages in 21 of 58 (36.2%) patients with 14 upstaged and 7 downstaged, therefore, the management decisions were modified in 16 (27.6%) patients. 2. Among 32 patients who underwent surgery, PET/CT staging result was consistent with pathologic staging in 29 with one false negative and 2 false positive in lymph node staging. The sensitivity of PET/CT was 96.9% and accuracy 90.6%. 3. The differences of indexes including V(GTV) (P = 0.004), V(20) (P = 0.000) and MLD (P = 0.004) between the two radiotherapy plannings were statistically significant, whereas, the Ds, TCP and NTCP (left lung, right lung, skin and spinal cord) was not. CONCLUSION: 1. The impact PET/CT on clinical staging of NSCLC and PAR planning was remarkable. 2. PET/CT is more consistent with pathology in staging than CT and, therefore, is an important compensatory staging measure. 3. Compared with CT, PET/CT can reduce the V(GTV) in patients with atelectasis and obstructive pneumonitis when contouring the target volume, so can provide better protection for normal surrounding lung tissue. On the other hand, PET/CT is more sensitive in detecting mediastinal lymph node metastasis than CT, and the V(GTV) can be more precise and guaranteed. 4. Radiopneumonitis may be more effectively prevented because of significant decrease in V(20) and MLD by more precise planning based on PET/CT results. 5. PET/CT not only can provide satisfactory Ds, TCP and NTCP within clinical demand, but also more precise delineation of the radiation target volume and precise radiotherapy planning for NSCLC.